diff options
Diffstat (limited to 'arch')
| -rw-r--r-- | arch/x86/kernel/cpu/common.c | 26 |
1 files changed, 26 insertions, 0 deletions
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index cd43e525fde..7d35d659411 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -278,6 +278,31 @@ static __cpuinit void setup_smep(struct cpuinfo_x86 *c) } } +static int disable_smap __cpuinitdata; +static __init int setup_disable_smap(char *arg) +{ + disable_smap = 1; + return 1; +} +__setup("nosmap", setup_disable_smap); + +static __cpuinit void setup_smap(struct cpuinfo_x86 *c) +{ + if (cpu_has(c, X86_FEATURE_SMAP)) { + if (unlikely(disable_smap)) { + setup_clear_cpu_cap(X86_FEATURE_SMAP); + clear_in_cr4(X86_CR4_SMAP); + } else { + set_in_cr4(X86_CR4_SMAP); + /* + * Don't use clac() here since alternatives + * haven't run yet... + */ + asm volatile(__stringify(__ASM_CLAC) ::: "memory"); + } + } +} + /* * Some CPU features depend on higher CPUID levels, which may not always * be available due to CPUID level capping or broken virtualization @@ -713,6 +738,7 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c) filter_cpuid_features(c, false); setup_smep(c); + setup_smap(c); if (this_cpu->c_bsp_init) this_cpu->c_bsp_init(c); |