[binutils-gdb.git] / gdb / arm-tdep.c

/* Common target dependent code for GDB on ARM systems.

   Copyright (C) 1988, 1989, 1991, 1992, 1993, 1995, 1996, 1998, 1999, 2000,
   2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008
   Free Software Foundation, Inc.

   This file is part of GDB.

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 3 of the License, or
   (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */

#include <ctype.h>              /* XXX for isupper () */

#include "defs.h"
#include "frame.h"
#include "inferior.h"
#include "gdbcmd.h"
#include "gdbcore.h"
#include "gdb_string.h"
#include "dis-asm.h"            /* For register styles. */
#include "regcache.h"
#include "doublest.h"
#include "value.h"
#include "arch-utils.h"
#include "osabi.h"
#include "frame-unwind.h"
#include "frame-base.h"
#include "trad-frame.h"
#include "objfiles.h"
#include "dwarf2-frame.h"
#include "gdbtypes.h"
#include "prologue-value.h"
#include "target-descriptions.h"
#include "user-regs.h"

#include "arm-tdep.h"
#include "gdb/sim-arm.h"

#include "elf-bfd.h"
#include "coff/internal.h"
#include "elf/arm.h"

#include "gdb_assert.h"

static int arm_debug;

/* Macros for setting and testing a bit in a minimal symbol that marks
   it as Thumb function.  The MSB of the minimal symbol's "info" field
   is used for this purpose.

   MSYMBOL_SET_SPECIAL  Actually sets the "special" bit.
   MSYMBOL_IS_SPECIAL   Tests the "special" bit in a minimal symbol.  */

#define MSYMBOL_SET_SPECIAL(msym)                                       \
        MSYMBOL_INFO (msym) = (char *) (((long) MSYMBOL_INFO (msym))    \
                                        | 0x80000000)

#define MSYMBOL_IS_SPECIAL(msym)                                \
        (((long) MSYMBOL_INFO (msym) & 0x80000000) != 0)

/* The list of available "set arm ..." and "show arm ..." commands.  */
static struct cmd_list_element *setarmcmdlist = NULL;
static struct cmd_list_element *showarmcmdlist = NULL;

/* The type of floating-point to use.  Keep this in sync with enum
   arm_float_model, and the help string in _initialize_arm_tdep.  */
static const char *fp_model_strings[] =
{
  "auto",
  "softfpa",
  "fpa",
  "softvfp",
  "vfp",
  NULL
};

/* A variable that can be configured by the user.  */
static enum arm_float_model arm_fp_model = ARM_FLOAT_AUTO;
static const char *current_fp_model = "auto";

/* The ABI to use.  Keep this in sync with arm_abi_kind.  */
static const char *arm_abi_strings[] =
{
  "auto",
  "APCS",
  "AAPCS",
  NULL
};

/* A variable that can be configured by the user.  */
static enum arm_abi_kind arm_abi_global = ARM_ABI_AUTO;
static const char *arm_abi_string = "auto";

/* The execution mode to assume.  */
static const char *arm_mode_strings[] =
  {
    "auto",
    "arm",
    "thumb"
  };

static const char *arm_fallback_mode_string = "auto";
static const char *arm_force_mode_string = "auto";

/* Number of different reg name sets (options).  */
static int num_disassembly_options;

/* The standard register names, and all the valid aliases for them.  */
static const struct
{
  const char *name;
  int regnum;
} arm_register_aliases[] = {
  /* Basic register numbers.  */
  { "r0", 0 },
  { "r1", 1 },
  { "r2", 2 },
  { "r3", 3 },
  { "r4", 4 },
  { "r5", 5 },
  { "r6", 6 },
  { "r7", 7 },
  { "r8", 8 },
  { "r9", 9 },
  { "r10", 10 },
  { "r11", 11 },
  { "r12", 12 },
  { "r13", 13 },
  { "r14", 14 },
  { "r15", 15 },
  /* Synonyms (argument and variable registers).  */
  { "a1", 0 },
  { "a2", 1 },
  { "a3", 2 },
  { "a4", 3 },
  { "v1", 4 },
  { "v2", 5 },
  { "v3", 6 },
  { "v4", 7 },
  { "v5", 8 },
  { "v6", 9 },
  { "v7", 10 },
  { "v8", 11 },
  /* Other platform-specific names for r9.  */
  { "sb", 9 },
  { "tr", 9 },
  /* Special names.  */
  { "ip", 12 },
  { "sp", 13 },
  { "lr", 14 },
  { "pc", 15 },
  /* Names used by GCC (not listed in the ARM EABI).  */
  { "sl", 10 },
  { "fp", 11 },
  /* A special name from the older ATPCS.  */
  { "wr", 7 },
};

static const char *const arm_register_names[] =
{"r0",  "r1",  "r2",  "r3",     /*  0  1  2  3 */
 "r4",  "r5",  "r6",  "r7",     /*  4  5  6  7 */
 "r8",  "r9",  "r10", "r11",    /*  8  9 10 11 */
 "r12", "sp",  "lr",  "pc",     /* 12 13 14 15 */
 "f0",  "f1",  "f2",  "f3",     /* 16 17 18 19 */
 "f4",  "f5",  "f6",  "f7",     /* 20 21 22 23 */
 "fps", "cpsr" };               /* 24 25       */

/* Valid register name styles.  */
static const char **valid_disassembly_styles;

/* Disassembly style to use. Default to "std" register names.  */
static const char *disassembly_style;

/* This is used to keep the bfd arch_info in sync with the disassembly
   style.  */
static void set_disassembly_style_sfunc(char *, int,
                                         struct cmd_list_element *);
static void set_disassembly_style (void);

static void convert_from_extended (const struct floatformat *, const void *,
                                   void *, int);
static void convert_to_extended (const struct floatformat *, void *,
                                 const void *, int);

struct arm_prologue_cache
{
  /* The stack pointer at the time this frame was created; i.e. the
     caller's stack pointer when this function was called.  It is used
     to identify this frame.  */
  CORE_ADDR prev_sp;

  /* The frame base for this frame is just prev_sp - frame size.
     FRAMESIZE is the distance from the frame pointer to the
     initial stack pointer.  */

  int framesize;

  /* The register used to hold the frame pointer for this frame.  */
  int framereg;

  /* Saved register offsets.  */
  struct trad_frame_saved_reg *saved_regs;
};

/* Addresses for calling Thumb functions have the bit 0 set.
   Here are some macros to test, set, or clear bit 0 of addresses.  */
#define IS_THUMB_ADDR(addr)     ((addr) & 1)
#define MAKE_THUMB_ADDR(addr)   ((addr) | 1)
#define UNMAKE_THUMB_ADDR(addr) ((addr) & ~1)

/* Set to true if the 32-bit mode is in use.  */

int arm_apcs_32 = 1;

/* Determine if FRAME is executing in Thumb mode.  */

static int
arm_frame_is_thumb (struct frame_info *frame)
{
  CORE_ADDR cpsr;

  /* Every ARM frame unwinder can unwind the T bit of the CPSR, either
     directly (from a signal frame or dummy frame) or by interpreting
     the saved LR (from a prologue or DWARF frame).  So consult it and
     trust the unwinders.  */
  cpsr = get_frame_register_unsigned (frame, ARM_PS_REGNUM);

  return (cpsr & CPSR_T) != 0;
}

/* Determine if the program counter specified in MEMADDR is in a Thumb
   function.  This function should be called for addresses unrelated to
   any executing frame; otherwise, prefer arm_frame_is_thumb.  */

static int
arm_pc_is_thumb (CORE_ADDR memaddr)
{
  struct minimal_symbol *sym;

  /* If bit 0 of the address is set, assume this is a Thumb address.  */
  if (IS_THUMB_ADDR (memaddr))
    return 1;

  /* If the user wants to override the symbol table, let him.  */
  if (strcmp (arm_force_mode_string, "arm") == 0)
    return 0;
  if (strcmp (arm_force_mode_string, "thumb") == 0)
    return 1;

  /* Thumb functions have a "special" bit set in minimal symbols.  */
  sym = lookup_minimal_symbol_by_pc (memaddr);
  if (sym)
    return (MSYMBOL_IS_SPECIAL (sym));

  /* If the user wants to override the fallback mode, let them.  */
  if (strcmp (arm_fallback_mode_string, "arm") == 0)
    return 0;
  if (strcmp (arm_fallback_mode_string, "thumb") == 0)
    return 1;

  /* If we couldn't find any symbol, but we're talking to a running
     target, then trust the current value of $cpsr.  This lets
     "display/i $pc" always show the correct mode (though if there is
     a symbol table we will not reach here, so it still may not be
     displayed in the mode it will be executed).  */
  if (target_has_registers)
    return arm_frame_is_thumb (get_current_frame ());

  /* Otherwise we're out of luck; we assume ARM.  */
  return 0;
}

/* Remove useless bits from addresses in a running program.  */
static CORE_ADDR
arm_addr_bits_remove (CORE_ADDR val)
{
  if (arm_apcs_32)
    return UNMAKE_THUMB_ADDR (val);
  else
    return (val & 0x03fffffc);
}

/* When reading symbols, we need to zap the low bit of the address,
   which may be set to 1 for Thumb functions.  */
static CORE_ADDR
arm_smash_text_address (CORE_ADDR val)
{
  return val & ~1;
}

/* Analyze a Thumb prologue, looking for a recognizable stack frame
   and frame pointer.  Scan until we encounter a store that could
   clobber the stack frame unexpectedly, or an unknown instruction.  */

static CORE_ADDR
thumb_analyze_prologue (struct gdbarch *gdbarch,
                        CORE_ADDR start, CORE_ADDR limit,
                        struct arm_prologue_cache *cache)
{
  int i;
  pv_t regs[16];
  struct pv_area *stack;
  struct cleanup *back_to;
  CORE_ADDR offset;

  for (i = 0; i < 16; i++)
    regs[i] = pv_register (i, 0);
  stack = make_pv_area (ARM_SP_REGNUM);
  back_to = make_cleanup_free_pv_area (stack);

  while (start < limit)
    {
      unsigned short insn;

      insn = read_memory_unsigned_integer (start, 2);

      if ((insn & 0xfe00) == 0xb400)            /* push { rlist } */
        {
          int regno;
          int mask;

          if (pv_area_store_would_trash (stack, regs[ARM_SP_REGNUM]))
            break;

          /* Bits 0-7 contain a mask for registers R0-R7.  Bit 8 says
             whether to save LR (R14).  */
          mask = (insn & 0xff) | ((insn & 0x100) << 6);

          /* Calculate offsets of saved R0-R7 and LR.  */
          for (regno = ARM_LR_REGNUM; regno >= 0; regno--)
            if (mask & (1 << regno))
              {
                regs[ARM_SP_REGNUM] = pv_add_constant (regs[ARM_SP_REGNUM],
                                                       -4);
                pv_area_store (stack, regs[ARM_SP_REGNUM], 4, regs[regno]);
              }
        }
      else if ((insn & 0xff00) == 0xb000)       /* add sp, #simm  OR  
                                                   sub sp, #simm */
        {
          offset = (insn & 0x7f) << 2;          /* get scaled offset */
          if (insn & 0x80)                      /* Check for SUB.  */
            regs[ARM_SP_REGNUM] = pv_add_constant (regs[ARM_SP_REGNUM],
                                                   -offset);
          else
            regs[ARM_SP_REGNUM] = pv_add_constant (regs[ARM_SP_REGNUM],
                                                   offset);
        }
      else if ((insn & 0xff00) == 0xaf00)       /* add r7, sp, #imm */
        regs[THUMB_FP_REGNUM] = pv_add_constant (regs[ARM_SP_REGNUM],
                                                 (insn & 0xff) << 2);
      else if ((insn & 0xff00) == 0x4600)       /* mov hi, lo or mov lo, hi */
        {
          int dst_reg = (insn & 0x7) + ((insn & 0x80) >> 4);
          int src_reg = (insn & 0x78) >> 3;
          regs[dst_reg] = regs[src_reg];
        }
      else if ((insn & 0xf800) == 0x9000)       /* str rd, [sp, #off] */
        {
          /* Handle stores to the stack.  Normally pushes are used,
             but with GCC -mtpcs-frame, there may be other stores
             in the prologue to create the frame.  */
          int regno = (insn >> 8) & 0x7;
          pv_t addr;

          offset = (insn & 0xff) << 2;
          addr = pv_add_constant (regs[ARM_SP_REGNUM], offset);

          if (pv_area_store_would_trash (stack, addr))
            break;

          pv_area_store (stack, addr, 4, regs[regno]);
        }
      else
        {
          /* We don't know what this instruction is.  We're finished
             scanning.  NOTE: Recognizing more safe-to-ignore
             instructions here will improve support for optimized
             code.  */
          break;
        }

      start += 2;
    }

  if (cache == NULL)
    {
      do_cleanups (back_to);
      return start;
    }

  if (pv_is_register (regs[ARM_FP_REGNUM], ARM_SP_REGNUM))
    {
      /* Frame pointer is fp.  Frame size is constant.  */
      cache->framereg = ARM_FP_REGNUM;
      cache->framesize = -regs[ARM_FP_REGNUM].k;
    }
  else if (pv_is_register (regs[THUMB_FP_REGNUM], ARM_SP_REGNUM))
    {
      /* Frame pointer is r7.  Frame size is constant.  */
      cache->framereg = THUMB_FP_REGNUM;
      cache->framesize = -regs[THUMB_FP_REGNUM].k;
    }
  else if (pv_is_register (regs[ARM_SP_REGNUM], ARM_SP_REGNUM))
    {
      /* Try the stack pointer... this is a bit desperate.  */
      cache->framereg = ARM_SP_REGNUM;
      cache->framesize = -regs[ARM_SP_REGNUM].k;
    }
  else
    {
      /* We're just out of luck.  We don't know where the frame is.  */
      cache->framereg = -1;
      cache->framesize = 0;
    }

  for (i = 0; i < 16; i++)
    if (pv_area_find_reg (stack, gdbarch, i, &offset))
      cache->saved_regs[i].addr = offset;

  do_cleanups (back_to);
  return start;
}

/* Advance the PC across any function entry prologue instructions to
   reach some "real" code.

