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pr14158, hole in powerpc64 .eh_frame
- From: Alan Modra <amodra at gmail dot com>
- To: binutils at sourceware dot org
- Date: Thu, 24 May 2012 15:50:12 +0930
- Subject: pr14158, hole in powerpc64 .eh_frame
PowerPC64 linker generated .eh_frame for PLT call stubs uses
DW_EH_PE_pcrel | DW_EH_PE_sdata4 encoding for addresses, and thus
aligns .eh_frame to 4 bytes. Current gcc uses the same encoding, but
probably because gcc hasn't changed its .eh_frame alignment from the
days it generated 8-byte addresses, aligns to 8 bytes. This means ld
will insert padding between the linker generated .eh_frame and user
.eh_frame sections. The padding is seen as a terminator, which breaks
exception handling for anyone not reading the FDEs via .eh_frame_hdr.
The common case of course is to call ld with --eh-frame-hdr, which is
why I hadn't seen this problem until now.
PR ld/14158
* elf64-ppc.c (ppc64_elf_size_stubs): Round up glink_eh_frame
size to output section alignment.
(ppc64_elf_build_stubs): Likewise, and extend last FDE to cover.
Index: bfd/elf64-ppc.c
===================================================================
RCS file: /cvs/src/src/bfd/elf64-ppc.c,v
retrieving revision 1.383
diff -u -p -r1.383 elf64-ppc.c
--- bfd/elf64-ppc.c 17 May 2012 02:43:34 -0000 1.383
+++ bfd/elf64-ppc.c 24 May 2012 04:49:55 -0000
@@ -11664,7 +11664,7 @@ ppc64_elf_size_stubs (struct bfd_link_in
&& !bfd_is_abs_section (htab->glink_eh_frame->output_section)
&& (htab->glink_eh_frame->flags & SEC_EXCLUDE) == 0)
{
- bfd_size_type size = 0;
+ size_t size = 0, align;
for (stub_sec = htab->stub_bfd->sections;
stub_sec != NULL;
@@ -11675,6 +11675,10 @@ ppc64_elf_size_stubs (struct bfd_link_in
size += 24;
if (size != 0)
size += sizeof (glink_eh_frame_cie);
+ align = 1;
+ align <<= htab->glink_eh_frame->output_section->alignment_power;
+ align -= 1;
+ size = (size + align) & ~align;
htab->glink_eh_frame->rawsize = htab->glink_eh_frame->size;
htab->glink_eh_frame->size = size;
}
@@ -11916,17 +11920,21 @@ ppc64_elf_build_stubs (bfd_boolean emit_
&& htab->glink_eh_frame->size != 0)
{
bfd_vma val;
+ bfd_byte *last_fde;
+ size_t last_fde_len, size, align, pad;
p = bfd_zalloc (htab->glink_eh_frame->owner, htab->glink_eh_frame->size);
if (p == NULL)
return FALSE;
htab->glink_eh_frame->contents = p;
+ last_fde = p;
htab->glink_eh_frame->rawsize = htab->glink_eh_frame->size;
memcpy (p, glink_eh_frame_cie, sizeof (glink_eh_frame_cie));
/* CIE length (rewrite in case little-endian). */
- bfd_put_32 (htab->elf.dynobj, sizeof (glink_eh_frame_cie) - 4, p);
+ last_fde_len = sizeof (glink_eh_frame_cie) - 4;
+ bfd_put_32 (htab->elf.dynobj, last_fde_len, p);
p += sizeof (glink_eh_frame_cie);
for (stub_sec = htab->stub_bfd->sections;
@@ -11934,6 +11942,8 @@ ppc64_elf_build_stubs (bfd_boolean emit_
stub_sec = stub_sec->next)
if ((stub_sec->flags & SEC_LINKER_CREATED) == 0)
{
+ last_fde = p;
+ last_fde_len = 16;
/* FDE length. */
bfd_put_32 (htab->elf.dynobj, 16, p);
p += 4;
@@ -11966,6 +11976,8 @@ ppc64_elf_build_stubs (bfd_boolean emit_
}
if (htab->glink != NULL && htab->glink->size != 0)
{
+ last_fde = p;
+ last_fde_len = 20;
/* FDE length. */
bfd_put_32 (htab->elf.dynobj, 20, p);
p += 4;
@@ -12003,7 +12015,16 @@ ppc64_elf_build_stubs (bfd_boolean emit_
*p++ = DW_CFA_restore_extended;
*p++ = 65;
}
- htab->glink_eh_frame->size = p - htab->glink_eh_frame->contents;
+ /* Subsume any padding into the last FDE if user .eh_frame
+ sections are aligned more than glink_eh_frame. Otherwise any
+ zero padding will be seen as a terminator. */
+ size = p - htab->glink_eh_frame->contents;
+ align = 1;
+ align <<= htab->glink_eh_frame->output_section->alignment_power;
+ align -= 1;
+ pad = ((size + align) & ~align) - size;
+ htab->glink_eh_frame->size = size + pad;
+ bfd_put_32 (htab->elf.dynobj, last_fde_len + pad, last_fde);
}
/* Build the stubs as directed by the stub hash table. */
--
Alan Modra
Australia Development Lab, IBM