S/390: Disable relocation sort against code sections.

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.

diff --git a/bfd/ChangeLog b/bfd/ChangeLog
index 68b8549..06f13b2 100644 (file)
--- a/bfd/ChangeLog
+++ b/bfd/ChangeLog
@@ -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

diff --git a/bfd/elf-s390-common.c b/bfd/elf-s390-common.c
index 6fd1027..462da16 100644 (file)
--- a/bfd/elf-s390-common.c
+++ b/bfd/elf-s390-common.c
@@ -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;
+}

diff --git a/bfd/elf32-s390.c b/bfd/elf32-s390.c
index f5403e2..0127eab 100644 (file)
--- a/bfd/elf32-s390.c
+++ b/bfd/elf32-s390.c
@@ -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

diff --git a/bfd/elf64-s390.c b/bfd/elf64-s390.c
index e002f06..f06b58a 100644 (file)
--- a/bfd/elf64-s390.c
+++ b/bfd/elf64-s390.c
@@ -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