linux-kernel - [tip:x86/build] x86, boot: Fix word-size assumptions in has

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Message-ID: <tip-9b3614ccfa5492f57f743f3856253f285b10a702@git.kernel.org>
Date:	Wed, 29 Jan 2014 09:13:21 -0800
From:	tip-bot for David Woodhouse <tipbot@...or.com>
To:	linux-tip-commits@...r.kernel.org
Cc:	linux-kernel@...r.kernel.org, hpa@...or.com, mingo@...nel.org,
	dwmw2@...radead.org, keescook@...omium.org, tglx@...utronix.de,
	hpa@...ux.intel.com, David.Woodhouse@...el.com
Subject: [tip:x86/build] x86, boot: Fix word-size assumptions in has_eflag
 () inline asm

Commit-ID:  9b3614ccfa5492f57f743f3856253f285b10a702
Gitweb:     http://git.kernel.org/tip/9b3614ccfa5492f57f743f3856253f285b10a702
Author:     David Woodhouse <dwmw2@...radead.org>
AuthorDate: Wed, 29 Jan 2014 12:01:37 +0000
Committer:  H. Peter Anvin <hpa@...ux.intel.com>
CommitDate: Wed, 29 Jan 2014 09:09:40 -0800

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.

[ hpa: we use plain "pushf" in the equivalent code elsewhere which may
  be compiled as either 32- or 64-bit code.  In those cases we want
  the assembler to pick the appropriate size for us.  However, this is
  *16-bit* code and we still need these to be 32-bit operations. ]

Signed-off-by: David Woodhouse <David.Woodhouse@...el.com>
Link: http://lkml.kernel.org/r/1390996897.20153.123.camel@i7.infradead.org
Signed-off-by: Kees Cook <keescook@...omium.org>
Signed-off-by: H. Peter Anvin <hpa@...ux.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));
 
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