linux-kernel - [PATCH] x86, relocs: add percpu fixup for GNU ld 2.23

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Message-ID: <20131016064314.GA2739@www.outflux.net>
Date:	Tue, 15 Oct 2013 23:43:14 -0700
From:	Kees Cook <keescook@...omium.org>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	linux-kernel@...r.kernel.org, Thomas Gleixner <tglx@...utronix.de>,
	"H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
	Michael Davidson <md@...gle.com>, Cong Ding <dinggnu@...il.com>
Subject: [PATCH] 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@...nel.org>
Signed-off-by: Kees Cook <keescook@...omium.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 1fa291f..7a85f29 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);
 }
 
-- 
1.7.9.5


-- 
Kees Cook
Chrome OS Security
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