arch/x86/kernel/fpu/xstate.h - linux - Git at Google

 /* SPDX-License-Identifier: GPL-2.0 */
 #ifndef __X86_KERNEL_FPU_XSTATE_H
 #define __X86_KERNEL_FPU_XSTATE_H

 #include <asm/cpufeature.h>
 #include <asm/fpu/xstate.h>
 #include <asm/fpu/xcr.h>

 #ifdef CONFIG_X86_64
 DECLARE_PER_CPU(u64, xfd_state);
 #endif

 static inline void xstate_init_xcomp_bv(struct xregs_state *xsave, u64 mask)
 {
 	/*
 	 * XRSTORS requires these bits set in xcomp_bv, or it will
 	 * trigger #GP:
 	 */
 	if (cpu_feature_enabled(X86_FEATURE_XSAVES))
 		xsave->header.xcomp_bv = mask | XCOMP_BV_COMPACTED_FORMAT;
 }

 static inline u64 xstate_get_group_perm(bool guest)
 {
 	struct fpu *fpu = &current->group_leader->thread.fpu;
 	struct fpu_state_perm *perm;

 	/* Pairs with WRITE_ONCE() in xstate_request_perm() */
 	perm = guest ? &fpu->guest_perm : &fpu->perm;
 	return READ_ONCE(perm->__state_perm);
 }

 static inline u64 xstate_get_host_group_perm(void)
 {
 	return xstate_get_group_perm(false);
 }

 enum xstate_copy_mode {
 	XSTATE_COPY_FP,
 	XSTATE_COPY_FX,
 	XSTATE_COPY_XSAVE,
 };

 struct membuf;
 extern void __copy_xstate_to_uabi_buf(struct membuf to, struct fpstate *fpstate,
 				      u32 pkru_val, enum xstate_copy_mode copy_mode);
 extern void copy_xstate_to_uabi_buf(struct membuf to, struct task_struct *tsk,
 				    enum xstate_copy_mode mode);
 extern int copy_uabi_from_kernel_to_xstate(struct fpstate *fpstate, const void *kbuf);
 extern int copy_sigframe_from_user_to_xstate(struct fpstate *fpstate, const void __user *ubuf);


 extern void fpu__init_cpu_xstate(void);
 extern void fpu__init_system_xstate(unsigned int legacy_size);

 extern void *get_xsave_addr(struct xregs_state *xsave, int xfeature_nr);

 static inline u64 xfeatures_mask_supervisor(void)
 {
 	return fpu_kernel_cfg.max_features & XFEATURE_MASK_SUPERVISOR_SUPPORTED;
 }

 static inline u64 xfeatures_mask_independent(void)
 {
 	if (!cpu_feature_enabled(X86_FEATURE_ARCH_LBR))
 		return XFEATURE_MASK_INDEPENDENT & ~XFEATURE_MASK_LBR;

 	return XFEATURE_MASK_INDEPENDENT;
 }

 /* XSAVE/XRSTOR wrapper functions */

 #ifdef CONFIG_X86_64
 #define REX_PREFIX	"0x48, "
 #else
 #define REX_PREFIX
 #endif

 /* These macros all use (%edi)/(%rdi) as the single memory argument. */
 #define XSAVE		".byte " REX_PREFIX "0x0f,0xae,0x27"
 #define XSAVEOPT	".byte " REX_PREFIX "0x0f,0xae,0x37"
 #define XSAVES		".byte " REX_PREFIX "0x0f,0xc7,0x2f"
 #define XRSTOR		".byte " REX_PREFIX "0x0f,0xae,0x2f"
 #define XRSTORS		".byte " REX_PREFIX "0x0f,0xc7,0x1f"

 /*
  * After this @err contains 0 on success or the trap number when the
  * operation raises an exception.
  */
 #define XSTATE_OP(op, st, lmask, hmask, err)				\
 	asm volatile("1:" op "\n\t"					\
 		     "xor %[err], %[err]\n"				\
 		     "2:\n\t"						\
 		     _ASM_EXTABLE_TYPE(1b, 2b, EX_TYPE_FAULT_MCE_SAFE)	\
 		     : [err] "=a" (err)					\
 		     : "D" (st), "m" (*st), "a" (lmask), "d" (hmask)	\
 		     : "memory")

