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S/390: Disable relocation sort against code sections.

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When downgrading from GD to IE model we rewrite the call to
__tls_get_offset to a 64 bit load instruction. This relies on the fact
that the additional relocation for the call target has already been
executed when doing the rewrite.

   f1018:       e3 20 d0 00 00 04       lg      %r2,0(%r13)
   f101e:       c0 e5 00 00 00 00       brasl   %r14,f101e <__res_init+0x1e>
                        f101e: R_390_TLS_GDCALL __libc_resp
                        f1020: R_390_PLT32DBL   __tls_get_offset+0x2

0000000f1020  39f6c00000014 R_390_PLT32DBL    0000000000000000 __tls_get_offset + 2
0000000f101e  3afb700000026 R_390_TLS_GDCALL  0000000000000008 __libc_resp + 0

Due to the reloc sorting the order changed an the PLT32DBL reloc is
executed after the rewrite and overwrites part of the load instruction
with garbage.

bfd/
2015-03-14  Andreas Krebbel  <krebbel@linux.vnet.ibm.com>

	* elf-s390-common.c (elf_s390_elf_sort_relocs_p): Don't sort
	relocs against code sections.
	* elf32-s390.c: Define elf_backend_sort_relocs_p.
	* elf64-s390.c: Likewise.
This commit is contained in:
Andreas Krebbel 2015-03-14 11:45:05 +01:00
parent 5cddc23a3a
commit b9005ba76e
4 changed files with 21 additions and 0 deletions
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7
bfd/ChangeLog
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@ -1,3 +1,10 @@
2015-03-14 Andreas Krebbel <krebbel@linux.vnet.ibm.com>
* elf-s390-common.c (elf_s390_elf_sort_relocs_p): Don't sort
relocs against code sections.
* elf32-s390.c: Define elf_backend_sort_relocs_p.
* elf64-s390.c: Likewise.
2015-03-11 Alan Modra <amodra@gmail.com>
* elf32-ppc.c (ppc_elf_get_synthetic_symtab): Examine stubs in

12
bfd/elf-s390-common.c
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@ -242,3 +242,15 @@ elf_s390_add_symbol_hook (bfd *abfd,
return TRUE;
}
/* Whether to sort relocs output by ld -r or ld --emit-relocs, by
r_offset. Don't do so for code sections. We want to keep ordering
of GDCALL / PLT32DBL for TLS optimizations as is. On the other
hand, elf-eh-frame.c processing requires .eh_frame relocs to be
sorted. */
static bfd_boolean
elf_s390_elf_sort_relocs_p (asection *sec)
{
return (sec->flags & SEC_CODE) == 0;
}

1
bfd/elf32-s390.c
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@ -4028,6 +4028,7 @@ elf32_s390_merge_private_bfd_data (bfd *ibfd, bfd *obfd)
#define elf_backend_grok_prstatus elf_s390_grok_prstatus
#define elf_backend_plt_sym_val elf_s390_plt_sym_val
#define elf_backend_add_symbol_hook elf_s390_add_symbol_hook
#define elf_backend_sort_relocs_p elf_s390_elf_sort_relocs_p
#define bfd_elf32_mkobject elf_s390_mkobject
#define elf_backend_object_p elf_s390_object_p

1
bfd/elf64-s390.c
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@ -3840,6 +3840,7 @@ const struct elf_size_info s390_elf64_size_info =
#define elf_backend_init_index_section _bfd_elf_init_1_index_section
#define elf_backend_plt_sym_val elf_s390_plt_sym_val
#define elf_backend_add_symbol_hook elf_s390_add_symbol_hook
#define elf_backend_sort_relocs_p elf_s390_elf_sort_relocs_p
#define bfd_elf64_mkobject elf_s390_mkobject
#define elf_backend_object_p elf_s390_object_p