Messages in this thread Patch in this message | | | From | "Chang S. Bae" <> | Subject | [PATCH v11 28/29] x86/arch_prctl: ARCH_GET_FEATURES_WITH_KERNEL_ASSISTANCE | Date | Fri, 1 Oct 2021 15:37:27 -0700 |
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arch_prctl(ARCH_GET_FEATURES_WITH_KERNEL_ASSISTANCE, u64 *bitmask) Return the bitmask of the kernel-supported features. If XSAVE is disabled, the bitmask indicates only legacy states.
Suggested-by: Borislav Petkov <bp@suse.de> Signed-off-by: Chang S. Bae <chang.seok.bae@intel.com> Cc: x86@kernel.org Cc: linux-kernel@vger.kernel.org --- Changes from v9: * Add as a new patch. (Thiago Macieira and Borislav Petkov) --- arch/x86/include/uapi/asm/prctl.h | 23 +++++++++++---------- arch/x86/kernel/fpu/xstate.c | 34 ++++++++++++++++++++----------- arch/x86/kernel/process.c | 1 + 3 files changed, 35 insertions(+), 23 deletions(-)
diff --git a/arch/x86/include/uapi/asm/prctl.h b/arch/x86/include/uapi/asm/prctl.h index c73e141ce90a..6912d5fe85f3 100644 --- a/arch/x86/include/uapi/asm/prctl.h +++ b/arch/x86/include/uapi/asm/prctl.h @@ -2,19 +2,20 @@ #ifndef _ASM_X86_PRCTL_H #define _ASM_X86_PRCTL_H -#define ARCH_SET_GS 0x1001 -#define ARCH_SET_FS 0x1002 -#define ARCH_GET_FS 0x1003 -#define ARCH_GET_GS 0x1004 +#define ARCH_SET_GS 0x1001 +#define ARCH_SET_FS 0x1002 +#define ARCH_GET_FS 0x1003 +#define ARCH_GET_GS 0x1004 -#define ARCH_GET_CPUID 0x1011 -#define ARCH_SET_CPUID 0x1012 +#define ARCH_GET_CPUID 0x1011 +#define ARCH_SET_CPUID 0x1012 -#define ARCH_SET_STATE_ENABLE 0x1021 -#define ARCH_GET_STATE_ENABLE 0x1022 +#define ARCH_GET_FEATURES_WITH_KERNEL_ASSISTANCE 0x1020 +#define ARCH_SET_STATE_ENABLE 0x1021 +#define ARCH_GET_STATE_ENABLE 0x1022 -#define ARCH_MAP_VDSO_X32 0x2001 -#define ARCH_MAP_VDSO_32 0x2002 -#define ARCH_MAP_VDSO_64 0x2003 +#define ARCH_MAP_VDSO_X32 0x2001 +#define ARCH_MAP_VDSO_32 0x2002 +#define ARCH_MAP_VDSO_64 0x2003 #endif /* _ASM_X86_PRCTL_H */ diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c index 81566a18643b..75db4def5ec5 100644 --- a/arch/x86/kernel/fpu/xstate.c +++ b/arch/x86/kernel/fpu/xstate.c @@ -1299,6 +1299,24 @@ int realloc_xstate_buffer(struct fpu *fpu, u64 mask) return 0; } +/** + * get_features_mask_uabi - Get a feature list that the kernel supports + * Return: A bitmap that indicates which state the kernel enabled. + */ +static u64 get_features_mask_uabi(void) +{ + if (!cpu_feature_enabled(X86_FEATURE_FPU)) + return 0; + + if (use_xsave()) + return xfeatures_mask_uabi(); + + if (use_fxsr()) + return XFEATURE_MASK_FPSSE; + + return XFEATURE_MASK_FP; +} + /** * reset_state_perm - Reset a task's permission for dynamic user state * @@ -1329,7 +1347,7 @@ void reset_state_perm(struct task_struct *tsk) } /** - * do_arch_prctl_state - Read or write the state permission. + * do_arch_prctl_state - Handle xstate-related buffer or usage control * @fpu: A struct task_struct * pointer * @option: A subfunction of arch_prctl() * @arg2: Either a pointer to userspace memory or state-component @@ -1338,22 +1356,14 @@ void reset_state_perm(struct task_struct *tsk) */ long do_arch_prctl_state(struct task_struct *tsk, int option, unsigned long arg2) { - u64 features_mask; - - if (!cpu_feature_enabled(X86_FEATURE_FPU)) - features_mask = 0; - else if (use_fxsr()) - features_mask = XFEATURE_MASK_FPSSE; - else - features_mask = XFEATURE_MASK_FP; + u64 features_mask = get_features_mask_uabi(); switch (option) { + case ARCH_GET_FEATURES_WITH_KERNEL_ASSISTANCE: + return put_user(features_mask, (unsigned long __user *)arg2); case ARCH_SET_STATE_ENABLE: { u64 state_perm = arg2; - if (use_xsave()) - features_mask = xfeatures_mask_uabi(); - if (state_perm & ~features_mask) return -EINVAL; diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index b43e2b0f52f2..ae53ffd76882 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -1023,6 +1023,7 @@ long do_arch_prctl_common(struct task_struct *task, int option, return get_cpuid_mode(); case ARCH_SET_CPUID: return set_cpuid_mode(task, arg2); + case ARCH_GET_FEATURES_WITH_KERNEL_ASSISTANCE: case ARCH_SET_STATE_ENABLE: case ARCH_GET_STATE_ENABLE: return do_arch_prctl_state(task, option, arg2); -- 2.17.1
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