diff options
Diffstat (limited to 'arch/x86/kernel/cpu/common.c')
| -rw-r--r-- | arch/x86/kernel/cpu/common.c | 99 |
1 files changed, 70 insertions, 29 deletions
diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c index 8394b3d1f94f..0fe6953f421c 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); @@ -310,6 +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) @@ -430,7 +437,7 @@ void load_percpu_segment(int cpu) #ifdef CONFIG_X86_32 loadsegment(fs, __KERNEL_PERCPU); #else - loadsegment(gs, 0); + __loadsegment_simple(gs, 0); wrmsrl(MSR_GS_BASE, (unsigned long)per_cpu(irq_stack_union.gs_base, cpu)); #endif load_stack_canary_segment(); @@ -717,6 +724,13 @@ void get_cpu_cap(struct cpuinfo_x86 *c) } } + if (c->extended_cpuid_level >= 0x80000007) { + cpuid(0x80000007, &eax, &ebx, &ecx, &edx); + + c->x86_capability[CPUID_8000_0007_EBX] = ebx; + c->x86_power = edx; + } + if (c->extended_cpuid_level >= 0x80000008) { cpuid(0x80000008, &eax, &ebx, &ecx, &edx); @@ -729,9 +743,6 @@ void get_cpu_cap(struct cpuinfo_x86 *c) c->x86_phys_bits = 36; #endif - if (c->extended_cpuid_level >= 0x80000007) - c->x86_power = cpuid_edx(0x80000007); - if (c->extended_cpuid_level >= 0x8000000a) c->x86_capability[CPUID_8000_000A_EDX] = cpuid_edx(0x8000000a); @@ -862,30 +873,34 @@ static void detect_nopl(struct cpuinfo_x86 *c) #else set_cpu_cap(c, X86_FEATURE_NOPL); #endif +} +static void detect_null_seg_behavior(struct cpuinfo_x86 *c) +{ +#ifdef CONFIG_X86_64 /* - * ESPFIX is a strange bug. All real CPUs have it. Paravirt - * systems that run Linux at CPL > 0 may or may not have the - * issue, but, even if they have the issue, there's absolutely - * nothing we can do about it because we can't use the real IRET - * instruction. + * Empirically, writing zero to a segment selector on AMD does + * not clear the base, whereas writing zero to a segment + * selector on Intel does clear the base. Intel's behavior + * allows slightly faster context switches in the common case + * where GS is unused by the prev and next threads. * - * NB: For the time being, only 32-bit kernels support - * X86_BUG_ESPFIX as such. 64-bit kernels directly choose - * whether to apply espfix using paravirt hooks. If any - * non-paravirt system ever shows up that does *not* have the - * ESPFIX issue, we can change this. + * Since neither vendor documents this anywhere that I can see, + * detect it directly instead of hardcoding the choice by + * vendor. + * + * I've designated AMD's behavior as the "bug" because it's + * counterintuitive and less friendly. */ -#ifdef CONFIG_X86_32 -#ifdef CONFIG_PARAVIRT - do { - extern void native_iret(void); - if (pv_cpu_ops.iret == native_iret) - set_cpu_bug(c, X86_BUG_ESPFIX); - } while (0); -#else - set_cpu_bug(c, X86_BUG_ESPFIX); -#endif + + unsigned long old_base, tmp; + rdmsrl(MSR_FS_BASE, old_base); + wrmsrl(MSR_FS_BASE, 1); + loadsegment(fs, 0); + rdmsrl(MSR_FS_BASE, tmp); + if (tmp != 0) + set_cpu_bug(c, X86_BUG_NULL_SEG); + wrmsrl(MSR_FS_BASE, old_base); #endif } @@ -921,6 +936,33 @@ static void generic_identify(struct cpuinfo_x86 *c) get_model_name(c); /* Default name */ detect_nopl(c); + + detect_null_seg_behavior(c); + + /* + * ESPFIX is a strange bug. All real CPUs have it. Paravirt + * systems that run Linux at CPL > 0 may or may not have the + * issue, but, even if they have the issue, there's absolutely + * nothing we can do about it because we can't use the real IRET + * instruction. + * + * NB: For the time being, only 32-bit kernels support + * X86_BUG_ESPFIX as such. 64-bit kernels directly choose + * whether to apply espfix using paravirt hooks. If any + * non-paravirt system ever shows up that does *not* have the + * ESPFIX issue, we can change this. + */ +#ifdef CONFIG_X86_32 +# ifdef CONFIG_PARAVIRT + do { + extern void native_iret(void); + if (pv_cpu_ops.iret == native_iret) + set_cpu_bug(c, X86_BUG_ESPFIX); + } while (0); +# else + set_cpu_bug(c, X86_BUG_ESPFIX); +# endif +#endif } static void x86_init_cache_qos(struct cpuinfo_x86 *c) @@ -1076,12 +1118,12 @@ void enable_sep_cpu(void) struct tss_struct *tss; int cpu; + if (!boot_cpu_has(X86_FEATURE_SEP)) + return; + cpu = get_cpu(); tss = &per_cpu(cpu_tss, cpu); - if (!boot_cpu_has(X86_FEATURE_SEP)) - goto out; - /* * We cache MSR_IA32_SYSENTER_CS's value in the TSS's ss1 field -- * see the big comment in struct x86_hw_tss's definition. @@ -1096,7 +1138,6 @@ void enable_sep_cpu(void) wrmsr(MSR_IA32_SYSENTER_EIP, (unsigned long)entry_SYSENTER_32, 0); -out: put_cpu(); } #endif @@ -1528,7 +1569,7 @@ void cpu_init(void) pr_info("Initializing CPU#%d\n", cpu); if (cpu_feature_enabled(X86_FEATURE_VME) || - cpu_has_tsc || + boot_cpu_has(X86_FEATURE_TSC) || boot_cpu_has(X86_FEATURE_DE)) cr4_clear_bits(X86_CR4_VME|X86_CR4_PVI|X86_CR4_TSD|X86_CR4_DE); |