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/* .eh_frame section optimization. Copyright 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009 Free Software Foundation, Inc. Written by Jakub Jelinek <jakub@redhat.com>. This file is part of BFD, the Binary File Descriptor library. 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, write to the Free Software Foundation, Inc., 51 Franklin Street - Fifth Floor, Boston, MA 02110-1301, USA. */ #include "sysdep.h" #include "bfd.h" #include "libbfd.h" #include "elf-bfd.h" #include "dwarf2.h" #define EH_FRAME_HDR_SIZE 8 struct cie { unsigned int length; unsigned int hash; unsigned char version; unsigned char local_personality; char augmentation[20]; bfd_vma code_align; bfd_signed_vma data_align; bfd_vma ra_column; bfd_vma augmentation_size; union { struct elf_link_hash_entry *h; bfd_vma val; unsigned int reloc_index; } personality; asection *output_sec; struct eh_cie_fde *cie_inf; unsigned char per_encoding; unsigned char lsda_encoding; unsigned char fde_encoding; unsigned char initial_insn_length; unsigned char can_make_lsda_relative; unsigned char initial_instructions[50]; }; /* If *ITER hasn't reached END yet, read the next byte into *RESULT and move onto the next byte. Return true on success. */ static inline bfd_boolean read_byte (bfd_byte **iter, bfd_byte *end, unsigned char *result) { if (*iter >= end) return FALSE; *result = *((*iter)++); return TRUE; } /* Move *ITER over LENGTH bytes, or up to END, whichever is closer. Return true it was possible to move LENGTH bytes. */ static inline bfd_boolean skip_bytes (bfd_byte **iter, bfd_byte *end, bfd_size_type length) { if ((bfd_size_type) (end - *iter) < length) { *iter = end; return FALSE; } *iter += length; return TRUE; } /* Move *ITER over an leb128, stopping at END. Return true if the end of the leb128 was found. */ static bfd_boolean skip_leb128 (bfd_byte **iter, bfd_byte *end) { unsigned char byte; do if (!read_byte (iter, end, &byte)) return FALSE; while (byte & 0x80); return TRUE; } /* Like skip_leb128, but treat the leb128 as an unsigned value and store it in *VALUE. */ static bfd_boolean read_uleb128 (bfd_byte **iter, bfd_byte *end, bfd_vma *value) { bfd_byte *start, *p; start = *iter; if (!skip_leb128 (iter, end)) return FALSE; p = *iter; *value = *--p; while (p > start) *value = (*value << 7) | (*--p & 0x7f); return TRUE; } /* Like read_uleb128, but for signed values. */ static bfd_boolean read_sleb128 (bfd_byte **iter, bfd_byte *end, bfd_signed_vma *value) { bfd_byte *start, *p; start = *iter; if (!skip_leb128 (iter, end)) return FALSE; p = *iter; *value = ((*--p & 0x7f) ^ 0x40) - 0x40; while (p > start) *value = (*value << 7) | (*--p & 0x7f); return TRUE; } /* Return 0 if either encoding is variable width, or not yet known to bfd. */ static int get_DW_EH_PE_width (int encoding, int ptr_size) { /* DW_EH_PE_ values of 0x60 and 0x70 weren't defined at the time .eh_frame was added to bfd. */ if ((encoding & 0x60) == 0x60) return 0; switch (encoding & 7) { case DW_EH_PE_udata2: return 2; case DW_EH_PE_udata4: return 4; case DW_EH_PE_udata8: return 8; case DW_EH_PE_absptr: return ptr_size; default: break; } return 0; } #define get_DW_EH_PE_signed(encoding) (((encoding) & DW_EH_PE_signed) != 0) /* Read a width sized value from memory. */ static bfd_vma read_value (bfd *abfd, bfd_byte *buf, int width, int is_signed) { bfd_vma value; switch (width) { case 2: if (is_signed) value = bfd_get_signed_16 (abfd, buf); else value = bfd_get_16 (abfd, buf); break; case 4: if (is_signed) value = bfd_get_signed_32 (abfd, buf); else value = bfd_get_32 (abfd, buf); break; case 8: if (is_signed) value = bfd_get_signed_64 (abfd, buf); else value = bfd_get_64 (abfd, buf); break; default: BFD_FAIL (); return 0; } return value; } /* Store a width sized value to memory. */ static void write_value (bfd *abfd, bfd_byte *buf, bfd_vma value, int width) { switch (width) { case 2: bfd_put_16 (abfd, value, buf); break; case 4: bfd_put_32 (abfd, value, buf); break; case 8: bfd_put_64 (abfd, value, buf); break; default: BFD_FAIL (); } } /* Return one if C1 and C2 CIEs can be merged. */ static int cie_eq (const void *e1, const void *e2) { const struct cie *c1 = (const struct cie *) e1; const struct cie *c2 = (const struct cie *) e2; if (c1->hash == c2->hash && c1->length == c2->length && c1->version == c2->version && c1->local_personality == c2->local_personality && strcmp (c1->augmentation, c2->augmentation) == 0 && strcmp (c1->augmentation, "eh") != 0 && c1->code_align == c2->code_align && c1->data_align == c2->data_align && c1->ra_column == c2->ra_column && c1->augmentation_size == c2->augmentation_size && memcmp (&c1->personality, &c2->personality, sizeof (c1->personality)) == 0 && c1->output_sec == c2->output_sec && c1->per_encoding == c2->per_encoding && c1->lsda_encoding == c2->lsda_encoding && c1->fde_encoding == c2->fde_encoding && c1->initial_insn_length == c2->initial_insn_length && memcmp (c1->initial_instructions, c2->initial_instructions, c1->initial_insn_length) == 0) return 1; return 0; } static hashval_t cie_hash (const void *e) { const struct cie *c = (const struct cie *) e; return c->hash; } static hashval_t cie_compute_hash (struct cie *c) { hashval_t h = 0; h = iterative_hash_object (c->length, h); h = iterative_hash_object (c->version, h); h = iterative_hash (c->augmentation, strlen (c->augmentation) + 1, h); h = iterative_hash_object (c->code_align, h); h = iterative_hash_object (c->data_align, h); h = iterative_hash_object (c->ra_column, h); h = iterative_hash_object (c->augmentation_size, h); h = iterative_hash_object (c->personality, h); h = iterative_hash_object (c->output_sec, h); h = iterative_hash_object (c->per_encoding, h); h = iterative_hash_object (c->lsda_encoding, h); h = iterative_hash_object (c->fde_encoding, h); h = iterative_hash_object (c->initial_insn_length, h); h = iterative_hash (c->initial_instructions, c->initial_insn_length, h); c->hash = h; return h; } /* Return the number of extra bytes that we'll be inserting into ENTRY's augmentation string. */ static INLINE unsigned int extra_augmentation_string_bytes (struct eh_cie_fde *entry) { unsigned int size = 0; if (entry->cie) { if (entry->add_augmentation_size) size++; if (entry->u.cie.add_fde_encoding) size++; } return size; } /* Likewise ENTRY's augmentation data. */ static INLINE unsigned int extra_augmentation_data_bytes (struct eh_cie_fde *entry) { unsigned int size = 0; if (entry->add_augmentation_size) size++; if (entry->cie && entry->u.cie.add_fde_encoding) size++; return size; } /* Return the size that ENTRY will have in the output. ALIGNMENT is the required alignment of ENTRY in bytes. */ static unsigned int size_of_output_cie_fde (struct eh_cie_fde *entry, unsigned int alignment) { if (entry->removed) return 0; if (entry->size == 4) return 4; return (entry->size + extra_augmentation_string_bytes (entry) + extra_augmentation_data_bytes (entry) + alignment - 1) & -alignment; } /* Assume that the bytes between *ITER and END are CFA instructions. Try to move *ITER past the first instruction and return true on success. ENCODED_PTR_WIDTH gives the width of pointer entries. */ static bfd_boolean skip_cfa_op (bfd_byte **iter, bfd_byte *end, unsigned int encoded_ptr_width) { bfd_byte op; bfd_vma length; if (!read_byte (iter, end, &op)) return FALSE; switch (op & 0xc0 ? op & 0xc0 : op) { case DW_CFA_nop: case DW_CFA_advance_loc: case DW_CFA_restore: case DW_CFA_remember_state: case DW_CFA_restore_state: case DW_CFA_GNU_window_save: /* No arguments. */ return TRUE; case DW_CFA_offset: case DW_CFA_restore_extended: case DW_CFA_undefined: case DW_CFA_same_value: case DW_CFA_def_cfa_register: case DW_CFA_def_cfa_offset: case DW_CFA_def_cfa_offset_sf: case DW_CFA_GNU_args_size: /* One leb128 argument. */ return skip_leb128 (iter, end); case DW_CFA_val_offset: case DW_CFA_val_offset_sf: case DW_CFA_offset_extended: case DW_CFA_register: case DW_CFA_def_cfa: case DW_CFA_offset_extended_sf: case DW_CFA_GNU_negative_offset_extended: case DW_CFA_def_cfa_sf: /* Two leb128 arguments. */ return (skip_leb128 (iter, end) && skip_leb128 (iter, end)); case DW_CFA_def_cfa_expression: /* A variable-length argument. */ return (read_uleb128 (iter, end, &length) && skip_bytes (iter, end, length)); case DW_CFA_expression: case DW_CFA_val_expression: /* A leb128 followed by a variable-length argument. */ return (skip_leb128 (iter, end) && read_uleb128 (iter, end, &length) && skip_bytes (iter, end, length)); case DW_CFA_set_loc: return skip_bytes (iter, end, encoded_ptr_width); case DW_CFA_advance_loc1: return skip_bytes (iter, end, 1); case DW_CFA_advance_loc2: return skip_bytes (iter, end, 2); case DW_CFA_advance_loc4: return skip_bytes (iter, end, 4); case DW_CFA_MIPS_advance_loc8: return skip_bytes (iter, end, 8); default: return FALSE; } } /* Try to interpret the bytes between BUF and END as CFA instructions. If every byte makes sense, return a pointer to the first DW_CFA_nop padding byte, or END if there is no padding. Return null otherwise. ENCODED_PTR_WIDTH is as for skip_cfa_op. */ static bfd_byte * skip_non_nops (bfd_byte *buf, bfd_byte *end, unsigned int encoded_ptr_width, unsigned int *set_loc_count) { bfd_byte *last; last = buf; while (buf < end) if (*buf == DW_CFA_nop) buf++; else { if (*buf == DW_CFA_set_loc) ++*set_loc_count; if (!skip_cfa_op (&buf, end, encoded_ptr_width)) return 0; last = buf; } return last; } /* Convert absolute encoding ENCODING into PC-relative form. SIZE is the size of a pointer. */ static unsigned char make_pc_relative (unsigned char encoding, unsigned int ptr_size) { if ((encoding & 0x7f) == DW_EH_PE_absptr) switch (ptr_size) { case 2: encoding |= DW_EH_PE_sdata2; break; case 4: encoding |= DW_EH_PE_sdata4; break; case 8: encoding |= DW_EH_PE_sdata8; break; } return encoding | DW_EH_PE_pcrel; } /* Called before calling _bfd_elf_parse_eh_frame on every input bfd's .eh_frame section. */ void _bfd_elf_begin_eh_frame_parsing (struct bfd_link_info *info) { struct eh_frame_hdr_info *hdr_info; hdr_info = &elf_hash_table (info)->eh_info; hdr_info->merge_cies = !info->relocatable; } /* Try to parse .eh_frame section SEC, which belongs to ABFD. Store the information in the section's sec_info field on success. COOKIE describes the relocations in SEC. */ void _bfd_elf_parse_eh_frame (bfd *abfd, struct bfd_link_info *info, asection *sec, struct elf_reloc_cookie *cookie) { #define REQUIRE(COND) \ do \ if (!(COND)) \ goto free_no_table; \ while (0) bfd_byte *ehbuf = NULL, *buf, *end; bfd_byte *last_fde; struct eh_cie_fde *this_inf; unsigned int hdr_length, hdr_id; unsigned int cie_count; struct cie *cie, *local_cies = NULL; struct elf_link_hash_table *htab; struct eh_frame_hdr_info *hdr_info; struct eh_frame_sec_info *sec_info = NULL; unsigned int ptr_size; unsigned int num_cies; unsigned int num_entries; elf_gc_mark_hook_fn gc_mark_hook; htab = elf_hash_table (info); hdr_info = &htab->eh_info; if (hdr_info->parsed_eh_frames) return; if (sec->size == 0) { /* This file does not contain .eh_frame information. */ return; } if (bfd_is_abs_section (sec->output_section)) { /* At least one of the sections is being discarded from the link, so we should just ignore them. */ return; } /* Read the frame unwind information from abfd. */ REQUIRE (bfd_malloc_and_get_section (abfd, sec, &ehbuf)); if (sec->size >= 4 && bfd_get_32 (abfd, ehbuf) == 0 && cookie->rel == cookie->relend) { /* Empty .eh_frame section. */ free (ehbuf); return; } /* If .eh_frame section size doesn't fit into int, we cannot handle