[PATCH] x86/cpufeature, x86/mm/pkeys: fix broken compile-time disabling of pkeys

[Dave Hansen]

From: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>

When I added support for the Memory Protection Keys processor
feature, I had to reindent the REQUIRED/DISABLED_MASK macros, and
also consult the later cpufeature words.

I'm not quite sure how I bungled it, but I consulted the wrong
word at the end.  This only affected required or disabled cpu
features in cpufeature words 14, 15 and 16.  So, only Protection
Keys itself was screwed over here.

The result was that if you disabled pkeys in your .config, you
might still see some code show up that should have been compiled
out.  There should be no functional problems, though.

In verifying this patch I also realized that the DISABLE_PKU/OSPKE
macros were defined backwards and that the cpu_has() check in
setup_pku() was not doing the compile-time disabled checks.

So also fix the macro for DISABLE_PKU/OSPKE and add a compile-time
check for pkeys being enabled in setup_pku().

Fixes: dfb4a70f20c5 ("x86/cpufeature, x86/mm/pkeys: Add protection keys related CPUID definitions")
Signed-off-by: Dave Hansen <dave.hansen@xxxxxxxxxxxxxxx>
Cc: x86@xxxxxxxxxx
---

 b/arch/x86/include/asm/cpufeature.h        |   12 ++++++------
 b/arch/x86/include/asm/disabled-features.h |    6 +++---
 b/arch/x86/kernel/cpu/common.c             |    4 ++++
 3 files changed, 13 insertions(+), 9 deletions(-)

diff -puN arch/x86/include/asm/cpufeature.h~x86-cpufeature-fix-mismerge arch/x86/include/asm/cpufeature.h
--- a/arch/x86/include/asm/cpufeature.h~x86-cpufeature-fix-mismerge	2016-05-13 09:32:20.760121219 -0700
+++ b/arch/x86/include/asm/cpufeature.h	2016-05-13 09:32:20.770121668 -0700
@@ -63,9 +63,9 @@ extern const char * const x86_bug_flags[
 	   (((bit)>>5)==11 && (1UL<<((bit)&31) & REQUIRED_MASK11)) ||	\
 	   (((bit)>>5)==12 && (1UL<<((bit)&31) & REQUIRED_MASK12)) ||	\
 	   (((bit)>>5)==13 && (1UL<<((bit)&31) & REQUIRED_MASK13)) ||	\
-	   (((bit)>>5)==13 && (1UL<<((bit)&31) & REQUIRED_MASK14)) ||	\
-	   (((bit)>>5)==13 && (1UL<<((bit)&31) & REQUIRED_MASK15)) ||	\
-	   (((bit)>>5)==14 && (1UL<<((bit)&31) & REQUIRED_MASK16)) )
+	   (((bit)>>5)==14 && (1UL<<((bit)&31) & REQUIRED_MASK14)) ||	\
+	   (((bit)>>5)==15 && (1UL<<((bit)&31) & REQUIRED_MASK15)) ||	\
+	   (((bit)>>5)==16 && (1UL<<((bit)&31) & REQUIRED_MASK16)) )
 
 #define DISABLED_MASK_BIT_SET(bit)					\
 	 ( (((bit)>>5)==0  && (1UL<<((bit)&31) & DISABLED_MASK0 )) ||	\
@@ -82,9 +82,9 @@ extern const char * const x86_bug_flags[
 	   (((bit)>>5)==11 && (1UL<<((bit)&31) & DISABLED_MASK11)) ||	\
 	   (((bit)>>5)==12 && (1UL<<((bit)&31) & DISABLED_MASK12)) ||	\
 	   (((bit)>>5)==13 && (1UL<<((bit)&31) & DISABLED_MASK13)) ||	\
-	   (((bit)>>5)==13 && (1UL<<((bit)&31) & DISABLED_MASK14)) ||	\
-	   (((bit)>>5)==13 && (1UL<<((bit)&31) & DISABLED_MASK15)) ||	\
-	   (((bit)>>5)==14 && (1UL<<((bit)&31) & DISABLED_MASK16)) )
+	   (((bit)>>5)==14 && (1UL<<((bit)&31) & DISABLED_MASK14)) ||	\
+	   (((bit)>>5)==15 && (1UL<<((bit)&31) & DISABLED_MASK15)) ||	\
+	   (((bit)>>5)==16 && (1UL<<((bit)&31) & DISABLED_MASK16)) )
 
 #define cpu_has(c, bit)							\
 	(__builtin_constant_p(bit) && REQUIRED_MASK_BIT_SET(bit) ? 1 :	\
diff -puN arch/x86/include/asm/disabled-features.h~x86-cpufeature-fix-mismerge arch/x86/include/asm/disabled-features.h
--- a/arch/x86/include/asm/disabled-features.h~x86-cpufeature-fix-mismerge	2016-05-13 09:32:20.761121264 -0700
+++ b/arch/x86/include/asm/disabled-features.h	2016-05-13 09:32:20.779122073 -0700
@@ -29,11 +29,11 @@
 #endif /* CONFIG_X86_64 */
 
 #ifdef CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS
-# define DISABLE_PKU		(1<<(X86_FEATURE_PKU))
-# define DISABLE_OSPKE		(1<<(X86_FEATURE_OSPKE))
-#else
 # define DISABLE_PKU		0
 # define DISABLE_OSPKE		0
+#else
+# define DISABLE_PKU		(1<<(X86_FEATURE_PKU & 31))
+# define DISABLE_OSPKE		(1<<(X86_FEATURE_OSPKE & 31))
 #endif /* CONFIG_X86_INTEL_MEMORY_PROTECTION_KEYS */
 
 /*
diff -puN arch/x86/kernel/cpu/common.c~x86-cpufeature-fix-mismerge arch/x86/kernel/cpu/common.c
--- a/arch/x86/kernel/cpu/common.c~x86-cpufeature-fix-mismerge	2016-05-13 09:32:20.766121489 -0700
+++ b/arch/x86/kernel/cpu/common.c	2016-05-13 09:44:00.471588326 -0700
@@ -313,6 +313,10 @@ static bool pku_disabled;
 
 static __always_inline void setup_pku(struct cpuinfo_x86 *c)
 {
+	/* check the boot processor, plus compile options for PKU: */
+	if (!cpu_feature_enabled(X86_FEATURE_PKU))
+		return;
+	/* checks the actual processor's cpuid bits: */
 	if (!cpu_has(c, X86_FEATURE_PKU))
 		return;
 	if (pku_disabled)
_