diff options
Diffstat (limited to 'arch/x86/kernel/fpu')
| -rw-r--r-- | arch/x86/kernel/fpu/Makefile | 6 | ||||
| -rw-r--r-- | arch/x86/kernel/fpu/bugs.c | 59 | ||||
| -rw-r--r-- | arch/x86/kernel/fpu/context.h | 82 | ||||
| -rw-r--r-- | arch/x86/kernel/fpu/core.c | 865 | ||||
| -rw-r--r-- | arch/x86/kernel/fpu/init.c | 229 | ||||
| -rw-r--r-- | arch/x86/kernel/fpu/internal.h | 28 | ||||
| -rw-r--r-- | arch/x86/kernel/fpu/legacy.h | 111 | ||||
| -rw-r--r-- | arch/x86/kernel/fpu/regset.c | 386 | ||||
| -rw-r--r-- | arch/x86/kernel/fpu/signal.c | 542 | ||||
| -rw-r--r-- | arch/x86/kernel/fpu/xstate.c | 1843 | ||||
| -rw-r--r-- | arch/x86/kernel/fpu/xstate.h | 327 |
11 files changed, 4478 insertions, 0 deletions
diff --git a/arch/x86/kernel/fpu/Makefile b/arch/x86/kernel/fpu/Makefile new file mode 100644 index 000000000..78c562145 --- /dev/null +++ b/arch/x86/kernel/fpu/Makefile @@ -0,0 +1,6 @@ +# SPDX-License-Identifier: GPL-2.0-only +# +# Build rules for the FPU support code: +# + +obj-y += init.o bugs.o core.o regset.o signal.o xstate.o diff --git a/arch/x86/kernel/fpu/bugs.c b/arch/x86/kernel/fpu/bugs.c new file mode 100644 index 000000000..794e70151 --- /dev/null +++ b/arch/x86/kernel/fpu/bugs.c @@ -0,0 +1,59 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * x86 FPU bug checks: + */ +#include <asm/fpu/api.h> + +/* + * Boot time CPU/FPU FDIV bug detection code: + */ + +static double __initdata x = 4195835.0; +static double __initdata y = 3145727.0; + +/* + * This used to check for exceptions.. + * However, it turns out that to support that, + * the XMM trap handlers basically had to + * be buggy. So let's have a correct XMM trap + * handler, and forget about printing out + * some status at boot. + * + * We should really only care about bugs here + * anyway. Not features. + */ +void __init fpu__init_check_bugs(void) +{ + s32 fdiv_bug; + + /* kernel_fpu_begin/end() relies on patched alternative instructions. */ + if (!boot_cpu_has(X86_FEATURE_FPU)) + return; + + kernel_fpu_begin(); + + /* + * trap_init() enabled FXSR and company _before_ testing for FP + * problems here. + * + * Test for the divl bug: http://en.wikipedia.org/wiki/Fdiv_bug + */ + __asm__("fninit\n\t" + "fldl %1\n\t" + "fdivl %2\n\t" + "fmull %2\n\t" + "fldl %1\n\t" + "fsubp %%st,%%st(1)\n\t" + "fistpl %0\n\t" + "fwait\n\t" + "fninit" + : "=m" (*&fdiv_bug) + : "m" (*&x), "m" (*&y)); + + kernel_fpu_end(); + + if (fdiv_bug) { + set_cpu_bug(&boot_cpu_data, X86_BUG_FDIV); + pr_warn("Hmm, FPU with FDIV bug\n"); + } +} diff --git a/arch/x86/kernel/fpu/context.h b/arch/x86/kernel/fpu/context.h new file mode 100644 index 000000000..71b5059e0 --- /dev/null +++ b/arch/x86/kernel/fpu/context.h @@ -0,0 +1,82 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef __X86_KERNEL_FPU_CONTEXT_H +#define __X86_KERNEL_FPU_CONTEXT_H + +#include <asm/fpu/xstate.h> +#include <asm/trace/fpu.h> + +/* Functions related to FPU context tracking */ + +/* + * The in-register FPU state for an FPU context on a CPU is assumed to be + * valid if the fpu->last_cpu matches the CPU, and the fpu_fpregs_owner_ctx + * matches the FPU. + * + * If the FPU register state is valid, the kernel can skip restoring the + * FPU state from memory. + * + * Any code that clobbers the FPU registers or updates the in-memory + * FPU state for a task MUST let the rest of the kernel know that the + * FPU registers are no longer valid for this task. + * + * Invalidate a resource you control: CPU if using the CPU for something else + * (with preemption disabled), FPU for the current task, or a task that + * is prevented from running by the current task. + */ +static inline void __cpu_invalidate_fpregs_state(void) +{ + __this_cpu_write(fpu_fpregs_owner_ctx, NULL); +} + +static inline void __fpu_invalidate_fpregs_state(struct fpu *fpu) +{ + fpu->last_cpu = -1; +} + +static inline int fpregs_state_valid(struct fpu *fpu, unsigned int cpu) +{ + return fpu == this_cpu_read(fpu_fpregs_owner_ctx) && cpu == fpu->last_cpu; +} + +static inline void fpregs_deactivate(struct fpu *fpu) +{ + __this_cpu_write(fpu_fpregs_owner_ctx, NULL); + trace_x86_fpu_regs_deactivated(fpu); +} + +static inline void fpregs_activate(struct fpu *fpu) +{ + __this_cpu_write(fpu_fpregs_owner_ctx, fpu); + trace_x86_fpu_regs_activated(fpu); +} + +/* Internal