From: H. Peter Anvin <hpa@linux.intel.com>
Date: Thu, 13 Feb 2014 15:34:30 +0000 (-0800)
Subject: x86, smap: Don't enable SMAP if CONFIG_X86_SMAP is disabled
X-Git-Tag: v3.14-rc3~8^2~2
X-Git-Url: http://review.tizen.org/git/?a=commitdiff_plain;h=03bbd596ac04fef47ce93a730b8f086d797c3021;p=profile%2Fivi%2Fkernel-x86-ivi.git

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+
---

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 24b6fd1..8e28bf2 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -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
+	}
 }
 
 /*