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Remove .eh_frame zero terminators

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The machinery to do this was there, but not enabled if the terminator
was the only thing in the section.

bfd/
	* elf-eh-frame.c (_bfd_elf_parse_eh_frame): Don't exit early
	for a section containing just a terminator.  Allow multiple
	terminators at end of section.
	* elflink.c (bfd_elf_discard_info): Iterate over .eh_frame
	sections when not adding alignment.  Assert on terminator in
	the middle of FDEs.
ld/
	* testsuite/ld-elf/eh3.d: Update.
	* testsuite/ld-elf/eh4.d: Update.
This commit is contained in:
Alan Modra 2017-08-31 19:39:14 +09:30
parent 654670a4f0
commit 9866ffe25a
6 changed files with 52 additions and 55 deletions
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9
bfd/ChangeLog
View file

@ -1,3 +1,12 @@
2017-08-31 Alan Modra <amodra@gmail.com>
* elf-eh-frame.c (_bfd_elf_parse_eh_frame): Don't exit early
for a section containing just a terminator. Allow multiple
terminators at end of section.
* elflink.c (bfd_elf_discard_info): Iterate over .eh_frame
sections when not adding alignment. Assert on terminator in
the middle of FDEs.
2017-08-31 Alan Modra <amodra@gmail.com>
PR 21441

20
bfd/elf-eh-frame.c
View file

@ -619,15 +619,6 @@ _bfd_elf_parse_eh_frame (bfd *abfd, struct bfd_link_info *info,
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);
@ -669,8 +660,11 @@ _bfd_elf_parse_eh_frame (bfd *abfd, struct bfd_link_info *info,
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);
if (num_cies)
{
local_cies = (struct cie *) bfd_zmalloc (num_cies * sizeof (*local_cies));
REQUIRE (local_cies);
}
/* FIXME: octets_per_byte. */
#define ENSURE_NO_RELOCS(buf) \
@ -724,7 +718,9 @@ _bfd_elf_parse_eh_frame (bfd *abfd, struct bfd_link_info *info,
if (hdr_length == 0)
{
/* A zero-length CIE should only be found at the end of
the section. */
the section, but allow multiple terminators. */
while (skip_bytes (&buf, ehbuf + sec->size, 4))
REQUIRE (bfd_get_32 (abfd, buf - 4) == 0);
REQUIRE ((bfd_size_type) (buf - ehbuf) == sec->size);
ENSURE_NO_RELOCS (buf);
sec_info->count++;

57
bfd/elflink.c
View file

@ -13862,39 +13862,36 @@ bfd_elf_discard_info (bfd *output_bfd, struct bfd_link_info *info)
fini_reloc_cookie_for_section (&cookie, i);
}
eh_alignment = 1 << o->alignment_power;
if (eh_alignment > 4)
{
/* Skip over zero terminator, and prevent empty sections
from adding alignment padding at the end. */
for (i = o->map_tail.s; i != NULL; i = i->map_tail.s)
if (i->size == 0)
i->flags |= SEC_EXCLUDE;
else if (i->size > 4)
break;
/* The last non-empty eh_frame section doesn't need padding. */
if (i != NULL)
i = i->map_tail.s;
/* Any prior sections must pad the last FDE out to the
output section alignment. Otherwise we might have zero
padding between sections, which would be seen as a
terminator. If there is a terminator in the middle of
FDEs, don't increase its size as that will write bogus
data of whatever was after the terminator in the input
file, to the output file. */
for (; i != NULL; i = i->map_tail.s)
if (i->size != 4)
/* Skip over zero terminator, and prevent empty sections from
adding alignment padding at the end. */
for (i = o->map_tail.s; i != NULL; i = i->map_tail.s)
if (i->size == 0)
i->flags |= SEC_EXCLUDE;
else if (i->size > 4)
break;
/* The last non-empty eh_frame section doesn't need padding. */
if (i != NULL)
i = i->map_tail.s;
/* Any prior sections must pad the last FDE out to the output
section alignment. Otherwise we might have zero padding
between sections, which would be seen as a terminator. */
for (; i != NULL; i = i->map_tail.s)
if (i->size == 4)
/* All but the last zero terminator should have been removed. */
BFD_FAIL ();
else
{
bfd_size_type size
= (i->size + eh_alignment - 1) & -eh_alignment;
if (i->size != size)
{
bfd_size_type size
= (i->size + eh_alignment - 1) & -eh_alignment;
if (i->size != size)
{
i->size = size;
changed = 1;
eh_changed = 1;
}
i->size = size;
changed = 1;
eh_changed = 1;
}
}
}
if (eh_changed)
elf_link_hash_traverse (elf_hash_table (info),
_bfd_elf_adjust_eh_frame_global_symbol, NULL);

5
ld/ChangeLog
View file

@ -1,3 +1,8 @@
2017-08-31 Alan Modra <amodra@gmail.com>
* testsuite/ld-elf/eh3.d: Update.
* testsuite/ld-elf/eh4.d: Update.
2017-08-30 Maciej W. Rozycki <macro@imgtec.com>
* testsuite/ld-elf/orphan-11.ld: Also discard `.MIPS.options'

12
ld/testsuite/ld-elf/eh3.d
View file

@ -23,20 +23,12 @@ Contents of the .eh_frame section:
DW_CFA_nop
DW_CFA_nop
0+0018 0+0024 0+001c FDE cie=0+0000 pc=0+400078\.\.0+400090
0+0018 0+001c 0+001c FDE cie=0+0000 pc=0+400078\.\.0+400090
DW_CFA_advance_loc: 8 to 0+400080
DW_CFA_def_cfa_offset: 16
DW_CFA_offset: r6 \(rbp\) at cfa-16
DW_CFA_advance_loc: 8 to 0+400088
DW_CFA_def_cfa_register: r6 \(rbp\)
DW_CFA_nop
DW_CFA_nop
DW_CFA_nop
DW_CFA_nop
DW_CFA_nop
DW_CFA_nop
DW_CFA_nop
DW_CFA_nop
0+0040 ZERO terminator
0+0038 ZERO terminator
#pass

4
ld/testsuite/ld-elf/eh4.d
View file

@ -28,14 +28,12 @@ Contents of the .eh_frame section:
DW_CFA_set_loc: 0+0417
DW_CFA_def_cfa_offset: 80
0+0048 0+0024 0+004c FDE cie=0+0000 pc=[0-9a-f]+\.\.[0-9a-f]+
0+0048 0+002[04] 0+004c FDE cie=0+0000 pc=[0-9a-f]+\.\.[0-9a-f]+
DW_CFA_def_cfa_offset: 16
DW_CFA_advance_loc: [0-9a-f]+ to [0-9a-f]+
DW_CFA_def_cfa_offset: 24
DW_CFA_advance_loc: [0-9a-f]+ to [0-9a-f]+
DW_CFA_def_cfa_expression \(DW_OP_breg7 \(rsp\): 8; DW_OP_breg16 \(rip\): 0;.*
DW_CFA_nop
#...
[0-9a-f]+ ZERO terminator
#pass