 /*
  * If XSAVES is enabled, it replaces XSAVEOPT because it supports a compact
  * format and supervisor states in addition to modified optimization in
  * XSAVEOPT.
  *
  * Otherwise, if XSAVEOPT is enabled, XSAVEOPT replaces XSAVE because XSAVEOPT
  * supports modified optimization which is not supported by XSAVE.
  *
  * We use XSAVE as a fallback.
  *
  * The 661 label is defined in the ALTERNATIVE* macros as the address of the
  * original instruction which gets replaced. We need to use it here as the
  * address of the instruction where we might get an exception at.
  */
 #define XSTATE_XSAVE(st, lmask, hmask, err)				\
 	asm volatile(ALTERNATIVE_2(XSAVE,				\
 				   XSAVEOPT, X86_FEATURE_XSAVEOPT,	\
 				   XSAVES,   X86_FEATURE_XSAVES)	\
 		     "\n"						\
 		     "xor %[err], %[err]\n"				\
 		     "3:\n"						\
 		     _ASM_EXTABLE_TYPE_REG(661b, 3b, EX_TYPE_EFAULT_REG, %[err]) \
 		     : [err] "=r" (err)					\
 		     : "D" (st), "m" (*st), "a" (lmask), "d" (hmask)	\
 		     : "memory")

 /*
  * Use XRSTORS to restore context if it is enabled. XRSTORS supports compact
  * XSAVE area format.
  */
 #define XSTATE_XRESTORE(st, lmask, hmask)				\
 	asm volatile(ALTERNATIVE(XRSTOR,				\
 				 XRSTORS, X86_FEATURE_XSAVES)		\
 		     "\n"						\
 		     "3:\n"						\
 		     _ASM_EXTABLE_TYPE(661b, 3b, EX_TYPE_FPU_RESTORE)	\
 		     :							\
 		     : "D" (st), "m" (*st), "a" (lmask), "d" (hmask)	\
 		     : "memory")

 #if defined(CONFIG_X86_64) && defined(CONFIG_X86_DEBUG_FPU)
 extern void xfd_validate_state(struct fpstate *fpstate, u64 mask, bool rstor);
 #else
 static inline void xfd_validate_state(struct fpstate *fpstate, u64 mask, bool rstor) { }
 #endif

 #ifdef CONFIG_X86_64
 static inline void xfd_update_state(struct fpstate *fpstate)
 {
 	if (fpu_state_size_dynamic()) {
 		u64 xfd = fpstate->xfd;

 		if (__this_cpu_read(xfd_state) != xfd) {
 			wrmsrl(MSR_IA32_XFD, xfd);
 			__this_cpu_write(xfd_state, xfd);
 		}
 	}
 }

 extern int __xfd_enable_feature(u64 which, struct fpu_guest *guest_fpu);
 #else
 static inline void xfd_update_state(struct fpstate *fpstate) { }

 static inline int __xfd_enable_feature(u64 which, struct fpu_guest *guest_fpu) {
 	return -EPERM;
 }
 #endif

 /*
  * Save processor xstate to xsave area.
  *
  * Uses either XSAVE or XSAVEOPT or XSAVES depending on the CPU features
  * and command line options. The choice is permanent until the next reboot.
  */
 static inline void os_xsave(struct fpstate *fpstate)
 {
 	u64 mask = fpstate->xfeatures;
 	u32 lmask = mask;
 	u32 hmask = mask >> 32;
 	int err;

 	WARN_ON_FPU(!alternatives_patched);
 	xfd_validate_state(fpstate, mask, false);

 	XSTATE_XSAVE(&fpstate->regs.xsave, lmask, hmask, err);

 	/* We should never fault when copying to a kernel buffer: */
 	WARN_ON_FPU(err);
 }

