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)
{
#define REQUIRE(COND) \
do \
if (!(COND)) \
goto free_no_table; \
while (0)
bfd_byte *ehbuf = NULL, *buf;
bfd_byte *last_fde;
struct eh_cie_fde *ent, *this_inf;
unsigned int hdr_length, hdr_id;
struct extended_cie
{
struct cie cie;
unsigned int offset;
unsigned int usage_count;
unsigned int entry;
} *ecies = NULL, *ecie;
unsigned int ecie_count = 0, ecie_alloced = 0;
struct cie *cie;
struct elf_link_hash_table *htab;
struct eh_frame_hdr_info *hdr_info;
struct eh_frame_sec_info *sec_info = NULL;
unsigned int offset;
unsigned int ptr_size;
unsigned int entry_alloced;
if (sec->size == 0)
{
/* This file does not contain .eh_frame information. */
return FALSE;
}
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 FALSE;
}
htab = elf_hash_table (info);
hdr_info = &htab->eh_info;
if (hdr_info->cies == NULL && !info->relocatable)
hdr_info->cies = htab_try_create (1, cie_hash, cie_eq, free);
/* 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 FALSE;
}
/* 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);
buf = ehbuf;
sec_info = bfd_zmalloc (sizeof (struct eh_frame_sec_info)
+ 99 * sizeof (struct eh_cie_fde));
REQUIRE (sec_info);
entry_alloced = 100;
#define ENSURE_NO_RELOCS(buf) \
REQUIRE (!(cookie->rel < cookie->relend \
&& (cookie->rel->r_offset \
< (bfd_size_type) ((buf) - ehbuf)) \
&& cookie->rel->r_info != 0))
#define SKIP_RELOCS(buf) \
while (cookie->rel < cookie->relend \
&& (cookie->rel->r_offset \
< (bfd_size_type) ((buf) - ehbuf))) \
cookie->rel++
#define GET_RELOC(buf) \
((cookie->rel < cookie->relend \
&& (cookie->rel->r_offset \
== (bfd_size_type) ((buf) - ehbuf))) \
? cookie->rel : NULL)
for (;;)
{
char *aug;
bfd_byte *start, *end, *insns, *insns_end;
bfd_size_type length;
unsigned int set_loc_count;
if (sec_info->count == entry_alloced)
{
sec_info = bfd_realloc (sec_info,
sizeof (struct eh_frame_sec_info)
+ ((entry_alloced + 99)
* sizeof (struct eh_cie_fde)));
REQUIRE (sec_info);
memset (&sec_info->entry[entry_alloced], 0,
100 * sizeof (struct eh_cie_fde));
entry_alloced += 100;
}
this_inf = sec_info->entry + sec_info->count;
last_fde = buf;
if ((bfd_size_type) (buf - ehbuf) == sec->size)
break;
/* Read the length of the entry. */
REQUIRE (skip_bytes (&buf, ehbuf + sec->size, 4));
hdr_length = bfd_get_32 (abfd, buf - 4);
/* 64-bit .eh_frame is not supported. */
REQUIRE (hdr_length != 0xffffffff);
/* 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;
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;
if (ecie_count == ecie_alloced)
{
ecies = bfd_realloc (ecies,
(ecie_alloced + 20) * sizeof (*ecies));
REQUIRE (ecies);
memset (&ecies[ecie_alloced], 0, 20 * sizeof (*ecies));
ecie_alloced += 20;
}
cie = &ecies[ecie_count].cie;
ecies[ecie_count].offset = this_inf->offset;
ecies[ecie_count++].entry = sec_info->count;
cie->length = hdr_length;
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 & 0xf0) == DW_EH_PE_aligned)
{
length = -(buf - ehbuf) & (per_width - 1);
REQUIRE (skip_bytes (&buf, end, length));
}
ENSURE_NO_RELOCS (buf);
/* Ensure we have a reloc here. */
if (GET_RELOC (buf) != NULL)
{
unsigned long r_symndx;
#ifdef BFD64
if (ptr_size == 8)
r_symndx = ELF64_R_SYM (cookie->rel->r_info);
else
#endif
r_symndx = ELF32_R_SYM (cookie->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;
}
else
{
Elf_Internal_Sym *sym;
asection *sym_sec;
bfd_vma val;
sym = &cookie->locsyms[r_symndx];
sym_sec = (bfd_section_from_elf_index
(abfd, sym->st_shndx));
if (sym_sec != NULL)
{
if (sym_sec->kept_section != NULL)
sym_sec = sym_sec->kept_section;
if (sym_sec->output_section != NULL)
{
val = (sym->st_value
+ sym_sec->output_offset
+ sym_sec->output_section->vma);
cie->personality.val = val;
cie->local_personality = 1;
}
}
}
/* Cope with MIPS-style composite relocations. */
do
cookie->rel++;
while (GET_RELOC (buf) != NULL);
}
REQUIRE (skip_bytes (&buf, end, per_width));
REQUIRE (cie->local_personality || cie->personality.h);
}