   The APCS (ARM Procedure Call Standard) defines the following
   prologue:

   mov          ip, sp
   [stmfd       sp!, {a1,a2,a3,a4}]
   stmfd        sp!, {...,fp,ip,lr,pc}
   [stfe        f7, [sp, #-12]!]
   [stfe        f6, [sp, #-12]!]
   [stfe        f5, [sp, #-12]!]
   [stfe        f4, [sp, #-12]!]
   sub fp, ip, #nn @@ nn == 20 or 4 depending on second insn */

static CORE_ADDR
arm_skip_prologue (struct gdbarch *gdbarch, CORE_ADDR pc)
{
  unsigned long inst;
  CORE_ADDR skip_pc;
  CORE_ADDR func_addr, func_end = 0;
  char *func_name;
  struct symtab_and_line sal;

  /* If we're in a dummy frame, don't even try to skip the prologue.  */
  if (deprecated_pc_in_call_dummy (pc))
    return pc;

  /* See what the symbol table says.  */

  if (find_pc_partial_function (pc, &func_name, &func_addr, &func_end))
    {
      struct symbol *sym;

      /* Found a function.  */
      sym = lookup_symbol (func_name, NULL, VAR_DOMAIN, NULL, NULL);
      if (sym && SYMBOL_LANGUAGE (sym) != language_asm)
        {
          /* Don't use this trick for assembly source files.  */
          sal = find_pc_line (func_addr, 0);
          if ((sal.line != 0) && (sal.end < func_end))
            return sal.end;
        }
    }

  /* Can't find the prologue end in the symbol table, try it the hard way
     by disassembling the instructions.  */

  /* Like arm_scan_prologue, stop no later than pc + 64. */
  if (func_end == 0 || func_end > pc + 64)
    func_end = pc + 64;

  /* Check if this is Thumb code.  */
  if (arm_pc_is_thumb (pc))
    return thumb_analyze_prologue (gdbarch, pc, func_end, NULL);

  for (skip_pc = pc; skip_pc < func_end; skip_pc += 4)
    {
      inst = read_memory_unsigned_integer (skip_pc, 4);

      /* "mov ip, sp" is no longer a required part of the prologue.  */
      if (inst == 0xe1a0c00d)                   /* mov ip, sp */
        continue;

      if ((inst & 0xfffff000) == 0xe28dc000)    /* add ip, sp #n */
        continue;

      if ((inst & 0xfffff000) == 0xe24dc000)    /* sub ip, sp #n */
        continue;

      /* Some prologues begin with "str lr, [sp, #-4]!".  */
      if (inst == 0xe52de004)                   /* str lr, [sp, #-4]! */
        continue;

      if ((inst & 0xfffffff0) == 0xe92d0000)    /* stmfd sp!,{a1,a2,a3,a4} */
        continue;

      if ((inst & 0xfffff800) == 0xe92dd800)    /* stmfd sp!,{fp,ip,lr,pc} */
        continue;

      /* Any insns after this point may float into the code, if it makes
         for better instruction scheduling, so we skip them only if we
         find them, but still consider the function to be frame-ful.  */

      /* We may have either one sfmfd instruction here, or several stfe
         insns, depending on the version of floating point code we
         support.  */
      if ((inst & 0xffbf0fff) == 0xec2d0200)    /* sfmfd fn, <cnt>, [sp]! */
        continue;

      if ((inst & 0xffff8fff) == 0xed6d0103)    /* stfe fn, [sp, #-12]! */
        continue;

      if ((inst & 0xfffff000) == 0xe24cb000)    /* sub fp, ip, #nn */
        continue;

      if ((inst & 0xfffff000) == 0xe24dd000)    /* sub sp, sp, #nn */
        continue;

      if ((inst & 0xffffc000) == 0xe54b0000 ||  /* strb r(0123),[r11,#-nn] */
          (inst & 0xffffc0f0) == 0xe14b00b0 ||  /* strh r(0123),[r11,#-nn] */
          (inst & 0xffffc000) == 0xe50b0000)    /* str  r(0123),[r11,#-nn] */
        continue;

      if ((inst & 0xffffc000) == 0xe5cd0000 ||  /* strb r(0123),[sp,#nn] */
          (inst & 0xffffc0f0) == 0xe1cd00b0 ||  /* strh r(0123),[sp,#nn] */
          (inst & 0xffffc000) == 0xe58d0000)    /* str  r(0123),[sp,#nn] */
        continue;

      /* Un-recognized instruction; stop scanning.  */
      break;
    }

  return skip_pc;               /* End of prologue */
}

/* *INDENT-OFF* */
/* Function: thumb_scan_prologue (helper function for arm_scan_prologue)
   This function decodes a Thumb function prologue to determine:
     1) the size of the stack frame
     2) which registers are saved on it
     3) the offsets of saved regs
     4) the offset from the stack pointer to the frame pointer

   A typical Thumb function prologue would create this stack frame
   (offsets relative to FP)
     old SP ->  24  stack parameters
                20  LR
                16  R7
     R7 ->       0  local variables (16 bytes)
     SP ->     -12  additional stack space (12 bytes)
   The frame size would thus be 36 bytes, and the frame offset would be
   12 bytes.  The frame register is R7. 
   
   The comments for thumb_skip_prolog() describe the algorithm we use
   to detect the end of the prolog.  */
/* *INDENT-ON* */

static void
thumb_scan_prologue (struct gdbarch *gdbarch, CORE_ADDR prev_pc,
                     CORE_ADDR block_addr, struct arm_prologue_cache *cache)
{
  CORE_ADDR prologue_start;
  CORE_ADDR prologue_end;
  CORE_ADDR current_pc;

  if (find_pc_partial_function (block_addr, NULL, &prologue_start,
                                &prologue_end))
    {
      struct symtab_and_line sal = find_pc_line (prologue_start, 0);

      if (sal.line == 0)                /* no line info, use current PC  */
        prologue_end = prev_pc;
      else if (sal.end < prologue_end)  /* next line begins after fn end */
        prologue_end = sal.end;         /* (probably means no prologue)  */
    }
  else
    /* We're in the boondocks: we have no idea where the start of the
       function is.  */
    return;

  prologue_end = min (prologue_end, prev_pc);

  thumb_analyze_prologue (gdbarch, prologue_start, prologue_end, cache);
}

/* This function decodes an ARM function prologue to determine:
   1) the size of the stack frame
   2) which registers are saved on it
   3) the offsets of saved regs
   4) the offset from the stack pointer to the frame pointer
   This information is stored in the "extra" fields of the frame_info.

   There are two basic forms for the ARM prologue.  The fixed argument
   function call will look like:

   mov    ip, sp
   stmfd  sp!, {fp, ip, lr, pc}
   sub    fp, ip, #4
   [sub sp, sp, #4]

   Which would create this stack frame (offsets relative to FP):
   IP ->   4    (caller's stack)
   FP ->   0    PC (points to address of stmfd instruction + 8 in callee)
   -4   LR (return address in caller)
   -8   IP (copy of caller's SP)
   -12  FP (caller's FP)
   SP -> -28    Local variables

   The frame size would thus be 32 bytes, and the frame offset would be
   28 bytes.  The stmfd call can also save any of the vN registers it
   plans to use, which increases the frame size accordingly.

   Note: The stored PC is 8 off of the STMFD instruction that stored it
   because the ARM Store instructions always store PC + 8 when you read
   the PC register.

   A variable argument function call will look like:

   mov    ip, sp
   stmfd  sp!, {a1, a2, a3, a4}
   stmfd  sp!, {fp, ip, lr, pc}
   sub    fp, ip, #20

   Which would create this stack frame (offsets relative to FP):
   IP ->  20    (caller's stack)
   16  A4
   12  A3
   8  A2
   4  A1
   FP ->   0    PC (points to address of stmfd instruction + 8 in callee)
   -4   LR (return address in caller)
   -8   IP (copy of caller's SP)
   -12  FP (caller's FP)
   SP -> -28    Local variables

   The frame size would thus be 48 bytes, and the frame offset would be
   28 bytes.

   There is another potential complication, which is that the optimizer
   will try to separate the store of fp in the "stmfd" instruction from
   the "sub fp, ip, #NN" instruction.  Almost anything can be there, so
   we just key on the stmfd, and then scan for the "sub fp, ip, #NN"...

   Also, note, the original version of the ARM toolchain claimed that there
   should be an

   instruction at the end of the prologue.  I have never seen GCC produce
   this, and the ARM docs don't mention it.  We still test for it below in
   case it happens...

 */

static void
arm_scan_prologue (struct frame_info *this_frame,
                   struct arm_prologue_cache *cache)
{
  struct gdbarch *gdbarch = get_frame_arch (this_frame);
  int regno;
  CORE_ADDR prologue_start, prologue_end, current_pc;
  CORE_ADDR prev_pc = get_frame_pc (this_frame);
  CORE_ADDR block_addr = get_frame_address_in_block (this_frame);
  pv_t regs[ARM_FPS_REGNUM];
  struct pv_area *stack;
  struct cleanup *back_to;
  CORE_ADDR offset;

  /* Assume there is no frame until proven otherwise.  */
  cache->framereg = ARM_SP_REGNUM;
  cache->framesize = 0;

  /* Check for Thumb prologue.  */
  if (arm_frame_is_thumb (this_frame))
    {
      thumb_scan_prologue (gdbarch, prev_pc, block_addr, cache);
      return;
    }

  /* Find the function prologue.  If we can't find the function in
     the symbol table, peek in the stack frame to find the PC.  */
  if (find_pc_partial_function (block_addr, NULL, &prologue_start,
                                &prologue_end))
    {
      /* One way to find the end of the prologue (which works well
         for unoptimized code) is to do the following:

            struct symtab_and_line sal = find_pc_line (prologue_start, 0);

            if (sal.line == 0)
              prologue_end = prev_pc;
            else if (sal.end < prologue_end)
              prologue_end = sal.end;

         This mechanism is very accurate so long as the optimizer
         doesn't move any instructions from the function body into the
         prologue.  If this happens, sal.end will be the last
         instruction in the first hunk of prologue code just before
         the first instruction that the scheduler has moved from
         the body to the prologue.

         In order to make sure that we scan all of the prologue
         instructions, we use a slightly less accurate mechanism which
         may scan more than necessary.  To help compensate for this
         lack of accuracy, the prologue scanning loop below contains
         several clauses which'll cause the loop to terminate early if
         an implausible prologue instruction is encountered.  
         
         The expression
         
              prologue_start + 64
            
         is a suitable endpoint since it accounts for the largest
         possible prologue plus up to five instructions inserted by
         the scheduler.  */
         
      if (prologue_end > prologue_start + 64)
        {
          prologue_end = prologue_start + 64;   /* See above.  */
        }
    }
  else
    {
      /* We have no symbol information.  Our only option is to assume this
         function has a standard stack frame and the normal frame register.
         Then, we can find the value of our frame pointer on entrance to
         the callee (or at the present moment if this is the innermost frame).
         The value stored there should be the address of the stmfd + 8.  */
      CORE_ADDR frame_loc;
      LONGEST return_value;

      frame_loc = get_frame_register_unsigned (this_frame, ARM_FP_REGNUM);
      if (!safe_read_memory_integer (frame_loc, 4, &return_value))
        return;
      else
        {
          prologue_start = gdbarch_addr_bits_remove 
                             (gdbarch, return_value) - 8;
          prologue_end = prologue_start + 64;   /* See above.  */
        }
    }

  if (prev_pc < prologue_end)
    prologue_end = prev_pc;

  /* Now search the prologue looking for instructions that set up the
     frame pointer, adjust the stack pointer, and save registers.

     Be careful, however, and if it doesn't look like a prologue,
     don't try to scan it.  If, for instance, a frameless function
     begins with stmfd sp!, then we will tell ourselves there is
     a frame, which will confuse stack traceback, as well as "finish" 
     and other operations that rely on a knowledge of the stack
     traceback.

     In the APCS, the prologue should start with  "mov ip, sp" so
     if we don't see this as the first insn, we will stop.  

     [Note: This doesn't seem to be true any longer, so it's now an
     optional part of the prologue.  - Kevin Buettner, 2001-11-20]

     [Note further: The "mov ip,sp" only seems to be missing in
     frameless functions at optimization level "-O2" or above,
     in which case it is often (but not always) replaced by
     "str lr, [sp, #-4]!".  - Michael Snyder, 2002-04-23]  */

  for (regno = 0; regno < ARM_FPS_REGNUM; regno++)
    regs[regno] = pv_register (regno, 0);
  stack = make_pv_area (ARM_SP_REGNUM);
  back_to = make_cleanup_free_pv_area (stack);

  for (current_pc = prologue_start;
       current_pc < prologue_end;
       current_pc += 4)
    {
      unsigned int insn = read_memory_unsigned_integer (current_pc, 4);

      if (insn == 0xe1a0c00d)           /* mov ip, sp */
        {
          regs[ARM_IP_REGNUM] = regs[ARM_SP_REGNUM];
          continue;
        }
      else if ((insn & 0xfffff000) == 0xe28dc000) /* add ip, sp #n */
        {
          unsigned imm = insn & 0xff;                   /* immediate value */
          unsigned rot = (insn & 0xf00) >> 7;           /* rotate amount */
          imm = (imm >> rot) | (imm << (32 - rot));
          regs[ARM_IP_REGNUM] = pv_add_constant (regs[ARM_SP_REGNUM], imm);
          continue;
        }
      else if ((insn & 0xfffff000) == 0xe24dc000) /* sub ip, sp #n */
        {
          unsigned imm = insn & 0xff;                   /* immediate value */
          unsigned rot = (insn & 0xf00) >> 7;           /* rotate amount */
          imm = (imm >> rot) | (imm << (32 - rot));
          regs[ARM_IP_REGNUM] = pv_add_constant (regs[ARM_SP_REGNUM], -imm);
          continue;
        }
      else if (insn == 0xe52de004)      /* str lr, [sp, #-4]! */
        {
          if (pv_area_store_would_trash (stack, regs[ARM_SP_REGNUM]))
            break;
          regs[ARM_SP_REGNUM] = pv_add_constant (regs[ARM_SP_REGNUM], -4);
          pv_area_store (stack, regs[ARM_SP_REGNUM], 4, regs[ARM_LR_REGNUM]);
          continue;
        }
      else if ((insn & 0xffff0000) == 0xe92d0000)
        /* stmfd sp!, {..., fp, ip, lr, pc}
           or
           stmfd sp!, {a1, a2, a3, a4}  */
        {
          int mask = insn & 0xffff;

          if (pv_area_store_would_trash (stack, regs[ARM_SP_REGNUM]))
            break;

