From: Ingo Molnar <mingo@kernel.org>
To: Jakub Jelinek <jakub@redhat.com>
Cc: Richard Henderson <rth@twiddle.net>,
Peter Zijlstra <peterz@infradead.org>,
Oleg Nesterov <oleg@redhat.com>,
Fengguang Wu <fengguang.wu@intel.com>,
Linus Torvalds <torvalds@linux-foundation.org>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>
Subject: [PATCH, -v3] compiler/gcc4: Add quirk for 'asm goto' miscompilation bug
Date: Thu, 10 Oct 2013 17:12:19 +0200 [thread overview]
Message-ID: <20131010151219.GC5167@gmail.com> (raw)
In-Reply-To: <20131010142703.GI30970@tucnak.zalov.cz>
* Jakub Jelinek <jakub@redhat.com> wrote:
> On Thu, Oct 10, 2013 at 07:04:18AM -0700, Richard Henderson wrote:
> > On 10/10/2013 01:31 AM, Jakub Jelinek wrote:
> > > Also, for the bitops patch, you probably want an asm_volatile_goto variant.
> >
> > Why? Asm without output (which asm goto must be) are automatically volatile.
>
> You're right.
Indeed. Something like the updated version below?
[ I kept the asm_volatile_goto() naming to make sure the implicit volatile
is visible. ]
Thanks,
Ingo
--------------------->
>From 1ab592e8d55576880b90c131529111f51c188284 Mon Sep 17 00:00:00 2001
From: Ingo Molnar <mingo@kernel.org>
Date: Thu, 10 Oct 2013 10:16:30 +0200
Subject: [PATCH] compiler/gcc4: Add quirk for 'asm goto' miscompilation bug
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-by: Fengguang Wu <fengguang.wu@intel.com>
Reported-by: Oleg Nesterov <oleg@redhat.com>
Reported-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
Suggested-by: Jakub Jelinek <jakub@redhat.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
---
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 ++--
arch/x86/include/asm/rmwcc.h | 2 +-
include/linux/compiler-gcc4.h | 15 +++++++++++++++
10 files changed, 27 insertions(+), 12 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/arch/x86/include/asm/rmwcc.h b/arch/x86/include/asm/rmwcc.h
index 735f184..1ff990f 100644
--- a/arch/x86/include/asm/rmwcc.h
+++ b/arch/x86/include/asm/rmwcc.h
@@ -5,7 +5,7 @@
#define __GEN_RMWcc(fullop, var, cc, ...) \
do { \
- asm volatile goto (fullop "; j" cc " %l[cc_label]" \
+ asm_volatile_goto (fullop "; j" cc " %l[cc_label]" \
: : "m" (var), ## __VA_ARGS__ \
: "memory" : cc_label); \
return 0; \
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
next prev parent reply other threads:[~2013-10-10 15:12 UTC|newest]
Thread overview: 69+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-10-05 23:44 [x86] BUG: unable to handle kernel paging request at 00740060 Fengguang Wu
2013-10-05 23:47 ` [x86] BUG: unable to handle kernel paging request at 08000060 Fengguang Wu
2013-10-06 7:27 ` Mike Galbraith
2013-10-06 7:36 ` Fengguang Wu
2013-10-07 8:49 ` Peter Zijlstra
2013-10-07 9:17 ` Fengguang Wu
2013-10-07 9:36 ` Peter Zijlstra
2013-10-07 9:46 ` Fengguang Wu
2013-10-07 8:55 ` [x86] BUG: unable to handle kernel paging request at 00740060 Peter Zijlstra
2013-10-07 9:08 ` Peter Zijlstra
2013-10-07 11:32 ` Fengguang Wu
2013-10-07 9:27 ` Fengguang Wu
2013-10-07 18:47 ` Linus Torvalds
2013-10-08 7:51 ` Fengguang Wu
2013-10-08 16:21 ` Linus Torvalds
2013-10-08 17:15 ` [x86] BUG: unable to handle kernel NULL pointer dereference at (null) Fengguang Wu
2013-10-08 17:31 ` Linus Torvalds
2013-10-09 1:09 ` Fengguang Wu
2013-10-09 1:33 ` Linus Torvalds
2013-10-08 18:51 ` [x86] BUG: unable to handle kernel paging request at 00740060 Oleg Nesterov
2013-10-08 19:05 ` Jakub Jelinek
2013-10-08 19:20 ` Linus Torvalds
2013-10-08 19:34 ` Linus Torvalds
2013-10-08 19:35 ` Oleg Nesterov
2013-10-08 19:49 ` Linus Torvalds
2013-10-09 1:43 ` Mike Galbraith
2013-10-08 19:05 ` Linus Torvalds
2013-10-08 16:46 ` Oleg Nesterov
2013-10-08 14:34 ` Oleg Nesterov
2013-10-09 8:04 ` Fengguang Wu
2013-10-09 12:19 ` Fengguang Wu
2013-10-09 12:21 ` Fengguang Wu
2013-10-09 12:27 ` Peter Zijlstra
2013-10-09 12:52 ` Ingo Molnar
2013-10-09 17:18 ` Ingo Molnar
2013-10-10 2:15 ` Mike Galbraith
2013-10-09 12:56 ` Fengguang Wu
2013-10-09 12:43 ` Oleg Nesterov
2013-10-09 14:07 ` Peter Zijlstra
2013-10-09 14:17 ` Oleg Nesterov
2013-10-09 14:32 ` Ingo Molnar
2013-10-09 14:33 ` Peter Zijlstra
2013-10-09 14:46 ` Peter Zijlstra
2013-10-09 18:16 ` Jakub Jelinek
2013-10-09 18:54 ` Linus Torvalds
2013-10-09 19:02 ` Peter Zijlstra
2013-10-09 19:08 ` Jakub Jelinek
2013-10-10 6:22 ` Ingo Molnar
2013-10-10 6:51 ` Jakub Jelinek
2013-10-10 8:04 ` Jakub Jelinek
2013-10-10 8:24 ` [PATCH] gcc4: Add 'asm goto' miscompilation quirk Ingo Molnar
2013-10-10 8:31 ` Jakub Jelinek
2013-10-10 8:45 ` Ingo Molnar
2013-10-10 8:55 ` [PATCH, -v2] compiler/gcc4: Add quirk for 'asm goto' miscompilation bug Ingo Molnar
2013-10-10 11:56 ` Peter Zijlstra
2013-10-10 12:32 ` Jakub Jelinek
2013-10-10 13:10 ` Peter Zijlstra
2013-10-10 15:04 ` Ingo Molnar
2013-10-10 14:04 ` [PATCH] gcc4: Add 'asm goto' miscompilation quirk Richard Henderson
2013-10-10 14:27 ` Jakub Jelinek
2013-10-10 15:12 ` Ingo Molnar [this message]
2013-10-10 16:15 ` [PATCH, -v3] compiler/gcc4: Add quirk for 'asm goto' miscompilation bug Richard Henderson
2013-10-10 16:49 ` Ingo Molnar
2013-10-11 4:35 ` Fengguang Wu
2013-10-11 5:46 ` Ingo Molnar
2013-10-11 6:51 ` Fengguang Wu
2013-10-11 9:30 ` Fengguang Wu
2013-10-12 17:03 ` Ingo Molnar
2013-10-10 8:34 ` [PATCH] gcc4: Add 'asm goto' miscompilation quirk Ingo Molnar
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