linux-kernel - Re: [PATCH 1/3] x86/hash: fix build failure with older binutils

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Date:	Fri, 21 Feb 2014 14:16:12 +0000
From:	"Jan Beulich" <JBeulich@...e.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	<davem@...emloft.net>, <mingo@...e.hu>, <tglx@...utronix.de>,
	<dborkman@...hat.com>, <ffusco@...hat.com>, <tgraf@...hat.com>,
	<linux-kernel@...r.kernel.org>
Subject: Re: [PATCH 1/3] x86/hash: fix build failure with older
 binutils

>>> On 21.02.14 at 13:51, "H. Peter Anvin" <hpa@...or.com> wrote:
> How old?

2.16.91.0.5 (SLE10)

Jan

> On February 21, 2014 2:32:50 AM PST, Jan Beulich <JBeulich@...e.com> 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 <jbeulich@...e.com>
>>Cc: Francesco Fusco <ffusco@...hat.com>
>>Cc: Daniel Borkmann <dborkman@...hat.com>
>>Cc: Thomas Graf <tgraf@...hat.com>
>>Cc: David S. Miller <davem@...emloft.net>
>>---
>> arch/x86/Makefile   |    1 +
>> arch/x86/lib/hash.c |    4 ++++
>> 2 files changed, 5 insertions(+)
>>
>>--- 3.14-rc3-x86-hash-crc32.orig/arch/x86/Makefile
>>+++ 3.14-rc3-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-rc3-x86-hash-crc32.orig/arch/x86/lib/hash.c
>>+++ 3.14-rc3-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;
>> }
>> 
> 
> -- 
> Sent from my mobile phone.  Please pardon brevity and lack of formatting.



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