          /* Calculate offsets of saved registers.  */
          for (regno = ARM_PC_REGNUM; regno >= 0; regno--)
            if (mask & (1 << regno))
              {
                regs[ARM_SP_REGNUM] = pv_add_constant (regs[ARM_SP_REGNUM], -4);
                pv_area_store (stack, regs[ARM_SP_REGNUM], 4, regs[regno]);
              }
        }
      else if ((insn & 0xffffc000) == 0xe54b0000 ||     /* strb rx,[r11,#-n] */
               (insn & 0xffffc0f0) == 0xe14b00b0 ||     /* strh rx,[r11,#-n] */
               (insn & 0xffffc000) == 0xe50b0000)       /* str  rx,[r11,#-n] */
        {
          /* No need to add this to saved_regs -- it's just an arg reg.  */
          continue;
        }
      else if ((insn & 0xffffc000) == 0xe5cd0000 ||     /* strb rx,[sp,#n] */
               (insn & 0xffffc0f0) == 0xe1cd00b0 ||     /* strh rx,[sp,#n] */
               (insn & 0xffffc000) == 0xe58d0000)       /* str  rx,[sp,#n] */
        {
          /* No need to add this to saved_regs -- it's just an arg reg.  */
          continue;
        }
      else if ((insn & 0xfffff000) == 0xe24cb000)       /* sub fp, ip #n */
        {
          unsigned imm = insn & 0xff;                   /* immediate value */
          unsigned rot = (insn & 0xf00) >> 7;           /* rotate amount */
          imm = (imm >> rot) | (imm << (32 - rot));
          regs[ARM_FP_REGNUM] = pv_add_constant (regs[ARM_IP_REGNUM], -imm);
        }
      else if ((insn & 0xfffff000) == 0xe24dd000)       /* sub sp, sp #n */
        {
          unsigned imm = insn & 0xff;                   /* immediate value */
          unsigned rot = (insn & 0xf00) >> 7;           /* rotate amount */
          imm = (imm >> rot) | (imm << (32 - rot));
          regs[ARM_SP_REGNUM] = pv_add_constant (regs[ARM_SP_REGNUM], -imm);
        }
      else if ((insn & 0xffff7fff) == 0xed6d0103        /* stfe f?, [sp, -#c]! */
               && gdbarch_tdep (gdbarch)->have_fpa_registers)
        {
          if (pv_area_store_would_trash (stack, regs[ARM_SP_REGNUM]))
            break;

          regs[ARM_SP_REGNUM] = pv_add_constant (regs[ARM_SP_REGNUM], -12);
          regno = ARM_F0_REGNUM + ((insn >> 12) & 0x07);
          pv_area_store (stack, regs[ARM_SP_REGNUM], 12, regs[regno]);
        }
      else if ((insn & 0xffbf0fff) == 0xec2d0200        /* sfmfd f0, 4, [sp!] */
               && gdbarch_tdep (gdbarch)->have_fpa_registers)
        {
          int n_saved_fp_regs;
          unsigned int fp_start_reg, fp_bound_reg;

          if (pv_area_store_would_trash (stack, regs[ARM_SP_REGNUM]))
            break;

          if ((insn & 0x800) == 0x800)          /* N0 is set */
            {
              if ((insn & 0x40000) == 0x40000)  /* N1 is set */
                n_saved_fp_regs = 3;
              else
                n_saved_fp_regs = 1;
            }
          else
            {
              if ((insn & 0x40000) == 0x40000)  /* N1 is set */
                n_saved_fp_regs = 2;
              else
                n_saved_fp_regs = 4;
            }

          fp_start_reg = ARM_F0_REGNUM + ((insn >> 12) & 0x7);
          fp_bound_reg = fp_start_reg + n_saved_fp_regs;
          for (; fp_start_reg < fp_bound_reg; fp_start_reg++)
            {
              regs[ARM_SP_REGNUM] = pv_add_constant (regs[ARM_SP_REGNUM], -12);
              pv_area_store (stack, regs[ARM_SP_REGNUM], 12,
                             regs[fp_start_reg++]);
            }
        }
      else if ((insn & 0xf0000000) != 0xe0000000)
        break;                  /* Condition not true, exit early */
      else if ((insn & 0xfe200000) == 0xe8200000)       /* ldm? */
        break;                  /* Don't scan past a block load */
      else
        /* The optimizer might shove anything into the prologue,
           so we just skip what we don't recognize.  */
        continue;
    }

  /* The frame size is just the distance from the frame register
     to the original stack pointer.  */
  if (pv_is_register (regs[ARM_FP_REGNUM], ARM_SP_REGNUM))
    {
      /* Frame pointer is fp.  */
      cache->framereg = ARM_FP_REGNUM;
      cache->framesize = -regs[ARM_FP_REGNUM].k;
    }
  else if (pv_is_register (regs[ARM_SP_REGNUM], ARM_SP_REGNUM))
    {
      /* Try the stack pointer... this is a bit desperate.  */
      cache->framereg = ARM_SP_REGNUM;
      cache->framesize = -regs[ARM_SP_REGNUM].k;
    }
  else
    {
      /* We're just out of luck.  We don't know where the frame is.  */
      cache->framereg = -1;
      cache->framesize = 0;
    }

  for (regno = 0; regno < ARM_FPS_REGNUM; regno++)
    if (pv_area_find_reg (stack, gdbarch, regno, &offset))
      cache->saved_regs[regno].addr = offset;

  do_cleanups (back_to);
}

static struct arm_prologue_cache *
arm_make_prologue_cache (struct frame_info *this_frame)
{
  int reg;
  struct arm_prologue_cache *cache;
  CORE_ADDR unwound_fp;

  cache = FRAME_OBSTACK_ZALLOC (struct arm_prologue_cache);
  cache->saved_regs = trad_frame_alloc_saved_regs (this_frame);

  arm_scan_prologue (this_frame, cache);

  unwound_fp = get_frame_register_unsigned (this_frame, cache->framereg);
  if (unwound_fp == 0)
    return cache;

  cache->prev_sp = unwound_fp + cache->framesize;

  /* Calculate actual addresses of saved registers using offsets
     determined by arm_scan_prologue.  */
  for (reg = 0; reg < gdbarch_num_regs (get_frame_arch (this_frame)); reg++)
    if (trad_frame_addr_p (cache->saved_regs, reg))
      cache->saved_regs[reg].addr += cache->prev_sp;

  return cache;
}

/* Our frame ID for a normal frame is the current function's starting PC
   and the caller's SP when we were called.  */

static void
arm_prologue_this_id (struct frame_info *this_frame,
                      void **this_cache,
                      struct frame_id *this_id)
{
  struct arm_prologue_cache *cache;
  struct frame_id id;
  CORE_ADDR pc, func;

  if (*this_cache == NULL)
    *this_cache = arm_make_prologue_cache (this_frame);
  cache = *this_cache;

  /* This is meant to halt the backtrace at "_start".  */
  pc = get_frame_pc (this_frame);
  if (pc <= gdbarch_tdep (get_frame_arch (this_frame))->lowest_pc)
    return;

  /* If we've hit a wall, stop.  */
  if (cache->prev_sp == 0)
    return;

  func = get_frame_func (this_frame);
  id = frame_id_build (cache->prev_sp, func);
  *this_id = id;
}

static struct value *
arm_prologue_prev_register (struct frame_info *this_frame,
                            void **this_cache,
                            int prev_regnum)
{
  struct arm_prologue_cache *cache;

  if (*this_cache == NULL)
    *this_cache = arm_make_prologue_cache (this_frame);
  cache = *this_cache;

  /* If we are asked to unwind the PC, then we need to return the LR
     instead.  The prologue may save PC, but it will point into this
     frame's prologue, not the next frame's resume location.  Also
     strip the saved T bit.  A valid LR may have the low bit set, but
     a valid PC never does.  */
  if (prev_regnum == ARM_PC_REGNUM)
    {
      CORE_ADDR lr;

      lr = frame_unwind_register_unsigned (this_frame, ARM_LR_REGNUM);
      return frame_unwind_got_constant (this_frame, prev_regnum,
                                        arm_addr_bits_remove (lr));
    }

  /* SP is generally not saved to the stack, but this frame is
     identified by the next frame's stack pointer at the time of the call.
     The value was already reconstructed into PREV_SP.  */
  if (prev_regnum == ARM_SP_REGNUM)
    return frame_unwind_got_constant (this_frame, prev_regnum, cache->prev_sp);

  /* The CPSR may have been changed by the call instruction and by the
     called function.  The only bit we can reconstruct is the T bit,
     by checking the low bit of LR as of the call.  This is a reliable
     indicator of Thumb-ness except for some ARM v4T pre-interworking
     Thumb code, which could get away with a clear low bit as long as
     the called function did not use bx.  Guess that all other
     bits are unchanged; the condition flags are presumably lost,
     but the processor status is likely valid.  */
  if (prev_regnum == ARM_PS_REGNUM)
    {
      CORE_ADDR lr, cpsr;

      cpsr = get_frame_register_unsigned (this_frame, prev_regnum);
      lr = frame_unwind_register_unsigned (this_frame, ARM_LR_REGNUM);
      if (IS_THUMB_ADDR (lr))
        cpsr |= CPSR_T;
      else
        cpsr &= ~CPSR_T;
      return frame_unwind_got_constant (this_frame, prev_regnum, cpsr);
    }

  return trad_frame_get_prev_register (this_frame, cache->saved_regs,
                                       prev_regnum);
}

struct frame_unwind arm_prologue_unwind = {
  NORMAL_FRAME,
  arm_prologue_this_id,
  arm_prologue_prev_register,
  NULL,
  default_frame_sniffer
};

static struct arm_prologue_cache *
arm_make_stub_cache (struct frame_info *this_frame)
{
  int reg;
  struct arm_prologue_cache *cache;
  CORE_ADDR unwound_fp;

  cache = FRAME_OBSTACK_ZALLOC (struct arm_prologue_cache);
  cache->saved_regs = trad_frame_alloc_saved_regs (this_frame);

  cache->prev_sp = get_frame_register_unsigned (this_frame, ARM_SP_REGNUM);

  return cache;
}

/* Our frame ID for a stub frame is the current SP and LR.  */

static void
arm_stub_this_id (struct frame_info *this_frame,
                  void **this_cache,
                  struct frame_id *this_id)
{
  struct arm_prologue_cache *cache;

  if (*this_cache == NULL)
    *this_cache = arm_make_stub_cache (this_frame);
  cache = *this_cache;

  *this_id = frame_id_build (cache->prev_sp, get_frame_pc (this_frame));
}

static int
arm_stub_unwind_sniffer (const struct frame_unwind *self,
                         struct frame_info *this_frame,
                         void **this_prologue_cache)
{
  CORE_ADDR addr_in_block;
  char dummy[4];

  addr_in_block = get_frame_address_in_block (this_frame);
  if (in_plt_section (addr_in_block, NULL)
      || target_read_memory (get_frame_pc (this_frame), dummy, 4) != 0)
    return 1;

  return 0;
}

struct frame_unwind arm_stub_unwind = {
  NORMAL_FRAME,
  arm_stub_this_id,
  arm_prologue_prev_register,
  NULL,
  arm_stub_unwind_sniffer
};

static CORE_ADDR
arm_normal_frame_base (struct frame_info *this_frame, void **this_cache)
{
  struct arm_prologue_cache *cache;

  if (*this_cache == NULL)
    *this_cache = arm_make_prologue_cache (this_frame);
  cache = *this_cache;

  return cache->prev_sp - cache->framesize;
}

struct frame_base arm_normal_base = {
  &arm_prologue_unwind,
  arm_normal_frame_base,
  arm_normal_frame_base,
  arm_normal_frame_base
};

/* Assuming THIS_FRAME is a dummy, return the frame ID of that
   dummy frame.  The frame ID's base needs to match the TOS value
   saved by save_dummy_frame_tos() and returned from
   arm_push_dummy_call, and the PC needs to match the dummy frame's
   breakpoint.  */

static struct frame_id
arm_dummy_id (struct gdbarch *gdbarch, struct frame_info *this_frame)
{
  return frame_id_build (get_frame_register_unsigned (this_frame, ARM_SP_REGNUM),
                         get_frame_pc (this_frame));
}

/* Given THIS_FRAME, find the previous frame's resume PC (which will
   be used to construct the previous frame's ID, after looking up the
   containing function).  */

static CORE_ADDR
arm_unwind_pc (struct gdbarch *gdbarch, struct frame_info *this_frame)
{
  CORE_ADDR pc;
  pc = frame_unwind_register_unsigned (this_frame, ARM_PC_REGNUM);
  return arm_addr_bits_remove (pc);
}

static CORE_ADDR
arm_unwind_sp (struct gdbarch *gdbarch, struct frame_info *this_frame)
{
  return frame_unwind_register_unsigned (this_frame, ARM_SP_REGNUM);
}

static struct value *
arm_dwarf2_prev_register (struct frame_info *this_frame, void **this_cache,
                          int regnum)
{
  CORE_ADDR lr, cpsr;

  switch (regnum)
    {
    case ARM_PC_REGNUM:
      /* The PC is normally copied from the return column, which
         describes saves of LR.  However, that version may have an
         extra bit set to indicate Thumb state.  The bit is not
         part of the PC.  */
      lr = frame_unwind_register_unsigned (this_frame, ARM_LR_REGNUM);
      return frame_unwind_got_constant (this_frame, regnum,
                                        arm_addr_bits_remove (lr));

    case ARM_PS_REGNUM:
      /* Reconstruct the T bit; see arm_prologue_prev_register for details.  */
      cpsr = get_frame_register_unsigned (this_frame, regnum);
      lr = frame_unwind_register_unsigned (this_frame, ARM_LR_REGNUM);
      if (IS_THUMB_ADDR (lr))
        cpsr |= CPSR_T;
      else
        cpsr &= ~CPSR_T;
      return frame_unwind_got_constant (this_frame, regnum, cpsr);

    default:
      internal_error (__FILE__, __LINE__,
                      _("Unexpected register %d"), regnum);
    }
}

static void
arm_dwarf2_frame_init_reg (struct gdbarch *gdbarch, int regnum,
                           struct dwarf2_frame_state_reg *reg,
                           struct frame_info *this_frame)
{
  switch (regnum)
    {
    case ARM_PC_REGNUM:
    case ARM_PS_REGNUM:
      reg->how = DWARF2_FRAME_REG_FN;
      reg->loc.fn = arm_dwarf2_prev_register;
      break;
    case ARM_SP_REGNUM:
      reg->how = DWARF2_FRAME_REG_CFA;
      break;
    }
}

/* When arguments must be pushed onto the stack, they go on in reverse
   order.  The code below implements a FILO (stack) to do this.  */

struct stack_item
{
  int len;
  struct stack_item *prev;
  void *data;
};

static struct stack_item *
push_stack_item (struct stack_item *prev, void *contents, int len)
{
  struct stack_item *si;
  si = xmalloc (sizeof (struct stack_item));
  si->data = xmalloc (len);
  si->len = len;
  si->prev = prev;
  memcpy (si->data, contents, len);
  return si;
}

static struct stack_item *
pop_stack_item (struct stack_item *si)
{
  struct stack_item *dead = si;
  si = si->prev;
  xfree (dead->data);
  xfree (dead);
  return si;
}


