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Date: Wed, 25 Aug 2021 08:54:13 -0700
From: "Chang S. Bae" <chang.seok.bae@...el.com>
To: bp@...e.de, luto@...nel.org, tglx@...utronix.de, mingo@...nel.org,
x86@...nel.org
Cc: len.brown@...el.com, lenb@...nel.org, dave.hansen@...el.com,
thiago.macieira@...el.com, jing2.liu@...el.com,
ravi.v.shankar@...el.com, linux-kernel@...r.kernel.org,
chang.seok.bae@...el.com
Subject: [PATCH v10 28/28] x86/arch_prctl: ARCH_GET_FEATURES_WITH_KERNEL_ASSISTANCE
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@...e.de>
Signed-off-by: Chang S. Bae <chang.seok.bae@...el.com>
Cc: x86@...nel.org
Cc: linux-kernel@...r.kernel.org
---
Changes from v9:
* Add as a new patch. (Thiago Macieira and Borislav Petkov)
---
arch/x86/include/asm/fpu/xstate.h | 1 +
arch/x86/include/uapi/asm/prctl.h | 23 ++++++++---------
arch/x86/kernel/fpu/xstate.c | 41 +++++++++++++++++++------------
arch/x86/kernel/process.c | 2 ++
4 files changed, 40 insertions(+), 27 deletions(-)
diff --git a/arch/x86/include/asm/fpu/xstate.h b/arch/x86/include/asm/fpu/xstate.h
index 013478c1aa42..4aa7049cc079 100644
--- a/arch/x86/include/asm/fpu/xstate.h
+++ b/arch/x86/include/asm/fpu/xstate.h
@@ -194,6 +194,7 @@ static inline bool dynamic_state_permitted(struct task_struct *tsk, u64 state_ma
}
void reset_dynamic_state_perm(struct task_struct *tsk);
+u64 get_features_mask_uabi(void);
long set_group_state_perm(struct task_struct *tsk, u64 state_perm);
u64 get_group_state_perm(struct task_struct *tsk);
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 2c62872e4fef..6622366d51ae 100644
--- a/arch/x86/kernel/fpu/xstate.c
+++ b/arch/x86/kernel/fpu/xstate.c
@@ -1297,6 +1297,25 @@ int realloc_xstate_buffer(struct fpu *fpu, u64 mask)
return 0;
}
+/**
+ * get_features_mask_uabi - Get feature list that the kernel supports
+ * Return: A bitmap to indicate which state is available
+ *
+ */
+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;
+}
+
/**
* set_group_state_perm - Set a per-process permission for dynamic user
* states.
@@ -1306,16 +1325,7 @@ int realloc_xstate_buffer(struct fpu *fpu, u64 mask)
*/
long set_group_state_perm(struct task_struct *tsk, u64 state_perm)
{
- u64 features_mask;
-
- if (!cpu_feature_enabled(X86_FEATURE_FPU))
- features_mask = 0;
- else if (use_xsave())
- features_mask = xfeatures_mask_uabi();
- else if (use_fxsr())
- features_mask = XFEATURE_MASK_FPSSE;
- else
- features_mask = XFEATURE_MASK_FP;
+ u64 features_mask = get_features_mask_uabi();
if (state_perm & ~features_mask)
return -EINVAL;
@@ -1365,17 +1375,16 @@ void reset_dynamic_state_perm(struct task_struct *tsk)
*/
u64 get_group_state_perm(struct task_struct *tsk)
{
+ u64 mask = get_features_mask_uabi();
+
if (!cpu_feature_enabled(X86_FEATURE_FPU))
return 0;
if (use_xsave())
- return (xfeatures_mask_uabi() & ~xfeatures_mask_user_dynamic) |
+ return (mask & ~xfeatures_mask_user_dynamic) |
get_group_dynamic_state_perm(tsk);
-
- if (use_fxsr())
- return XFEATURE_MASK_FPSSE;
-
- return XFEATURE_MASK_FP;
+ else
+ return mask;
}
static void copy_feature(bool from_xstate, struct membuf *to, void *xstate,
diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c
index beab1bf76d1a..544b0c4f3aed 100644
--- a/arch/x86/kernel/process.c
+++ b/arch/x86/kernel/process.c
@@ -1023,6 +1023,8 @@ 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:
+ return put_user(get_features_mask_uabi(), (unsigned long __user *)arg2);
case ARCH_SET_STATE_ENABLE:
return set_group_state_perm(task, arg2);
case ARCH_GET_STATE_ENABLE:
--
2.17.1
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