diff options
| -rw-r--r-- | arch/x86/include/uapi/asm/prctl.h | 1 | ||||
| -rw-r--r-- | arch/x86/kernel/shstk.c | 43 |
2 files changed, 43 insertions, 1 deletions
diff --git a/arch/x86/include/uapi/asm/prctl.h b/arch/x86/include/uapi/asm/prctl.h index 6a8e0e1bff4a..eedfde3b63be 100644 --- a/arch/x86/include/uapi/asm/prctl.h +++ b/arch/x86/include/uapi/asm/prctl.h @@ -36,5 +36,6 @@ /* ARCH_SHSTK_ features bits */ #define ARCH_SHSTK_SHSTK (1ULL << 0) +#define ARCH_SHSTK_WRSS (1ULL << 1) #endif /* _ASM_X86_PRCTL_H */ diff --git a/arch/x86/kernel/shstk.c b/arch/x86/kernel/shstk.c index 04c37b33a625..ea0bf113f9cf 100644 --- a/arch/x86/kernel/shstk.c +++ b/arch/x86/kernel/shstk.c @@ -390,6 +390,47 @@ void shstk_free(struct task_struct *tsk) unmap_shadow_stack(shstk->base, shstk->size); } +static int wrss_control(bool enable) +{ + u64 msrval; + + if (!cpu_feature_enabled(X86_FEATURE_USER_SHSTK)) + return -EOPNOTSUPP; + + /* + * Only enable WRSS if shadow stack is enabled. If shadow stack is not + * enabled, WRSS will already be disabled, so don't bother clearing it + * when disabling. + */ + if (!features_enabled(ARCH_SHSTK_SHSTK)) + return -EPERM; + + /* Already enabled/disabled? */ + if (features_enabled(ARCH_SHSTK_WRSS) == enable) + return 0; + + fpregs_lock_and_load(); + rdmsrl(MSR_IA32_U_CET, msrval); + + if (enable) { + features_set(ARCH_SHSTK_WRSS); + msrval |= CET_WRSS_EN; + } else { + features_clr(ARCH_SHSTK_WRSS); + if (!(msrval & CET_WRSS_EN)) + goto unlock; + + msrval &= ~CET_WRSS_EN; + } + + wrmsrl(MSR_IA32_U_CET, msrval); + +unlock: + fpregs_unlock(); + + return 0; +} + static int shstk_disable(void) { if (!cpu_feature_enabled(X86_FEATURE_USER_SHSTK)) @@ -406,7 +447,7 @@ static int shstk_disable(void) fpregs_unlock(); shstk_free(current); - features_clr(ARCH_SHSTK_SHSTK); + features_clr(ARCH_SHSTK_SHSTK | ARCH_SHSTK_WRSS); return 0; } |