/* Return the alignment (in bytes) of the given type.  */

static int
arm_type_align (struct type *t)
{
  int n;
  int align;
  int falign;

  t = check_typedef (t);
  switch (TYPE_CODE (t))
    {
    default:
      /* Should never happen.  */
      internal_error (__FILE__, __LINE__, _("unknown type alignment"));
      return 4;

    case TYPE_CODE_PTR:
    case TYPE_CODE_ENUM:
    case TYPE_CODE_INT:
    case TYPE_CODE_FLT:
    case TYPE_CODE_SET:
    case TYPE_CODE_RANGE:
    case TYPE_CODE_BITSTRING:
    case TYPE_CODE_REF:
    case TYPE_CODE_CHAR:
    case TYPE_CODE_BOOL:
      return TYPE_LENGTH (t);

    case TYPE_CODE_ARRAY:
    case TYPE_CODE_COMPLEX:
      /* TODO: What about vector types?  */
      return arm_type_align (TYPE_TARGET_TYPE (t));

    case TYPE_CODE_STRUCT:
    case TYPE_CODE_UNION:
      align = 1;
      for (n = 0; n < TYPE_NFIELDS (t); n++)
        {
          falign = arm_type_align (TYPE_FIELD_TYPE (t, n));
          if (falign > align)
            align = falign;
        }
      return align;
    }
}

/* We currently only support passing parameters in integer registers.  This
   conforms with GCC's default model.  Several other variants exist and
   we should probably support some of them based on the selected ABI.  */

static CORE_ADDR
arm_push_dummy_call (struct gdbarch *gdbarch, struct value *function,
                     struct regcache *regcache, CORE_ADDR bp_addr, int nargs,
                     struct value **args, CORE_ADDR sp, int struct_return,
                     CORE_ADDR struct_addr)
{
  int argnum;
  int argreg;
  int nstack;
  struct stack_item *si = NULL;

  /* Set the return address.  For the ARM, the return breakpoint is
     always at BP_ADDR.  */
  /* XXX Fix for Thumb.  */
  regcache_cooked_write_unsigned (regcache, ARM_LR_REGNUM, bp_addr);

  /* Walk through the list of args and determine how large a temporary
     stack is required.  Need to take care here as structs may be
     passed on the stack, and we have to to push them.  */
  nstack = 0;

  argreg = ARM_A1_REGNUM;
  nstack = 0;

  /* The struct_return pointer occupies the first parameter
     passing register.  */
  if (struct_return)
    {
      if (arm_debug)
        fprintf_unfiltered (gdb_stdlog, "struct return in %s = 0x%s\n",
                            gdbarch_register_name (gdbarch, argreg),
                            paddr (struct_addr));
      regcache_cooked_write_unsigned (regcache, argreg, struct_addr);
      argreg++;
    }

  for (argnum = 0; argnum < nargs; argnum++)
    {
      int len;
      struct type *arg_type;
      struct type *target_type;
      enum type_code typecode;
      bfd_byte *val;
      int align;

      arg_type = check_typedef (value_type (args[argnum]));
      len = TYPE_LENGTH (arg_type);
      target_type = TYPE_TARGET_TYPE (arg_type);
      typecode = TYPE_CODE (arg_type);
      val = value_contents_writeable (args[argnum]);

      align = arm_type_align (arg_type);
      /* Round alignment up to a whole number of words.  */
      align = (align + INT_REGISTER_SIZE - 1) & ~(INT_REGISTER_SIZE - 1);
      /* Different ABIs have different maximum alignments.  */
      if (gdbarch_tdep (gdbarch)->arm_abi == ARM_ABI_APCS)
        {
          /* The APCS ABI only requires word alignment.  */
          align = INT_REGISTER_SIZE;
        }
      else
        {
          /* The AAPCS requires at most doubleword alignment.  */
          if (align > INT_REGISTER_SIZE * 2)
            align = INT_REGISTER_SIZE * 2;
        }

      /* Push stack padding for dowubleword alignment.  */
      if (nstack & (align - 1))
        {
          si = push_stack_item (si, val, INT_REGISTER_SIZE);
          nstack += INT_REGISTER_SIZE;
        }
      
      /* Doubleword aligned quantities must go in even register pairs.  */
      if (argreg <= ARM_LAST_ARG_REGNUM
          && align > INT_REGISTER_SIZE
          && argreg & 1)
        argreg++;

      /* If the argument is a pointer to a function, and it is a
         Thumb function, create a LOCAL copy of the value and set
         the THUMB bit in it.  */
      if (TYPE_CODE_PTR == typecode
          && target_type != NULL
          && TYPE_CODE_FUNC == TYPE_CODE (target_type))
        {
          CORE_ADDR regval = extract_unsigned_integer (val, len);
          if (arm_pc_is_thumb (regval))
            {
              val = alloca (len);
              store_unsigned_integer (val, len, MAKE_THUMB_ADDR (regval));
            }
        }

      /* Copy the argument to general registers or the stack in
         register-sized pieces.  Large arguments are split between
         registers and stack.  */
      while (len > 0)
        {
          int partial_len = len < INT_REGISTER_SIZE ? len : INT_REGISTER_SIZE;

          if (argreg <= ARM_LAST_ARG_REGNUM)
            {
              /* The argument is being passed in a general purpose
                 register.  */
              CORE_ADDR regval = extract_unsigned_integer (val, partial_len);
              if (gdbarch_byte_order (gdbarch) == BFD_ENDIAN_BIG)
                regval <<= (INT_REGISTER_SIZE - partial_len) * 8;
              if (arm_debug)
                fprintf_unfiltered (gdb_stdlog, "arg %d in %s = 0x%s\n",
                                    argnum,
                                    gdbarch_register_name
                                      (gdbarch, argreg),
                                    phex (regval, INT_REGISTER_SIZE));
              regcache_cooked_write_unsigned (regcache, argreg, regval);
              argreg++;
            }
          else
            {
              /* Push the arguments onto the stack.  */
              if (arm_debug)
                fprintf_unfiltered (gdb_stdlog, "arg %d @ sp + %d\n",
                                    argnum, nstack);
              si = push_stack_item (si, val, INT_REGISTER_SIZE);
              nstack += INT_REGISTER_SIZE;
            }
              
          len -= partial_len;
          val += partial_len;
        }
    }
  /* If we have an odd number of words to push, then decrement the stack
     by one word now, so first stack argument will be dword aligned.  */
  if (nstack & 4)
    sp -= 4;

  while (si)
    {
      sp -= si->len;
      write_memory (sp, si->data, si->len);
      si = pop_stack_item (si);
    }

  /* Finally, update teh SP register.  */
  regcache_cooked_write_unsigned (regcache, ARM_SP_REGNUM, sp);

  return sp;
}


/* Always align the frame to an 8-byte boundary.  This is required on
   some platforms and harmless on the rest.  */

static CORE_ADDR
arm_frame_align (struct gdbarch *gdbarch, CORE_ADDR sp)
{
  /* Align the stack to eight bytes.  */
  return sp & ~ (CORE_ADDR) 7;
}

static void
print_fpu_flags (int flags)
{
  if (flags & (1 << 0))
    fputs ("IVO ", stdout);
  if (flags & (1 << 1))
    fputs ("DVZ ", stdout);
  if (flags & (1 << 2))
    fputs ("OFL ", stdout);
  if (flags & (1 << 3))
    fputs ("UFL ", stdout);
  if (flags & (1 << 4))
    fputs ("INX ", stdout);
  putchar ('\n');
}

/* Print interesting information about the floating point processor
   (if present) or emulator.  */
static void
arm_print_float_info (struct gdbarch *gdbarch, struct ui_file *file,
                      struct frame_info *frame, const char *args)
{
  unsigned long status = get_frame_register_unsigned (frame, ARM_FPS_REGNUM);
  int type;

  type = (status >> 24) & 127;
  if (status & (1 << 31))
    printf (_("Hardware FPU type %d\n"), type);
  else
    printf (_("Software FPU type %d\n"), type);
  /* i18n: [floating point unit] mask */
  fputs (_("mask: "), stdout);
  print_fpu_flags (status >> 16);
  /* i18n: [floating point unit] flags */
  fputs (_("flags: "), stdout);
  print_fpu_flags (status);
}

/* Return the GDB type object for the "standard" data type of data in
   register N.  */

static struct type *
arm_register_type (struct gdbarch *gdbarch, int regnum)
{
  if (regnum >= ARM_F0_REGNUM && regnum < ARM_F0_REGNUM + NUM_FREGS)
    return builtin_type_arm_ext;
  else if (regnum == ARM_SP_REGNUM)
    return builtin_type_void_data_ptr;
  else if (regnum == ARM_PC_REGNUM)
    return builtin_type_void_func_ptr;
  else if (regnum >= ARRAY_SIZE (arm_register_names))
    /* These registers are only supported on targets which supply
       an XML description.  */
    return builtin_type_int0;
  else
    return builtin_type_uint32;
}

/* Map a DWARF register REGNUM onto the appropriate GDB register
   number.  */

static int
arm_dwarf_reg_to_regnum (struct gdbarch *gdbarch, int reg)
{
  /* Core integer regs.  */
  if (reg >= 0 && reg <= 15)
    return reg;

  /* Legacy FPA encoding.  These were once used in a way which
     overlapped with VFP register numbering, so their use is
     discouraged, but GDB doesn't support the ARM toolchain
     which used them for VFP.  */
  if (reg >= 16 && reg <= 23)
    return ARM_F0_REGNUM + reg - 16;

  /* New assignments for the FPA registers.  */
  if (reg >= 96 && reg <= 103)
    return ARM_F0_REGNUM + reg - 96;

  /* WMMX register assignments.  */
  if (reg >= 104 && reg <= 111)
    return ARM_WCGR0_REGNUM + reg - 104;

  if (reg >= 112 && reg <= 127)
    return ARM_WR0_REGNUM + reg - 112;

  if (reg >= 192 && reg <= 199)
    return ARM_WC0_REGNUM + reg - 192;

  return -1;
}

/* Map GDB internal REGNUM onto the Arm simulator register numbers.  */
static int
arm_register_sim_regno (struct gdbarch *gdbarch, int regnum)
{
  int reg = regnum;
  gdb_assert (reg >= 0 && reg < gdbarch_num_regs (gdbarch));

  if (regnum >= ARM_WR0_REGNUM && regnum <= ARM_WR15_REGNUM)
    return regnum - ARM_WR0_REGNUM + SIM_ARM_IWMMXT_COP0R0_REGNUM;

  if (regnum >= ARM_WC0_REGNUM && regnum <= ARM_WC7_REGNUM)
    return regnum - ARM_WC0_REGNUM + SIM_ARM_IWMMXT_COP1R0_REGNUM;

  if (regnum >= ARM_WCGR0_REGNUM && regnum <= ARM_WCGR7_REGNUM)
    return regnum - ARM_WCGR0_REGNUM + SIM_ARM_IWMMXT_COP1R8_REGNUM;

  if (reg < NUM_GREGS)
    return SIM_ARM_R0_REGNUM + reg;
  reg -= NUM_GREGS;

  if (reg < NUM_FREGS)
    return SIM_ARM_FP0_REGNUM + reg;
  reg -= NUM_FREGS;

  if (reg < NUM_SREGS)
    return SIM_ARM_FPS_REGNUM + reg;
  reg -= NUM_SREGS;

  internal_error (__FILE__, __LINE__, _("Bad REGNUM %d"), regnum);
}

/* NOTE: cagney/2001-08-20: Both convert_from_extended() and
   convert_to_extended() use floatformat_arm_ext_littlebyte_bigword.
   It is thought that this is is the floating-point register format on
   little-endian systems.  */

static void
convert_from_extended (const struct floatformat *fmt, const void *ptr,
                       void *dbl, int endianess)
{
  DOUBLEST d;

  if (endianess == BFD_ENDIAN_BIG)
    floatformat_to_doublest (&floatformat_arm_ext_big, ptr, &d);
  else
    floatformat_to_doublest (&floatformat_arm_ext_littlebyte_bigword,
                             ptr, &d);
  floatformat_from_doublest (fmt, &d, dbl);
}

static void
convert_to_extended (const struct floatformat *fmt, void *dbl, const void *ptr,
                     int endianess)
{
  DOUBLEST d;

  floatformat_to_doublest (fmt, ptr, &d);
  if (endianess == BFD_ENDIAN_BIG)
    floatformat_from_doublest (&floatformat_arm_ext_big, &d, dbl);
  else
    floatformat_from_doublest (&floatformat_arm_ext_littlebyte_bigword,
                               &d, dbl);
}

static int
condition_true (unsigned long cond, unsigned long status_reg)
{
  if (cond == INST_AL || cond == INST_NV)
    return 1;

  switch (cond)
    {
    case INST_EQ:
      return ((status_reg & FLAG_Z) != 0);
    case INST_NE:
      return ((status_reg & FLAG_Z) == 0);
    case INST_CS:
      return ((status_reg & FLAG_C) != 0);
    case INST_CC:
      return ((status_reg & FLAG_C) == 0);
    case INST_MI:
      return ((status_reg & FLAG_N) != 0);
    case INST_PL:
      return ((status_reg & FLAG_N) == 0);
    case INST_VS:
      return ((status_reg & FLAG_V) != 0);
    case INST_VC:
      return ((status_reg & FLAG_V) == 0);
    case INST_HI:
      return ((status_reg & (FLAG_C | FLAG_Z)) == FLAG_C);
    case INST_LS:
      return ((status_reg & (FLAG_C | FLAG_Z)) != FLAG_C);
    case INST_GE:
      return (((status_reg & FLAG_N) == 0) == ((status_reg & FLAG_V) == 0));
    case INST_LT:
      return (((status_reg & FLAG_N) == 0) != ((status_reg & FLAG_V) == 0));
    case INST_GT:
      return (((status_reg & FLAG_Z) == 0) &&
              (((status_reg & FLAG_N) == 0) == ((status_reg & FLAG_V) == 0)));
    case INST_LE:
      return (((status_reg & FLAG_Z) != 0) ||
              (((status_reg & FLAG_N) == 0) != ((status_reg & FLAG_V) == 0)));
    }
  return 1;
}

