[tip:x86/hash] x86, hash: Fix build failure with older binutils

From: tip-bot for Jan Beulich
Date: Wed Mar 19 2014 - 19:55:40 EST

Commit-ID: 06325190bd577e11429444d54f454b9d13f560c9
Gitweb: http://git.kernel.org/tip/06325190bd577e11429444d54f454b9d13f560c9
Author: Jan Beulich <JBeulich@xxxxxxxx>
AuthorDate: Thu, 27 Feb 2014 08:47:02 +0000
Committer: H. Peter Anvin <hpa@xxxxxxxxxxxxxxx>
CommitDate: Wed, 19 Mar 2014 16:51:04 -0700

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).

[ hpa: tagging for -stable as a build fix ]

Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx>
Link: http://lkml.kernel.org/r/530F0996020000780011FBE7@xxxxxxxxxxxxxxxxxxxx
Cc: Francesco Fusco <ffusco@xxxxxxxxxx>
Cc: Thomas Graf <tgraf@xxxxxxxxxx>
Cc: David S. Miller <davem@xxxxxxxxxxxxx>
Acked-by: Daniel Borkmann <dborkman@xxxxxxxxxx>
Signed-off-by: H. Peter Anvin <hpa@xxxxxxxxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> # v3.14
arch/x86/Makefile | 1 +
arch/x86/lib/hash.c | 4 ++++
2 files changed, 5 insertions(+)

diff --git a/arch/x86/Makefile b/arch/x86/Makefile
index eeda43a..f8842c4 100644
--- a/arch/x86/Makefile
+++ b/arch/x86/Makefile
@@ -152,6 +152,7 @@ cfi-sections := $(call as-instr,.cfi_sections .debug_frame,-DCONFIG_AS_CFI_SECTI

# 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)

diff --git a/arch/x86/lib/hash.c b/arch/x86/lib/hash.c
index 3056702..060cc44 100644
--- a/arch/x86/lib/hash.c
+++ b/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));
+ asm (".byte 0xf2, 0x0f, 0x38, 0xf1, 0xc1" : "+a" (crc) : "c" (val));
return crc;

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/