2014-02-27 08:46:52

by Jan Beulich

Subject: [PATCH v2 1/3] x86/hash: fix build failure with older binutils

Just like for other ISA extension instruction uses we should check
whether the assembler actually supports them. The fallback here simply
is to encode an instruction with fixed operands (%eax and %ecx).

Signed-off-by: Jan Beulich <[email protected]>
Cc: Francesco Fusco <[email protected]>
Cc: Daniel Borkmann <[email protected]>
Cc: Thomas Graf <[email protected]>
Cc: David S. Miller <[email protected]>
---
arch/x86/Makefile | 1 +
arch/x86/lib/hash.c | 4 ++++
2 files changed, 5 insertions(+)

--- 3.14-rc4-x86-hash-crc32.orig/arch/x86/Makefile
+++ 3.14-rc4-x86-hash-crc32/arch/x86/Makefile
@@ -152,6 +152,7 @@ cfi-sections := $(call as-instr,.cfi_sec

# does binutils support specific instructions?
asinstr := $(call as-instr,fxsaveq (%rax),-DCONFIG_AS_FXSAVEQ=1)
+asinstr += $(call as-instr,crc32l %eax$(comma)%eax,-DCONFIG_AS_CRC32=1)
avx_instr := $(call as-instr,vxorps %ymm0$(comma)%ymm1$(comma)%ymm2,-DCONFIG_AS_AVX=1)
avx2_instr :=$(call as-instr,vpbroadcastb %xmm0$(comma)%ymm1,-DCONFIG_AS_AVX2=1)

--- 3.14-rc4-x86-hash-crc32.orig/arch/x86/lib/hash.c
+++ 3.14-rc4-x86-hash-crc32/arch/x86/lib/hash.c
@@ -39,7 +39,11 @@

static inline u32 crc32_u32(u32 crc, u32 val)
{
+#ifdef CONFIG_AS_CRC32
asm ("crc32l %1,%0\n" : "+r" (crc) : "rm" (val));
+#else
+ asm (".byte 0xf2, 0x0f, 0x38, 0xf1, 0xc1" : "+a" (crc) : "c" (val));
+#endif
return crc;
}

2014-02-27 09:26:40

by Daniel Borkmann

Subject: Re: [PATCH v2 1/3] x86/hash: fix build failure with older binutils

On 02/27/2014 09:47 AM, Jan Beulich wrote:
> Just like for other ISA extension instruction uses we should check
> whether the assembler actually supports them. The fallback here simply
> is to encode an instruction with fixed operands (%eax and %ecx).
>
> Signed-off-by: Jan Beulich <[email protected]>
> Cc: Francesco Fusco <[email protected]>
> Cc: Daniel Borkmann <[email protected]>
> Cc: Thomas Graf <[email protected]>
> Cc: David S. Miller <[email protected]>

Acked-by: Daniel Borkmann <[email protected]>