 /*
  * Restore processor xstate from xsave area.
  *
  * Uses XRSTORS when XSAVES is used, XRSTOR otherwise.
  */
 static inline void os_xrstor(struct fpstate *fpstate, u64 mask)
 {
 	u32 lmask = mask;
 	u32 hmask = mask >> 32;

 	xfd_validate_state(fpstate, mask, true);
 	XSTATE_XRESTORE(&fpstate->regs.xsave, lmask, hmask);
 }

 /* Restore of supervisor state. Does not require XFD */
 static inline void os_xrstor_supervisor(struct fpstate *fpstate)
 {
 	u64 mask = xfeatures_mask_supervisor();
 	u32 lmask = mask;
 	u32 hmask = mask >> 32;

 	XSTATE_XRESTORE(&fpstate->regs.xsave, lmask, hmask);
 }

 /*
  * XSAVE itself always writes all requested xfeatures.  Removing features
  * from the request bitmap reduces the features which are written.
  * Generate a mask of features which must be written to a sigframe.  The
  * unset features can be optimized away and not written.
  *
  * This optimization is user-visible.  Only use for states where
  * uninitialized sigframe contents are tolerable, like dynamic features.
  *
  * Users of buffers produced with this optimization must check XSTATE_BV
  * to determine which features have been optimized out.
  */
 static inline u64 xfeatures_need_sigframe_write(void)
 {
 	u64 xfeaures_to_write;

 	/* In-use features must be written: */
 	xfeaures_to_write = xfeatures_in_use();

 	/* Also write all non-optimizable sigframe features: */
 	xfeaures_to_write |= XFEATURE_MASK_USER_SUPPORTED &
 			     ~XFEATURE_MASK_SIGFRAME_INITOPT;

 	return xfeaures_to_write;
 }

 /*
  * Save xstate to user space xsave area.
  *
  * We don't use modified optimization because xrstor/xrstors might track
  * a different application.
  *
  * We don't use compacted format xsave area for backward compatibility for
  * old applications which don't understand the compacted format of the
  * xsave area.
  *
  * The caller has to zero buf::header before calling this because XSAVE*
  * does not touch the reserved fields in the header.
  */
 static inline int xsave_to_user_sigframe(struct xregs_state __user *buf)
 {
 	/*
 	 * Include the features which are not xsaved/rstored by the kernel
 	 * internally, e.g. PKRU. That's user space ABI and also required
 	 * to allow the signal handler to modify PKRU.
 	 */
 	struct fpstate *fpstate = current->thread.fpu.fpstate;
 	u64 mask = fpstate->user_xfeatures;
 	u32 lmask;
 	u32 hmask;
 	int err;

 	/* Optimize away writing unnecessary xfeatures: */
 	if (fpu_state_size_dynamic())
 		mask &= xfeatures_need_sigframe_write();

 	lmask = mask;
 	hmask = mask >> 32;
 	xfd_validate_state(fpstate, mask, false);

 	stac();
 	XSTATE_OP(XSAVE, buf, lmask, hmask, err);
 	clac();

 	return err;
 }

 /*
  * Restore xstate from user space xsave area.
  */
 static inline int xrstor_from_user_sigframe(struct xregs_state __user *buf, u64 mask)
 {
 	struct xregs_state *xstate = ((__force struct xregs_state *)buf);
 	u32 lmask = mask;
 	u32 hmask = mask >> 32;
 	int err;

 	xfd_validate_state(current->thread.fpu.fpstate, mask, true);

 	stac();
 	XSTATE_OP(XRSTOR, xstate, lmask, hmask, err);
 	clac();

 	return err;
 }

 /*
  * Restore xstate from kernel space xsave area, return an error code instead of
  * an exception.
  */
 static inline int os_xrstor_safe(struct fpstate *fpstate, u64 mask)
 {
 	struct xregs_state *xstate = &fpstate->regs.xsave;
 	u32 lmask = mask;
 	u32 hmask = mask >> 32;
 	int err;

