diff options
| author | Fenghua Yu <fenghua.yu@intel.com> | 2011-05-11 16:51:05 -0700 |
|---|---|---|
| committer | H. Peter Anvin <hpa@linux.intel.com> | 2011-05-17 21:22:00 -0700 |
| commit | de5397ad5b9ad22e2401c4dacdf1bb3b19c05679 (patch) | |
| tree | e8c612c4f84efe458d8ec3c23f1bfd834f20c0f2 /arch/x86/kernel/cpu/common.c | |
| parent | dc23c0bccf5eea171c87b3db285d032b9a5f06c4 (diff) | |
x86, cpu: Enable/disable Supervisor Mode Execution Protection
Enable/disable newly documented SMEP (Supervisor Mode Execution Protection) CPU
feature in kernel. CR4.SMEP (bit 20) is 0 at power-on. If the feature is
supported by CPU (X86_FEATURE_SMEP), enable SMEP by setting CR4.SMEP. New kernel
option nosmep disables the feature even if the feature is supported by CPU.
[ hpa: moved the call to setup_smep() until after the vendor-specific
initialization; that ensures that CPUID features are unmasked. We
will still run it before we have userspace (never mind uncontrolled
userspace). ]
Signed-off-by: Fenghua Yu <fenghua.yu@intel.com>
LKML-Reference: <1305157865-31727-1-git-send-email-fenghua.yu@intel.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>
Diffstat (limited to 'arch/x86/kernel/cpu/common.c')
| -rw-r--r-- | arch/x86/kernel/cpu/common.c | 23 |
1 files changed, 23 insertions, 0 deletions
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 173f3a3fa1a..cbc70a27430 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -254,6 +254,25 @@ static inline void squash_the_stupid_serial_number(struct cpuinfo_x86 *c) } #endif +static int disable_smep __initdata; +static __init int setup_disable_smep(char *arg) +{ + disable_smep = 1; + return 1; +} +__setup("nosmep", setup_disable_smep); + +static __init void setup_smep(struct cpuinfo_x86 *c) +{ + if (cpu_has(c, X86_FEATURE_SMEP)) { + if (unlikely(disable_smep)) { + setup_clear_cpu_cap(X86_FEATURE_SMEP); + clear_in_cr4(X86_CR4_SMEP); + } else + set_in_cr4(X86_CR4_SMEP); + } +} + /* * Some CPU features depend on higher CPUID levels, which may not always * be available due to CPUID level capping or broken virtualization @@ -667,6 +686,8 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c) c->cpu_index = 0; #endif filter_cpuid_features(c, false); + + setup_smep(c); } void __init early_cpu_init(void) @@ -752,6 +773,8 @@ static void __cpuinit generic_identify(struct cpuinfo_x86 *c) #endif } + setup_smep(c); + get_model_name(c); /* Default name */ detect_nopl(c); |