From 7f0c12ed449f88fa4cfd83151d61669445ba9672 Mon Sep 17 00:00:00 2001 From: Michal Ludvig Date: Fri, 21 Jun 2002 12:12:34 +0000 Subject: [PATCH] 2002-06-21 Michal Ludvig * dwarf2cfi.c (read_encoded_pointer): Don't handle pointer encoding anymore. (pointer_encoding, enum ptr_encoding): New. (execute_cfa_program): Take care about pointer encoding. (dwarf2_build_frame_info): Only call parse_frame_info for .debug_frame and .eh_frame. (parse_frame_info): New, derived from former dwarf2_build_frame_info. fixed augmentation handling, added relative addressing, ignore duplicate FDEs. Added comments. --- gdb/ChangeLog | 12 ++ gdb/dwarf2cfi.c | 338 +++++++++++++++++++++++++++++++++++------------- 2 files changed, 261 insertions(+), 89 deletions(-) diff --git a/gdb/ChangeLog b/gdb/ChangeLog index f69031bfaae..76c3a8cd517 100644 --- a/gdb/ChangeLog +++ b/gdb/ChangeLog @@ -1,3 +1,15 @@ +2002-06-21 Michal Ludvig + + * dwarf2cfi.c (read_encoded_pointer): Don't handle pointer + encoding anymore. + (pointer_encoding, enum ptr_encoding): New. + (execute_cfa_program): Take care about pointer encoding. + (dwarf2_build_frame_info): Only call parse_frame_info for + .debug_frame and .eh_frame. + (parse_frame_info): New, derived from former dwarf2_build_frame_info. + fixed augmentation handling, added relative addressing, + ignore duplicate FDEs. Added comments. + 2002-06-20 Elena Zannoni * event-top.c (command_handler): Don't use space_at_cmd_start diff --git a/gdb/dwarf2cfi.c b/gdb/dwarf2cfi.c index ea501551c8e..ed319fb64b6 100644 --- a/gdb/dwarf2cfi.c +++ b/gdb/dwarf2cfi.c @@ -34,7 +34,7 @@ Frame Descriptors. */ struct cie_unit { - /* Offset of this unit in dwarf_frame_buffer. */ + /* Offset of this unit in .debug_frame or .eh_frame. */ ULONGEST offset; /* A null-terminated string that identifies the augmentation to this CIE or @@ -176,6 +176,14 @@ struct frame_state struct objfile *objfile; }; +enum ptr_encoding { + PE_absptr = DW_EH_PE_absptr, + PE_pcrel = DW_EH_PE_pcrel, + PE_textrel = DW_EH_PE_textrel, + PE_datarel = DW_EH_PE_datarel, + PE_funcrel = DW_EH_PE_funcrel +}; + #define UNWIND_CONTEXT(fi) ((struct context *) (fi->context)) @@ -188,8 +196,6 @@ extern file_ptr dwarf_frame_offset; extern unsigned int dwarf_frame_size; extern file_ptr dwarf_eh_frame_offset; extern unsigned int dwarf_eh_frame_size; - -static char *dwarf_frame_buffer; extern char *dwarf2_read_section (struct objfile *objfile, file_ptr offset, @@ -219,6 +225,7 @@ static LONGEST read_sleb128 (bfd * abfd, char **p); static CORE_ADDR read_pointer (bfd * abfd, char **p); static CORE_ADDR read_encoded_pointer (bfd * abfd, char **p, unsigned char encoding); +static enum ptr_encoding pointer_encoding (unsigned char encoding); static LONGEST read_initial_length (bfd * abfd, char *buf, int *bytes_read); static ULONGEST read_length (bfd * abfd, char *buf, int *bytes_read, @@ -494,6 +501,9 @@ read_pointer (bfd * abfd, char **p) } } +/* This functions only reads appropriate amount of data from *p + * and returns the resulting value. Calling function must handle + * different encoding possibilities itself! */ static CORE_ADDR read_encoded_pointer (bfd * abfd, char **p, unsigned char encoding) { @@ -537,22 +547,34 @@ read_encoded_pointer (bfd * abfd, char **p, unsigned char encoding) "read_encoded_pointer: unknown pointer encoding"); } - if (ret != 0) - switch (encoding & 0xf0) - { - case DW_EH_PE_absptr: - break; - case DW_EH_PE_pcrel: - ret += (CORE_ADDR) * p; - break; - case DW_EH_PE_textrel: - case DW_EH_PE_datarel: - case DW_EH_PE_funcrel: - default: - internal_error (__FILE__, __LINE__, - "read_encoded_pointer: unknown pointer encoding"); - } + return ret; +} + +/* Variable 