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PowerPC64: Downgrade ifunc with textrel error to a warning 

For ppc64 I set flags when recording the dynamic relocation rather
than when allocating space.  That allows you to distinguish three
cases:
1) The dynamic ifunc relocation is in an executable and will always be
   to an ifunc resolver in the executable.
2) The dynamic ifunc relocation is in a shared library which provides
   an ifunc resolver, but that may be overridden at runtime to use a
   resolver in another binary.
3) The dynamic ifunc relocation is not to a locally defined ifunc
   resolver.

Case (3) won't cause a segfault trying to run resolver code that is
non-exec on older glibc.

I made case (1) an error for ppc64, but since newer glibc ld.so does
allow running ifunc resolvers when segments are writable I suppose I
should downgrade that to a warning like case (2).

	* elf64-ppc.c (struct ppc_link_hash_table): Delete
	maybe_local_ifunc_resolver field.
	(build_global_entry_stubs_and_plt): Set local_ifunc_resolver in
	cases where maybe_local_ifunc_resolver was set.
	(ppc64_elf_relocate_section): Likewise.
	(ppc64_elf_finish_dynamic_sections): Downgrade ifunc with textrel
	error to a warning.
This commit is contained in:
Alan Modra 2020-06-09 09:32:10 +09:30
parent c3cd66019e
commit efb2a7b412
2 changed files with 13 additions and 12 deletions
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10
bfd/ChangeLog
View File

@ -1,3 +1,13 @@
2020-06-09 Alan Modra <amodra@gmail.com>
* elf64-ppc.c (struct ppc_link_hash_table): Delete
maybe_local_ifunc_resolver field.
(build_global_entry_stubs_and_plt): Set local_ifunc_resolver in
cases where maybe_local_ifunc_resolver was set.
(ppc64_elf_relocate_section): Likewise.
(ppc64_elf_finish_dynamic_sections): Downgrade ifunc with textrel
error to a warning.
2020-06-08 H.J. Lu <hongjiu.lu@intel.com>
* elf-bfd.h (elf_link_hash_entry): Add tlsdesc_plt and

15
bfd/elf64-ppc.c
View File

@ -3242,7 +3242,6 @@ struct ppc_link_hash_table
/* Whether there exist local gnu indirect function resolvers,
referenced by dynamic relocations. */
unsigned int local_ifunc_resolver:1;
unsigned int maybe_local_ifunc_resolver:1;
/* Whether plt calls for ELFv2 localentry:0 funcs have been optimized. */
unsigned int has_plt_localentry0:1;
@ -13935,7 +13934,7 @@ build_global_entry_stubs_and_plt (struct elf_link_hash_entry *h, void *inf)
+ ((ent->plt.offset - PLT_INITIAL_ENTRY_SIZE (htab))
/ PLT_ENTRY_SIZE (htab) * sizeof (Elf64_External_Rela)));
if (h->type == STT_GNU_IFUNC && is_static_defined (h))
htab->maybe_local_ifunc_resolver = 1;
htab->local_ifunc_resolver = 1;
bfd_elf64_swap_reloca_out (info->output_bfd, &rela, loc);
}
}
@ -16103,10 +16102,8 @@ ppc64_elf_relocate_section (bfd *output_bfd,
if (ifunc)
{
relgot = htab->elf.irelplt;
if (indx == 0)
if (indx == 0 || is_static_defined (&h->elf))
htab->local_ifunc_resolver = 1;
else if (is_static_defined (&h->elf))
htab->maybe_local_ifunc_resolver = 1;
}
else if (indx != 0
|| (bfd_link_pic (info)
@ -16635,10 +16632,8 @@ ppc64_elf_relocate_section (bfd *output_bfd,
: ELF_ST_TYPE (sym->st_info) == STT_GNU_IFUNC)
{
sreloc = htab->elf.irelplt;
if (indx == 0)
if (indx == 0 || is_static_defined (&h->elf))
htab->local_ifunc_resolver = 1;
else if (is_static_defined (&h->elf))
htab->maybe_local_ifunc_resolver = 1;
}
if (sreloc == NULL)
abort ();
@ -17403,10 +17398,6 @@ ppc64_elf_finish_dynamic_sections (bfd *output_bfd,
case DT_TEXTREL:
if (htab->local_ifunc_resolver)
info->callbacks->einfo
(_("%X%P: text relocations and GNU indirect "
"functions will result in a segfault at runtime\n"));
else if (htab->maybe_local_ifunc_resolver)
info->callbacks->einfo
(_("%P: warning: text relocations and GNU indirect "
"functions may result in a segfault at runtime\n"));