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x86-64: Add ENDBR64 to the TLSDESC PLT entry 

The TLSDESC entry in a lazy procedure linkage table is called indirectly
with "callq *(%rax)".  This patch adds an ENDBR64 to support indirect
branch tracking in Intel CET.  The TLSDESC PLT entry now looks like:

0xf3, 0x0f, 0x1e, 0xfa,  /* endbr64             */
0xff, 0x35, 8, 0, 0, 0,  /* pushq GOT+8(%rip)   */
0xff, 0x25, 16, 0, 0, 0  /* jmpq *GOT+TDG(%rip)  */

The BND prefix isn't needed since MPX isn't used for TLSDESC.

bfd/

	PR ld/23000
	* elf64-x86-64.c (elf_x86_64_finish_dynamic_sections): Add
	ENDBR64 to the TLSDESC PLT entry.

ld/

	PR ld/23000
	* testsuite/ld-x86-64/tlsdesc.pd: Updated.
This commit is contained in:
H.J. Lu 2018-03-25 05:02:17 -07:00
parent b3ee71e749
commit bf54968b12
4 changed files with 31 additions and 14 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
bfd/ChangeLog
View File

@ -1,3 +1,9 @@
2018-03-25 H.J. Lu <hongjiu.lu@intel.com>
PR ld/23000
* elf64-x86-64.c (elf_x86_64_finish_dynamic_sections): Add
ENDBR64 to the TLSDESC PLT entry.
2018-03-21 Alan Modra <amodra@gmail.com>
* elf64-ppc.c (ppc64_elf_get_synthetic_symtab): Trim uninteresting

32
bfd/elf64-x86-64.c
View File

@ -4411,15 +4411,23 @@ elf_x86_64_finish_dynamic_sections (bfd *output_bfd,
if (htab->tlsdesc_plt)
{
/* The TLSDESC entry in a lazy procedure linkage table. */
static const bfd_byte tlsdesc_plt_entry[LAZY_PLT_ENTRY_SIZE] =
{
0xf3, 0x0f, 0x1e, 0xfa, /* endbr64 */
0xff, 0x35, 8, 0, 0, 0, /* pushq GOT+8(%rip) */
0xff, 0x25, 16, 0, 0, 0 /* jmpq *GOT+TDG(%rip) */
};
bfd_put_64 (output_bfd, (bfd_vma) 0,
htab->elf.sgot->contents + htab->tlsdesc_got);
memcpy (htab->elf.splt->contents + htab->tlsdesc_plt,
htab->lazy_plt->plt0_entry,
htab->lazy_plt->plt0_entry_size);
tlsdesc_plt_entry, LAZY_PLT_ENTRY_SIZE);
/* Add offset for pushq GOT+8(%rip), since the
instruction uses 6 bytes subtract this value. */
/* Add offset for pushq GOT+8(%rip), since ENDBR64 uses 4
bytes and the instruction uses 6 bytes, subtract these
values. */
bfd_put_32 (output_bfd,
(htab->elf.sgotplt->output_section->vma
+ htab->elf.sgotplt->output_offset
@ -4427,14 +4435,13 @@ elf_x86_64_finish_dynamic_sections (bfd *output_bfd,
- htab->elf.splt->output_section->vma
- htab->elf.splt->output_offset
- htab->tlsdesc_plt
- 6),
- 4 - 6),
(htab->elf.splt->contents
+ htab->tlsdesc_plt
+ htab->lazy_plt->plt0_got1_offset));
/* Add offset for the PC-relative instruction accessing
GOT+TDG, where TDG stands for htab->tlsdesc_got,
subtracting the offset to the end of that
instruction. */
+ 4 + 2));
/* Add offset for indirect branch via GOT+TDG, where TDG
stands for htab->tlsdesc_got, subtracting the offset
to the end of that instruction. */
bfd_put_32 (output_bfd,
(htab->elf.sgot->output_section->vma
+ htab->elf.sgot->output_offset
@ -4442,10 +4449,9 @@ elf_x86_64_finish_dynamic_sections (bfd *output_bfd,
- htab->elf.splt->output_section->vma
- htab->elf.splt->output_offset
- htab->tlsdesc_plt
- htab->lazy_plt->plt0_got2_insn_end),
- 4 - 6 - 6),
(htab->elf.splt->contents
+ htab->tlsdesc_plt
+ htab->lazy_plt->plt0_got2_offset));
+ htab->tlsdesc_plt + 4 + 6 + 2));
}
}

5
ld/ChangeLog
View File

@ -1,3 +1,8 @@
2018-03-25 H.J. Lu <hongjiu.lu@intel.com>
PR ld/23000
* testsuite/ld-x86-64/tlsdesc.pd: Updated.
2018-03-23 Nick Clifton <nickc@redhat.com>
PR 22948

2
ld/testsuite/ld-x86-64/tlsdesc.pd
View File

@ -13,7 +13,7 @@ Disassembly of section .plt:
[0-9a-f]+: ff 35 .. .. 20 00 pushq .*\(%rip\) # 201358 <_GLOBAL_OFFSET_TABLE_\+0x8>
[0-9a-f]+: ff 25 .. .. 20 00 jmpq \*.*\(%rip\) # 201360 <_GLOBAL_OFFSET_TABLE_\+0x10>
[0-9a-f]+: 0f 1f 40 00 nopl 0x0\(%rax\)
[0-9a-f]+: f3 0f 1e fa endbr64
[0-9a-f]+: ff 35 .. .. 20 00 pushq .*\(%rip\) # 201358 <_GLOBAL_OFFSET_TABLE_\+0x8>
[0-9a-f]+: ff 25 .. .. 20 00 jmpq \*.*\(%rip\) # 201348 <.*>
[0-9a-f]+: 0f 1f 40 00 nopl 0x0\(%rax\)