'encoding' carries 3 different flags: + * - encoding & 0x0f : size of the address (handled in read_encoded_pointer()) + * - encoding & 0x70 : type (absolute, relative, ...) + * - encoding & 0x80 : indirect flag (DW_EH_PE_indirect == 0x80). */ +enum ptr_encoding +pointer_encoding (unsigned char encoding) +{ + int ret; + if (encoding & DW_EH_PE_indirect) + warning ("CFI: Unsupported pointer encoding: DW_EH_PE_indirect"); + + switch (encoding & 0x70) + { + case DW_EH_PE_absptr: + case DW_EH_PE_pcrel: + case DW_EH_PE_textrel: + case DW_EH_PE_datarel: + case DW_EH_PE_funcrel: + ret = encoding & 0x70; + break; + default: + internal_error (__FILE__, __LINE__, + "CFI: unknown pointer encoding"); + } return ret; } @@ -627,6 +649,10 @@ execute_cfa_program (struct objfile *objfile, char *insn_ptr, char *insn_end, case DW_CFA_set_loc: fs->pc = read_encoded_pointer (objfile->obfd, &insn_ptr, fs->addr_encoding); + + if (pointer_encoding (fs->addr_encoding) != PE_absptr) + warning ("CFI: DW_CFA_set_loc uses relative addressing"); + break; case DW_CFA_advance_loc1: @@ -1380,39 +1406,46 @@ compare_fde_unit (const void *a, const void *b) } /* Build the cie_chunks and fde_chunks tables from informations - in .debug_frame section. */ -void -dwarf2_build_frame_info (struct objfile *objfile) + found in .debug_frame and .eh_frame sections. */ +/* We can handle both of these sections almost in the same way, however there + are some exceptions: + - CIE ID is -1 in debug_frame, but 0 in eh_frame + - eh_frame may contain some more information that are used only by gcc + (eg. personality pointer, LSDA pointer, ...). Most of them we can ignore. + - In debug_frame FDE's item cie_id contains offset of it's parent CIE. + In eh_frame FDE's item cie_id is a relative pointer to the parent CIE. + Anyway we don't need to bother with this, because we are smart enough + to keep the pointer to the parent CIE of oncomming FDEs in 'last_cie'. + - Although debug_frame items can contain Augmentation as well as + eh_frame ones, I have never seen them non-empty. Thus only in eh_frame + we can encounter for example non-absolute pointers (Aug. 'R'). + -- mludvig */ +static void +parse_frame_info (struct objfile *objfile, file_ptr frame_offset, + unsigned int frame_size, int eh_frame) { bfd *abfd = objfile->obfd; + asection *curr_section_ptr; char *start = NULL; char *end = NULL; - int from_eh = 0; + char *frame_buffer = NULL; + char *curr_section_name, *aug_data; + struct cie_unit *last_cie = NULL; + int last_dup_fde = 0; + int aug_len, i; + CORE_ADDR curr_section_vma = 0; unwind_tmp_obstack_init (); - dwarf_frame_buffer = 0; + frame_buffer = dwarf2_read_section (objfile, frame_offset, frame_size); - if (dwarf_frame_offset) - { - dwarf_frame_buffer = dwarf2_read_section (objfile, - dwarf_frame_offset, - dwarf_frame_size); + start = frame_buffer; + end = frame_buffer + frame_size; - start = dwarf_frame_buffer; - end = dwarf_frame_buffer + dwarf_frame_size; - } - else if (dwarf_eh_frame_offset) - { - dwarf_frame_buffer = dwarf2_read_section (objfile, - dwarf_eh_frame_offset, - dwarf_eh_frame_size); - - start = dwarf_frame_buffer; - end = dwarf_frame_buffer + dwarf_eh_frame_size; - - from_eh = 1; - } + curr_section_name = eh_frame ? ".eh_frame" : ".debug_frame"; + curr_section_ptr = bfd_get_section_by_name (abfd, curr_section_name); + if (curr_section_ptr) + curr_section_vma = curr_section_ptr->vma; if (start) { @@ -1420,9 +1453,8 @@ dwarf2_build_frame_info (struct objfile *objfile) { unsigned long length; ULONGEST cie_id; - ULONGEST unit_offset = start - dwarf_frame_buffer; - int bytes_read; - int dwarf64; + ULONGEST unit_offset = start - frame_buffer; + int