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| author | Borislav Petkov <bp@suse.de> | 2013-06-09 10:07:32 (GMT) |
|---|---|---|
| committer | H. Peter Anvin <hpa@linux.intel.com> | 2013-06-21 00:37:19 (GMT) |
| commit | 5700f743b597951743da9c7d891d3989aac0486e (patch) | |
| tree | e0482b8bb6ec72bc1db19bcd853922efb97b36bc /arch/x86/kernel/cpu | |
| parent | c3b83598c1eeb1507603b461f5843ec2a49e3033 (diff) | |
| download | linux-5700f743b597951743da9c7d891d3989aac0486e.tar.xz | |
x86: Sanity-check static_cpu_has usage
static_cpu_has may be used only after alternatives have run. Before that
it always returns false if constant folding with __builtin_constant_p()
doesn't happen. And you don't want that.
This patch is the result of me debugging an issue where I overzealously
put static_cpu_has in code which executed before alternatives have run
and had to spend some time with scratching head and cursing at the
monitor.
So add a jump to a warning which screams loudly when we use this
function too early. The alternatives patch that check away in
conjunction with patching the rest of the kernel image.
[ hpa: factored this into its own configuration option. If we want to
have an overarching option, it should be an option which selects
other options, not as a group option in the source code. ]
Signed-off-by: Borislav Petkov <bp@suse.de>
Link: http://lkml.kernel.org/r/1370772454-6106-4-git-send-email-bp@alien8.de
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Diffstat (limited to 'arch/x86/kernel/cpu')
| -rw-r--r-- | arch/x86/kernel/cpu/common.c | 8 |
1 files changed, 8 insertions, 0 deletions
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index d388ce1..59adaa1 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -1364,3 +1364,11 @@ void __cpuinit cpu_init(void) fpu_init(); } #endif + +#ifdef CONFIG_X86_DEBUG_STATIC_CPU_HAS +void warn_pre_alternatives(void) +{ + WARN(1, "You're using static_cpu_has before alternatives have run!\n"); +} +EXPORT_SYMBOL_GPL(warn_pre_alternatives); +#endif |