 	/* Ensure that XFD is up to date */
 	xfd_update_state(fpstate);

 	if (cpu_feature_enabled(X86_FEATURE_XSAVES))
 		XSTATE_OP(XRSTORS, xstate, lmask, hmask, err);
 	else
 		XSTATE_OP(XRSTOR, xstate, lmask, hmask, err);

 	return err;
 }


 #endif
	/* SPDX-License-Identifier: GPL-2.0 */
	#ifndef __X86_KERNEL_FPU_XSTATE_H
	#define __X86_KERNEL_FPU_XSTATE_H

	#include <asm/cpufeature.h>
	#include <asm/fpu/xstate.h>
	#include <asm/fpu/xcr.h>

	#ifdef CONFIG_X86_64
	DECLARE_PER_CPU(u64, xfd_state);
	#endif

	static inline void xstate_init_xcomp_bv(struct xregs_state *xsave, u64 mask)
	{
	/*
	* XRSTORS requires these bits set in xcomp_bv, or it will
	* trigger #GP:
	*/
	if (cpu_feature_enabled(X86_FEATURE_XSAVES))
	xsave->header.xcomp_bv = mask \| XCOMP_BV_COMPACTED_FORMAT;
	}

	static inline u64 xstate_get_group_perm(bool guest)
	{
	struct fpu *fpu = &current->group_leader->thread.fpu;
	struct fpu_state_perm *perm;

	/* Pairs with WRITE_ONCE() in xstate_request_perm() */
	perm = guest ? &fpu->guest_perm : &fpu->perm;
	return READ_ONCE(perm->__state_perm);
	}

	static inline u64 xstate_get_host_group_perm(void)
	{
	return xstate_get_group_perm(false);
	}

	enum xstate_copy_mode {
	XSTATE_COPY_FP,
	XSTATE_COPY_FX,
	XSTATE_COPY_XSAVE,
	};

	struct membuf;
	extern void __copy_xstate_to_uabi_buf(struct membuf to, struct fpstate *fpstate,
	u32 pkru_val, enum xstate_copy_mode copy_mode);
	extern void copy_xstate_to_uabi_buf(struct membuf to, struct task_struct *tsk,
	enum xstate_copy_mode mode);
	extern int copy_uabi_from_kernel_to_xstate(struct fpstate fpstate, const void kbuf);
	extern int copy_sigframe_from_user_to_xstate(struct fpstate fpstate, const void __user ubuf);


	extern void fpu__init_cpu_xstate(void);
	extern void fpu__init_system_xstate(unsigned int legacy_size);

	extern void get_xsave_addr(struct xregs_state xsave, int xfeature_nr);

	static inline u64 xfeatures_mask_supervisor(void)
	{
	return fpu_kernel_cfg.max_features & XFEATURE_MASK_SUPERVISOR_SUPPORTED;
	}

	static inline u64 xfeatures_mask_independent(void)
	{
	if (!cpu_feature_enabled(X86_FEATURE_ARCH_LBR))
	return XFEATURE_MASK_INDEPENDENT & ~XFEATURE_MASK_LBR;

	return XFEATURE_MASK_INDEPENDENT;
	}

	/* XSAVE/XRSTOR wrapper functions */

	#ifdef CONFIG_X86_64
	#define REX_PREFIX "0x48, "
	#else
	#define REX_PREFIX
	#endif

	/* These macros all use (%edi)/(%rdi) as the single memory argument. */
	#define XSAVE ".byte " REX_PREFIX "0x0f,0xae,0x27"
	#define XSAVEOPT ".byte " REX_PREFIX "0x0f,0xae,0x37"
	#define XSAVES ".byte " REX_PREFIX "0x0f,0xc7,0x2f"
	#define XRSTOR ".byte " REX_PREFIX "0x0f,0xae,0x2f"
	#define XRSTORS ".byte " REX_PREFIX "0x0f,0xc7,0x1f"

