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Date: Wed, 29 Jan 2014 12:01:37 +0000
From: David Woodhouse <dwmw2@...radead.org>
To: Kees Cook <keescook@...omium.org>
Cc: linux-kernel@...r.kernel.org, x86@...nel.org,
kernel-hardening@...ts.openwall.com, adurbin@...gle.com, Eric Northup
<digitaleric@...gle.com>, jln@...gle.com, wad@...gle.com, Mathias Krause
<minipli@...glemail.com>, Zhang Yanfei <zhangyanfei@...fujitsu.com>, "H.
Peter Anvin"
<hpa@...or.com>
Subject: [PATCH] x86, boot: fix word-size assumptions in has_eflag() inline
asm
Commit dd78b97367bd575918204cc89107c1479d3fc1a7 ("x86, boot: Move CPU
flags out of cpucheck") introduced ambiguous inline asm in the
has_eflag() function. We want the instruction to be 'pushfl', but we
just say 'pushf' and hope the compiler does what we wanted.
When building with 'clang -m16', it won't, because clang doesn't use
the horrid '.code16gcc' hack that even 'gcc -m16' uses internally.
Say what we mean and don't make the compiler make assumptions.
Signed-off-by: David Woodhouse <David.Woodhouse@...el.com>
---
arch/x86/boot/cpuflags.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/arch/x86/boot/cpuflags.c b/arch/x86/boot/cpuflags.c
index a9fcb7c..168dd25 100644
--- a/arch/x86/boot/cpuflags.c
+++ b/arch/x86/boot/cpuflags.c
@@ -32,16 +32,16 @@ int has_eflag(unsigned long mask)
{
unsigned long f0, f1;
- asm volatile("pushf \n\t"
- "pushf \n\t"
+ asm volatile("pushfl \n\t"
+ "pushfl \n\t"
"pop %0 \n\t"
"mov %0,%1 \n\t"
"xor %2,%1 \n\t"
"push %1 \n\t"
- "popf \n\t"
- "pushf \n\t"
+ "popfl \n\t"
+ "pushfl \n\t"
"pop %1 \n\t"
- "popf"
+ "popfl"
: "=&r" (f0), "=&r" (f1)
: "ri" (mask));
--
1.8.5.3
--
dwmw2
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