[tip:x86/kaslr] x86/relocs: Add percpu fixup for GNU ld 2.23

[tip-bot for Kees Cook <tipbot@zytor.com>]

Commit-ID:  aec58bafaf89279522c44ec8ca9211eabb2b6976
Gitweb:     http://git.kernel.org/tip/aec58bafaf89279522c44ec8ca9211eabb2b6976
Author:     Kees Cook <keescook@chromium.org>
AuthorDate: Tue, 15 Oct 2013 23:43:14 -0700
Committer:  Ingo Molnar <mingo@kernel.org>
CommitDate: Fri, 18 Oct 2013 08:45:09 +0200

x86/relocs: Add percpu fixup for GNU ld 2.23

The GNU linker tries to put __per_cpu_load into the percpu area,
resulting in a lack of its relocation. Force this symbol to be
relocated. Seen starting with GNU ld 2.23 and later.

Reported-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Kees Cook <keescook@chromium.org>
Cc: Michael Davidson <md@google.com>
Cc: Cong Ding <dinggnu@gmail.com>
Link: http://lkml.kernel.org/r/20131016064314.GA2739@www.outflux.net
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
 arch/x86/tools/relocs.c | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/arch/x86/tools/relocs.c b/arch/x86/tools/relocs.c
index 71a2533..11f9285 100644
--- a/arch/x86/tools/relocs.c
+++ b/arch/x86/tools/relocs.c
@@ -729,6 +729,7 @@ static void percpu_init(void)
  *
  * The GNU linker incorrectly associates:
  *	__init_begin
+ *	__per_cpu_load
  *
  * The "gold" linker incorrectly associates:
  *	init_per_cpu__irq_stack_union
@@ -738,6 +739,7 @@ static int is_percpu_sym(ElfW(Sym) *sym, const char *symname)
 {
 	return (sym->st_shndx == per_cpu_shndx) &&
 		strcmp(symname, "__init_begin") &&
+		strcmp(symname, "__per_cpu_load") &&
 		strncmp(symname, "init_per_cpu_", 13);
 }