Messages in this thread Patch in this message | | | From | Arnd Bergmann <> | Subject | Re: [PATCH] x86: do not expose CONFIG_BSWAP to userspace | Date | Tue, 3 Feb 2009 19:19:55 +0100 |
| |
On Thursday 29 January 2009, H. Peter Anvin wrote: > Harvey Harrison wrote: > > On Wed, 2009-01-28 at 15:27 -0800, H. Peter Anvin wrote: > >> Harvey Harrison wrote: > >>> Well, that's unfortunate, how about we just export the BSWAP version > >>> unconditionally and hope pure i386 just goes away someday? > >>> > >> Well, we already have MOVBE coming up, too... > >> > > > > Is someone already working on an __arch_swab{16|32|64}p to use them? > > > > Not that I know of, but it's trivial enough. They can also be used for > all-register swapping, too, with the advantage that you get register > decoupling.
I just realized that gcc-4.3 and higher have the __builtin_bswap{16,32,64} functions on x86, which are supposed to do the right thing on any platform. Maybe a patch like the one below can solve this for both the kernel and for other users of the byteorder headers. Unfortunately, I could not find out whether the builtins are available on all other platforms as well.
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
--- a/arch/x86/include/asm/swab.h +++ b/arch/x86/include/asm/swab.h @@ -4,9 +4,17 @@ #include <linux/types.h> #include <linux/compiler.h> +#ifdef __CHECKER__ +extern unsigned long __builtin_bswap_32(unsigned long x); +extern unsigned long long __builtin_bswap_64(unsigned long long x); +#endif + static inline __attribute_const__ __u32 __arch_swab32(__u32 val) { -#ifdef __i386__ +#if defined(__GNUC__) && ((__GNUC__ > 4) || \ + ((__GNUC__ == 4) && (__GNUC_MINOR__ >= 3))) + val = __builtin_bswap32(val); +#elif defined (__i386__) # ifdef CONFIG_X86_BSWAP asm("bswap %0" : "=r" (val) : "0" (val)); # else @@ -28,7 +36,10 @@ static inline __attribute_const__ __u32 __arch_swab32(__u32 val) static inline __attribute_const__ __u64 __arch_swab64(__u64 val) { -#ifdef __i386__ +#if defined(__GNUC__) && ((__GNUC__ > 4) || \ + ((__GNUC__ == 4) && (__GNUC_MINOR__ >= 3))) + return __builtin_bswap64(val); +#elif defined (__i386__) union { struct { __u32 a; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
| |