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 & 0xf0) == DW_EH_PE_absptr)
cie->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 & 0xf0) != DW_EH_PE_aligned)
{
if (*cie->augmentation == 0)
this_inf->add_augmentation_size = 1;
this_inf->add_fde_encoding = 1;
cie->make_relative = 1;
}
}
if (info->shared
&& (get_elf_backend_data (abfd)
->elf_backend_can_make_lsda_relative_eh_frame
(abfd, info, sec))
&& (cie->lsda_encoding & 0xf0) == DW_EH_PE_absptr)
cie->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);
}
else
{
/* Find the corresponding CIE. */
unsigned int cie_offset = this_inf->offset + 4 - hdr_id;
for (ecie = ecies; ecie < ecies + ecie_count; ++ecie)
if (cie_offset == ecie->offset)
break;
/* Ensure this FDE references one of the CIEs in this input
section. */
REQUIRE (ecie != ecies + ecie_count);
cie = &ecie->cie;
ENSURE_NO_RELOCS (buf);
REQUIRE (GET_RELOC (buf));
if ((*reloc_symbol_deleted_p) (buf - ehbuf, cookie))
/* This is a FDE against a discarded section. It should
be deleted. */
this_inf->removed = 1;
else
{
if (info->shared
&& (((cie->fde_encoding & 0xf0) == DW_EH_PE_absptr
&& cie->make_relative == 0)
|| (cie->fde_encoding & 0xf0) == 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);
}
ecie->usage_count++;
hdr_info->fde_count++;
this_inf->cie_inf = (void *) (ecie - ecies);
}
/* 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)
{
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;
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 & 0xf0) == DW_EH_PE_pcrel
|| cie->make_relative))
{
unsigned int cnt;
bfd_byte *p;
this_inf->set_loc = 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->fde_encoding = cie->fde_encoding;
this_inf->lsda_encoding = cie->lsda_encoding;
sec_info->count++;
}
elf_section_data (sec)->sec_info = sec_info;
sec->sec_info_type = ELF_INFO_TYPE_EH_FRAME;
/* Look at all CIEs in this section and determine which can be
removed as unused, which can be merged with previous duplicate
CIEs and which need to be kept. */
for (ecie = ecies; ecie < ecies + ecie_count; ++ecie)
{
if (ecie->usage_count == 0)
{
sec_info->entry[ecie->entry].removed = 1;
continue;
}
ecie->cie.output_sec = sec->output_section;
ecie->cie.cie_inf = sec_info->entry + ecie->entry;
cie_compute_hash (&ecie->cie);
if (hdr_info->cies != NULL)
{
void **loc = htab_find_slot_with_hash (hdr_info->cies, &ecie->cie,
ecie->cie.hash, INSERT);
if (loc != NULL)
{
if (*loc != HTAB_EMPTY_ENTRY)
{
sec_info->entry[ecie->entry].removed = 1;
ecie->cie.cie_inf = ((struct cie *) *loc)->cie_inf;
continue;
}
*loc = malloc (sizeof (struct cie));
if (*loc == NULL)
*loc = HTAB_DELETED_ENTRY;
else
memcpy (*loc, &ecie->cie, sizeof (struct cie));
}
}
ecie->cie.cie_inf->make_relative = ecie->cie.make_relative;
ecie->cie.cie_inf->make_lsda_relative = ecie->cie.make_lsda_relative;
ecie->cie.cie_inf->per_encoding_relative
= (ecie->cie.per_encoding & 0x70) == DW_EH_PE_pcrel;
}
/* Ok, now we can assign new offsets. */
offset = 0;
for (ent = sec_info->entry; ent < sec_info->entry + sec_info->count; ++ent)
if (!ent->removed)
{
if (!ent->cie)
{
ecie = ecies + (bfd_hostptr_t) ent->cie_inf;
ent->cie_inf = ecie->cie.cie_inf;
}
ent->new_offset = offset;
offset += size_of_output_cie_fde (ent, ptr_size);
}
/* Resize the sec as needed. */
sec->rawsize = sec->size;
sec->size = offset;
free (ehbuf);
if (ecies)
free (ecies);
return offset != sec->rawsize;
free_no_table:
(*info->callbacks->einfo)
(_("%P: error in %B(%A); no .eh_frame_hdr table will be created.\n"),
abfd, sec);
if (ehbuf)
free (ehbuf);
if (sec_info)
free (sec_info);
if (ecies)
free (ecies);
hdr_info->table = FALSE;
return FALSE;
#undef REQUIRE
}
static struct eh_cie_fde *
find_merged_cie (bfd *abfd, 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)
{
/* 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;
}
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);
}
}
/* 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 = 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;
}