it (it would need to use 64-bit .eh_frame format anyway). */ REQUIRE (sec->size == (unsigned int) sec->size); ptr_size = (get_elf_backend_data (abfd) ->elf_backend_eh_frame_address_size (abfd, sec)); REQUIRE (ptr_size != 0); /* Go through the section contents and work out how many FDEs and CIEs there are. */ buf = ehbuf; end = ehbuf + sec->size; num_cies = 0; num_entries = 0; while (buf != end) { num_entries++; /* Read the length of the entry. */ REQUIRE (skip_bytes (&buf, end, 4)); hdr_length = bfd_get_32 (abfd, buf - 4); /* 64-bit .eh_frame is not supported. */ REQUIRE (hdr_length != 0xffffffff); if (hdr_length == 0) break; REQUIRE (skip_bytes (&buf, end, 4)); hdr_id = bfd_get_32 (abfd, buf - 4); if (hdr_id == 0) num_cies++; REQUIRE (skip_bytes (&buf, end, hdr_length - 4)); } sec_info = (struct eh_frame_sec_info *) bfd_zmalloc (sizeof (struct eh_frame_sec_info) + (num_entries - 1) * sizeof (struct eh_cie_fde)); REQUIRE (sec_info); /* We need to have a "struct cie" for each CIE in this section. */ local_cies = (struct cie *) bfd_zmalloc (num_cies * sizeof (*local_cies)); REQUIRE (local_cies); /* FIXME: octets_per_byte. */ #define ENSURE_NO_RELOCS(buf) \ REQUIRE (!(cookie->rel < cookie->relend \ && (cookie->rel->r_offset \ < (bfd_size_type) ((buf) - ehbuf)) \ && cookie->rel->r_info != 0)) /* FIXME: octets_per_byte. */ #define SKIP_RELOCS(buf) \ while (cookie->rel < cookie->relend \ && (cookie->rel->r_offset \ < (bfd_size_type) ((buf) - ehbuf))) \ cookie->rel++ /* FIXME: octets_per_byte. */ #define GET_RELOC(buf) \ ((cookie->rel < cookie->relend \ && (cookie->rel->r_offset \ == (bfd_size_type) ((buf) - ehbuf))) \ ? cookie->rel : NULL) buf = ehbuf; cie_count = 0; gc_mark_hook = get_elf_backend_data (abfd)->gc_mark_hook; while ((bfd_size_type) (buf - ehbuf) != sec->size) { char *aug; bfd_byte *start, *insns, *insns_end; bfd_size_type length; unsigned int set_loc_count; this_inf = sec_info->entry + sec_info->count; last_fde = buf; /* Read the length of the entry. */ REQUIRE (skip_bytes (&buf, ehbuf + sec->size, 4)); hdr_length = bfd_get_32 (abfd, buf - 4); /* The CIE/FDE must be fully contained in this input section. */ REQUIRE ((bfd_size_type) (buf - ehbuf) + hdr_length <= sec->size); end = buf + hdr_length; this_inf->offset = last_fde - ehbuf; this_inf->size = 4 + hdr_length; this_inf->reloc_index = cookie->rel - cookie->rels; if (hdr_length == 0) { /* A zero-length CIE should only be found at the end of the section. */ REQUIRE ((bfd_size_type) (buf - ehbuf) == sec->size); ENSURE_NO_RELOCS (buf); sec_info->count++; break; } REQUIRE (skip_bytes (&buf, end, 4)); hdr_id = bfd_get_32 (abfd, buf - 4); if (hdr_id == 0) { unsigned int initial_insn_length; /* CIE */ this_inf->cie = 1; /* Point CIE to one of the section-local cie structures. */ cie = local_cies + cie_count++; cie->cie_inf = this_inf; cie->length = hdr_length; cie->output_sec = sec->output_section; start = buf; REQUIRE (read_byte (&buf, end, &cie->version)); /* Cannot handle unknown versions. */ REQUIRE (cie->version == 1 || cie->version == 3); REQUIRE (strlen ((char *) buf) < sizeof (cie->augmentation)); strcpy (cie->augmentation, (char *) buf); buf = (bfd_byte *) strchr ((char *) buf, '\0') + 1; ENSURE_NO_RELOCS (buf); if (buf[0] == 'e' && buf[1] == 'h') { /* GCC < 3.0 .eh_frame CIE */ /* We cannot merge "eh" CIEs because __EXCEPTION_TABLE__ is private to each CIE, so we don't need it for anything. Just skip it. */ REQUIRE (skip_bytes (&buf, end, ptr_size)); SKIP_RELOCS (buf); } REQUIRE (read_uleb128 (&buf, end, &cie->code_align)); REQUIRE (read_sleb128 (&buf, end, &cie->data_align)); if (cie->version == 1) { REQUIRE (buf < end); cie->ra_column = *buf++; } else REQUIRE (read_uleb128 (&buf, end, &cie->ra_column)); ENSURE_NO_RELOCS (buf); cie->lsda_encoding = DW_EH_PE_omit; cie->fde_encoding = DW_EH_PE_omit; cie->per_encoding = DW_EH_PE_omit; aug = cie->augmentation; if (aug[0] != 'e' || aug[1] != 'h') { if (*aug == 'z') { aug++; REQUIRE (read_uleb128 (&buf, end, &cie->augmentation_size)); ENSURE_NO_RELOCS (buf); } while (*aug != '\0') switch (*aug++) { case 'L': REQUIRE (read_byte (&buf, end, &cie->lsda_encoding)); ENSURE_NO_RELOCS (buf); REQUIRE (get_DW_EH_PE_width (cie->lsda_encoding, ptr_size)); break; case 'R': REQUIRE (read_byte (&buf, end, &cie->fde_encoding)); ENSURE_NO_RELOCS (buf); REQUIRE (get_DW_EH_PE_width (cie->fde_encoding, ptr_size)); break; case 'S': break; case 'P': { int per_width; REQUIRE (read_byte (&buf, end, &cie->per_encoding)); per_width = get_DW_EH_PE_width (cie->per_encoding, ptr_size); REQUIRE (per_width); if ((cie->per_encoding & 0x70) == DW_EH_PE_aligned) { length = -(buf - ehbuf) & (per_width - 1); REQUIRE (skip_bytes (&buf, end, length)); } this_inf->u.cie.personality_offset = buf - start; ENSURE_NO_RELOCS (buf); /* Ensure we have a reloc here. */ REQUIRE (GET_RELOC (buf)); cie->personality.reloc_index = cookie->rel - cookie->rels; /* Cope with MIPS-style composite relocations. */ do cookie->rel++; while (GET_RELOC (buf) != NULL); REQUIRE (skip_bytes (&buf, end, per_width)); } break; default: /* Unrecognized augmentation. Better bail out. */ goto free_no_table; } } /* For shared libraries, try to get rid of as many RELATIVE relocs as possible. */ if (info->shared && (get_elf_backend_data (abfd) ->elf_backend_can_make_relative_eh_frame (abfd, info, sec))) { if ((cie->fde_encoding & 0x70) == DW_EH_PE_absptr) this_inf->make_relative = 1; /* If the CIE doesn't already have an 'R' entry, it's fairly easy to add one, provided that there's no aligned data after the augmentation string. */ else if (cie->fde_encoding == DW_EH_PE_omit && (cie->per_encoding & 0x70) != DW_EH_PE_aligned) { if (*cie->augmentation == 0) this_inf->add_augmentation_size = 1; this_inf->u.cie.add_fde_encoding = 1; this_inf->make_relative = 1; } if ((cie->lsda_encoding & 0x70) == DW_EH_PE_absptr) cie->can_make_lsda_relative = 1; } /* If FDE encoding was not specified, it defaults to DW_EH_absptr. */ if (cie->fde_encoding == DW_EH_PE_omit) cie->fde_encoding = DW_EH_PE_absptr; initial_insn_length = end - buf; if (initial_insn_length <= sizeof (cie->initial_instructions)) { cie->initial_insn_length = initial_insn_length; memcpy (cie->initial_instructions, buf, initial_insn_length); } insns = buf; buf += initial_insn_length; ENSURE_NO_RELOCS (buf); if (hdr_info->merge_cies) this_inf->u.cie.u.full_cie = cie; this_inf->u.cie.per_encoding_relative = (cie->per_encoding & 0x70) == DW_EH_PE_pcrel; } else { asection *rsec; /* Find the corresponding CIE. */ unsigned int cie_offset = this_inf->offset + 4 - hdr_id; for (cie = local_cies; cie < local_cies + cie_count; cie++) if (cie_offset == cie->cie_inf->offset) break; /* Ensure this FDE references one of the CIEs in this input section. */ REQUIRE (cie != local_cies + cie_count); this_inf->u.fde.cie_inf = cie->cie_inf; this_inf->make_relative = cie->cie_inf->make_relative; this_inf->add_augmentation_size = cie->cie_inf->add_augmentation_size; ENSURE_NO_RELOCS (buf); REQUIRE (GET_RELOC (buf)); /* Chain together the FDEs for each section. */ rsec = _bfd_elf_gc_mark_rsec (info, sec, gc_mark_hook, cookie); /* RSEC will be NULL if FDE was cleared out as it was belonging to a discarded SHT_GROUP. */ if (rsec) { REQUIRE (rsec->owner == abfd); this_inf->u.fde.next_for_section = elf_fde_list (rsec); elf_fde_list (rsec) = this_inf; } /* Skip the initial location and address range. */ start = buf; length = get_DW_EH_PE_width (cie->fde_encoding, ptr_size); REQUIRE (skip_bytes (&buf, end, 2 * length)); /* Skip the augmentation size, if present. */ if (cie->augmentation[0] == 'z') REQUIRE (read_uleb128 (&buf, end, &length)); else length = 0; /* Of the supported augmentation characters above, only 'L' adds augmentation data to the FDE. This code would need to be adjusted if any future augmentations do the same thing. */ if (cie->lsda_encoding != DW_EH_PE_omit) { SKIP_RELOCS (buf); if (cie->can_make_lsda_relative && GET_RELOC (buf)) cie->cie_inf->u.cie.make_lsda_relative = 1; this_inf->lsda_offset = buf - start; /* If there's no 'z' augmentation, we don't know where the CFA insns begin. Assume no padding. */ if (cie->augmentation[0] != 'z') length = end - buf; } /* Skip over the augmentation data. */ REQUIRE (skip_bytes (&buf, end, length)); insns = buf; buf = last_fde + 4 + hdr_length; /* For NULL RSEC (cleared FDE belonging to a discarded section) the relocations are commonly cleared. We do not sanity check if all these relocations are cleared as (1) relocations to .gcc_except_table will remain uncleared (they will get dropped with the drop of this unused FDE) and (2) BFD already safely drops relocations of any type to .eh_frame by elf_section_ignore_discarded_relocs. TODO: The .gcc_except_table entries should be also filtered as .eh_frame entries; or GCC could rather use COMDAT for them. */ SKIP_RELOCS (buf); } /* Try to interpret the CFA instructions and find the first padding nop. Shrink this_inf's size so that it doesn't include the padding. */ length = get_DW_EH_PE_width (cie->fde_encoding, ptr_size); set_loc_count = 0; insns_end = skip_non_nops (insns, end, length, &set_loc_count); /* If we don't understand the CFA instructions, we can't know what needs to be adjusted there. */ if (insns_end == NULL /* For the time being we don't support DW_CFA_set_loc in CIE instructions. */ || (set_loc_count && this_inf->cie)) goto free_no_table; this_inf->size -= end - insns_end; if (insns_end != end && this_inf->cie) { cie->initial_insn_length -= end - insns_end; cie->length -= end - insns_end; } if (set_loc_count && ((cie->fde_encoding & 0x70) == DW_EH_PE_pcrel || this_inf->make_relative)) { unsigned int cnt; bfd_byte *p; this_inf->set_loc = (unsigned int *) bfd_malloc ((set_loc_count + 1) * sizeof (unsigned int)); REQUIRE (this_inf->set_loc); this_inf->set_loc[0] = set_loc_count; p = insns; cnt = 0; while (p < end) { if (*p == DW_CFA_set_loc) this_inf->set_loc[++cnt] = p + 1 - start; REQUIRE (skip_cfa_op (&p, end, length)); } } this_inf->removed = 1; this_inf->fde_encoding = cie->fde_encoding; this_inf->lsda_encoding = cie->lsda_encoding; sec_info->count++; } BFD_ASSERT (sec_info->count == num_entries); BFD_ASSERT (cie_count == num_cies); elf_section_data (sec)->sec_info = sec_info; sec->sec_info_type = ELF_INFO_TYPE_EH_FRAME; if (hdr_info->merge_cies) { sec_info->cies = local_cies; local_cies = NULL; } goto success; free_no_table: (*info->callbacks->einfo) (_("%P: error in %B(%A); no .eh_frame_hdr table will be created.\n"), abfd, sec); hdr_info->table = FALSE; if (sec_info) free (sec_info); success: if (ehbuf) free (ehbuf); if (local_cies) free (local_cies); #undef REQUIRE } /* Finish a pass over all .eh_frame sections. */ void _bfd_elf_end_eh_frame_parsing (struct bfd_link_info *info) { struct eh_frame_hdr_info *hdr_info; hdr_info = &elf_hash_table (info)->eh_info; hdr_info->parsed_eh_frames = TRUE; } /* Mark all relocations against CIE or FDE ENT, which occurs in .eh_frame section SEC. COOKIE describes the relocations in SEC; its "rel" field can be changed freely. */ static bfd_boolean mark_entry (struct bfd_link_info *info, asection *sec, struct eh_cie_fde *ent, elf_gc_mark_hook_fn gc_mark_hook, struct elf_reloc_cookie *cookie) { /* FIXME: octets_per_byte. */ for (cookie->rel = cookie->rels + ent->reloc_index; cookie->rel < cookie->relend && cookie->rel->r_offset < ent->offset + ent->size; cookie->rel++) if (!