compiler/gcc4: Add quirk for 'asm goto' miscompilation bug

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@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>
Reviewed-by: Richard Henderson <rth@twiddle.net>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Andrew Morton <akpm@linux-foundation.org>
Link: http://lkml.kernel.org/r/20131015062351.GA4666@gmail.com
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arm/include/asm/jump_label.h b/arch/arm/include/asm/jump_label.h
index bfc198c759130109d44b73b4506ea853d01fba28..863c892b4aaa7403c3bde97b7de3b2cd9a75519c 100644 (file)
--- 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 4d6d77ed9b9d679cd955e2fafe2dbc16527db65c..e194f957ca8c42a0af82f0621c425308a25e4d53 100644 (file)
--- 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 ae098c438f009eb0e312fc8b78a6ce07f4311cc6..f016bb699b5f6200268d3b8e5bf4e2bd003dbbf7 100644 (file)
--- 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 6c32190dc73e880255175049fe36965e647101eb..346b1c85ffb40d890078550dc72c2dedcb275a2e 100644 (file)
--- 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 5080d16a832ffec0c813b30cf546340e5047a7fd..ec2e2e2aba7d8f15419aa12bc6f790993f8c54d4 100644 (file)
--- 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 e99ac27f95b2cbcf9c0c5458cce4a946b7917b5e..4af181dacf9eca5dd949bbd3143ecbcc71e6ba76 100644 (file)
--- a/arch/x86/include/asm/cpufeature.h
+++ b/arch/x86/include/asm/cpufeature.h
@@ -365,7 +365,7 @@ 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 3a16c1483b459a144b32b042dd202d0467814646..029766958e69f7e01992a978bd22eaa2d2df73cc 100644 (file)
--- 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 842de225055fc5b8c769c59ff37e5afa81574f38..ded429966c1f447db9106359b174fb742fd3fe54 100644 (file)
--- 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