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Message-Id: <1383069882-11437-20-git-send-email-kamal@canonical.com>
Date: Tue, 29 Oct 2013 11:03:40 -0700
From: Kamal Mostafa <kamal@...onical.com>
To: linux-kernel@...r.kernel.org, stable@...r.kernel.org,
kernel-team@...ts.ubuntu.com
Cc: Linus Torvalds <torvalds@...ux-foundation.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Ingo Molnar <mingo@...nel.org>,
Kamal Mostafa <kamal@...onical.com>
Subject: [PATCH 3.8 19/81] compiler/gcc4: Add quirk for 'asm goto' miscompilation bug
3.8.13.12 -stable review patch. If anyone has any objections, please let me know.
------------------
From: Ingo Molnar <mingo@...nel.org>
commit 3f0116c3238a96bc18ad4b4acefe4e7be32fa861 upstream.
Fengguang Wu, Oleg Nesterov and Peter Zijlstra tracked down
a kernel crash to a GCC bug: GCC miscompiles certain 'asm goto'
constructs, as outlined here:
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58670
Implement a workaround suggested by Jakub Jelinek.
Reported-and-tested-by: Fengguang Wu <fengguang.wu@...el.com>
Reported-by: Oleg Nesterov <oleg@...hat.com>
Reported-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Suggested-by: Jakub Jelinek <jakub@...hat.com>
Reviewed-by: Richard Henderson <rth@...ddle.net>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@...nel.org>
[ kamal: backport to 3.8 ]
Signed-off-by: Kamal Mostafa <kamal@...onical.com>
---
arch/arm/include/asm/jump_label.h | 2 +-
arch/mips/include/asm/jump_label.h | 2 +-
arch/powerpc/include/asm/jump_label.h | 2 +-
arch/s390/include/asm/jump_label.h | 2 +-
arch/sparc/include/asm/jump_label.h | 2 +-
arch/x86/include/asm/cpufeature.h | 2 +-
arch/x86/include/asm/jump_label.h | 2 +-
include/linux/compiler-gcc4.h | 15 +++++++++++++++
8 files changed, 22 insertions(+), 7 deletions(-)
diff --git a/arch/arm/include/asm/jump_label.h b/arch/arm/include/asm/jump_label.h
index bfc198c..863c892 100644
--- a/arch/arm/include/asm/jump_label.h
+++ b/arch/arm/include/asm/jump_label.h
@@ -16,7 +16,7 @@
static __always_inline bool arch_static_branch(struct static_key *key)
{
- asm goto("1:\n\t"
+ asm_volatile_goto("1:\n\t"
JUMP_LABEL_NOP "\n\t"
".pushsection __jump_table, \"aw\"\n\t"
".word 1b, %l[l_yes], %c0\n\t"
diff --git a/arch/mips/include/asm/jump_label.h b/arch/mips/include/asm/jump_label.h
index 4d6d77e..e194f95 100644
--- a/arch/mips/include/asm/jump_label.h
+++ b/arch/mips/include/asm/jump_label.h
@@ -22,7 +22,7 @@
static __always_inline bool arch_static_branch(struct static_key *key)
{
- asm goto("1:\tnop\n\t"
+ asm_volatile_goto("1:\tnop\n\t"
"nop\n\t"
".pushsection __jump_table, \"aw\"\n\t"
WORD_INSN " 1b, %l[l_yes], %0\n\t"
diff --git a/arch/powerpc/include/asm/jump_label.h b/arch/powerpc/include/asm/jump_label.h
index ae098c4..f016bb6 100644
--- a/arch/powerpc/include/asm/jump_label.h
+++ b/arch/powerpc/include/asm/jump_label.h
@@ -19,7 +19,7 @@
static __always_inline bool arch_static_branch(struct static_key *key)
{
- asm goto("1:\n\t"
+ asm_volatile_goto("1:\n\t"
"nop\n\t"
".pushsection __jump_table, \"aw\"\n\t"
JUMP_ENTRY_TYPE "1b, %l[l_yes], %c0\n\t"
diff --git a/arch/s390/include/asm/jump_label.h b/arch/s390/include/asm/jump_label.h
index 6c32190..346b1c8 100644
--- a/arch/s390/include/asm/jump_label.h
+++ b/arch/s390/include/asm/jump_label.h
@@ -15,7 +15,7 @@
static __always_inline bool arch_static_branch(struct static_key *key)
{
- asm goto("0: brcl 0,0\n"
+ asm_volatile_goto("0: brcl 0,0\n"
".pushsection __jump_table, \"aw\"\n"
ASM_ALIGN "\n"
ASM_PTR " 0b, %l[label], %0\n"
diff --git a/arch/sparc/include/asm/jump_label.h b/arch/sparc/include/asm/jump_label.h
index 5080d16..ec2e2e2 100644
--- a/arch/sparc/include/asm/jump_label.h
+++ b/arch/sparc/include/asm/jump_label.h
@@ -9,7 +9,7 @@
static __always_inline bool arch_static_branch(struct static_key *key)
{
- asm goto("1:\n\t"
+ asm_volatile_goto("1:\n\t"
"nop\n\t"
"nop\n\t"
".pushsection __jump_table, \"aw\"\n\t"
diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h
index 2d9075e..d3f0db1 100644
--- a/arch/x86/include/asm/cpufeature.h
+++ b/arch/x86/include/asm/cpufeature.h
@@ -346,7 +346,7 @@ extern const char * const x86_power_flags[32];
static __always_inline __pure bool __static_cpu_has(u16 bit)
{
#if __GNUC__ > 4 || __GNUC_MINOR__ >= 5
- asm goto("1: jmp %l[t_no]\n"
+ asm_volatile_goto("1: jmp %l[t_no]\n"
"2:\n"
".section .altinstructions,\"a\"\n"
" .long 1b - .\n"
diff --git a/arch/x86/include/asm/jump_label.h b/arch/x86/include/asm/jump_label.h
index 3a16c14..0297669 100644
--- a/arch/x86/include/asm/jump_label.h
+++ b/arch/x86/include/asm/jump_label.h
@@ -13,7 +13,7 @@
static __always_inline bool arch_static_branch(struct static_key *key)
{
- asm goto("1:"
+ asm_volatile_goto("1:"
STATIC_KEY_INITIAL_NOP
".pushsection __jump_table, \"aw\" \n\t"
_ASM_ALIGN "\n\t"
diff --git a/include/linux/compiler-gcc4.h b/include/linux/compiler-gcc4.h
index c9785c2..e8f0bf9 100644
--- a/include/linux/compiler-gcc4.h
+++ b/include/linux/compiler-gcc4.h
@@ -67,6 +67,21 @@
#define __visible __attribute__((externally_visible))
#endif
+/*
+ * GCC 'asm goto' miscompiles certain code sequences:
+ *
+ * http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58670
+ *
+ * Work it around via a compiler barrier quirk suggested by Jakub Jelinek.
+ * Fixed in GCC 4.8.2 and later versions.
+ *
+ * (asm goto is automatically volatile - the naming reflects this.)
+ */
+#if GCC_VERSION <= 40801
+# define asm_volatile_goto(x...) do { asm goto(x); asm (""); } while (0)
+#else
+# define asm_volatile_goto(x...) do { asm goto(x); } while (0)
+#endif
#ifdef CONFIG_ARCH_USE_BUILTIN_BSWAP
#if __GNUC_MINOR__ >= 4
--
1.8.1.2
--
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