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Message-ID: <20131012171007.GA17167@gmail.com>
Date: Sat, 12 Oct 2013 19:10:08 +0200
From: Ingo Molnar <mingo@...nel.org>
To: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: linux-kernel@...r.kernel.org,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Jakub Jelinek <jakub@...hat.com>,
Oleg Nesterov <oleg@...hat.com>,
Fengguang Wu <fengguang.wu@...el.com>,
Richard Henderson <rth@...ddle.net>,
Thomas Gleixner <tglx@...utronix.de>,
Andrew Morton <akpm@...ux-foundation.org>
Subject: [GIT PULL] compiler/gcc4: Add quirk for 'asm goto' miscompilation bug
Linus,
Please pull the latest core-urgent-for-linus git tree from:
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip.git core-urgent-for-linus
HEAD: 3f0116c3238a96bc18ad4b4acefe4e7be32fa861 compiler/gcc4: Add quirk for 'asm goto' miscompilation bug
This is the fix for the GCC miscompilation discussed in the following lkml
thread:
[x86] BUG: unable to handle kernel paging request at 00740060
The bug in GCC has been fixed by Jakub and the fix will be part of the GCC
4.8.2 release expected to be released next week - so the quirk's version
test checks for <= 4.8.1.
The quirk is only added to compiler-gcc4.h and not to the higher level
compiler.h because all asm goto uses are behind a feature check.
Thanks,
Ingo
------------------>
Ingo Molnar (1):
compiler/gcc4: Add quirk for 'asm goto' miscompilation bug
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 | 6 +++---
arch/x86/include/asm/jump_label.h | 2 +-
arch/x86/include/asm/mutex_64.h | 4 ++--
include/linux/compiler-gcc4.h | 15 +++++++++++++++
9 files changed, 26 insertions(+), 11 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 d3f5c63..89270b4 100644
--- a/arch/x86/include/asm/cpufeature.h
+++ b/arch/x86/include/asm/cpufeature.h
@@ -374,7 +374,7 @@ static __always_inline __pure bool __static_cpu_has(u16 bit)
* Catch too early usage of this before alternatives
* have run.
*/
- asm goto("1: jmp %l[t_warn]\n"
+ asm_volatile_goto("1: jmp %l[t_warn]\n"
"2:\n"
".section .altinstructions,\"a\"\n"
" .long 1b - .\n"
@@ -388,7 +388,7 @@ static __always_inline __pure bool __static_cpu_has(u16 bit)
#endif
- 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"
@@ -453,7 +453,7 @@ static __always_inline __pure bool _static_cpu_has_safe(u16 bit)
* have. Thus, we force the jump to the widest, 4-byte, signed relative
* offset even though the last would often fit in less bytes.
*/
- asm goto("1: .byte 0xe9\n .long %l[t_dynamic] - 2f\n"
+ asm_volatile_goto("1: .byte 0xe9\n .long %l[t_dynamic] - 2f\n"
"2:\n"
".section .altinstructions,\"a\"\n"
" .long 1b - .\n" /* src offset */
diff --git a/arch/x86/include/asm/jump_label.h b/arch/x86/include/asm/jump_label.h
index 64507f3..6a2cefb 100644
--- a/arch/x86/include/asm/jump_label.h
+++ b/arch/x86/include/asm/jump_label.h
@@ -18,7 +18,7 @@
static __always_inline bool arch_static_branch(struct static_key *key)
{
- asm goto("1:"
+ asm_volatile_goto("1:"
".byte " __stringify(STATIC_KEY_INIT_NOP) "\n\t"
".pushsection __jump_table, \"aw\" \n\t"
_ASM_ALIGN "\n\t"
diff --git a/arch/x86/include/asm/mutex_64.h b/arch/x86/include/asm/mutex_64.h
index e7e6751..07537a4 100644
--- a/arch/x86/include/asm/mutex_64.h
+++ b/arch/x86/include/asm/mutex_64.h
@@ -20,7 +20,7 @@
static inline void __mutex_fastpath_lock(atomic_t *v,
void (*fail_fn)(atomic_t *))
{
- asm volatile goto(LOCK_PREFIX " decl %0\n"
+ asm_volatile_goto(LOCK_PREFIX " decl %0\n"
" jns %l[exit]\n"
: : "m" (v->counter)
: "memory", "cc"
@@ -75,7 +75,7 @@ static inline int __mutex_fastpath_lock_retval(atomic_t *count)
static inline void __mutex_fastpath_unlock(atomic_t *v,
void (*fail_fn)(atomic_t *))
{
- asm volatile goto(LOCK_PREFIX " incl %0\n"
+ asm_volatile_goto(LOCK_PREFIX " incl %0\n"
" jg %l[exit]\n"
: : "m" (v->counter)
: "memory", "cc"
diff --git a/include/linux/compiler-gcc4.h b/include/linux/compiler-gcc4.h
index 842de22..ded4299 100644
--- a/include/linux/compiler-gcc4.h
+++ b/include/linux/compiler-gcc4.h
@@ -65,6 +65,21 @@
#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 GCC_VERSION >= 40400
--
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