diff options
| -rw-r--r-- | arch/x86/include/asm/bugs.h | 8 | ||||
| -rw-r--r-- | arch/x86/kernel/cpu/common.c | 3 | ||||
| -rw-r--r-- | arch/x86/kernel/cpu/intel.c | 37 |
3 files changed, 48 insertions, 0 deletions
diff --git a/arch/x86/include/asm/bugs.h b/arch/x86/include/asm/bugs.h index 08abf639075f..5490bbaf71d5 100644 --- a/arch/x86/include/asm/bugs.h +++ b/arch/x86/include/asm/bugs.h @@ -1,8 +1,16 @@ #ifndef _ASM_X86_BUGS_H #define _ASM_X86_BUGS_H +#include <asm/processor.h> + extern void check_bugs(void); +#if defined(CONFIG_CPU_SUP_INTEL) +void check_mpx_erratum(struct cpuinfo_x86 *c); +#else +static inline void check_mpx_erratum(struct cpuinfo_x86 *c) {} +#endif + #if defined(CONFIG_CPU_SUP_INTEL) && defined(CONFIG_X86_32) int ppro_with_ram_bug(void); #else diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index f45a4b9d28c8..62ff5255ae16 100644 --- a/arch/x86/kernel/cpu/common.c +++ b/arch/x86/kernel/cpu/common.c @@ -37,6 +37,7 @@ #include <asm/mtrr.h> #include <linux/numa.h> #include <asm/asm.h> +#include <asm/bugs.h> #include <asm/cpu.h> #include <asm/mce.h> #include <asm/msr.h> @@ -270,6 +271,8 @@ static inline void squash_the_stupid_serial_number(struct cpuinfo_x86 *c) static __init int setup_disable_smep(char *arg) { setup_clear_cpu_cap(X86_FEATURE_SMEP); + /* Check for things that depend on SMEP being enabled: */ + check_mpx_erratum(&boot_cpu_data); return 1; } __setup("nosmep", setup_disable_smep); diff --git a/arch/x86/kernel/cpu/intel.c b/arch/x86/kernel/cpu/intel.c index e4393bfc7f0d..b47df99dc5d2 100644 --- a/arch/x86/kernel/cpu/intel.c +++ b/arch/x86/kernel/cpu/intel.c @@ -25,6 +25,41 @@ #include <asm/apic.h> #endif +/* + * Just in case our CPU detection goes bad, or you have a weird system, + * allow a way to override the automatic disabling of MPX. + */ +static int forcempx; + +static int __init forcempx_setup(char *__unused) +{ + forcempx = 1; + + return 1; +} +__setup("intel-skd-046-workaround=disable", forcempx_setup); + +void check_mpx_erratum(struct cpuinfo_x86 *c) +{ + if (forcempx) + return; + /* + * Turn off the MPX feature on CPUs where SMEP is not + * available or disabled. + * + * Works around Intel Erratum SKD046: "Branch Instructions + * May Initialize MPX Bound Registers Incorrectly". + * + * This might falsely disable MPX on systems without + * SMEP, like Atom processors without SMEP. But there + * is no such hardware known at the moment. + */ + if (cpu_has(c, X86_FEATURE_MPX) && !cpu_has(c, X86_FEATURE_SMEP)) { + setup_clear_cpu_cap(X86_FEATURE_MPX); + pr_warn("x86/mpx: Disabling MPX since SMEP not present\n"); + } +} + static void early_init_intel(struct cpuinfo_x86 *c) { u64 misc_enable; @@ -173,6 +208,8 @@ static void early_init_intel(struct cpuinfo_x86 *c) if (edx & (1U << 28)) c->x86_coreid_bits = get_count_order((ebx >> 16) & 0xff); } + + check_mpx_erratum(c); } #ifdef CONFIG_X86_32 |