	/*
	* After this @err contains 0 on success or the trap number when the
	* operation raises an exception.
	*/
	#define XSTATE_OP(op, st, lmask, hmask, err) \
	asm volatile("1:" op "\n\t" \
	"xor %[err], %[err]\n" \
	"2:\n\t" \
	_ASM_EXTABLE_TYPE(1b, 2b, EX_TYPE_FAULT_MCE_SAFE) \
	: [err] "=a" (err) \
	: "D" (st), "m" (*st), "a" (lmask), "d" (hmask) \
	: "memory")

	/*
	* If XSAVES is enabled, it replaces XSAVEOPT because it supports a compact
	* format and supervisor states in addition to modified optimization in
	* XSAVEOPT.
	*
	* Otherwise, if XSAVEOPT is enabled, XSAVEOPT replaces XSAVE because XSAVEOPT
	* supports modified optimization which is not supported by XSAVE.
	*
	* We use XSAVE as a fallback.
	*
	* The 661 label is defined in the ALTERNATIVE* macros as the address of the
	* original instruction which gets replaced. We need to use it here as the
	* address of the instruction where we might get an exception at.
	*/
	#define XSTATE_XSAVE(st, lmask, hmask, err) \
	asm volatile(ALTERNATIVE_2(XSAVE, \
	XSAVEOPT, X86_FEATURE_XSAVEOPT, \
	XSAVES, X86_FEATURE_XSAVES) \
	"\n" \
	"xor %[err], %[err]\n" \
	"3:\n" \
	_ASM_EXTABLE_TYPE_REG(661b, 3b, EX_TYPE_EFAULT_REG, %[err]) \
	: [err] "=r" (err) \
	: "D" (st), "m" (*st), "a" (lmask), "d" (hmask) \
	: "memory")

	/*
	* Use XRSTORS to restore context if it is enabled. XRSTORS supports compact
	* XSAVE area format.
	*/
	#define XSTATE_XRESTORE(st, lmask, hmask) \
	asm volatile(ALTERNATIVE(XRSTOR, \
	XRSTORS, X86_FEATURE_XSAVES) \
	"\n" \
	"3:\n" \
	_ASM_EXTABLE_TYPE(661b, 3b, EX_TYPE_FPU_RESTORE) \
	: \
	: "D" (st), "m" (*st), "a" (lmask), "d" (hmask) \
	: "memory")

	#if defined(CONFIG_X86_64) && defined(CONFIG_X86_DEBUG_FPU)
	extern void xfd_validate_state(struct fpstate *fpstate, u64 mask, bool rstor);
	#else
	static inline void xfd_validate_state(struct fpstate *fpstate, u64 mask, bool rstor) { }
	#endif

	#ifdef CONFIG_X86_64
	static inline void xfd_update_state(struct fpstate *fpstate)
	{
	if (fpu_state_size_dynamic()) {
	u64 xfd = fpstate->xfd;

	if (__this_cpu_read(xfd_state) != xfd) {
	wrmsrl(MSR_IA32_XFD, xfd);
	__this_cpu_write(xfd_state, xfd);
	}
	}
	}

	extern int __xfd_enable_feature(u64 which, struct fpu_guest *guest_fpu);
	#else
	static inline void xfd_update_state(struct fpstate *fpstate) { }

	static inline int __xfd_enable_feature(u64 which, struct fpu_guest *guest_fpu) {
	return -EPERM;
	}
	#endif

	/*
	* Save processor xstate to xsave area.
	*
	* Uses either XSAVE or XSAVEOPT or XSAVES depending on the CPU features
	* and command line options. The choice is permanent until the next reboot.
	*/
	static inline void os_xsave(struct fpstate *fpstate)
	{
	u64 mask = fpstate->xfeatures;
	u32 lmask = mask;
	u32 hmask = mask >> 32;
	int err;

	WARN_ON_FPU(!alternatives_patched);
	xfd_validate_state(fpstate, mask, false);

	XSTATE_XSAVE(&fpstate->regs.xsave, lmask, hmask, err);

	/* We should never fault when copying to a kernel buffer: */
	WARN_ON_FPU(err);
	}

