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bfd: allow negative offsets to _GLOBAL_OFFSET_TABLE_ in elf64 SPARC 

The code compiled with the -fpic model in SPARC uses 13-bit signed
immediate PC-relative loads to fetch entries from the GOT table.  In
theory this would allow using a GOT table (.got section) containing up
to 1024 entries in elf32 or 512 entries in elf64.

However, in elf64 sparc GNU targets _GLOBAL_OFFSET_TABLE_ is always
placed at the beginning of the .got section, making it impossible to use
negative offsets.  This limits the usage of -fpic to GOT tables
containing a maximum of 257 entries in elf64.

This patch activates an optimization that is already used in sparc-elf32
also in sparc-elf64, that sets _GLOBAL_OFFSET_TABLE_ to point 0x1000
into the .got section if the section size is bigger than 0x1000.

2016-09-19  Jose E. Marchesi  <jose.marchesi@oracle.com>

	* elfxx-sparc.c (_bfd_sparc_elf_size_dynamic_sections): Allow
	negative offsets to _GLOBAL_OFFSET_TABLE_ if the .got section is
	bigger than 0x1000 bytes.
This commit is contained in:
Jose E. Marchesi 2016-09-19 05:19:14 -07:00
parent 2387dd9049
commit b19753ce31
2 changed files with 14 additions and 8 deletions
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6
bfd/ChangeLog
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@ -1,3 +1,9 @@
2016-09-19 Jose E. Marchesi <jose.marchesi@oracle.com>
* elfxx-sparc.c (_bfd_sparc_elf_size_dynamic_sections): Allow
negative offsets to _GLOBAL_OFFSET_TABLE_ if the .got section is
bigger than 0x1000 bytes.
2016-09-14 Thomas Preud'homme <thomas.preudhomme@arm.com>
* elf32-arm.c (elf32_arm_gc_mark_extra_sections): Only mark section

16
bfd/elfxx-sparc.c
View File

@ -2661,19 +2661,19 @@ _bfd_sparc_elf_size_dynamic_sections (bfd *output_bfd,
/* Allocate .plt and .got entries, and space for local symbols. */
htab_traverse (htab->loc_hash_table, allocate_local_dynrelocs, info);
if (! ABI_64_P (output_bfd)
&& !htab->is_vxworks
if (!htab->is_vxworks
&& elf_hash_table (info)->dynamic_sections_created)
{
/* Make space for the trailing nop in .plt. */
if (htab->elf.splt->size > 0)
htab->elf.splt->size += 1 * SPARC_INSN_BYTES;
if (! ABI_64_P (output_bfd))
{
/* Make space for the trailing nop in .plt. */
if (htab->elf.splt->size > 0)
htab->elf.splt->size += 1 * SPARC_INSN_BYTES;
}
/* If the .got section is more than 0x1000 bytes, we add
0x1000 to the value of _GLOBAL_OFFSET_TABLE_, so that 13
bit relocations have a greater chance of working.
FIXME: Make this optimization work for 64-bit too. */
bit relocations have a greater chance of working. */
if (htab->elf.sgot->size >= 0x1000
&& elf_hash_table (info)->hgot->root.u.def.value == 0)
elf_hash_table (info)->hgot->root.u.def.value = 0x1000;