libgcc/config/pa/linux-unwind.h

   1 /* DWARF2 EH unwinding support for PA Linux.
   2    Copyright (C) 2004, 2005, 2009, 2012 Free Software Foundation, Inc.
   3
   4 This file is part of GCC.
   5
   6 GCC is free software; you can redistribute it and/or modify
   7 it under the terms of the GNU General Public License as published by
   8 the Free Software Foundation; either version 3, or (at your option)
   9 any later version.
  10
  11 GCC is distributed in the hope that it will be useful,
  12 but WITHOUT ANY WARRANTY; without even the implied warranty of
  13 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14 GNU General Public License for more details.
  15
  16 Under Section 7 of GPL version 3, you are granted additional
  17 permissions described in the GCC Runtime Library Exception, version
  18 3.1, as published by the Free Software Foundation.
  19
  20 You should have received a copy of the GNU General Public License and
  21 a copy of the GCC Runtime Library Exception along with this program;
  22 see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
  23 <http://www.gnu.org/licenses/>.  */
  24
  25
  26 /* Do code reading to identify a signal frame, and set the frame
  27    state data appropriately.  See unwind-dw2.c for the structs.  */
  28
  29 /* Don't use this if inhibit_libc is set.
  30    The build for this target will fail trying to include missing headers. */
  31 #ifndef inhibit_libc
  32 #include <signal.h>
  33 #include <sys/ucontext.h>
  34
  35 /* Unfortunately, because of various bugs and changes to the kernel,
  36    we have several cases to deal with.
  37
  38    In 2.4, the signal trampoline is 4 words, and (CONTEXT)->ra should
  39    point directly at the beginning of the trampoline and struct rt_sigframe.
  40
  41    In <= 2.6.5-rc2-pa3, the signal trampoline is 9 words, and
  42    (CONTEXT)->ra points at the 4th word in the trampoline structure.  This
  43    is wrong, it should point at the 5th word.  This is fixed in 2.6.5-rc2-pa4.
  44
  45    To detect these cases, we first take (CONTEXT)->ra, align it to 64-bytes
  46    to get the beginning of the signal frame, and then check offsets 0, 4
  47    and 5 to see if we found the beginning of the trampoline.  This will
  48    tell us how to locate the sigcontext structure.
  49
  50    Note that with a 2.4 64-bit kernel, the signal context is not properly
  51    passed back to userspace so the unwind will not work correctly.  */
  52
  53 #define MD_FALLBACK_FRAME_STATE_FOR pa32_fallback_frame_state
  54
  55 static _Unwind_Reason_Code
  56 pa32_fallback_frame_state (struct _Unwind_Context *context,
  57                            _Unwind_FrameState *fs)
  58 {
  59   unsigned long sp = (unsigned long)context->ra & ~63;
  60   unsigned int *pc = (unsigned int *)sp;
  61   unsigned long off;
  62   _Unwind_Ptr new_cfa;
  63   int i;
  64   struct sigcontext *sc;
  65   struct rt_sigframe {
  66     siginfo_t info;
  67     struct ucontext uc;
  68   } *frame;
  69
  70   /* rt_sigreturn trampoline:
  71      3419000x ldi 0, %r25 or ldi 1, %r25   (x = 0 or 2)
  72      3414015a ldi __NR_rt_sigreturn, %r20
  73      e4008200 be,l 0x100(%sr2, %r0), %sr0, %r31
  74      08000240 nop  */
  75
  76   if (pc[0] == 0x34190000 || pc[0] == 0x34190002)
  77     off = 4*4;
  78   else if (pc[4] == 0x34190000 || pc[4] == 0x34190002)
  79     {
  80       pc += 4;
  81       off = 10 * 4;
  82     }
  83   else if (pc[5] == 0x34190000 || pc[5] == 0x34190002)
  84     {
  85       pc += 5;
  86       off = 10 * 4;
  87     }
  88   else
  89     {
  90       /* We may have to unwind through an alternate signal stack.
  91          We assume that the alignment of the alternate signal stack
  92          is BIGGEST_ALIGNMENT (i.e., that it has been allocated using
  93          malloc).  As a result, we can't distinguish trampolines
  94          used prior to 2.6.5-rc2-pa4.  However after 2.6.5-rc2-pa4,
  95          the return address of a signal trampoline will be on an odd
  96          word boundary and we can then determine the frame offset.  */
  97       sp = (unsigned long)context->ra;
  98       pc = (unsigned int *)sp;
  99       if ((pc[0] == 0x34190000 || pc[0] == 0x34190002) && (sp & 4))
 100         off = 5 * 4;
 101       else
 102         return _URC_END_OF_STACK;
 103     }
 104
 105   if (pc[1] != 0x3414015a
 106       || pc[2] != 0xe4008200
 107       || pc[3] != 0x08000240)
 108     return _URC_END_OF_STACK;
 109
 110   frame = (struct rt_sigframe *)(sp + off);
 111   sc = &frame->uc.uc_mcontext;
 112
 113   new_cfa = sc->sc_gr[30];
 114   fs->regs.cfa_how = CFA_REG_OFFSET;
 115   fs->regs.cfa_reg = 30;
 116   fs->regs.cfa_offset = new_cfa - (long) context->cfa;
 117   for (i = 1; i <= 31; i++)
 118     {
 119       fs->regs.reg[i].how = REG_SAVED_OFFSET;
 120       fs->regs.reg[i].loc.offset = (long)&sc->sc_gr[i] - new_cfa;
 121     }
 122   for (i = 4; i <= 31; i++)
 123     {
 124       /* FP regs have left and right halves */
 125       fs->regs.reg[2*i+24].how = REG_SAVED_OFFSET;
 126       fs->regs.reg[2*i+24].loc.offset
 127         = (long)&sc->sc_fr[i] - new_cfa;
 128       fs->regs.reg[2*i+24+1].how = REG_SAVED_OFFSET;
 129       fs->regs.reg[2*i+24+1].loc.offset
 130         = (long)&sc->sc_fr[i] + 4 - new_cfa;
 131     }
 132   fs->regs.reg[88].how = REG_SAVED_OFFSET;
 133   fs->regs.reg[88].loc.offset = (long) &sc->sc_sar - new_cfa;
 134   fs->regs.reg[DWARF_ALT_FRAME_RETURN_COLUMN].how = REG_SAVED_OFFSET;
 135   fs->regs.reg[DWARF_ALT_FRAME_RETURN_COLUMN].loc.offset
 136     = (long) &sc->sc_iaoq[0] - new_cfa;
 137   fs->retaddr_column = DWARF_ALT_FRAME_RETURN_COLUMN;
 138   fs->signal_frame = 1;
 139   return _URC_NO_REASON;
 140 }
 141 #endif /* inhibit_libc */