FRV: ip_fast_csum() requires a memory clobber on its inline asm

ip_fast_csum() requires a memory clobber on its inline asm as it accesses memory in a fashion that gcc can't predict. The GCC manual says: If your assembler instructions access memory in an unpredictable fashion, add `memory' to the list of clobbered registers. This will cause GCC to not keep memory values cached in registers across the assembler instruction and not optimize stores or loads to that memory. The bug hasn't been noticed in FRV, but it has been seen in PA-RISC. Signed-off-by: David Howells <[email protected]> Signed-off-by: Linus Torvalds <[email protected]>
yshchan · Jun 5, 2008 · 609a70a · 609a70a
1 parent 5a515bc
commit 609a70a
Showing 1 changed file with 1 addition and 1 deletion.
diff --git a/include/asm-frv/checksum.h b/include/asm-frv/checksum.h
@@ -75,7 +75,7 @@ __sum16 ip_fast_csum(const void *iph, unsigned int ihl)
 	    : "=r" (sum), "=r" (iph), "=r" (ihl), "=r" (inc), "=&r"(tmp)
 	    : "0" (sum), "1" (iph), "2" (ihl), "3" (4),
 	    "m"(*(volatile struct { int _[100]; } *)iph)
-	    : "icc0", "icc1"
+	    : "icc0", "icc1", "memory"
 	    );
 
 	return (__force __sum16)~sum;