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author | 2014-11-14 11:05:06 -0800 | |
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committer | 2014-11-14 16:36:25 -0500 | |
commit | a77f9c5dcdf8480a93332792c336fa2bf9d31229 (patch) | |
tree | 003964de0cc772f361d254385406fa75f3fcbff2 /arch | |
parent | openvswitch: Fix build failure. (diff) | |
download | linux-a77f9c5dcdf8480a93332792c336fa2bf9d31229.tar.gz linux-a77f9c5dcdf8480a93332792c336fa2bf9d31229.tar.bz2 linux-a77f9c5dcdf8480a93332792c336fa2bf9d31229.zip |
Revert "fast_hash: avoid indirect function calls"
This reverts commit e5a2c899957659cd1a9f789bc462f9c0b35f5150.
Commit e5a2c899 introduced an alternative_call, arch_fast_hash2,
that selects between __jhash2 and __intel_crc4_2_hash based on the
X86_FEATURE_XMM4_2.
Unfortunately, the alternative_call system does not appear to be
suitable for use with C functions, as register usage is not handled
properly for the called functions. The __jhash2 function in particular
clobbers registers that are not preserved when called via
alternative_call, resulting in a panic for direct callers of
arch_fast_hash2 on older CPUs lacking sse4_2. It is possible that
__intel_crc4_2_hash works merely by chance because it uses fewer
registers.
This commit was suggested as the source of the problem by Jesse
Gross <jesse@nicira.com>.
Signed-off-by: Jay Vosburgh <jay.vosburgh@canonical.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'arch')
-rw-r--r-- | arch/x86/include/asm/hash.h | 51 | ||||
-rw-r--r-- | arch/x86/lib/hash.c | 29 |
2 files changed, 17 insertions, 63 deletions
diff --git a/arch/x86/include/asm/hash.h b/arch/x86/include/asm/hash.h index a881d784f044..e8c58f88b1d4 100644 --- a/arch/x86/include/asm/hash.h +++ b/arch/x86/include/asm/hash.h @@ -1,48 +1,7 @@ -#ifndef __ASM_X86_HASH_H -#define __ASM_X86_HASH_H +#ifndef _ASM_X86_HASH_H +#define _ASM_X86_HASH_H -#include <linux/cpufeature.h> -#include <asm/alternative.h> +struct fast_hash_ops; +extern void setup_arch_fast_hash(struct fast_hash_ops *ops); -u32 __intel_crc4_2_hash(const void *data, u32 len, u32 seed); -u32 __intel_crc4_2_hash2(const u32 *data, u32 len, u32 seed); - -/* - * non-inline versions of jhash so gcc does not need to generate - * duplicate code in every object file - */ -u32 __jhash(const void *data, u32 len, u32 seed); -u32 __jhash2(const u32 *data, u32 len, u32 seed); - -/* - * for documentation of these functions please look into - * <include/asm-generic/hash.h> - */ - -static inline u32 arch_fast_hash(const void *data, u32 len, u32 seed) -{ - u32 hash; - - alternative_call(__jhash, __intel_crc4_2_hash, X86_FEATURE_XMM4_2, -#ifdef CONFIG_X86_64 - "=a" (hash), "D" (data), "S" (len), "d" (seed)); -#else - "=a" (hash), "a" (data), "d" (len), "c" (seed)); -#endif - return hash; -} - -static inline u32 arch_fast_hash2(const u32 *data, u32 len, u32 seed) -{ - u32 hash; - - alternative_call(__jhash2, __intel_crc4_2_hash2, X86_FEATURE_XMM4_2, -#ifdef CONFIG_X86_64 - "=a" (hash), "D" (data), "S" (len), "d" (seed)); -#else - "=a" (hash), "a" (data), "d" (len), "c" (seed)); -#endif - return hash; -} - -#endif /* __ASM_X86_HASH_H */ +#endif /* _ASM_X86_HASH_H */ diff --git a/arch/x86/lib/hash.c b/arch/x86/lib/hash.c index e14327198835..ff4fa51a5b1f 100644 --- a/arch/x86/lib/hash.c +++ b/arch/x86/lib/hash.c @@ -31,13 +31,13 @@ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. */ +#include <linux/hash.h> +#include <linux/init.h> + #include <asm/processor.h> #include <asm/cpufeature.h> #include <asm/hash.h> -#include <linux/hash.h> -#include <linux/jhash.h> - static inline u32 crc32_u32(u32 crc, u32 val) { #ifdef CONFIG_AS_CRC32 @@ -48,7 +48,7 @@ static inline u32 crc32_u32(u32 crc, u32 val) return crc; } -u32 __intel_crc4_2_hash(const void *data, u32 len, u32 seed) +static u32 intel_crc4_2_hash(const void *data, u32 len, u32 seed) { const u32 *p32 = (const u32 *) data; u32 i, tmp = 0; @@ -71,27 +71,22 @@ u32 __intel_crc4_2_hash(const void *data, u32 len, u32 seed) return seed; } -EXPORT_SYMBOL(__intel_crc4_2_hash); -u32 __intel_crc4_2_hash2(const u32 *data, u32 len, u32 seed) +static u32 intel_crc4_2_hash2(const u32 *data, u32 len, u32 seed) { + const u32 *p32 = (const u32 *) data; u32 i; for (i = 0; i < len; i++) - seed = crc32_u32(seed, *data++); + seed = crc32_u32(seed, *p32++); return seed; } -EXPORT_SYMBOL(__intel_crc4_2_hash2); -u32 __jhash(const void *data, u32 len, u32 seed) +void __init setup_arch_fast_hash(struct fast_hash_ops *ops) { - return jhash(data, len, seed); -} -EXPORT_SYMBOL(__jhash); - -u32 __jhash2(const u32 *data, u32 len, u32 seed) -{ - return jhash2(data, len, seed); + if (cpu_has_xmm4_2) { + ops->hash = intel_crc4_2_hash; + ops->hash2 = intel_crc4_2_hash2; + } } -EXPORT_SYMBOL(__jhash2); |