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Error on shared lib call to @local ifunc
- From: Alan Modra <amodra at gmail dot com>
- To: binutils at sourceware dot org
- Date: Mon, 13 Jan 2014 15:46:59 +1030
- Subject: Error on shared lib call to @local ifunc
- Authentication-results: sourceware.org; auth=none
On powerpc32, making ifuncs have non-default visibility in shared
libraries or pies can result in runtime failures. The problem is that
if gcc is told that a given function has non-default visibility, then
calls to that function are assumed to be local (which is true) and
thus need not go via a plt call stub (which is false for ifunc). If
the caller has no other reason to set up the got pointer (r30), code
won't be emitted to do so. However, a pic plt call stub makes use of
r30 to load the plt entry. So a call to an ifunc, which always needs
a plt entry, will fail.
This patch makes ld emit an error for the problem case, and allows
calls to non-default visibility ifuncs to work in normal executables.
I also fix some cases where ifuncs fail when using the old bss-plt.
* elf32-ppc.c (ppc_elf_check_relocs): For @local call to ifunc,
error when shared and force a plt call otherwise.
(ppc_elf_size_dynamic_sections): Don't emit DT_PPC_GOT unless
plt_type == PLT_NEW.
(ppc_elf_relocate_section): Add missing test to resolve ifuncs to
the appropriate call stub.
diff --git a/bfd/elf32-ppc.c b/bfd/elf32-ppc.c
index b601f05..61c45d8 100644
--- a/bfd/elf32-ppc.c
+++ b/bfd/elf32-ppc.c
@@ -4283,6 +4283,20 @@ ppc_elf_check_relocs (bfd *abfd,
htab->plt_type = PLT_OLD;
htab->old_bfd = abfd;
}
+ if (h != NULL && h->type == STT_GNU_IFUNC)
+ {
+ if (info->shared)
+ {
+ info->callbacks->einfo (_("%P: %H: @local call to ifunc %s\n"),
+ abfd, sec, rel->r_offset,
+ h->root.root.string);
+ bfd_set_error (bfd_error_bad_value);
+ return FALSE;
+ }
+ h->needs_plt = 1;
+ if (!update_plt_info (abfd, &h->plt.plist, NULL, 0))
+ return FALSE;
+ }
break;
/* This relocation describes the C++ object vtable hierarchy.
@@ -6481,7 +6495,9 @@ ppc_elf_size_dynamic_sections (bfd *output_bfd ATTRIBUTE_UNUSED,
return FALSE;
}
- if (htab->glink != NULL && htab->glink->size != 0)
+ if (htab->plt_type == PLT_NEW
+ && htab->glink != NULL
+ && htab->glink->size != 0)
{
if (!add_dynamic_entry (DT_PPC_GOT, 0))
return FALSE;
@@ -7863,7 +7879,8 @@ ppc_elf_relocate_section (bfd *output_bfd,
unresolved_reloc = FALSE;
if (htab->plt_type == PLT_NEW
|| !htab->elf.dynamic_sections_created
- || h == NULL)
+ || h == NULL
+ || h->dynindx == -1)
relocation = (htab->glink->output_section->vma
+ htab->glink->output_offset
+ (ent->glink_offset & ~1));
--
Alan Modra
Australia Development Lab, IBM