gc sections and .eh_frame
Alan Modra
amodra@bigpond.net.au
Wed Jun 29 13:54:00 GMT 2005
On Wed, Jun 29, 2005 at 10:54:01AM +0930, Alan Modra wrote:
> I think we can do without it by marking sections
> referenced from .eh_frame specially, and keeping them iff the associated
> .text section is marked.
Committing mainline.
bfd/
* elflink.c (_bfd_elf_gc_mark): Mark sections referenced by
.eh_frame specially..
(bfd_elf_gc_sections): ..rather than totally ignoring .eh_frame.
Don't recheck sections we have already marked.
(elf_gc_sweep): Keep non-code sections referenced from .eh_frame.
* section.c (struct bfd_section): Add gc_mark_from_eh.
(STD_SECTION): Adjust.
* ecoff.c (bfd_debug_section): Adjust.
* bfd-in2.h: Regenerate.
ld/
* scripttempl/elf.sc (.gcc_except_table): Don't KEEP.
Index: bfd/elflink.c
===================================================================
RCS file: /cvs/src/src/bfd/elflink.c,v
retrieving revision 1.168
diff -u -p -r1.168 elflink.c
--- bfd/elflink.c 14 Jun 2005 19:25:45 -0000 1.168
+++ bfd/elflink.c 29 Jun 2005 13:02:15 -0000
@@ -8733,6 +8733,7 @@ _bfd_elf_gc_mark (struct bfd_link_info *
gc_mark_hook_fn gc_mark_hook)
{
bfd_boolean ret;
+ bfd_boolean is_eh;
asection *group_sec;
sec->gc_mark = 1;
@@ -8745,6 +8746,7 @@ _bfd_elf_gc_mark (struct bfd_link_info *
/* Look through the section relocs. */
ret = TRUE;
+ is_eh = strcmp (sec->name, ".eh_frame") == 0;
if ((sec->flags & SEC_RELOC) != 0 && sec->reloc_count > 0)
{
Elf_Internal_Rela *relstart, *rel, *relend;
@@ -8821,6 +8823,8 @@ _bfd_elf_gc_mark (struct bfd_link_info *
{
if (bfd_get_flavour (rsec->owner) != bfd_target_elf_flavour)
rsec->gc_mark = 1;
+ else if (is_eh)
+ rsec->gc_mark_from_eh = 1;
else if (!_bfd_elf_gc_mark (info, rsec, gc_mark_hook))
{
ret = FALSE;
@@ -8891,6 +8895,41 @@ elf_gc_sweep (struct bfd_link_info *info
if (o->gc_mark)
continue;
+ /* Keep .gcc_except_table.* if the associated .text.* is
+ marked. This isn't very nice, but the proper solution,
+ splitting .eh_frame up and using comdat doesn't pan out
+ easily due to needing special relocs to handle the
+ difference of two symbols in separate sections.
+ Don't keep code sections referenced by .eh_frame. */
+ if (o->gc_mark_from_eh && (o->flags & SEC_CODE) == 0)
+ {
+ if (strncmp (o->name, ".gcc_except_table.", 18) == 0)
+ {
+ unsigned long len;
+ char *fn_name;
+ asection *fn_text;
+
+ len = strlen (o->name + 18) + 1;
+ fn_name = bfd_malloc (len + 6);
+ if (fn_name == NULL)
+ return FALSE;
+ memcpy (fn_name, ".text.", 6);
+ memcpy (fn_name + 6, o->name + 18, len);
+ fn_text = bfd_get_section_by_name (sub, fn_name);
+ free (fn_name);
+ if (fn_text != NULL && fn_text->gc_mark)
+ o->gc_mark = 1;
+ }
+
+ /* If not using specially named exception table section,
+ then keep whatever we are using. */
+ else
+ o->gc_mark = 1;
+
+ if (o->gc_mark)
+ continue;
+ }
+
/* Skip sweeping sections already excluded. */
if (o->flags & SEC_EXCLUDE)
continue;
@@ -9123,18 +9164,9 @@ bfd_elf_gc_sections (bfd *abfd, struct b
continue;
for (o = sub->sections; o != NULL; o = o->next)
- {
- if (o->flags & SEC_KEEP)
- {
- /* _bfd_elf_discard_section_eh_frame knows how to discard
- orphaned FDEs so don't mark sections referenced by the
- EH frame section. */
- if (strcmp (o->name, ".eh_frame") == 0)
- o->gc_mark = 1;
- else if (!_bfd_elf_gc_mark (info, o, gc_mark_hook))
- return FALSE;
- }
- }
+ if ((o->flags & SEC_KEEP) != 0 && !o->gc_mark)
+ if (!_bfd_elf_gc_mark (info, o, gc_mark_hook))
+ return FALSE;
}
/* ... and mark SEC_EXCLUDE for those that go. */
Index: bfd/section.c
===================================================================
RCS file: /cvs/src/src/bfd/section.c,v
retrieving revision 1.88
diff -u -p -r1.88 section.c
--- bfd/section.c 17 May 2005 19:44:55 -0000 1.88
+++ bfd/section.c 29 Jun 2005 13:02:16 -0000
@@ -354,8 +354,9 @@ CODE_FRAGMENT
. output sections that have an input section. *}
. unsigned int linker_has_input : 1;
.
-. {* A mark flag used by some linker backends for garbage collection. *}
+. {* Mark flags used by some linker backends for garbage collection. *}
. unsigned int gc_mark : 1;
+. unsigned int gc_mark_from_eh : 1;
.
