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x86, smap: Don't enable SMAP if CONFIG_X86_SMAP is disabled

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If SMAP support is not compiled into the kernel, don't enable SMAP in
CR4 -- in fact, we should clear it, because the kernel doesn't contain
the proper STAC/CLAC instructions for SMAP support.

Found by Fengguang Wu's test system.

Reported-by: Fengguang Wu <fengguang.wu@intel.com>
Link: http://lkml.kernel.org/r/20140213124550.GA30497@localhost
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Cc: <stable@vger.kernel.org> # v3.7+
This commit is contained in:
H. Peter Anvin 2014-02-13 07:34:30 -08:00
parent a9f180345f
commit 03bbd596ac
1 changed files with 6 additions and 1 deletions
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7
arch/x86/kernel/cpu/common.c
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@ -284,8 +284,13 @@ static __always_inline void setup_smap(struct cpuinfo_x86 *c)
raw_local_save_flags(eflags);
BUG_ON(eflags & X86_EFLAGS_AC);
if (cpu_has(c, X86_FEATURE_SMAP))
if (cpu_has(c, X86_FEATURE_SMAP)) {
#ifdef CONFIG_X86_SMAP
set_in_cr4(X86_CR4_SMAP);
#else
clear_in_cr4(X86_CR4_SMAP);
#endif
}
}
/*