Commit 03bbd596 authored Feb 13, 2014 by H. Peter Anvin

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



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+

parent a9f18034

arch/x86/kernel/cpu/common.c

+6 −1

Original line number	Diff line number	Diff line
		@@ -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
		}
		}

		/*