diff options
| author | Hannes Frederic Sowa <hannes@stressinduktion.org> | 2015-10-16 11:32:42 +0200 |
|---|---|---|
| committer | David S. Miller <davem@davemloft.net> | 2015-10-23 02:49:35 -0700 |
| commit | 79907146fb5b1778035870db895fb2bf64061284 (patch) | |
| tree | de48a8a1009dc237100ccdfff795da27aae4e61c /include | |
| parent | c80dbe04612986fd6104b4a1be21681b113b5ac9 (diff) | |
overflow-arith: begin to add support for overflow builtin functions
The idea of the overflow-arith.h header is to collect overflow checking
functions in one central place.
If gcc compiler supports the __builtin_overflow_* builtins we use them
because they might give better performance, otherwise the code falls
back to normal overflow checking functions.
The builtin_overflow functions are supported by gcc-5 and clang. The
matter of supporting clang is to just provide a corresponding
CC_HAVE_BUILTIN_OVERFLOW, because the specific overflow checking builtins
don't differ between gcc and clang.
I just provide overflow_usub function here as I intend this to get merged
into net, more functions will definitely follow as they are needed.
Signed-off-by: Hannes Frederic Sowa <hannes@stressinduktion.org>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/compiler-gcc.h | 4 | ||||
| -rw-r--r-- | include/linux/overflow-arith.h | 18 |
2 files changed, 22 insertions, 0 deletions
diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h index dfaa7b3e9ae9..82c159e0532a 100644 --- a/include/linux/compiler-gcc.h +++ b/include/linux/compiler-gcc.h @@ -237,6 +237,10 @@ #define KASAN_ABI_VERSION 3 #endif +#if GCC_VERSION >= 50000 +#define CC_HAVE_BUILTIN_OVERFLOW +#endif + #endif /* gcc version >= 40000 specific checks */ #if !defined(__noclone) diff --git a/include/linux/overflow-arith.h b/include/linux/overflow-arith.h new file mode 100644 index 000000000000..e12ccf854a70 --- /dev/null +++ b/include/linux/overflow-arith.h @@ -0,0 +1,18 @@ +#pragma once + +#include <linux/kernel.h> + +#ifdef CC_HAVE_BUILTIN_OVERFLOW + +#define overflow_usub __builtin_usub_overflow + +#else + +static inline bool overflow_usub(unsigned int a, unsigned int b, + unsigned int *res) +{ + *res = a - b; + return *res > a ? true : false; +} + +#endif |