/* Support routines for single stepping.  Calculate the next PC value.  */
#define submask(x) ((1L << ((x) + 1)) - 1)
#define bit(obj,st) (((obj) >> (st)) & 1)
#define bits(obj,st,fn) (((obj) >> (st)) & submask ((fn) - (st)))
#define sbits(obj,st,fn) \
  ((long) (bits(obj,st,fn) | ((long) bit(obj,fn) * ~ submask (fn - st))))
#define BranchDest(addr,instr) \
  ((CORE_ADDR) (((long) (addr)) + 8 + (sbits (instr, 0, 23) << 2)))
#define ARM_PC_32 1

static unsigned long
shifted_reg_val (struct frame_info *frame, unsigned long inst, int carry,
                 unsigned long pc_val, unsigned long status_reg)
{
  unsigned long res, shift;
  int rm = bits (inst, 0, 3);
  unsigned long shifttype = bits (inst, 5, 6);

  if (bit (inst, 4))
    {
      int rs = bits (inst, 8, 11);
      shift = (rs == 15 ? pc_val + 8
                        : get_frame_register_unsigned (frame, rs)) & 0xFF;
    }
  else
    shift = bits (inst, 7, 11);

  res = (rm == 15
         ? ((pc_val | (ARM_PC_32 ? 0 : status_reg))
            + (bit (inst, 4) ? 12 : 8))
         : get_frame_register_unsigned (frame, rm));

  switch (shifttype)
    {
    case 0:                     /* LSL */
      res = shift >= 32 ? 0 : res << shift;
      break;

    case 1:                     /* LSR */
      res = shift >= 32 ? 0 : res >> shift;
      break;

    case 2:                     /* ASR */
      if (shift >= 32)
        shift = 31;
      res = ((res & 0x80000000L)
             ? ~((~res) >> shift) : res >> shift);
      break;

    case 3:                     /* ROR/RRX */
      shift &= 31;
      if (shift == 0)
        res = (res >> 1) | (carry ? 0x80000000L : 0);
      else
        res = (res >> shift) | (res << (32 - shift));
      break;
    }

  return res & 0xffffffff;
}

/* Return number of 1-bits in VAL.  */

static int
bitcount (unsigned long val)
{
  int nbits;
  for (nbits = 0; val != 0; nbits++)
    val &= val - 1;             /* delete rightmost 1-bit in val */
  return nbits;
}

static CORE_ADDR
thumb_get_next_pc (struct frame_info *frame, CORE_ADDR pc)
{
  struct gdbarch *gdbarch = get_frame_arch (frame);
  unsigned long pc_val = ((unsigned long) pc) + 4;      /* PC after prefetch */
  unsigned short inst1 = read_memory_unsigned_integer (pc, 2);
  CORE_ADDR nextpc = pc + 2;            /* default is next instruction */
  unsigned long offset;

  if ((inst1 & 0xff00) == 0xbd00)       /* pop {rlist, pc} */
    {
      CORE_ADDR sp;

      /* Fetch the saved PC from the stack.  It's stored above
         all of the other registers.  */
      offset = bitcount (bits (inst1, 0, 7)) * INT_REGISTER_SIZE;
      sp = get_frame_register_unsigned (frame, ARM_SP_REGNUM);
      nextpc = (CORE_ADDR) read_memory_unsigned_integer (sp + offset, 4);
      nextpc = gdbarch_addr_bits_remove (gdbarch, nextpc);
      if (nextpc == pc)
        error (_("Infinite loop detected"));
    }
  else if ((inst1 & 0xf000) == 0xd000)  /* conditional branch */
    {
      unsigned long status = get_frame_register_unsigned (frame, ARM_PS_REGNUM);
      unsigned long cond = bits (inst1, 8, 11);
      if (cond != 0x0f && condition_true (cond, status))    /* 0x0f = SWI */
        nextpc = pc_val + (sbits (inst1, 0, 7) << 1);
    }
  else if ((inst1 & 0xf800) == 0xe000)  /* unconditional branch */
    {
      nextpc = pc_val + (sbits (inst1, 0, 10) << 1);
    }
  else if ((inst1 & 0xf800) == 0xf000)  /* long branch with link, and blx */
    {
      unsigned short inst2 = read_memory_unsigned_integer (pc + 2, 2);
      offset = (sbits (inst1, 0, 10) << 12) + (bits (inst2, 0, 10) << 1);
      nextpc = pc_val + offset;
      /* For BLX make sure to clear the low bits.  */
      if (bits (inst2, 11, 12) == 1)
        nextpc = nextpc & 0xfffffffc;
    }
  else if ((inst1 & 0xff00) == 0x4700)  /* bx REG, blx REG */
    {
      if (bits (inst1, 3, 6) == 0x0f)
        nextpc = pc_val;
      else
        nextpc = get_frame_register_unsigned (frame, bits (inst1, 3, 6));

      nextpc = gdbarch_addr_bits_remove (gdbarch, nextpc);
      if (nextpc == pc)
        error (_("Infinite loop detected"));
    }

  return nextpc;
}

CORE_ADDR
arm_get_next_pc (struct frame_info *frame, CORE_ADDR pc)
{
  struct gdbarch *gdbarch = get_frame_arch (frame);
  unsigned long pc_val;
  unsigned long this_instr;
  unsigned long status;
  CORE_ADDR nextpc;

  if (arm_frame_is_thumb (frame))
    return thumb_get_next_pc (frame, pc);

  pc_val = (unsigned long) pc;
  this_instr = read_memory_unsigned_integer (pc, 4);
  status = get_frame_register_unsigned (frame, ARM_PS_REGNUM);
  nextpc = (CORE_ADDR) (pc_val + 4);    /* Default case */

  if (bits (this_instr, 28, 31) == INST_NV)
    switch (bits (this_instr, 24, 27))
      {
      case 0xa:
      case 0xb:
        {
          /* Branch with Link and change to Thumb.  */
          nextpc = BranchDest (pc, this_instr);
          nextpc |= bit (this_instr, 24) << 1;

          nextpc = gdbarch_addr_bits_remove (gdbarch, nextpc);
          if (nextpc == pc)
            error (_("Infinite loop detected"));
          break;
        }
      case 0xc:
      case 0xd:
      case 0xe:
        /* Coprocessor register transfer.  */
        if (bits (this_instr, 12, 15) == 15)
          error (_("Invalid update to pc in instruction"));
        break;
      }
  else if (condition_true (bits (this_instr, 28, 31), status))
    {
      switch (bits (this_instr, 24, 27))
        {
        case 0x0:
        case 0x1:                       /* data processing */
        case 0x2:
        case 0x3:
          {
            unsigned long operand1, operand2, result = 0;
            unsigned long rn;
            int c;

            if (bits (this_instr, 12, 15) != 15)
              break;

            if (bits (this_instr, 22, 25) == 0
                && bits (this_instr, 4, 7) == 9)        /* multiply */
              error (_("Invalid update to pc in instruction"));

            /* BX <reg>, BLX <reg> */
            if (bits (this_instr, 4, 27) == 0x12fff1
                || bits (this_instr, 4, 27) == 0x12fff3)
              {
                rn = bits (this_instr, 0, 3);
                result = (rn == 15) ? pc_val + 8
                                    : get_frame_register_unsigned (frame, rn);
                nextpc = (CORE_ADDR) gdbarch_addr_bits_remove
                                       (gdbarch, result);

                if (nextpc == pc)
                  error (_("Infinite loop detected"));

                return nextpc;
              }

            /* Multiply into PC */
            c = (status & FLAG_C) ? 1 : 0;
            rn = bits (this_instr, 16, 19);
            operand1 = (rn == 15) ? pc_val + 8
                                  : get_frame_register_unsigned (frame, rn);

            if (bit (this_instr, 25))
              {
                unsigned long immval = bits (this_instr, 0, 7);
                unsigned long rotate = 2 * bits (this_instr, 8, 11);
                operand2 = ((immval >> rotate) | (immval << (32 - rotate)))
                  & 0xffffffff;
              }
            else                /* operand 2 is a shifted register */
              operand2 = shifted_reg_val (frame, this_instr, c, pc_val, status);

            switch (bits (this_instr, 21, 24))
              {
              case 0x0: /*and */
                result = operand1 & operand2;
                break;

              case 0x1: /*eor */
                result = operand1 ^ operand2;
                break;

              case 0x2: /*sub */
                result = operand1 - operand2;
                break;

              case 0x3: /*rsb */
                result = operand2 - operand1;
                break;

              case 0x4: /*add */
                result = operand1 + operand2;
                break;

              case 0x5: /*adc */
                result = operand1 + operand2 + c;
                break;

              case 0x6: /*sbc */
                result = operand1 - operand2 + c;
                break;

              case 0x7: /*rsc */
                result = operand2 - operand1 + c;
                break;

              case 0x8:
              case 0x9:
              case 0xa:
              case 0xb: /* tst, teq, cmp, cmn */
                result = (unsigned long) nextpc;
                break;

              case 0xc: /*orr */
                result = operand1 | operand2;
                break;

              case 0xd: /*mov */
                /* Always step into a function.  */
                result = operand2;
                break;

              case 0xe: /*bic */
                result = operand1 & ~operand2;
                break;

              case 0xf: /*mvn */
                result = ~operand2;
                break;
              }
            nextpc = (CORE_ADDR) gdbarch_addr_bits_remove
                                   (gdbarch, result);

            if (nextpc == pc)
              error (_("Infinite loop detected"));
            break;
          }

        case 0x4:
        case 0x5:               /* data transfer */
        case 0x6:
        case 0x7:
          if (bit (this_instr, 20))
            {
              /* load */
              if (bits (this_instr, 12, 15) == 15)
                {
                  /* rd == pc */
                  unsigned long rn;
                  unsigned long base;

                  if (bit (this_instr, 22))
                    error (_("Invalid update to pc in instruction"));

                  /* byte write to PC */
                  rn = bits (this_instr, 16, 19);
                  base = (rn == 15) ? pc_val + 8
                                    : get_frame_register_unsigned (frame, rn);
                  if (bit (this_instr, 24))
                    {
                      /* pre-indexed */
                      int c = (status & FLAG_C) ? 1 : 0;
                      unsigned long offset =
                      (bit (this_instr, 25)
                       ? shifted_reg_val (frame, this_instr, c, pc_val, status)
                       : bits (this_instr, 0, 11));

                      if (bit (this_instr, 23))
                        base += offset;
                      else
                        base -= offset;
                    }
                  nextpc = (CORE_ADDR) read_memory_integer ((CORE_ADDR) base,
                                                            4);

                  nextpc = gdbarch_addr_bits_remove (gdbarch, nextpc);

                  if (nextpc == pc)
                    error (_("Infinite loop detected"));
                }
            }
          break;

        case 0x8:
        case 0x9:               /* block transfer */
          if (bit (this_instr, 20))
            {
              /* LDM */
              if (bit (this_instr, 15))
                {
                  /* loading pc */
                  int offset = 0;

                  if (bit (this_instr, 23))
                    {
                      /* up */
                      unsigned long reglist = bits (this_instr, 0, 14);
                      offset = bitcount (reglist) * 4;
                      if (bit (this_instr, 24))         /* pre */
                        offset += 4;
                    }
                  else if (bit (this_instr, 24))
                    offset = -4;

                  {
                    unsigned long rn_val =
                    get_frame_register_unsigned (frame,
                                                 bits (this_instr, 16, 19));
                    nextpc =
                      (CORE_ADDR) read_memory_integer ((CORE_ADDR) (rn_val
                                                                  + offset),
                                                       4);
                  }
                  nextpc = gdbarch_addr_bits_remove
                             (gdbarch, nextpc);
                  if (nextpc == pc)
                    error (_("Infinite loop detected"));
                }
            }
          break;

        case 0xb:               /* branch & link */
        case 0xa:               /* branch */
          {
            nextpc = BranchDest (pc, this_instr);

            nextpc = gdbarch_addr_bits_remove (gdbarch, nextpc);
            if (nextpc == pc)
              error (_("Infinite loop detected"));
            break;
          }

        case 0xc:
        case 0xd:
        case 0xe:               /* coproc ops */
        case 0xf:               /* SWI */
          break;

        default:
          fprintf_filtered (gdb_stderr, _("Bad bit-field extraction\n"));
          return (pc);
        }
    }

  return nextpc;
}

/* single_step() is called just before we want to resume the inferior,
   if we want to single-step it but there is no hardware or kernel
   single-step support.  We find the target of the coming instruction
   and breakpoint it.  */

int
arm_software_single_step (struct frame_info *frame)
{
  /* NOTE: This may insert the wrong breakpoint instruction when
     single-stepping over a mode-changing instruction, if the
     CPSR heuristics are used.  */

  CORE_ADDR next_pc = arm_get_next_pc (frame, get_frame_pc (frame));
  insert_single_step_breakpoint (next_pc);

  return 1;
}

#include "bfd-in2.h"
#include "libcoff.h"

static int
gdb_print_insn_arm (bfd_vma memaddr, disassemble_info *info)
{
  if (arm_pc_is_thumb (memaddr))
    {
      static asymbol *asym;
      static combined_entry_type ce;
      static struct coff_symbol_struct csym;
      static struct bfd fake_bfd;
      static bfd_target fake_target;

      if (csym.native == NULL)
        {
          /* Create a fake symbol vector containing a Thumb symbol.
             This is solely so that the code in print_insn_little_arm() 
             and print_insn_big_arm() in opcodes/arm-dis.c will detect
             the presence of a Thumb symbol and switch to decoding
             Thumb instructions.  */

          fake_target.flavour = bfd_target_coff_flavour;
          fake_bfd.xvec = &fake_target;
          ce.u.syment.n_sclass = C_THUMBEXTFUNC;
          csym.native = &ce;
          csym.symbol.the_bfd = &fake_bfd;
          csym.symbol.name = "fake";
          asym = (asymbol *) & csym;
        }

      memaddr = UNMAKE_THUMB_ADDR (memaddr);
      info->symbols = &asym;
    }
  else
    info->symbols = NULL;

  if (info->endian == BFD_ENDIAN_BIG)
    return print_insn_big_arm (memaddr, info);
  else
    return print_insn_little_arm (memaddr, info);
}

/* The following define instruction sequences that will cause ARM
   cpu's to take an undefined instruction trap.  These are used to
   signal a breakpoint to GDB.
   
   The newer ARMv4T cpu's are capable of operating in ARM or Thumb
   modes.  A different instruction is required for each mode.  The ARM
   cpu's can also be big or little endian.  Thus four different
   instructions are needed to support all cases.
   
   Note: ARMv4 defines several new instructions that will take the
   undefined instruction trap.  ARM7TDMI is nominally ARMv4T, but does
   not in fact add the new instructions.  The new undefined
   instructions in ARMv4 are all instructions that had no defined
   behaviour in earlier chips.  There is no guarantee that they will
   raise an exception, but may be treated as NOP's.  In practice, it
   may only safe to rely on instructions matching:
   
   3 3 2 2 2 2 2 2 2 2 2 2 1 1 1 1 1 1 1 1 1 1 
   1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0 9 8 7 6 5 4 3 2 1 0
   C C C C 0 1 1 x x x x x x x x x x x x x x x x x x x x 1 x x x x
   
   Even this may only true if the condition predicate is true. The
   following use a condition predicate of ALWAYS so it is always TRUE.
   
