diff options
| author | David Woodhouse <dwmw2@infradead.org> | 2014-01-30 11:00:28 +0000 |
|---|---|---|
| committer | H. Peter Anvin <hpa@linux.intel.com> | 2014-01-30 08:04:32 -0800 |
| commit | 5fbbc25a99d680feca99a3095f0440f65d4307cc (patch) | |
| tree | bfdb7c982c8d742d3a1c153558df8416073758fa | |
| parent | 4064e0ea3c0e9427e6c22392c4b69b4bfa1b7125 (diff) | |
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. In 16-bit mode 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: ideally we would be able to use the gcc %zN construct here, but
that is broken for 64-bit integers in gcc < 4.5.
The code with plain "pushf/popf" is fine for 32- or 64-bit mode, but
not for 16-bit mode; in 16-bit mode those are 16-bit instructions in
.code16 mode, and 32-bit instructions in .code16gcc mode. ]
Signed-off-by: David Woodhouse <David.Woodhouse@intel.com>
Link: http://lkml.kernel.org/r/1391079628.26079.82.camel@shinybook.infradead.org
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
| -rw-r--r-- | arch/x86/boot/cpuflags.c | 25 |
1 files changed, 20 insertions, 5 deletions
diff --git a/arch/x86/boot/cpuflags.c b/arch/x86/boot/cpuflags.c index a9fcb7cfb241..431fa5f84537 100644 --- a/arch/x86/boot/cpuflags.c +++ b/arch/x86/boot/cpuflags.c @@ -28,20 +28,35 @@ static int has_fpu(void) return fsw == 0 && (fcw & 0x103f) == 0x003f; } +/* + * For building the 16-bit code we want to explicitly specify 32-bit + * push/pop operations, rather than just saying 'pushf' or 'popf' and + * letting the compiler choose. But this is also included from the + * compressed/ directory where it may be 64-bit code, and thus needs + * to be 'pushfq' or 'popfq' in that case. + */ +#ifdef __x86_64__ +#define PUSHF "pushfq" +#define POPF "popfq" +#else +#define PUSHF "pushfl" +#define POPF "popfl" +#endif + int has_eflag(unsigned long mask) { unsigned long f0, f1; - asm volatile("pushf \n\t" - "pushf \n\t" + asm volatile(PUSHF " \n\t" + PUSHF " \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" + POPF " \n\t" + PUSHF " \n\t" "pop %1 \n\t" - "popf" + POPF : "=&r" (f0), "=&r" (f1) : "ri" (mask)); |