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>
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H. Peter Anvin

parent
c3b83598c1
commit
5700f743b5
@@ -1364,3 +1364,11 @@ void __cpuinit cpu_init(void)
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fpu_init();
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}
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#endif
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#ifdef CONFIG_X86_DEBUG_STATIC_CPU_HAS
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void warn_pre_alternatives(void)
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{
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WARN(1, "You're using static_cpu_has before alternatives have run!\n");
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}
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EXPORT_SYMBOL_GPL(warn_pre_alternatives);
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#endif
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