   There are other ways of forcing a breakpoint.  GNU/Linux, RISC iX,
   and NetBSD all use a software interrupt rather than an undefined
   instruction to force a trap.  This can be handled by by the
   abi-specific code during establishment of the gdbarch vector.  */

#define ARM_LE_BREAKPOINT {0xFE,0xDE,0xFF,0xE7}
#define ARM_BE_BREAKPOINT {0xE7,0xFF,0xDE,0xFE}
#define THUMB_LE_BREAKPOINT {0xbe,0xbe}
#define THUMB_BE_BREAKPOINT {0xbe,0xbe}

static const char arm_default_arm_le_breakpoint[] = ARM_LE_BREAKPOINT;
static const char arm_default_arm_be_breakpoint[] = ARM_BE_BREAKPOINT;
static const char arm_default_thumb_le_breakpoint[] = THUMB_LE_BREAKPOINT;
static const char arm_default_thumb_be_breakpoint[] = THUMB_BE_BREAKPOINT;

/* Determine the type and size of breakpoint to insert at PCPTR.  Uses
   the program counter value to determine whether a 16-bit or 32-bit
   breakpoint should be used.  It returns a pointer to a string of
   bytes that encode a breakpoint instruction, stores the length of
   the string to *lenptr, and adjusts the program counter (if
   necessary) to point to the actual memory location where the
   breakpoint should be inserted.  */

static const unsigned char *
arm_breakpoint_from_pc (struct gdbarch *gdbarch, CORE_ADDR *pcptr, int *lenptr)
{
  struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);

  if (arm_pc_is_thumb (*pcptr))
    {
      *pcptr = UNMAKE_THUMB_ADDR (*pcptr);
      *lenptr = tdep->thumb_breakpoint_size;
      return tdep->thumb_breakpoint;
    }
  else
    {
      *lenptr = tdep->arm_breakpoint_size;
      return tdep->arm_breakpoint;
    }
}

/* Extract from an array REGBUF containing the (raw) register state a
   function return value of type TYPE, and copy that, in virtual
   format, into VALBUF.  */

static void
arm_extract_return_value (struct type *type, struct regcache *regs,
                          gdb_byte *valbuf)
{
  struct gdbarch *gdbarch = get_regcache_arch (regs);

  if (TYPE_CODE_FLT == TYPE_CODE (type))
    {
      switch (gdbarch_tdep (gdbarch)->fp_model)
        {
        case ARM_FLOAT_FPA:
          {
            /* The value is in register F0 in internal format.  We need to
               extract the raw value and then convert it to the desired
               internal type.  */
            bfd_byte tmpbuf[FP_REGISTER_SIZE];

            regcache_cooked_read (regs, ARM_F0_REGNUM, tmpbuf);
            convert_from_extended (floatformat_from_type (type), tmpbuf,
                                   valbuf, gdbarch_byte_order (gdbarch));
          }
          break;

        case ARM_FLOAT_SOFT_FPA:
        case ARM_FLOAT_SOFT_VFP:
          regcache_cooked_read (regs, ARM_A1_REGNUM, valbuf);
          if (TYPE_LENGTH (type) > 4)
            regcache_cooked_read (regs, ARM_A1_REGNUM + 1,
                                  valbuf + INT_REGISTER_SIZE);
          break;

        default:
          internal_error
            (__FILE__, __LINE__,
             _("arm_extract_return_value: Floating point model not supported"));
          break;
        }
    }
  else if (TYPE_CODE (type) == TYPE_CODE_INT
           || TYPE_CODE (type) == TYPE_CODE_CHAR
           || TYPE_CODE (type) == TYPE_CODE_BOOL
           || TYPE_CODE (type) == TYPE_CODE_PTR
           || TYPE_CODE (type) == TYPE_CODE_REF
           || TYPE_CODE (type) == TYPE_CODE_ENUM)
    {
      /* If the the type is a plain integer, then the access is
         straight-forward.  Otherwise we have to play around a bit more.  */
      int len = TYPE_LENGTH (type);
      int regno = ARM_A1_REGNUM;
      ULONGEST tmp;

      while (len > 0)
        {
          /* By using store_unsigned_integer we avoid having to do
             anything special for small big-endian values.  */
          regcache_cooked_read_unsigned (regs, regno++, &tmp);
          store_unsigned_integer (valbuf, 
                                  (len > INT_REGISTER_SIZE
                                   ? INT_REGISTER_SIZE : len),
                                  tmp);
          len -= INT_REGISTER_SIZE;
          valbuf += INT_REGISTER_SIZE;
        }
    }
  else
    {
      /* For a structure or union the behaviour is as if the value had
         been stored to word-aligned memory and then loaded into 
         registers with 32-bit load instruction(s).  */
      int len = TYPE_LENGTH (type);
      int regno = ARM_A1_REGNUM;
      bfd_byte tmpbuf[INT_REGISTER_SIZE];

      while (len > 0)
        {
          regcache_cooked_read (regs, regno++, tmpbuf);
          memcpy (valbuf, tmpbuf,
                  len > INT_REGISTER_SIZE ? INT_REGISTER_SIZE : len);
          len -= INT_REGISTER_SIZE;
          valbuf += INT_REGISTER_SIZE;
        }
    }
}


/* Will a function return an aggregate type in memory or in a
   register?  Return 0 if an aggregate type can be returned in a
   register, 1 if it must be returned in memory.  */

static int
arm_return_in_memory (struct gdbarch *gdbarch, struct type *type)
{
  int nRc;
  enum type_code code;

  CHECK_TYPEDEF (type);

  /* In the ARM ABI, "integer" like aggregate types are returned in
     registers.  For an aggregate type to be integer like, its size
     must be less than or equal to INT_REGISTER_SIZE and the
     offset of each addressable subfield must be zero.  Note that bit
     fields are not addressable, and all addressable subfields of
     unions always start at offset zero.

     This function is based on the behaviour of GCC 2.95.1.
     See: gcc/arm.c: arm_return_in_memory() for details.

     Note: All versions of GCC before GCC 2.95.2 do not set up the
     parameters correctly for a function returning the following
     structure: struct { float f;}; This should be returned in memory,
     not a register.  Richard Earnshaw sent me a patch, but I do not
     know of any way to detect if a function like the above has been
     compiled with the correct calling convention.  */

  /* All aggregate types that won't fit in a register must be returned
     in memory.  */
  if (TYPE_LENGTH (type) > INT_REGISTER_SIZE)
    {
      return 1;
    }

  /* The AAPCS says all aggregates not larger than a word are returned
     in a register.  */
  if (gdbarch_tdep (gdbarch)->arm_abi != ARM_ABI_APCS)
    return 0;

  /* The only aggregate types that can be returned in a register are
     structs and unions.  Arrays must be returned in memory.  */
  code = TYPE_CODE (type);
  if ((TYPE_CODE_STRUCT != code) && (TYPE_CODE_UNION != code))
    {
      return 1;
    }

  /* Assume all other aggregate types can be returned in a register.
     Run a check for structures, unions and arrays.  */
  nRc = 0;

  if ((TYPE_CODE_STRUCT == code) || (TYPE_CODE_UNION == code))
    {
      int i;
      /* Need to check if this struct/union is "integer" like.  For
         this to be true, its size must be less than or equal to
         INT_REGISTER_SIZE and the offset of each addressable
         subfield must be zero.  Note that bit fields are not
         addressable, and unions always start at offset zero.  If any
         of the subfields is a floating point type, the struct/union
         cannot be an integer type.  */

      /* For each field in the object, check:
         1) Is it FP? --> yes, nRc = 1;
         2) Is it addressable (bitpos != 0) and
         not packed (bitsize == 0)?
         --> yes, nRc = 1  
       */

      for (i = 0; i < TYPE_NFIELDS (type); i++)
        {
          enum type_code field_type_code;
          field_type_code = TYPE_CODE (check_typedef (TYPE_FIELD_TYPE (type, i)));

          /* Is it a floating point type field?  */
          if (field_type_code == TYPE_CODE_FLT)
            {
              nRc = 1;
              break;
            }

          /* If bitpos != 0, then we have to care about it.  */
          if (TYPE_FIELD_BITPOS (type, i) != 0)
            {
              /* Bitfields are not addressable.  If the field bitsize is 
                 zero, then the field is not packed.  Hence it cannot be
                 a bitfield or any other packed type.  */
              if (TYPE_FIELD_BITSIZE (type, i) == 0)
                {
                  nRc = 1;
                  break;
                }
            }
        }
    }

  return nRc;
}

/* Write into appropriate registers a function return value of type
   TYPE, given in virtual format.  */

static void
arm_store_return_value (struct type *type, struct regcache *regs,
                        const gdb_byte *valbuf)
{
  struct gdbarch *gdbarch = get_regcache_arch (regs);

  if (TYPE_CODE (type) == TYPE_CODE_FLT)
    {
      char buf[MAX_REGISTER_SIZE];

      switch (gdbarch_tdep (gdbarch)->fp_model)
        {
        case ARM_FLOAT_FPA:

          convert_to_extended (floatformat_from_type (type), buf, valbuf,
                               gdbarch_byte_order (gdbarch));
          regcache_cooked_write (regs, ARM_F0_REGNUM, buf);
          break;

        case ARM_FLOAT_SOFT_FPA:
        case ARM_FLOAT_SOFT_VFP:
          regcache_cooked_write (regs, ARM_A1_REGNUM, valbuf);
          if (TYPE_LENGTH (type) > 4)
            regcache_cooked_write (regs, ARM_A1_REGNUM + 1, 
                                   valbuf + INT_REGISTER_SIZE);
          break;

        default:
          internal_error
            (__FILE__, __LINE__,
             _("arm_store_return_value: Floating point model not supported"));
          break;
        }
    }
  else if (TYPE_CODE (type) == TYPE_CODE_INT
           || TYPE_CODE (type) == TYPE_CODE_CHAR
           || TYPE_CODE (type) == TYPE_CODE_BOOL
           || TYPE_CODE (type) == TYPE_CODE_PTR
           || TYPE_CODE (type) == TYPE_CODE_REF
           || TYPE_CODE (type) == TYPE_CODE_ENUM)
    {
      if (TYPE_LENGTH (type) <= 4)
        {
          /* Values of one word or less are zero/sign-extended and
             returned in r0.  */
          bfd_byte tmpbuf[INT_REGISTER_SIZE];
          LONGEST val = unpack_long (type, valbuf);

          store_signed_integer (tmpbuf, INT_REGISTER_SIZE, val);
          regcache_cooked_write (regs, ARM_A1_REGNUM, tmpbuf);
        }
      else
        {
          /* Integral values greater than one word are stored in consecutive
             registers starting with r0.  This will always be a multiple of
             the regiser size.  */
          int len = TYPE_LENGTH (type);
          int regno = ARM_A1_REGNUM;

          while (len > 0)
            {
              regcache_cooked_write (regs, regno++, valbuf);
              len -= INT_REGISTER_SIZE;
              valbuf += INT_REGISTER_SIZE;
            }
        }
    }
  else
    {
      /* For a structure or union the behaviour is as if the value had
         been stored to word-aligned memory and then loaded into 
         registers with 32-bit load instruction(s).  */
      int len = TYPE_LENGTH (type);
      int regno = ARM_A1_REGNUM;
      bfd_byte tmpbuf[INT_REGISTER_SIZE];

      while (len > 0)
        {
          memcpy (tmpbuf, valbuf,
                  len > INT_REGISTER_SIZE ? INT_REGISTER_SIZE : len);
          regcache_cooked_write (regs, regno++, tmpbuf);
          len -= INT_REGISTER_SIZE;
          valbuf += INT_REGISTER_SIZE;
        }
    }
}


/* Handle function return values.  */

static enum return_value_convention
arm_return_value (struct gdbarch *gdbarch, struct type *func_type,
                  struct type *valtype, struct regcache *regcache,
                  gdb_byte *readbuf, const gdb_byte *writebuf)
{
  struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);

  if (TYPE_CODE (valtype) == TYPE_CODE_STRUCT
      || TYPE_CODE (valtype) == TYPE_CODE_UNION
      || TYPE_CODE (valtype) == TYPE_CODE_ARRAY)
    {
      if (tdep->struct_return == pcc_struct_return
          || arm_return_in_memory (gdbarch, valtype))
        return RETURN_VALUE_STRUCT_CONVENTION;
    }

  if (writebuf)
    arm_store_return_value (valtype, regcache, writebuf);

  if (readbuf)
    arm_extract_return_value (valtype, regcache, readbuf);

  return RETURN_VALUE_REGISTER_CONVENTION;
}


static int
arm_get_longjmp_target (struct frame_info *frame, CORE_ADDR *pc)
{
  CORE_ADDR jb_addr;
  char buf[INT_REGISTER_SIZE];
  struct gdbarch_tdep *tdep = gdbarch_tdep (get_frame_arch (frame));
  
  jb_addr = get_frame_register_unsigned (frame, ARM_A1_REGNUM);

  if (target_read_memory (jb_addr + tdep->jb_pc * tdep->jb_elt_size, buf,
                          INT_REGISTER_SIZE))
    return 0;

  *pc = extract_unsigned_integer (buf, INT_REGISTER_SIZE);
  return 1;
}

/* Recognize GCC and GNU ld's trampolines.  If we are in a trampoline,
   return the target PC.  Otherwise return 0.  */

CORE_ADDR
arm_skip_stub (struct frame_info *frame, CORE_ADDR pc)
{
  char *name;
  int namelen;
  CORE_ADDR start_addr;

  /* Find the starting address and name of the function containing the PC.  */
  if (find_pc_partial_function (pc, &name, &start_addr, NULL) == 0)
    return 0;

  /* If PC is in a Thumb call or return stub, return the address of the
     target PC, which is in a register.  The thunk functions are called
     _call_via_xx, where x is the register name.  The possible names
     are r0-r9, sl, fp, ip, sp, and lr.  */
  if (strncmp (name, "_call_via_", 10) == 0)
    {
      /* Use the name suffix to determine which register contains the
         target PC.  */
      static char *table[15] =
      {"r0", "r1", "r2", "r3", "r4", "r5", "r6", "r7",
       "r8", "r9", "sl", "fp", "ip", "sp", "lr"
      };
      int regno;
      int offset = strlen (name) - 2;

      for (regno = 0; regno <= 14; regno++)
        if (strcmp (&name[offset], table[regno]) == 0)
          return get_frame_register_unsigned (frame, regno);
    }