. {* The following flags are used by the ELF linker. *}
.
@@ -661,18 +662,18 @@ static const asymbol global_syms[] =
#define STD_SECTION(SEC, FLAGS, SYM, NAME, IDX) \
const asymbol * const SYM = (asymbol *) &global_syms[IDX]; \
- asection SEC = \
+ asection SEC = \
/* name, id, index, next, prev, flags, user_set_vma, */ \
{ NAME, IDX, 0, NULL, NULL, FLAGS, 0, \
\
- /* linker_mark, linker_has_input, gc_mark, segment_mark, */ \
+ /* linker_mark, linker_has_input, gc_mark, gc_mark_from_eh, */ \
0, 0, 1, 0, \
\
- /* sec_info_type, use_rela_p, has_tls_reloc, has_gp_reloc, */ \
- 0, 0, 0, 0, \
+ /* segment_mark, sec_info_type, use_rela_p, has_tls_reloc, */ \
+ 0, 0, 0, 0, \
\
- /* need_finalize_relax, reloc_done, */ \
- 0, 0, \
+ /* has_gp_reloc, need_finalize_relax, reloc_done, */ \
+ 0, 0, 0, \
\
/* vma, lma, size, rawsize */ \
0, 0, 0, 0, \
@@ -686,8 +687,8 @@ static const asymbol global_syms[] =
/* line_filepos, userdata, contents, lineno, lineno_count, */ \
0, NULL, NULL, NULL, 0, \
\
- /* entsize, kept_section, moving_line_filepos, */ \
- 0, NULL, 0, \
+ /* entsize, kept_section, moving_line_filepos, */ \
+ 0, NULL, 0, \
\
/* target_index, used_by_bfd, constructor_chain, owner, */ \
0, NULL, NULL, NULL, \
Index: bfd/ecoff.c
===================================================================
RCS file: /cvs/src/src/bfd/ecoff.c,v
retrieving revision 1.45
diff -u -p -r1.45 ecoff.c
--- bfd/ecoff.c 4 May 2005 15:53:07 -0000 1.45
+++ bfd/ecoff.c 29 Jun 2005 13:02:04 -0000
@@ -54,12 +54,12 @@ static asection bfd_debug_section =
{
/* name, id, index, next, prev, flags, user_set_vma, */
"*DEBUG*", 0, 0, NULL, NULL, 0, 0,
- /* linker_mark, linker_has_input, gc_mark, segment_mark, */
- 0, 0, 0, 0,
- /* sec_info_type, use_rela_p, has_tls_reloc, has_gp_reloc, */
- 0, 0, 0, 0,
- /* need_finalize_relax, reloc_done, */
- 0, 0,
+ /* linker_mark, linker_has_input, gc_mark, gc_mark_from_eh, */
+ 0, 0, 1, 0,
+ /* segment_mark, sec_info_type, use_rela_p, has_tls_reloc, */
+ 0, 0, 0, 0,
+ /* has_gp_reloc, need_finalize_relax, reloc_done, */
+ 0, 0, 0,
/* vma, lma, size, rawsize, */
0, 0, 0, 0,
/* output_offset, output_section, alignment_power, */
@@ -68,7 +68,7 @@ static asection bfd_debug_section =
NULL, NULL, 0, 0, 0,
/* line_filepos, userdata, contents, lineno, lineno_count, */
0, NULL, NULL, NULL, 0,
- /* entsize, kept_section, moving_line_filepos, */
+ /* entsize, kept_section, moving_line_filepos, */
0, NULL, 0,
/* target_index, used_by_bfd, constructor_chain, owner, */
0, NULL, NULL, NULL,
Index: ld/scripttempl/elf.sc
===================================================================
RCS file: /cvs/src/src/ld/scripttempl/elf.sc,v
retrieving revision 1.59
diff -u -p -r1.59 elf.sc
--- ld/scripttempl/elf.sc 10 Jun 2005 00:39:56 -0000 1.59
+++ ld/scripttempl/elf.sc 29 Jun 2005 13:02:21 -0000
@@ -329,7 +329,7 @@ cat <<EOF
${OTHER_READONLY_SECTIONS}
.eh_frame_hdr : { *(.eh_frame_hdr) }
.eh_frame ${RELOCATING-0} : ONLY_IF_RO { KEEP (*(.eh_frame)) }
- .gcc_except_table ${RELOCATING-0} : ONLY_IF_RO { KEEP (*(.gcc_except_table)) *(.gcc_except_table.*) }
+ .gcc_except_table ${RELOCATING-0} : ONLY_IF_RO { *(.gcc_except_table .gcc_except_table.*) }
/* Adjust the address for the data segment. We want to adjust up to
the same address within the page on the next page up. */
@@ -339,7 +339,7 @@ cat <<EOF
/* Exception handling */
.eh_frame ${RELOCATING-0} : ONLY_IF_RW { KEEP (*(.eh_frame)) }
- .gcc_except_table ${RELOCATING-0} : ONLY_IF_RW { KEEP (*(.gcc_except_table)) *(.gcc_except_table.*) }
+ .gcc_except_table ${RELOCATING-0} : ONLY_IF_RW { *(.gcc_except_table .gcc_except_table.*) }
/* Thread Local Storage sections */
.tdata ${RELOCATING-0} : { *(.tdata${RELOCATING+ .tdata.* .gnu.linkonce.td.*}) }
--
Alan Modra
IBM OzLabs - Linux Technology Centre
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