bytes_read, dwarf64, flag_pcrel; char *block_end; length = read_initial_length (abfd, start, &bytes_read); @@ -1430,10 +1462,16 @@ dwarf2_build_frame_info (struct objfile *objfile) dwarf64 = (bytes_read == 12); block_end = start + length; + if (length == 0) + { + start = block_end; + continue; + } + cie_id = read_length (abfd, start, &bytes_read, dwarf64); start += bytes_read; - if ((from_eh && cie_id == 0) || is_cie (cie_id, dwarf64)) + if ((eh_frame && cie_id == 0) || is_cie (cie_id, dwarf64)) { struct cie_unit *cie = cie_unit_alloc (); char *aug; @@ -1449,87 +1487,186 @@ dwarf2_build_frame_info (struct objfile *objfile) start++; /* version */ cie->augmentation = aug = start; - while (*start) - start++; - start++; /* skip past NUL */ + while (*start++); /* Skips last NULL as well */ cie->code_align = read_uleb128 (abfd, &start); cie->data_align = read_sleb128 (abfd, &start); cie->ra = read_1u (abfd, &start); + /* Augmentation: + z Indicates that a uleb128 is present to size the + augmentation section. + L Indicates the encoding (and thus presence) of + an LSDA pointer in the FDE augmentation. + R Indicates a non-default pointer encoding for + FDE code pointers. + P Indicates the presence of an encoding + language + personality routine in the CIE augmentation. + + [This info comes from GCC's dwarf2out.c] + */ if (*aug == 'z') { - int xtra = read_uleb128 (abfd, &start); - start += xtra; + aug_len = read_uleb128 (abfd, &start); + aug_data = start; + start += aug_len; ++aug; } + cie->data = start; + cie->data_length = block_end - cie->data; + while (*aug != '\0') { if (aug[0] == 'e' && aug[1] == 'h') { - start += sizeof (void *); - aug += 2; + aug_data += sizeof (void *); + aug++; } else if (aug[0] == 'R') + cie->addr_encoding = *aug_data++; + else if (aug[0] == 'P') { - cie->addr_encoding = *start++; - aug += 1; + CORE_ADDR pers_addr; + int pers_addr_enc; + + pers_addr_enc = *aug_data++; + /* We don't need pers_addr value and so we + don't care about it's encoding. */ + pers_addr = read_encoded_pointer (abfd, &aug_data, + pers_addr_enc); } - else if (aug[0] == 'P') + else if (aug[0] == 'L' && eh_frame) { - CORE_ADDR ptr; - ptr = read_encoded_pointer (abfd, &start, - cie->addr_encoding); - aug += 1; + int lsda_addr_enc; + + /* Perhaps we should save this to CIE for later use? + Do we need it for something in GDB? */ + lsda_addr_enc = *aug_data++; } else - warning ("%s(): unknown augmentation", __func__); + warning ("CFI warning: unknown augmentation \"%c\"" + " in \"%s\" of\n" + "\t%s", aug[0], curr_section_name, + objfile->name); + aug++; } - cie->data = start; - cie->data_length = block_end - start; + last_cie = cie; } else { struct fde_unit *fde; struct cie_unit *cie; + int dup = 0; + CORE_ADDR init_loc; + + /* We assume that debug_frame is in order + CIE,FDE,CIE,FDE,FDE,... and thus the CIE for this FDE + should be stored in last_cie pointer. If not, we'll + try to find it by the older way. */ + if (last_cie) + cie = last_cie; + else + { + warning ("CFI: last_cie == NULL. " + "Perhaps a malformed %s section in '%s'...?\n", + curr_section_name, objfile->name); - fde_chunks_need_space (); - fde = fde_unit_alloc (); + cie = cie_chunks; + while (cie) + { + if (cie->objfile == objfile) + { + if (eh_frame && + (cie->offset == + (unit_offset + bytes_read - cie_id))) + break; + if (!eh_frame && (cie->offset == cie_id)) + break; + } + + cie = cie->next; + } + if (!cie) + error ("CFI: can't find CIE pointer"); + } - fde_chunks.array[fde_chunks.elems++] = fde; + init_loc = read_encoded_pointer (abfd, &start, + cie->addr_encoding); - fde->initial_location = read_pointer (abfd, &start) - + ANOFFSET (objfile->section_offsets, - SECT_OFF_TEXT (objfile)); - fde->address_range = read_pointer (abfd, &start); + switch (pointer_encoding (cie->addr_encoding)) + { + case PE_absptr: + break; + case PE_pcrel: + /* start-frame_buffer gives offset from + the beginning of actual section. */ + init_loc += curr_section_vma + start - frame_buffer; + break; + default: + warning ("CFI: Unsupported pointer encoding\n"); + } - cie = cie_chunks; - while (cie) + /* For relocatable objects we must add an offset telling + where the section is actually mapped in the memory. */ + init_loc += ANOFFSET (objfile->section_offsets, + SECT_OFF_TEXT (objfile)); + + /* If we have both .debug_frame and .eh_frame present in + a file, we must eliminate duplicate FDEs. For now we'll + run through all entries in fde_chunks and check it one + by one. Perhaps in the future we can implement a faster + searching algorithm. */ + /* eh_frame==2 indicates, that this file has an already + parsed .debug_frame too. When eh_frame==1 it means, that no + .debug_frame is present and thus we don't need to check for + duplicities. eh_frame==0 means, that we parse .debug_frame + and don't need to care about duplicate FDEs, because + .debug_frame is parsed first. */ + if (eh_frame == 2) + for (i = 0; eh_frame == 2 && i < fde_chunks.elems; i++) { - if (cie->objfile == objfile) + /* We assume that FDEs in .debug_frame and .eh_frame + have the same order (if they are present, of course). + If we find a duplicate entry for one FDE and save + it's index to last_dup_fde it's very likely, that + we'll find an entry for the following FDE right after + the previous one. Thus in many cases we'll run this + loop only once. */ + last_dup_fde = (last_dup_fde + i) % fde_chunks.elems; + if (fde_chunks.array[last_dup_fde]->initial_location + == init_loc) { - if (from_eh - && (cie->offset == - (unit_offset + bytes_read - cie_id))) - break; - if (!from_eh && (cie->offset == cie_id)) - break; + dup = 1; + break; } - - cie = cie->next; } - if (!cie) - error ("%s(): can't find CIE pointer", __func__); - fde->cie_ptr = cie; + /* Allocate a new entry only if this FDE isn't a duplicate of + something we have already seen. */ + if (!dup) + { + fde_chunks_need_space (); + fde = fde_unit_alloc (); + + fde_chunks.array[fde_chunks.elems++] = fde; + + fde->initial_location = init_loc; + fde->address_range = read_encoded_pointer (abfd, &start, + cie-> + addr_encoding); - if (cie->augmentation[0] == 'z') - read_uleb128 (abfd, &start); + fde->cie_ptr = cie; - fde->data = start; - fde->data_length = block_end - start; + /* Here we intentionally ignore augmentation data + from FDE, because we don't need them. */ + if (cie->augmentation[0] == 'z') + start += read_uleb128 (abfd, &start); + + fde->data = start; + fde->data_length = block_end - start; + } } start = block_end; } @@ -1537,7 +1674,30 @@ dwarf2_build_frame_info (struct objfile *objfile) sizeof (struct fde_unit *), compare_fde_unit); } } - + +/* We must parse both .debug_frame section and .eh_frame because + * not all frames must be present in both of these sections. */ +void +dwarf2_build_frame_info (struct objfile *objfile) +{ + int after_debug_frame = 0; + + /* If we have .debug_frame then the parser is called with + eh_frame==0 for .debug_frame and eh_frame==2 for .eh_frame, + otherwise it's only called once for .eh_frame with argument + eh_frame==1. */ + + if (dwarf_frame_offset) + { + parse_frame_info (objfile, dwarf_frame_offset, + dwarf_frame_size, 0 /* = debug_frame */); + after_debug_frame = 1; + } + + if (dwarf_eh_frame_offset) + parse_frame_info (objfile, dwarf_eh_frame_offset, dwarf_eh_frame_size, + 1 /* = eh_frame */ + after_debug_frame); +} /* Return the frame address. */ CORE_ADDR -- 2.30.2