diff options
Diffstat (limited to 'arch/x86/kernel/fpu/xstate.h')
| -rw-r--r-- | arch/x86/kernel/fpu/xstate.h | 327 |
1 files changed, 327 insertions, 0 deletions
diff --git a/arch/x86/kernel/fpu/xstate.h b/arch/x86/kernel/fpu/xstate.h new file mode 100644 index 0000000000..3518fb26d0 --- /dev/null +++ b/arch/x86/kernel/fpu/xstate.h @@ -0,0 +1,327 @@ +/* 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_XCOMPACTED)) + xsave->header.xcomp_bv = mask | XCOMP_BV_COMPACTED_FORMAT; +} + +static inline u64 xstate_get_group_perm(bool guest) +{ + struct fpu *fpu = ¤t->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, + u64 xfeatures, 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, u32 *pkru); +extern int copy_sigframe_from_user_to_xstate(struct task_struct *tsk, 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 XSAVEC ".byte " REX_PREFIX "0x0f,0xc7,0x27" +#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 XSAVEC because it supports supervisor + * states in addition to XSAVEC. + * + * Otherwise if XSAVEC is enabled, it replaces XSAVEOPT because it supports + * compacted storage format in addition to 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_3(XSAVE, \ + XSAVEOPT, X86_FEATURE_XSAVEOPT, \ + XSAVEC, X86_FEATURE_XSAVEC, \ + 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 |