_bfd_elf_gc_mark_reloc (info, sec, gc_mark_hook, cookie)) return FALSE; return TRUE; } /* Mark all the relocations against FDEs that relate to code in input section SEC. The FDEs belong to .eh_frame section EH_FRAME, whose relocations are described by COOKIE. */ bfd_boolean _bfd_elf_gc_mark_fdes (struct bfd_link_info *info, asection *sec, asection *eh_frame, elf_gc_mark_hook_fn gc_mark_hook, struct elf_reloc_cookie *cookie) { struct eh_cie_fde *fde, *cie; for (fde = elf_fde_list (sec); fde; fde = fde->u.fde.next_for_section) { if (!mark_entry (info, eh_frame, fde, gc_mark_hook, cookie)) return FALSE; /* At this stage, all cie_inf fields point to local CIEs, so we can use the same cookie to refer to them. */ cie = fde->u.fde.cie_inf; if (!cie->u.cie.gc_mark) { cie->u.cie.gc_mark = 1; if (!mark_entry (info, eh_frame, cie, gc_mark_hook, cookie)) return FALSE; } } return TRUE; } /* Input section SEC of ABFD is an .eh_frame section that contains the CIE described by CIE_INF. Return a version of CIE_INF that is going to be kept in the output, adding CIE_INF to the output if necessary. HDR_INFO is the .eh_frame_hdr information and COOKIE describes the relocations in REL. */ static struct eh_cie_fde * find_merged_cie (bfd *abfd, struct bfd_link_info *info, asection *sec, struct eh_frame_hdr_info *hdr_info, struct elf_reloc_cookie *cookie, struct eh_cie_fde *cie_inf) { unsigned long r_symndx; struct cie *cie, *new_cie; Elf_Internal_Rela *rel; void **loc; /* Use CIE_INF if we have already decided to keep it. */ if (!cie_inf->removed) return cie_inf; /* If we have merged CIE_INF with another CIE, use that CIE instead. */ if (cie_inf->u.cie.merged) return cie_inf->u.cie.u.merged_with; cie = cie_inf->u.cie.u.full_cie; /* Assume we will need to keep CIE_INF. */ cie_inf->removed = 0; cie_inf->u.cie.u.sec = sec; /* If we are not merging CIEs, use CIE_INF. */ if (cie == NULL) return cie_inf; if (cie->per_encoding != DW_EH_PE_omit) { bfd_boolean per_binds_local; /* Work out the address of personality routine, either as an absolute value or as a symbol. */ rel = cookie->rels + cie->personality.reloc_index; memset (&cie->personality, 0, sizeof (cie->personality)); #ifdef BFD64 if (elf_elfheader (abfd)->e_ident[EI_CLASS] == ELFCLASS64) r_symndx = ELF64_R_SYM (rel->r_info); else #endif r_symndx = ELF32_R_SYM (rel->r_info); if (r_symndx >= cookie->locsymcount || ELF_ST_BIND (cookie->locsyms[r_symndx].st_info) != STB_LOCAL) { struct elf_link_hash_entry *h; r_symndx -= cookie->extsymoff; h = cookie->sym_hashes[r_symndx]; while (h->root.type == bfd_link_hash_indirect || h->root.type == bfd_link_hash_warning) h = (struct elf_link_hash_entry *) h->root.u.i.link; cie->personality.h = h; per_binds_local = SYMBOL_REFERENCES_LOCAL (info, h); } else { Elf_Internal_Sym *sym; asection *sym_sec; sym = &cookie->locsyms[r_symndx]; sym_sec = bfd_section_from_elf_index (abfd, sym->st_shndx); if (sym_sec == NULL) return cie_inf; if (sym_sec->kept_section != NULL) sym_sec = sym_sec->kept_section; if (sym_sec->output_section == NULL) return cie_inf; cie->local_personality = 1; cie->personality.val = (sym->st_value + sym_sec->output_offset + sym_sec->output_section->vma); per_binds_local = TRUE; } if (per_binds_local && info->shared && (cie->per_encoding & 0x70) == DW_EH_PE_absptr && (get_elf_backend_data (abfd) ->elf_backend_can_make_relative_eh_frame (abfd, info, sec))) { cie_inf->u.cie.make_per_encoding_relative = 1; cie_inf->u.cie.per_encoding_relative = 1; } } /* See if we can merge this CIE with an earlier one. */ cie->output_sec = sec->output_section; cie_compute_hash (cie); if (hdr_info->cies == NULL) { hdr_info->cies = htab_try_create (1, cie_hash, cie_eq, free); if (hdr_info->cies == NULL) return cie_inf; } loc = htab_find_slot_with_hash (hdr_info->cies, cie, cie->hash, INSERT); if (loc == NULL) return cie_inf; new_cie = (struct cie *) *loc; if (new_cie == NULL) { /* Keep CIE_INF and record it in the hash table. */ new_cie = (struct cie *) malloc (sizeof (struct cie)); if (new_cie == NULL) return cie_inf; memcpy (new_cie, cie, sizeof (struct cie)); *loc = new_cie; } else { /* Merge CIE_INF with NEW_CIE->CIE_INF. */ cie_inf->removed = 1; cie_inf->u.cie.merged = 1; cie_inf->u.cie.u.merged_with = new_cie->cie_inf; if (cie_inf->u.cie.make_lsda_relative) new_cie->cie_inf->u.cie.make_lsda_relative = 1; } return new_cie->cie_inf; } /* This function is called for each input file before the .eh_frame section is relocated. It discards duplicate CIEs and FDEs for discarded functions. The function returns TRUE iff any entries have been deleted. */ bfd_boolean _bfd_elf_discard_section_eh_frame (bfd *abfd, struct bfd_link_info *info, asection *sec, bfd_boolean (*reloc_symbol_deleted_p) (bfd_vma, void *), struct elf_reloc_cookie *cookie) { struct eh_cie_fde *ent; struct eh_frame_sec_info *sec_info; struct eh_frame_hdr_info *hdr_info; unsigned int ptr_size, offset; sec_info = (struct eh_frame_sec_info *) elf_section_data (sec)->sec_info; if (sec_info == NULL) return FALSE; hdr_info = &elf_hash_table (info)->eh_info; for (ent = sec_info->entry; ent < sec_info->entry + sec_info->count; ++ent) if (ent->size == 4) /* There should only be one zero terminator, on the last input file supplying .eh_frame (crtend.o). Remove any others. */ ent->removed = sec->map_head.s != NULL; else if (!ent->cie) { cookie->rel = cookie->rels + ent->reloc_index; /* FIXME: octets_per_byte. */ BFD_ASSERT (cookie->rel < cookie->relend && cookie->rel->r_offset == ent->offset + 8); if (!(*reloc_symbol_deleted_p) (ent->offset + 8, cookie)) { if (info->shared && (((ent->fde_encoding & 0x70) == DW_EH_PE_absptr && ent->make_relative == 0) || (ent->fde_encoding & 0x70) == DW_EH_PE_aligned)) { /* If a shared library uses absolute pointers which we cannot turn into PC relative, don't create the binary search table, since it is affected by runtime relocations. */ hdr_info->table = FALSE; (*info->callbacks->einfo) (_("%P: fde encoding in %B(%A) prevents .eh_frame_hdr" " table being created.