[ovs-discuss] [PATCH net-next] fast_hash: clobber registers correctly for inline function use

Hannes Frederic Sowa hannes at stressinduktion.org
Fri Nov 14 14:06:55 UTC 2014


In case the arch_fast_hash call gets inlined we need to tell gcc which
registers are clobbered with. Most callers where fine, as rhashtable
used arch_fast_hash via function pointer and thus the compiler took care
of that. In case of openvswitch the call got inlined and arch_fast_hash
touched registeres which gcc didn't know about.

Also don't use conditional compilation inside arguments, as this confuses
sparse.

Reported-by: Jay Vosburgh <jay.vosburgh at canonical.com>
Cc: Pravin Shelar <pshelar at nicira.com>
Cc: Jesse Gross <jesse at nicira.com>
Signed-off-by: Hannes Frederic Sowa <hannes at stressinduktion.org>
---
 arch/x86/include/asm/hash.h | 18 ++++++++++++------
 1 file changed, 12 insertions(+), 6 deletions(-)

diff --git a/arch/x86/include/asm/hash.h b/arch/x86/include/asm/hash.h
index a881d78..771cee0 100644
--- a/arch/x86/include/asm/hash.h
+++ b/arch/x86/include/asm/hash.h
@@ -23,11 +23,14 @@ 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));
+	alternative_call(__jhash, __intel_crc4_2_hash, X86_FEATURE_XMM4_2,
+			 "=a" (hash), "D" (data), "S" (len), "d" (seed)
+			 : "rcx", "r8", "r9", "r10", "r11", "cc", "memory");
 #else
-			 "=a" (hash), "a" (data), "d" (len), "c" (seed));
+	alternative_call(__jhash, __intel_crc4_2_hash, X86_FEATURE_XMM4_2,
+			 "=a" (hash), "a" (data), "d" (len), "c" (seed)
+			 : "cc", "memory");
 #endif
 	return hash;
 }
@@ -36,11 +39,14 @@ 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));
+	alternative_call(__jhash2, __intel_crc4_2_hash2, X86_FEATURE_XMM4_2,
+			 "=a" (hash), "D" (data), "S" (len), "d" (seed)
+			 : "rcx", "r8", "r9", "r10", "r11", "cc", "memory");
 #else
-			 "=a" (hash), "a" (data), "d" (len), "c" (seed));
+	alternative_call(__jhash2, __intel_crc4_2_hash2, X86_FEATURE_XMM4_2,
+			 "=a" (hash), "a" (data), "d" (len), "c" (seed)
+			 : "cc", "memory");
 #endif
 	return hash;
 }
-- 
1.9.3




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