  /* GNU ld generates __foo_from_arm or __foo_from_thumb for
     non-interworking calls to foo.  We could decode the stubs
     to find the target but it's easier to use the symbol table.  */
  namelen = strlen (name);
  if (name[0] == '_' && name[1] == '_'
      && ((namelen > 2 + strlen ("_from_thumb")
           && strncmp (name + namelen - strlen ("_from_thumb"), "_from_thumb",
                       strlen ("_from_thumb")) == 0)
          || (namelen > 2 + strlen ("_from_arm")
              && strncmp (name + namelen - strlen ("_from_arm"), "_from_arm",
                          strlen ("_from_arm")) == 0)))
    {
      char *target_name;
      int target_len = namelen - 2;
      struct minimal_symbol *minsym;
      struct objfile *objfile;
      struct obj_section *sec;

      if (name[namelen - 1] == 'b')
        target_len -= strlen ("_from_thumb");
      else
        target_len -= strlen ("_from_arm");

      target_name = alloca (target_len + 1);
      memcpy (target_name, name + 2, target_len);
      target_name[target_len] = '\0';

      sec = find_pc_section (pc);
      objfile = (sec == NULL) ? NULL : sec->objfile;
      minsym = lookup_minimal_symbol (target_name, NULL, objfile);
      if (minsym != NULL)
        return SYMBOL_VALUE_ADDRESS (minsym);
      else
        return 0;
    }

  return 0;                     /* not a stub */
}

static void
set_arm_command (char *args, int from_tty)
{
  printf_unfiltered (_("\
\"set arm\" must be followed by an apporpriate subcommand.\n"));
  help_list (setarmcmdlist, "set arm ", all_commands, gdb_stdout);
}

static void
show_arm_command (char *args, int from_tty)
{
  cmd_show_list (showarmcmdlist, from_tty, "");
}

static void
arm_update_current_architecture (void)
{
  struct gdbarch_info info;

  /* If the current architecture is not ARM, we have nothing to do.  */
  if (gdbarch_bfd_arch_info (current_gdbarch)->arch != bfd_arch_arm)
    return;

  /* Update the architecture.  */
  gdbarch_info_init (&info);

  if (!gdbarch_update_p (info))
    internal_error (__FILE__, __LINE__, "could not update architecture");
}

static void
set_fp_model_sfunc (char *args, int from_tty,
                    struct cmd_list_element *c)
{
  enum arm_float_model fp_model;

  for (fp_model = ARM_FLOAT_AUTO; fp_model != ARM_FLOAT_LAST; fp_model++)
    if (strcmp (current_fp_model, fp_model_strings[fp_model]) == 0)
      {
        arm_fp_model = fp_model;
        break;
      }

  if (fp_model == ARM_FLOAT_LAST)
    internal_error (__FILE__, __LINE__, _("Invalid fp model accepted: %s."),
                    current_fp_model);

  arm_update_current_architecture ();
}

static void
show_fp_model (struct ui_file *file, int from_tty,
               struct cmd_list_element *c, const char *value)
{
  struct gdbarch_tdep *tdep = gdbarch_tdep (current_gdbarch);

  if (arm_fp_model == ARM_FLOAT_AUTO
      && gdbarch_bfd_arch_info (current_gdbarch)->arch == bfd_arch_arm)
    fprintf_filtered (file, _("\
The current ARM floating point model is \"auto\" (currently \"%s\").\n"),
                      fp_model_strings[tdep->fp_model]);
  else
    fprintf_filtered (file, _("\
The current ARM floating point model is \"%s\".\n"),
                      fp_model_strings[arm_fp_model]);
}

static void
arm_set_abi (char *args, int from_tty,
             struct cmd_list_element *c)
{
  enum arm_abi_kind arm_abi;

  for (arm_abi = ARM_ABI_AUTO; arm_abi != ARM_ABI_LAST; arm_abi++)
    if (strcmp (arm_abi_string, arm_abi_strings[arm_abi]) == 0)
      {
        arm_abi_global = arm_abi;
        break;
      }

  if (arm_abi == ARM_ABI_LAST)
    internal_error (__FILE__, __LINE__, _("Invalid ABI accepted: %s."),
                    arm_abi_string);

  arm_update_current_architecture ();
}

static void
arm_show_abi (struct ui_file *file, int from_tty,
             struct cmd_list_element *c, const char *value)
{
  struct gdbarch_tdep *tdep = gdbarch_tdep (current_gdbarch);

  if (arm_abi_global == ARM_ABI_AUTO
      && gdbarch_bfd_arch_info (current_gdbarch)->arch == bfd_arch_arm)
    fprintf_filtered (file, _("\
The current ARM ABI is \"auto\" (currently \"%s\").\n"),
                      arm_abi_strings[tdep->arm_abi]);
  else
    fprintf_filtered (file, _("The current ARM ABI is \"%s\".\n"),
                      arm_abi_string);
}

static void
arm_show_fallback_mode (struct ui_file *file, int from_tty,
                        struct cmd_list_element *c, const char *value)
{
  struct gdbarch_tdep *tdep = gdbarch_tdep (current_gdbarch);

  fprintf_filtered (file, _("\
The current execution mode assumed (when symbols are unavailable) is \"%s\".\n"),
                    arm_fallback_mode_string);
}

static void
arm_show_force_mode (struct ui_file *file, int from_tty,
                     struct cmd_list_element *c, const char *value)
{
  struct gdbarch_tdep *tdep = gdbarch_tdep (current_gdbarch);

  fprintf_filtered (file, _("\
The current execution mode assumed (even when symbols are available) is \"%s\".\n"),
                    arm_force_mode_string);
}

/* If the user changes the register disassembly style used for info
   register and other commands, we have to also switch the style used
   in opcodes for disassembly output.  This function is run in the "set
   arm disassembly" command, and does that.  */

static void
set_disassembly_style_sfunc (char *args, int from_tty,
                              struct cmd_list_element *c)
{
  set_disassembly_style ();
}
\f
/* Return the ARM register name corresponding to register I.  */
static const char *
arm_register_name (struct gdbarch *gdbarch, int i)
{
  if (i >= ARRAY_SIZE (arm_register_names))
    /* These registers are only supported on targets which supply
       an XML description.  */
    return "";

  return arm_register_names[i];
}

static void
set_disassembly_style (void)
{
  int current;

  /* Find the style that the user wants.  */
  for (current = 0; current < num_disassembly_options; current++)
    if (disassembly_style == valid_disassembly_styles[current])
      break;
  gdb_assert (current < num_disassembly_options);

  /* Synchronize the disassembler.  */
  set_arm_regname_option (current);
}

/* Test whether the coff symbol specific value corresponds to a Thumb
   function.  */

static int
coff_sym_is_thumb (int val)
{
  return (val == C_THUMBEXT ||
          val == C_THUMBSTAT ||
          val == C_THUMBEXTFUNC ||
          val == C_THUMBSTATFUNC ||
          val == C_THUMBLABEL);
}

/* arm_coff_make_msymbol_special()
   arm_elf_make_msymbol_special()
   
   These functions test whether the COFF or ELF symbol corresponds to
   an address in thumb code, and set a "special" bit in a minimal
   symbol to indicate that it does.  */
   
static void
arm_elf_make_msymbol_special(asymbol *sym, struct minimal_symbol *msym)
{
  /* Thumb symbols are of type STT_LOPROC, (synonymous with
     STT_ARM_TFUNC).  */
  if (ELF_ST_TYPE (((elf_symbol_type *)sym)->internal_elf_sym.st_info)
      == STT_LOPROC)
    MSYMBOL_SET_SPECIAL (msym);
}

static void
arm_coff_make_msymbol_special(int val, struct minimal_symbol *msym)
{
  if (coff_sym_is_thumb (val))
    MSYMBOL_SET_SPECIAL (msym);
}

static void
arm_write_pc (struct regcache *regcache, CORE_ADDR pc)
{
  regcache_cooked_write_unsigned (regcache, ARM_PC_REGNUM, pc);

  /* If necessary, set the T bit.  */
  if (arm_apcs_32)
    {
      ULONGEST val;
      regcache_cooked_read_unsigned (regcache, ARM_PS_REGNUM, &val);
      if (arm_pc_is_thumb (pc))
        regcache_cooked_write_unsigned (regcache, ARM_PS_REGNUM, val | CPSR_T);
      else
        regcache_cooked_write_unsigned (regcache, ARM_PS_REGNUM,
                                        val & ~(ULONGEST) CPSR_T);
    }
}

static struct value *
value_of_arm_user_reg (struct frame_info *frame, const void *baton)
{
  const int *reg_p = baton;
  return value_of_register (*reg_p, frame);
}
\f
static enum gdb_osabi
arm_elf_osabi_sniffer (bfd *abfd)
{
  unsigned int elfosabi;
  enum gdb_osabi osabi = GDB_OSABI_UNKNOWN;

  elfosabi = elf_elfheader (abfd)->e_ident[EI_OSABI];

  if (elfosabi == ELFOSABI_ARM)
    /* GNU tools use this value.  Check note sections in this case,
       as well.  */
    bfd_map_over_sections (abfd,
                           generic_elf_osabi_sniff_abi_tag_sections, 
                           &osabi);

  /* Anything else will be handled by the generic ELF sniffer.  */
  return osabi;
}

\f
/* Initialize the current architecture based on INFO.  If possible,
   re-use an architecture from ARCHES, which is a list of
   architectures already created during this debugging session.

   Called e.g. at program startup, when reading a core file, and when
   reading a binary file.  */

static struct gdbarch *
arm_gdbarch_init (struct gdbarch_info info, struct gdbarch_list *arches)
{
  struct gdbarch_tdep *tdep;
  struct gdbarch *gdbarch;
  struct gdbarch_list *best_arch;
  enum arm_abi_kind arm_abi = arm_abi_global;
  enum arm_float_model fp_model = arm_fp_model;
  struct tdesc_arch_data *tdesc_data = NULL;
  int i;
  int have_fpa_registers = 1;

  /* Check any target description for validity.  */
  if (tdesc_has_registers (info.target_desc))
    {
      /* For most registers we require GDB's default names; but also allow
         the numeric names for sp / lr / pc, as a convenience.  */
      static const char *const arm_sp_names[] = { "r13", "sp", NULL };
      static const char *const arm_lr_names[] = { "r14", "lr", NULL };
      static const char *const arm_pc_names[] = { "r15", "pc", NULL };

      const struct tdesc_feature *feature;
      int i, valid_p;

      feature = tdesc_find_feature (info.target_desc,
                                    "org.gnu.gdb.arm.core");
      if (feature == NULL)
        return NULL;

      tdesc_data = tdesc_data_alloc ();

      valid_p = 1;
      for (i = 0; i < ARM_SP_REGNUM; i++)
        valid_p &= tdesc_numbered_register (feature, tdesc_data, i,
                                            arm_register_names[i]);
      valid_p &= tdesc_numbered_register_choices (feature, tdesc_data,
                                                  ARM_SP_REGNUM,
                                                  arm_sp_names);
      valid_p &= tdesc_numbered_register_choices (feature, tdesc_data,
                                                  ARM_LR_REGNUM,
                                                  arm_lr_names);
      valid_p &= tdesc_numbered_register_choices (feature, tdesc_data,
                                                  ARM_PC_REGNUM,
                                                  arm_pc_names);
      valid_p &= tdesc_numbered_register (feature, tdesc_data,
                                          ARM_PS_REGNUM, "cpsr");

      if (!valid_p)
        {
          tdesc_data_cleanup (tdesc_data);
          return NULL;
        }

      feature = tdesc_find_feature (info.target_desc,
                                    "org.gnu.gdb.arm.fpa");
      if (feature != NULL)
        {
          valid_p = 1;
          for (i = ARM_F0_REGNUM; i <= ARM_FPS_REGNUM; i++)
            valid_p &= tdesc_numbered_register (feature, tdesc_data, i,
                                                arm_register_names[i]);
          if (!valid_p)
            {
              tdesc_data_cleanup (tdesc_data);
              return NULL;
            }
        }
      else
        have_fpa_registers = 0;

      feature = tdesc_find_feature (info.target_desc,
                                    "org.gnu.gdb.xscale.iwmmxt");
      if (feature != NULL)
        {
          static const char *const iwmmxt_names[] = {
            "wR0", "wR1", "wR2", "wR3", "wR4", "wR5", "wR6", "wR7",
            "wR8", "wR9", "wR10", "wR11", "wR12", "wR13", "wR14", "wR15",
            "wCID", "wCon", "wCSSF", "wCASF", "", "", "", "",
            "wCGR0", "wCGR1", "wCGR2", "wCGR3", "", "", "", "",
          };

          valid_p = 1;
          for (i = ARM_WR0_REGNUM; i <= ARM_WR15_REGNUM; i++)
            valid_p
              &= tdesc_numbered_register (feature, tdesc_data, i,
                                          iwmmxt_names[i - ARM_WR0_REGNUM]);

          /* Check for the control registers, but do not fail if they
             are missing.  */
          for (i = ARM_WC0_REGNUM; i <= ARM_WCASF_REGNUM; i++)
            tdesc_numbered_register (feature, tdesc_data, i,
                                     iwmmxt_names[i - ARM_WR0_REGNUM]);

          for (i = ARM_WCGR0_REGNUM; i <= ARM_WCGR3_REGNUM; i++)
            valid_p
              &= tdesc_numbered_register (feature, tdesc_data, i,
                                          iwmmxt_names[i - ARM_WR0_REGNUM]);

          if (!valid_p)
            {
              tdesc_data_cleanup (tdesc_data);
              return NULL;
            }
        }
    }

  /* If we have an object to base this architecture on, try to determine
     its ABI.  */

  if (arm_abi == ARM_ABI_AUTO && info.abfd != NULL)
    {
      int ei_osabi, e_flags;

      switch (bfd_get_flavour (info.abfd))
        {
        case bfd_target_aout_flavour:
          /* Assume it's an old APCS-style ABI.  */
          arm_abi = ARM_ABI_APCS;
          break;

        case bfd_target_coff_flavour:
          /* Assume it's an old APCS-style ABI.  */
          /* XXX WinCE?  */
          arm_abi = ARM_ABI_APCS;
          break;

        case bfd_target_elf_flavour:
          ei_osabi = elf_elfheader (info.abfd)->e_ident[EI_OSABI];
          e_flags = elf_elfheader (info.abfd)->e_flags;

          if (ei_osabi == ELFOSABI_ARM)
            {
              /* GNU tools used to use this value, but do not for EABI
                 objects.  There's nowhere to tag an EABI version
                 anyway, so assume APCS.  */
              arm_abi = ARM_ABI_APCS;
            }
          else if (ei_osabi == ELFOSABI_NONE)
            {
              int eabi_ver = EF_ARM_EABI_VERSION (e_flags);

              switch (eabi_ver)
                {
                case EF_ARM_EABI_UNKNOWN:
                  /* Assume GNU tools.  */
                  arm_abi = ARM_ABI_APCS;
                  break;

                case EF_ARM_EABI_VER4:
                case EF_ARM_EABI_VER5:
                  arm_abi = ARM_ABI_AAPCS;
                  /* EABI binaries default to VFP float ordering.  */
                  if (fp_model == ARM_FLOAT_AUTO)
                    fp_model = ARM_FLOAT_SOFT_VFP;
                  break;

                default:
                  /* Leave it as "auto".  */
                  warning (_("unknown ARM EABI version 0x%x"), eabi_ver);
                  break;
                }
            }

          if (fp_model == ARM_FLOAT_AUTO)
            {
              int e_flags = elf_elfheader (info.abfd)->e_flags;

              switch (e_flags & (EF_ARM_SOFT_FLOAT | EF_ARM_VFP_FLOAT))
                {
                case 0:
                  /* Leave it as "auto".  Strictly speaking this case
                     means FPA, but almost nobody uses that now, and
                     many toolchains fail to set the appropriate bits
                     for the floating-point model they use.  */
                  break;
                case EF_ARM_SOFT_FLOAT:
                  fp_model = ARM_FLOAT_SOFT_FPA;
                  break;
                case EF_ARM_VFP_FLOAT:
                  fp_model = ARM_FLOAT_VFP;
                  break;
                case EF_ARM_SOFT_FLOAT | EF_ARM_VFP_FLOAT:
                  fp_model = ARM_FLOAT_SOFT_VFP;
                  break;
                }
            }
          break;

        default:
          /* Leave it as "auto".  */
          break;
        }
    }

  /* If there is already a candidate, use it.  */
  for (best_arch = gdbarch_list_lookup_by_info (arches, &info);
       best_arch != NULL;
       best_arch = gdbarch_list_lookup_by_info (best_arch->next, &info))
    {
      if (arm_abi != ARM_ABI_AUTO
          && arm_abi != gdbarch_tdep (best_arch->gdbarch)->arm_abi)
        continue;

      if (fp_model != ARM_FLOAT_AUTO
          && fp_model != gdbarch_tdep (best_arch->gdbarch)->fp_model)
        continue;