\n"), abfd, sec); } ent->removed = 0; hdr_info->fde_count++; ent->u.fde.cie_inf = find_merged_cie (abfd, info, sec, hdr_info, cookie, ent->u.fde.cie_inf); } } if (sec_info->cies) { free (sec_info->cies); sec_info->cies = NULL; } ptr_size = (get_elf_backend_data (sec->owner) ->elf_backend_eh_frame_address_size (sec->owner, sec)); offset = 0; for (ent = sec_info->entry; ent < sec_info->entry + sec_info->count; ++ent) if (!ent->removed) { ent->new_offset = offset; offset += size_of_output_cie_fde (ent, ptr_size); } sec->rawsize = sec->size; sec->size = offset; return offset != sec->rawsize; } /* This function is called for .eh_frame_hdr section after _bfd_elf_discard_section_eh_frame has been called on all .eh_frame input sections. It finalizes the size of .eh_frame_hdr section. */ bfd_boolean _bfd_elf_discard_section_eh_frame_hdr (bfd *abfd, struct bfd_link_info *info) { struct elf_link_hash_table *htab; struct eh_frame_hdr_info *hdr_info; asection *sec; htab = elf_hash_table (info); hdr_info = &htab->eh_info; if (hdr_info->cies != NULL) { htab_delete (hdr_info->cies); hdr_info->cies = NULL; } sec = hdr_info->hdr_sec; if (sec == NULL) return FALSE; sec->size = EH_FRAME_HDR_SIZE; if (hdr_info->table) sec->size += 4 + hdr_info->fde_count * 8; elf_tdata (abfd)->eh_frame_hdr = sec; return TRUE; } /* This function is called from size_dynamic_sections. It needs to decide whether .eh_frame_hdr should be output or not, because when the dynamic symbol table has been sized it is too late to strip sections. */ bfd_boolean _bfd_elf_maybe_strip_eh_frame_hdr (struct bfd_link_info *info) { asection *o; bfd *abfd; struct elf_link_hash_table *htab; struct eh_frame_hdr_info *hdr_info; htab = elf_hash_table (info); hdr_info = &htab->eh_info; if (hdr_info->hdr_sec == NULL) return TRUE; if (bfd_is_abs_section (hdr_info->hdr_sec->output_section)) { hdr_info->hdr_sec = NULL; return TRUE; } abfd = NULL; if (info->eh_frame_hdr) for (abfd = info->input_bfds; abfd != NULL; abfd = abfd->link_next) { /* Count only sections which have at least a single CIE or FDE. There cannot be any CIE or FDE <= 8 bytes. */ o = bfd_get_section_by_name (abfd, ".eh_frame"); if (o && o->size > 8 && !bfd_is_abs_section (o->output_section)) break; } if (abfd == NULL) { hdr_info->hdr_sec->flags |= SEC_EXCLUDE; hdr_info->hdr_sec = NULL; return TRUE; } hdr_info->table = TRUE; return TRUE; } /* Adjust an address in the .eh_frame section. Given OFFSET within SEC, this returns the new offset in the adjusted .eh_frame section, or -1 if the address refers to a CIE/FDE which has been removed or to offset with dynamic relocation which is no longer needed. */ bfd_vma _bfd_elf_eh_frame_section_offset (bfd *output_bfd ATTRIBUTE_UNUSED, struct bfd_link_info *info, asection *sec, bfd_vma offset) { struct eh_frame_sec_info *sec_info; struct elf_link_hash_table *htab; struct eh_frame_hdr_info *hdr_info; unsigned int lo, hi, mid; if (sec->sec_info_type != ELF_INFO_TYPE_EH_FRAME) return offset; sec_info = (struct eh_frame_sec_info *) elf_section_data (sec)->sec_info; if (offset >= sec->rawsize) return offset - sec->rawsize + sec->size; htab = elf_hash_table (info); hdr_info = &htab->eh_info; lo = 0; hi = sec_info->count; mid = 0; while (lo < hi) { mid = (lo + hi) / 2; if (offset < sec_info->entry[mid].offset) hi = mid; else if (offset >= sec_info->entry[mid].offset + sec_info->entry[mid].size) lo = mid + 1; else break; } BFD_ASSERT (lo < hi); /* FDE or CIE was removed. */ if (sec_info->entry[mid].removed) return (bfd_vma) -1; /* If converting personality pointers to DW_EH_PE_pcrel, there will be no need for run-time relocation against the personality field. */ if (sec_info->entry[mid].cie && sec_info->entry[mid].u.cie.make_per_encoding_relative && offset == (sec_info->entry[mid].offset + 8 + sec_info->entry[mid].u.cie.personality_offset)) return (bfd_vma) -2; /* If converting to DW_EH_PE_pcrel, there will be no need for run-time relocation against FDE's initial_location field. */ if (!sec_info->entry[mid].cie && sec_info->entry[mid].make_relative && offset == sec_info->entry[mid].offset + 8) return (bfd_vma) -2; /* If converting LSDA pointers to DW_EH_PE_pcrel, there will be no need for run-time relocation against LSDA field. */ if (!sec_info->entry[mid].cie && sec_info->entry[mid].u.fde.cie_inf->u.cie.make_lsda_relative && offset == (sec_info->entry[mid].offset + 8 + sec_info->entry[mid].lsda_offset)) return (bfd_vma) -2; /* If converting to DW_EH_PE_pcrel, there will be no need for run-time relocation against DW_CFA_set_loc's arguments. */ if (sec_info->entry[mid].set_loc && sec_info->entry[mid].make_relative && (offset >= sec_info->entry[mid].offset + 8 + sec_info->entry[mid].set_loc[1])) { unsigned int cnt; for (cnt = 1; cnt <= sec_info->entry[mid].set_loc[0]; cnt++) if (offset == sec_info->entry[mid].offset + 8 + sec_info->entry[mid].set_loc[cnt]) return (bfd_vma) -2; } /* Any new augmentation bytes go before the first relocation. */ return (offset + sec_info->entry[mid].new_offset - sec_info->entry[mid].offset + extra_augmentation_string_bytes (sec_info->entry + mid) + extra_augmentation_data_bytes (sec_info->entry + mid)); } /* Write out .eh_frame section. This is called with the relocated contents. */ bfd_boolean _bfd_elf_write_section_eh_frame (bfd *abfd, struct bfd_link_info *info, asection *sec, bfd_byte *contents) { struct eh_frame_sec_info *sec_info; struct elf_link_hash_table *htab; struct eh_frame_hdr_info *hdr_info; unsigned int ptr_size; struct eh_cie_fde *ent; if (sec->sec_info_type != ELF_INFO_TYPE_EH_FRAME) /* FIXME: octets_per_byte. */ return bfd_set_section_contents (abfd, sec->output_section, contents, sec->output_offset, sec->size); ptr_size = (get_elf_backend_data (abfd) ->elf_backend_eh_frame_address_size (abfd, sec)); BFD_ASSERT (ptr_size != 0); sec_info = (struct eh_frame_sec_info *) elf_section_data (sec)->sec_info; htab = elf_hash_table (info); hdr_info = &htab->eh_info; if (hdr_info->table && hdr_info->array == NULL) hdr_info->array = (struct eh_frame_array_ent *) bfd_malloc (hdr_info->fde_count * sizeof(*hdr_info->array)); if (hdr_info->array == NULL) hdr_info = NULL; /* The new offsets can be bigger or smaller than the original offsets. We therefore need to make two passes over the section: one backward pass to move entries up and one forward pass to move entries down. The two passes won't interfere with each other because entries are not reordered */ for (ent = sec_info->entry + sec_info->count; ent-- != sec_info->entry;) if (!ent->removed && ent->new_offset > ent->offset) memmove (contents + ent->new_offset, contents + ent->offset, ent->size); for (ent = sec_info->entry; ent < sec_info->entry + sec_info->count; ++ent) if (!ent->removed && ent->new_offset < ent->offset) memmove (contents + ent->new_offset, contents + ent->offset, ent->size); for (ent = sec_info->entry; ent < sec_info->entry + sec_info->count; ++ent) { unsigned char *buf, *end; unsigned int new_size; if (ent->removed) continue; if (ent->size == 4) { /* Any terminating FDE must be at the end of the section. */ BFD_ASSERT (ent == sec_info->entry + sec_info->count - 1); continue; } buf = contents + ent->new_offset; end = buf + ent->size; new_size = size_of_output_cie_fde (ent, ptr_size); /* Update the size. It may be shrinked. */ bfd_put_32 (abfd, new_size - 4, buf); /* Filling the extra bytes with DW_CFA_nops. */ if (new_size != ent->size) memset (end, 0, new_size - ent->size); if (ent->cie) { /* CIE */ if (ent->make_relative || ent->u.cie.make_lsda_relative || ent->u.cie.per_encoding_relative) { char *aug; unsigned int action, extra_string, extra_data; unsigned int per_width, per_encoding; /* Need to find 'R' or 'L' augmentation's argument and modify DW_EH_PE_* value. */ action = ((ent->make_relative ? 1 : 0) | (ent->u.cie.make_lsda_relative ? 2 : 0) | (ent->u.cie.per_encoding_relative ? 4 : 0)); extra_string = extra_augmentation_string_bytes (ent); extra_data = extra_augmentation_data_bytes (ent); /* Skip length, id and version. */ buf += 9; aug = (char *) buf; buf += strlen (aug) + 1; skip_leb128 (&buf, end); skip_leb128 (&buf, end); skip_leb128 (&buf, end); if (*aug == 'z') { /* The uleb128 will always be a single byte for the kind of augmentation strings that we're prepared to handle. */ *buf++ += extra_data; aug++; } /* Make room for the new augmentation string and data bytes. */ memmove (buf + extra_string + extra_data, buf, end - buf); memmove (aug + extra_string, aug, buf - (bfd_byte *) aug); buf += extra_string; end += extra_string + extra_data; if (ent->add_augmentation_size) { *aug++ = 'z'; *buf++ = extra_data - 1; } if (ent->u.cie.add_fde_encoding) { BFD_ASSERT (action & 1); *aug++ = 'R'; *buf++ = make_pc_relative (DW_EH_PE_absptr, ptr_size); action &= ~1; } while (action) switch (*aug++) { case 'L': if (action & 2) { BFD_ASSERT (*buf == ent->lsda_encoding); *buf = make_pc_relative (*buf, ptr_size); action &= ~2; } buf++; break; case 'P': if (ent->u.cie.make_per_encoding_relative) *buf = make_pc_relative (*buf, ptr_size); per_encoding = *buf++; per_width = get_DW_EH_PE_width (per_encoding, ptr_size); BFD_ASSERT (per_width != 0); BFD_ASSERT (((per_encoding & 0x70) == DW_EH_PE_pcrel) == ent->u.cie.per_encoding_relative); if ((per_encoding & 0x70) == DW_EH_PE_aligned) buf = (contents + ((buf - contents + per_width - 1) & ~((bfd_size_type) per_width - 1))); if (action & 4) { bfd_vma val; val = read_value (abfd, buf, per_width, get_DW_EH_PE_signed (per_encoding)); if (ent->u.cie.make_per_encoding_relative) val -= (sec->output_section->vma + sec->output_offset + (buf - contents)); else { val += (bfd_vma) ent->offset - ent->new_offset; val -= extra_string + extra_data; } write_value (abfd, buf, val, per_width); action &= ~4; } buf += per_width; break; case 'R': if (action & 1) { BFD_ASSERT (*buf == ent->fde_encoding); *buf = make_pc_relative (*buf, ptr_size); action &= ~1; } buf++; break; case 'S': break; default: BFD_FAIL (); } } } else { /* FDE */ bfd_vma value, address; unsigned int width; bfd_byte *start; struct eh_cie_fde *cie; /* Skip length. */ cie = ent->u.fde.cie_inf; buf += 4; value = ((ent->new_offset + sec->output_offset + 4) - (cie->new_offset + cie->u.cie.u.sec->output_offset)); bfd_put_32 (abfd, value, buf); buf += 4; width = get_DW_EH_PE_width (ent->fde_encoding, ptr_size); value = read_value (abfd, buf, width, get_DW_EH_PE_signed (ent->fde_encoding)); address = value; if (value) { switch (ent->fde_encoding & 0x70) { case DW_EH_PE_textrel: BFD_ASSERT (hdr_info == NULL); break; case DW_EH_PE_datarel: { asection *got = bfd_get_section_by_name (abfd, ".got"); BFD_ASSERT (got != NULL); address += got->vma; } break; case DW_EH_PE_pcrel: value += (bfd_vma) ent->offset - ent->new_offset; address += (sec->output_section->vma + sec->output_offset + ent->offset + 8); break; } if (ent->make_relative) value -= (sec->output_section->vma + sec->output_offset + ent->new_offset + 8); write_value (abfd, buf, value, width); } start = buf; if (hdr_info) { hdr_info->array[hdr_info->array_count].initial_loc = address; hdr_info->array[hdr_info->array_count++].fde = (sec->output_section->vma + sec->output_offset + ent->new_offset); } if ((ent->lsda_encoding & 0x70) == DW_EH_PE_pcrel || cie->u.cie.make_lsda_relative) { buf += ent->lsda_offset; width = get_DW_EH_PE_width (ent->lsda_encoding, ptr_size); value = read_value (abfd, buf, width, get_DW_EH_PE_signed (ent->lsda_encoding)); if (value) { if ((ent->lsda_encoding & 0x70) == DW_EH_PE_pcrel) value += (bfd_vma) ent->offset - ent->new_offset; else if (cie->u.cie.make_lsda_relative) value -= (sec->output_section->vma + sec->output_offset + ent->new_offset + 8 + ent->lsda_offset); write_value (abfd, buf, value, width); } } else if (ent->add_augmentation_size) { /* Skip the PC and length and insert a zero byte for the augmentation size. */ buf += width * 2; memmove (buf + 1, buf, end - buf); *buf = 0; } if (ent->set_loc) { /* Adjust DW_CFA_set_loc. */ unsigned int cnt; bfd_vma new_offset; width = get_DW_EH_PE_width (ent->fde_encoding, ptr_size); new_offset = ent->new_offset + 8 + extra_augmentation_string_bytes (ent) + extra_augmentation_data_bytes (ent); for (cnt = 1; cnt <= ent->set_loc[0]; cnt++) { buf = start + ent->set_loc[cnt]; value = read_value (abfd, buf, width, get_DW_EH_PE_signed (ent->fde_encoding)); if (!value) continue; if ((ent->fde_encoding & 0x70) == DW_EH_PE_pcrel) value += (bfd_vma) ent->offset + 8 - new_offset; if (ent->make_relative) value -= (sec->output_section->vma + sec->output_offset + new_offset + ent->set_loc[cnt]); write_value (abfd, buf, value, width); } } } } /* We don't align the section to its section alignment since the runtime library only expects all CIE/FDE records aligned at the pointer size. _bfd_elf_discard_section_eh_frame should have padded CIE/FDE records to multiple of pointer size with size_of_output_cie_fde. */ if ((sec->size % ptr_size) != 0) abort (); /* FIXME: octets_per_byte. */ return bfd_set_section_contents (abfd, sec->output_section, contents, (file_ptr) sec->output_offset, sec->size); } /* Helper function used to sort .eh_frame_hdr search table by increasing VMA of FDE initial location. */ static int vma_compare (const void *a, const void *b) { const struct eh_frame_array_ent *p = (const struct eh_frame_array_ent *) a; const struct eh_frame_array_ent *q = (const struct eh_frame_array_ent *) b; if (p->initial_loc > q->initial_loc) return 1; if (p->initial_loc < q->initial_loc) return -1; return 0; } /* Write out .eh_frame_hdr section. This must be called after _bfd_elf_write_section_eh_frame has been called on all input .eh_frame sections. .eh_frame_hdr format: ubyte version (currently 1) ubyte eh_frame_ptr_enc (DW_EH_PE_* encoding of pointer to start of .eh_frame section) ubyte fde_count_enc (DW_EH_PE_* encoding of total FDE count number (or DW_EH_PE_omit if there is no binary search table computed)) ubyte table_enc (DW_EH_PE_* encoding of binary search table, or DW_EH_PE_omit if not present. DW_EH_PE_datarel is using address of .eh_frame_hdr section start as base) [encoded] eh_frame_ptr (pointer to start of .eh_frame section) optionally followed by: [encoded] fde_count (total number of FDEs in .eh_frame section) fde_count x [encoded] initial_loc, fde (array of encoded pairs containing FDE initial_location field and FDE address, sorted by increasing initial_loc). */ bfd_boolean _bfd_elf_write_section_eh_frame_hdr (bfd *abfd, struct bfd_link_info *info) { struct elf_link_hash_table *htab; struct eh_frame_hdr_info *hdr_info; asection *sec; bfd_byte *contents; asection *eh_frame_sec; bfd_size_type size; bfd_boolean retval; bfd_vma encoded_eh_frame; htab = elf_hash_table (info); hdr_info = &htab->eh_info; sec = hdr_info->hdr_sec; if (sec == NULL) return TRUE; size = EH_FRAME_HDR_SIZE; if (hdr_info->array && hdr_info->array_count == hdr_info->fde_count) size += 4 + hdr_info->fde_count * 8; contents = (bfd_byte *) bfd_malloc (size); if (contents == NULL) return FALSE; eh_frame_sec = bfd_get_section_by_name (abfd, ".eh_frame"); if (eh_frame_sec == NULL) { free (contents); return FALSE; } memset (contents, 0, EH_FRAME_HDR_SIZE); contents[0] = 1; /* Version. */ contents[1] = get_elf_backend_data (abfd)->elf_backend_encode_eh_address (abfd, info, eh_frame_sec, 0, sec, 4, &encoded_eh_frame); /* .eh_frame offset. */ if (hdr_info->array && hdr_info->array_count == hdr_info->fde_count) { contents[2] = DW_EH_PE_udata4; /* FDE count encoding. */ contents[3] = DW_EH_PE_datarel | DW_EH_PE_sdata4; /* Search table enc. */ } else { contents[2] = DW_EH_PE_omit; contents[3] = DW_EH_PE_omit; } bfd_put_32 (abfd, encoded_eh_frame, contents + 4); if (contents[2] != DW_EH_PE_omit) { unsigned int i; bfd_put_32 (abfd, hdr_info->fde_count, contents + EH_FRAME_HDR_SIZE); qsort (hdr_info->array, hdr_info->fde_count, sizeof (*hdr_info->array), vma_compare); for (i = 0; i < hdr_info->fde_count; i++) { bfd_put_32 (abfd, hdr_info->array[i].initial_loc - sec->output_section->vma, contents + EH_FRAME_HDR_SIZE + i * 8 + 4); bfd_put_32 (abfd, hdr_info->array[i].fde - sec->output_section->vma, contents + EH_FRAME_HDR_SIZE + i * 8 + 8); } } /* FIXME: octets_per_byte. */ retval = bfd_set_section_contents (abfd, sec->output_section, contents, (file_ptr) sec->output_offset, sec->size); free (contents); return retval; } /* Return the width of FDE addresses. This is the default implementation. */ unsigned int _bfd_elf_eh_frame_address_size (bfd *abfd, asection *sec ATTRIBUTE_UNUSED) { return elf_elfheader (abfd)->e_ident[EI_CLASS] == ELFCLASS64 ? 8 : 4; } /* Decide whether we can use a PC-relative encoding within the given EH frame section. This is the default implementation. */ bfd_boolean _bfd_elf_can_make_relative (bfd *input_bfd ATTRIBUTE_UNUSED, struct bfd_link_info *info ATTRIBUTE_UNUSED, asection *eh_frame_section ATTRIBUTE_UNUSED) { return TRUE; } /* Select an encoding for the given address. Preference is given to PC-relative addressing modes. */ bfd_byte _bfd_elf_encode_eh_address (bfd *abfd ATTRIBUTE_UNUSED, struct bfd_link_info *info ATTRIBUTE_UNUSED, asection *osec, bfd_vma offset, asection *loc_sec, bfd_vma loc_offset, bfd_vma *encoded) { *encoded = osec->vma + offset - (loc_sec->output_section->vma + loc_sec->output_offset + loc_offset); return DW_EH_PE_pcrel | DW_EH_PE_sdata4; }
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