	/*
	* Restore processor xstate from xsave area.
	*
	* Uses XRSTORS when XSAVES is used, XRSTOR otherwise.
	*/
	static inline void os_xrstor(struct fpstate *fpstate, u64 mask)
	{
	u32 lmask = mask;
	u32 hmask = mask >> 32;

	xfd_validate_state(fpstate, mask, true);
	XSTATE_XRESTORE(&fpstate->regs.xsave, lmask, hmask);
	}

	/* Restore of supervisor state. Does not require XFD */
	static inline void os_xrstor_supervisor(struct fpstate *fpstate)
	{
	u64 mask = xfeatures_mask_supervisor();
	u32 lmask = mask;
	u32 hmask = mask >> 32;

	XSTATE_XRESTORE(&fpstate->regs.xsave, lmask, hmask);
	}

	/*
	* XSAVE itself always writes all requested xfeatures. Removing features
	* from the request bitmap reduces the features which are written.
	* Generate a mask of features which must be written to a sigframe. The
	* unset features can be optimized away and not written.
	*
	* This optimization is user-visible. Only use for states where
	* uninitialized sigframe contents are tolerable, like dynamic features.
	*
	* Users of buffers produced with this optimization must check XSTATE_BV
	* to determine which features have been optimized out.
	*/
	static inline u64 xfeatures_need_sigframe_write(void)
	{
	u64 xfeaures_to_write;

	/* In-use features must be written: */
	xfeaures_to_write = xfeatures_in_use();

	/* Also write all non-optimizable sigframe features: */
	xfeaures_to_write \|= XFEATURE_MASK_USER_SUPPORTED &
	~XFEATURE_MASK_SIGFRAME_INITOPT;

	return xfeaures_to_write;
	}

	/*
	* Save xstate to user space xsave area.
	*
	* We don't use modified optimization because xrstor/xrstors might track
	* a different application.
	*
	* We don't use compacted format xsave area for backward compatibility for
	* old applications which don't understand the compacted format of the
	* xsave area.
	*
	* The caller has to zero buf::header before calling this because XSAVE*
	* does not touch the reserved fields in the header.
	*/
	static inline int xsave_to_user_sigframe(struct xregs_state __user *buf)
	{
	/*
	* Include the features which are not xsaved/rstored by the kernel
	* internally, e.g. PKRU. That's user space ABI and also required
	* to allow the signal handler to modify PKRU.
	*/
	struct fpstate *fpstate = current->thread.fpu.fpstate;
	u64 mask = fpstate->user_xfeatures;
	u32 lmask;
	u32 hmask;
	int err;

	/* Optimize away writing unnecessary xfeatures: */
	if (fpu_state_size_dynamic())
	mask &= xfeatures_need_sigframe_write();

	lmask = mask;
	hmask = mask >> 32;
	xfd_validate_state(fpstate, mask, false);

	stac();
	XSTATE_OP(XSAVE, buf, lmask, hmask, err);
	clac();

	return err;
	}

	/*
	* Restore xstate from user space xsave area.
	*/
	static inline int xrstor_from_user_sigframe(struct xregs_state __user *buf, u64 mask)
	{
	struct xregs_state xstate = ((__force struct xregs_state )buf);
	u32 lmask = mask;
	u32 hmask = mask >> 32;
	int err;

	xfd_validate_state(current->thread.fpu.fpstate, mask, true);

	stac();
	XSTATE_OP(XRSTOR, xstate, lmask, hmask, err);
	clac();

	return err;
	}

	/*
	* Restore xstate from kernel space xsave area, return an error code instead of
	* an exception.
	*/
	static inline int os_xrstor_safe(struct fpstate *fpstate, u64 mask)
	{
	struct xregs_state *xstate = &fpstate->regs.xsave;
	u32 lmask = mask;
	u32 hmask = mask >> 32;
	int err;

	/* Ensure that XFD is up to date */
	xfd_update_state(fpstate);

	if (cpu_feature_enabled(X86_FEATURE_XSAVES))
	XSTATE_OP(XRSTORS, xstate, lmask, hmask, err);
	else
	XSTATE_OP(XRSTOR, xstate, lmask, hmask, err);

	return err;
	}


	#endif