From: David Woodhouse <dwmw2@infradead.org>
To: Kees Cook <keescook@chromium.org>
Cc: linux-kernel@vger.kernel.org, x86@kernel.org,
kernel-hardening@lists.openwall.com, adurbin@google.com,
Eric Northup <digitaleric@google.com>,
jln@google.com, wad@google.com,
Mathias Krause <minipli@googlemail.com>,
Zhang Yanfei <zhangyanfei@cn.fujitsu.com>,
"H. Peter Anvin" <hpa@zytor.com>
Subject: [PATCH] x86, boot: fix word-size assumptions in has_eflag() inline asm
Date: Wed, 29 Jan 2014 12:01:37 +0000 [thread overview]
Message-ID: <1390996897.20153.123.camel@i7.infradead.org> (raw)
In-Reply-To: <1380833605-26313-2-git-send-email-keescook@chromium.org>
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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@intel.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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next prev parent reply other threads:[~2014-01-29 12:01 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-10-03 20:53 [PATCH v7 0/7] Kernel base address randomization on x86 Kees Cook
2013-10-03 20:53 ` [PATCH 1/7] x86, boot: move CPU flags out of cpucheck Kees Cook
2014-01-29 12:01 ` David Woodhouse [this message]
2014-01-29 16:57 ` [PATCH] x86, boot: fix word-size assumptions in has_eflag() inline asm Kees Cook
2014-01-29 17:13 ` [tip:x86/build] x86, boot: Fix word-size assumptions in has_eflag () " tip-bot for David Woodhouse
2014-01-30 9:09 ` Ingo Molnar
2014-01-30 10:28 ` Woodhouse, David
2014-01-30 11:00 ` [PATCH v2] " David Woodhouse
2014-01-30 13:45 ` H. Peter Anvin
2014-01-30 14:08 ` David Woodhouse
2014-01-30 16:10 ` [tip:x86/build] " tip-bot for David Woodhouse
2014-01-30 23:01 ` [PATCH v2] " David Rientjes
2013-10-03 20:53 ` [PATCH 2/7] x86, kaslr: return location from decompress_kernel Kees Cook
2013-10-03 20:53 ` [PATCH 3/7] x86, kaslr: find minimum safe relocation position Kees Cook
2013-10-03 22:23 ` H. Peter Anvin
2013-10-03 22:43 ` Kees Cook
2013-10-03 22:46 ` H. Peter Anvin
2013-10-03 20:53 ` [PATCH 4/7] x86, kaslr: select random base offset Kees Cook
2013-10-03 20:53 ` [PATCH 5/7] x86, kaslr: select memory region from e820 maps Kees Cook
2013-10-03 20:53 ` [PATCH 6/7] x86, kaslr: report kernel offset on panic Kees Cook
2013-10-03 20:53 ` [PATCH 7/7] x86, kaslr: raise max positions to 1GiB on x86_64 Kees Cook
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