linux-kernel - [PATCH] include/linux/compiler*.h: add version detection to asm_volatile

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Date:   Fri,  7 Sep 2018 15:21:03 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     akpm@...ux-foundation.org
Cc:     miguel.ojeda.sandonis@...il.com,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Kees Cook <keescook@...omium.org>,
        Ingo Molnar <mingo@...nel.org>,
        Herbert Xu <herbert@...dor.apana.org.au>,
        Geert Uytterhoeven <geert@...ux-m68k.org>,
        Arnd Bergmann <arnd@...db.de>, Joe Perches <joe@...ches.com>,
        Rasmus Villemoes <linux@...musvillemoes.dk>,
        Paul Burton <paul.burton@...s.com>,
        Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Will Deacon <will.deacon@....com>, linux-kernel@...r.kernel.org
Subject: [PATCH] include/linux/compiler*.h: add version detection to asm_volatile_goto

The comment above asm_volatile_goto mentions working around a GCC bug,
and links to a bug report that claims this has been fixed in newer
versions of GCC.  Testing shows that this was resolved in GCC 4.8.2.
asm_volatile_goto should also be defined for other compilers that
support asm goto.

Signed-off-by: Nick Desaulniers <ndesaulniers@...gle.com>
---
 include/linux/compiler-gcc.h   | 7 ++++++-
 include/linux/compiler_types.h | 4 ++++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index 763bbad1e258..149f411b4366 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -171,7 +171,7 @@
 #endif
 
 /*
- * GCC 'asm goto' miscompiles certain code sequences:
+ * GCC < 4.8.2 'asm goto' miscompiles certain code sequences:
  *
  *   http://gcc.gnu.org/bugzilla/show_bug.cgi?id=58670
  *
@@ -179,7 +179,12 @@
  *
  * (asm goto is automatically volatile - the naming reflects this.)
  */
+#if GCC_VERSION < 40802
 #define asm_volatile_goto(x...)	do { asm goto(x); asm (""); } while (0)
+#else
+#define asm_volatile_goto(x...)	asm goto(x)
+#endif
+
 
 /*
  * sparse (__CHECKER__) pretends to be gcc, but can't do constant
diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h
index 3525c179698c..61449dbf30d8 100644
--- a/include/linux/compiler_types.h
+++ b/include/linux/compiler_types.h
@@ -151,6 +151,10 @@ struct ftrace_likely_data {
 #define __assume_aligned(a, ...)
 #endif
 
+#ifndef asm_volatile_goto
+#define asm_volatile_goto(x...) asm goto(x)
+#endif
+
 /* Are two types/vars the same type (ignoring qualifiers)? */
 #define __same_type(a, b) __builtin_types_compatible_p(typeof(a), typeof(b))
 
-- 
2.19.0.rc2.392.g5ba43deb5a-goog