      /* Found a match.  */
      break;
    }

  if (best_arch != NULL)
    {
      if (tdesc_data != NULL)
        tdesc_data_cleanup (tdesc_data);
      return best_arch->gdbarch;
    }

  tdep = xcalloc (1, sizeof (struct gdbarch_tdep));
  gdbarch = gdbarch_alloc (&info, tdep);

  /* Record additional information about the architecture we are defining.
     These are gdbarch discriminators, like the OSABI.  */
  tdep->arm_abi = arm_abi;
  tdep->fp_model = fp_model;
  tdep->have_fpa_registers = have_fpa_registers;

  /* Breakpoints.  */
  switch (info.byte_order)
    {
    case BFD_ENDIAN_BIG:
      tdep->arm_breakpoint = arm_default_arm_be_breakpoint;
      tdep->arm_breakpoint_size = sizeof (arm_default_arm_be_breakpoint);
      tdep->thumb_breakpoint = arm_default_thumb_be_breakpoint;
      tdep->thumb_breakpoint_size = sizeof (arm_default_thumb_be_breakpoint);

      break;

    case BFD_ENDIAN_LITTLE:
      tdep->arm_breakpoint = arm_default_arm_le_breakpoint;
      tdep->arm_breakpoint_size = sizeof (arm_default_arm_le_breakpoint);
      tdep->thumb_breakpoint = arm_default_thumb_le_breakpoint;
      tdep->thumb_breakpoint_size = sizeof (arm_default_thumb_le_breakpoint);

      break;

    default:
      internal_error (__FILE__, __LINE__,
                      _("arm_gdbarch_init: bad byte order for float format"));
    }

  /* On ARM targets char defaults to unsigned.  */
  set_gdbarch_char_signed (gdbarch, 0);

  /* This should be low enough for everything.  */
  tdep->lowest_pc = 0x20;
  tdep->jb_pc = -1;     /* Longjump support not enabled by default.  */

  /* The default, for both APCS and AAPCS, is to return small
     structures in registers.  */
  tdep->struct_return = reg_struct_return;

  set_gdbarch_push_dummy_call (gdbarch, arm_push_dummy_call);
  set_gdbarch_frame_align (gdbarch, arm_frame_align);

  set_gdbarch_write_pc (gdbarch, arm_write_pc);

  /* Frame handling.  */
  set_gdbarch_dummy_id (gdbarch, arm_dummy_id);
  set_gdbarch_unwind_pc (gdbarch, arm_unwind_pc);
  set_gdbarch_unwind_sp (gdbarch, arm_unwind_sp);

  frame_base_set_default (gdbarch, &arm_normal_base);

  /* Address manipulation.  */
  set_gdbarch_smash_text_address (gdbarch, arm_smash_text_address);
  set_gdbarch_addr_bits_remove (gdbarch, arm_addr_bits_remove);

  /* Advance PC across function entry code.  */
  set_gdbarch_skip_prologue (gdbarch, arm_skip_prologue);

  /* Skip trampolines.  */
  set_gdbarch_skip_trampoline_code (gdbarch, arm_skip_stub);

  /* The stack grows downward.  */
  set_gdbarch_inner_than (gdbarch, core_addr_lessthan);

  /* Breakpoint manipulation.  */
  set_gdbarch_breakpoint_from_pc (gdbarch, arm_breakpoint_from_pc);

  /* Information about registers, etc.  */
  set_gdbarch_deprecated_fp_regnum (gdbarch, ARM_FP_REGNUM);    /* ??? */
  set_gdbarch_sp_regnum (gdbarch, ARM_SP_REGNUM);
  set_gdbarch_pc_regnum (gdbarch, ARM_PC_REGNUM);
  set_gdbarch_num_regs (gdbarch, ARM_NUM_REGS);
  set_gdbarch_register_type (gdbarch, arm_register_type);

  /* This "info float" is FPA-specific.  Use the generic version if we
     do not have FPA.  */
  if (gdbarch_tdep (gdbarch)->have_fpa_registers)
    set_gdbarch_print_float_info (gdbarch, arm_print_float_info);

  /* Internal <-> external register number maps.  */
  set_gdbarch_dwarf_reg_to_regnum (gdbarch, arm_dwarf_reg_to_regnum);
  set_gdbarch_dwarf2_reg_to_regnum (gdbarch, arm_dwarf_reg_to_regnum);
  set_gdbarch_register_sim_regno (gdbarch, arm_register_sim_regno);

  set_gdbarch_register_name (gdbarch, arm_register_name);

  /* Returning results.  */
  set_gdbarch_return_value (gdbarch, arm_return_value);

  /* Disassembly.  */
  set_gdbarch_print_insn (gdbarch, gdb_print_insn_arm);

  /* Minsymbol frobbing.  */
  set_gdbarch_elf_make_msymbol_special (gdbarch, arm_elf_make_msymbol_special);
  set_gdbarch_coff_make_msymbol_special (gdbarch,
                                         arm_coff_make_msymbol_special);

  /* Virtual tables.  */
  set_gdbarch_vbit_in_delta (gdbarch, 1);

  /* Hook in the ABI-specific overrides, if they have been registered.  */
  gdbarch_init_osabi (info, gdbarch);

  dwarf2_frame_set_init_reg (gdbarch, arm_dwarf2_frame_init_reg);

  /* Add some default predicates.  */
  frame_unwind_append_unwinder (gdbarch, &arm_stub_unwind);
  dwarf2_append_unwinders (gdbarch);
  frame_unwind_append_unwinder (gdbarch, &arm_prologue_unwind);

  /* Now we have tuned the configuration, set a few final things,
     based on what the OS ABI has told us.  */

  /* If the ABI is not otherwise marked, assume the old GNU APCS.  EABI
     binaries are always marked.  */
  if (tdep->arm_abi == ARM_ABI_AUTO)
    tdep->arm_abi = ARM_ABI_APCS;

  /* We used to default to FPA for generic ARM, but almost nobody
     uses that now, and we now provide a way for the user to force
     the model.  So default to the most useful variant.  */
  if (tdep->fp_model == ARM_FLOAT_AUTO)
    tdep->fp_model = ARM_FLOAT_SOFT_FPA;

  if (tdep->jb_pc >= 0)
    set_gdbarch_get_longjmp_target (gdbarch, arm_get_longjmp_target);

  /* Floating point sizes and format.  */
  set_gdbarch_float_format (gdbarch, floatformats_ieee_single);
  if (tdep->fp_model == ARM_FLOAT_SOFT_FPA || tdep->fp_model == ARM_FLOAT_FPA)
    {
      set_gdbarch_double_format
        (gdbarch, floatformats_ieee_double_littlebyte_bigword);
      set_gdbarch_long_double_format
        (gdbarch, floatformats_ieee_double_littlebyte_bigword);
    }
  else
    {
      set_gdbarch_double_format (gdbarch, floatformats_ieee_double);
      set_gdbarch_long_double_format (gdbarch, floatformats_ieee_double);
    }

  if (tdesc_data)
    tdesc_use_registers (gdbarch, info.target_desc, tdesc_data);

  /* Add standard register aliases.  We add aliases even for those
     nanes which are used by the current architecture - it's simpler,
     and does no harm, since nothing ever lists user registers.  */
  for (i = 0; i < ARRAY_SIZE (arm_register_aliases); i++)
    user_reg_add (gdbarch, arm_register_aliases[i].name,
                  value_of_arm_user_reg, &arm_register_aliases[i].regnum);

  return gdbarch;
}

static void
arm_dump_tdep (struct gdbarch *gdbarch, struct ui_file *file)
{
  struct gdbarch_tdep *tdep = gdbarch_tdep (gdbarch);

  if (tdep == NULL)
    return;

  fprintf_unfiltered (file, _("arm_dump_tdep: Lowest pc = 0x%lx"),
                      (unsigned long) tdep->lowest_pc);
}

extern initialize_file_ftype _initialize_arm_tdep; /* -Wmissing-prototypes */

void
_initialize_arm_tdep (void)
{
  struct ui_file *stb;
  long length;
  struct cmd_list_element *new_set, *new_show;
  const char *setname;
  const char *setdesc;
  const char *const *regnames;
  int numregs, i, j;
  static char *helptext;
  char regdesc[1024], *rdptr = regdesc;
  size_t rest = sizeof (regdesc);

  gdbarch_register (bfd_arch_arm, arm_gdbarch_init, arm_dump_tdep);

  /* Register an ELF OS ABI sniffer for ARM binaries.  */
  gdbarch_register_osabi_sniffer (bfd_arch_arm,
                                  bfd_target_elf_flavour,
                                  arm_elf_osabi_sniffer);

  /* Get the number of possible sets of register names defined in opcodes.  */
  num_disassembly_options = get_arm_regname_num_options ();

  /* Add root prefix command for all "set arm"/"show arm" commands.  */
  add_prefix_cmd ("arm", no_class, set_arm_command,
                  _("Various ARM-specific commands."),
                  &setarmcmdlist, "set arm ", 0, &setlist);

  add_prefix_cmd ("arm", no_class, show_arm_command,
                  _("Various ARM-specific commands."),
                  &showarmcmdlist, "show arm ", 0, &showlist);

  /* Sync the opcode insn printer with our register viewer.  */
  parse_arm_disassembler_option ("reg-names-std");

  /* Initialize the array that will be passed to
     add_setshow_enum_cmd().  */
  valid_disassembly_styles
    = xmalloc ((num_disassembly_options + 1) * sizeof (char *));
  for (i = 0; i < num_disassembly_options; i++)
    {
      numregs = get_arm_regnames (i, &setname, &setdesc, &regnames);
      valid_disassembly_styles[i] = setname;
      length = snprintf (rdptr, rest, "%s - %s\n", setname, setdesc);
      rdptr += length;
      rest -= length;
      /* When we find the default names, tell the disassembler to use
         them.  */
      if (!strcmp (setname, "std"))
        {
          disassembly_style = setname;
          set_arm_regname_option (i);
        }
    }
  /* Mark the end of valid options.  */
  valid_disassembly_styles[num_disassembly_options] = NULL;

  /* Create the help text.  */
  stb = mem_fileopen ();
  fprintf_unfiltered (stb, "%s%s%s",
                      _("The valid values are:\n"),
                      regdesc,
                      _("The default is \"std\"."));
  helptext = ui_file_xstrdup (stb, &length);
  ui_file_delete (stb);

  add_setshow_enum_cmd("disassembler", no_class,
                       valid_disassembly_styles, &disassembly_style,
                       _("Set the disassembly style."),
                       _("Show the disassembly style."),
                       helptext,
                       set_disassembly_style_sfunc,
                       NULL, /* FIXME: i18n: The disassembly style is \"%s\".  */
                       &setarmcmdlist, &showarmcmdlist);

  add_setshow_boolean_cmd ("apcs32", no_class, &arm_apcs_32,
                           _("Set usage of ARM 32-bit mode."),
                           _("Show usage of ARM 32-bit mode."),
                           _("When off, a 26-bit PC will be used."),
                           NULL,
                           NULL, /* FIXME: i18n: Usage of ARM 32-bit mode is %s.  */
                           &setarmcmdlist, &showarmcmdlist);

  /* Add a command to allow the user to force the FPU model.  */
  add_setshow_enum_cmd ("fpu", no_class, fp_model_strings, &current_fp_model,
                        _("Set the floating point type."),
                        _("Show the floating point type."),
                        _("auto - Determine the FP typefrom the OS-ABI.\n\
softfpa - Software FP, mixed-endian doubles on little-endian ARMs.\n\
fpa - FPA co-processor (GCC compiled).\n\
softvfp - Software FP with pure-endian doubles.\n\
vfp - VFP co-processor."),
                        set_fp_model_sfunc, show_fp_model,
                        &setarmcmdlist, &showarmcmdlist);

  /* Add a command to allow the user to force the ABI.  */
  add_setshow_enum_cmd ("abi", class_support, arm_abi_strings, &arm_abi_string,
                        _("Set the ABI."),
                        _("Show the ABI."),
                        NULL, arm_set_abi, arm_show_abi,
                        &setarmcmdlist, &showarmcmdlist);

  /* Add two commands to allow the user to force the assumed
     execution mode.  */
  add_setshow_enum_cmd ("fallback-mode", class_support,
                        arm_mode_strings, &arm_fallback_mode_string,
                        _("Set the mode assumed when symbols are unavailable."),
                        _("Show the mode assumed when symbols are unavailable."),
                        NULL, NULL, arm_show_fallback_mode,
                        &setarmcmdlist, &showarmcmdlist);
  add_setshow_enum_cmd ("force-mode", class_support,
                        arm_mode_strings, &arm_force_mode_string,
                        _("Set the mode assumed even when symbols are available."),
                        _("Show the mode assumed even when symbols are available."),
                        NULL, NULL, arm_show_force_mode,
                        &setarmcmdlist, &showarmcmdlist);

  /* Debugging flag.  */
  add_setshow_boolean_cmd ("arm", class_maintenance, &arm_debug,
                           _("Set ARM debugging."),
                           _("Show ARM debugging."),
                           _("When on, arm-specific debugging is enabled."),
                           NULL,
                           NULL, /* FIXME: i18n: "ARM debugging is %s.  */
                           &setdebuglist, &showdebuglist);
}