helper for switch_fpu_return() and signal frame setup */ +static inline void fpregs_restore_userregs(void) +{ + struct fpu *fpu = ¤t->thread.fpu; + int cpu = smp_processor_id(); + + if (WARN_ON_ONCE(current->flags & (PF_KTHREAD | PF_IO_WORKER))) + return; + + if (!fpregs_state_valid(fpu, cpu)) { + /* + * This restores _all_ xstate which has not been + * established yet. + * + * If PKRU is enabled, then the PKRU value is already + * correct because it was either set in switch_to() or in + * flush_thread(). So it is excluded because it might be + * not up to date in current->thread.fpu.xsave state. + * + * XFD state is handled in restore_fpregs_from_fpstate(). + */ + restore_fpregs_from_fpstate(fpu->fpstate, XFEATURE_MASK_FPSTATE); + + fpregs_activate(fpu); + fpu->last_cpu = cpu; + } + clear_thread_flag(TIF_NEED_FPU_LOAD); +} + +#endif diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c new file mode 100644 index 000000000..1d190761d --- /dev/null +++ b/arch/x86/kernel/fpu/core.c @@ -0,0 +1,865 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright (C) 1994 Linus Torvalds + * + * Pentium III FXSR, SSE support + * General FPU state handling cleanups + * Gareth Hughes <gareth@valinux.com>, May 2000 + */ +#include <asm/fpu/api.h> +#include <asm/fpu/regset.h> +#include <asm/fpu/sched.h> +#include <asm/fpu/signal.h> +#include <asm/fpu/types.h> +#include <asm/traps.h> +#include <asm/irq_regs.h> + +#include <uapi/asm/kvm.h> + +#include <linux/hardirq.h> +#include <linux/pkeys.h> +#include <linux/vmalloc.h> + +#include "context.h" +#include "internal.h" +#include "legacy.h" +#include "xstate.h" + +#define CREATE_TRACE_POINTS +#include <asm/trace/fpu.h> + +#ifdef CONFIG_X86_64 +DEFINE_STATIC_KEY_FALSE(__fpu_state_size_dynamic); +DEFINE_PER_CPU(u64, xfd_state); +#endif + +/* The FPU state configuration data for kernel and user space */ +struct fpu_state_config fpu_kernel_cfg __ro_after_init; +struct fpu_state_config fpu_user_cfg __ro_after_init; + +/* + * Represents the initial FPU state. It's mostly (but not completely) zeroes, + * depending on the FPU hardware format: + */ +struct fpstate init_fpstate __ro_after_init; + +/* Track in-kernel FPU usage */ +static DEFINE_PER_CPU(bool, in_kernel_fpu); + +/* + * Track which context is using the FPU on the CPU: + */ +DEFINE_PER_CPU(struct fpu *, fpu_fpregs_owner_ctx); + +/* + * Can we use the FPU in kernel mode with the + * whole "kernel_fpu_begin/end()" sequence? + */ +bool irq_fpu_usable(void) +{ + if (WARN_ON_ONCE(in_nmi())) + return false; + + /* In kernel FPU usage already active? */ + if (this_cpu_read(in_kernel_fpu)) + return false; + + /* + * When not in NMI or hard interrupt context, FPU can be used in: + * + * - Task context except from within fpregs_lock()'ed critical + * regions. + * + * - Soft interrupt processing context which cannot happen + * while in a fpregs_lock()'ed critical region. + */ + if (!in_hardirq()) + return true; + + /* + * In hard interrupt context it's safe when soft interrupts + * are enabled, which means the interrupt did not hit in + * a fpregs_lock()'ed critical region. + */ + return !softirq_count(); +} +EXPORT_SYMBOL(irq_fpu_usable); + +/* + * Track AVX512 state use because it is known to slow the max clock + * speed of the core. + */ +static void update_avx_timestamp(struct fpu *fpu) +{ + +#define AVX512_TRACKING_MASK (XFEATURE_MASK_ZMM_Hi256 | XFEATURE_MASK_Hi16_ZMM) + + if (fpu->fpstate->regs.xsave.header.xfeatures & AVX512_TRACKING_MASK) + fpu->avx512_timestamp = jiffies; +} + +/* + * Save the FPU register state in fpu->fpstate->regs. The register state is + * preserved. + * + * Must be called with fpregs_lock() held. + * + * The legacy FNSAVE instruction clears all FPU state unconditionally, so + * register state has to be reloaded. That might be a pointless exercise + * when the FPU is going to be used by another task right after that. But + * this only affects 20+ years old 32bit systems and avoids conditionals all + * over the place. + * + * FXSAVE and all XSAVE variants preserve the FPU register state. + */ +void save_fpregs_to_fpstate(struct fpu *fpu) +{ + if (likely(use_xsave())) { + os_xsave(fpu->fpstate); + update_avx_timestamp(fpu); + return; + } + + if (likely(use_fxsr())) { + fxsave(&fpu->fpstate->regs.fxsave); + return; + } + + /* + * Legacy FPU register saving, FNSAVE always clears FPU registers, + * so we have to reload them from the memory state. + */ + asm volatile("fnsave %[fp]; fwait" : [fp] "=m" (fpu->fpstate->regs.fsave)); + frstor(&fpu->fpstate->regs.fsave); +} + +void restore_fpregs_from_fpstate(struct fpstate *fpstate, u64 mask) +{ + /* + * AMD K7/K8 and later CPUs up to Zen don't save/restore + * FDP/FIP/FOP unless an exception is pending. Clear the x87 state + * here by setting it to fixed values. "m" is a random variable + * that should be in L1. + */ + if (unlikely(static_cpu_has_bug(X86_BUG_FXSAVE_LEAK))) { + asm volatile( + "fnclex\n\t" + "emms\n\t" + "fildl %P[addr]" /* set F?P to defined value */ + : : [addr] "m" (fpstate)); + } + + if (use_xsave()) { + /* + * Dynamically enabled features are enabled in XCR0, but + * usage requires also that the corresponding bits in XFD + * are cleared. If the bits are set then using a related + * instruction will raise #NM. This allows to do the + * allocation of the larger FPU buffer lazy from #NM or if + * the task has no permission to kill it which would happen + * via #UD if the feature is disabled in XCR0. + * + * XFD state is following the same life time rules as + * XSTATE and to restore state correctly XFD has to be + * updated before XRSTORS otherwise the component would + * stay in or go into init state even if the bits are set + * in fpstate::regs::xsave::xfeatures. + */ + xfd_update_state(fpstate); + + /* + * Restoring state always needs to modify all features + * which are in @mask even if the current task cannot use + * extended features. + * + * So fpstate->xfeatures cannot be used here, because then + * a feature for which the task has no permission but was + * used by the previous task would not go into init state. + */ + mask = fpu_kernel_cfg.max_features & mask; + + os_xrstor(fpstate, mask); + } else { + if (use_fxsr()) + fxrstor(&fpstate->regs.fxsave); + else + frstor(&fpstate->regs.fsave); + } +} + +void fpu_reset_from_exception_fixup(void) +{ + restore_fpregs_from_fpstate(&init_fpstate, XFEATURE_MASK_FPSTATE); +} + +#if IS_ENABLED(CONFIG_KVM) +static void __fpstate_reset(struct fpstate *fpstate, u64 xfd); + +static void fpu_init_guest_permissions(struct fpu_guest *gfpu) +{ + struct fpu_state_perm *fpuperm; + u64 perm; + + if (!IS_ENABLED(CONFIG_X86_64)) + return; + + spin_lock_irq(¤t->sighand->siglock); + fpuperm = ¤t->group_leader->thread.fpu.guest_perm; + perm = fpuperm->__state_perm; + + /* First fpstate allocation locks down permissions. */ + WRITE_ONCE(fpuperm->__state_perm, perm | FPU_GUEST_PERM_LOCKED); + + spin_unlock_irq(¤t->sighand->siglock); + + gfpu->perm = perm & ~FPU_GUEST_PERM_LOCKED; +} + +bool fpu_alloc_guest_fpstate(struct fpu_guest *gfpu) +{ + struct fpstate *fpstate; + unsigned int size; + + size = fpu_user_cfg.default_size + ALIGN(offsetof(struct fpstate, regs), 64); + fpstate = vzalloc(size); + if (!fpstate) + return false; + + /* Leave xfd to 0 (the reset value defined by spec) */ + __fpstate_reset(fpstate, 0); + fpstate_init_user(fpstate); + fpstate->is_valloc = true; + fpstate->is_guest = true; + + gfpu->fpstate = fpstate; + gfpu->xfeatures = fpu_user_cfg.default_features; + gfpu->perm = fpu_user_cfg.default_features; + + /* + * KVM sets the FP+SSE bits in the XSAVE header when copying FPU state + * to userspace, even when XSAVE is unsupported, so that restoring FPU + * state on a different CPU that does support XSAVE can cleanly load + * the incoming state using its natural XSAVE. In other words, KVM's + * uABI size may be larger than this host's default size. Conversely, + * the default size should never be larger than KVM's base uABI size; + * all features that can expand the uABI size must be opt-in. + */ + gfpu->uabi_size = sizeof(struct kvm_xsave); + if (WARN_ON_ONCE(fpu_user_cfg.default_size > gfpu->uabi_size)) + gfpu->uabi_size = fpu_user_cfg.default_size; + + fpu_init_guest_permissions(gfpu); + + return true; +} +EXPORT_SYMBOL_GPL(fpu_alloc_guest_fpstate); + +void fpu_free_guest_fpstate(struct fpu_guest *gfpu) +{ + struct fpstate *fps = gfpu->fpstate; + + if (!fps) + return; + + if (WARN_ON_ONCE(!fps->is_valloc || !fps->is_guest || fps->in_use)) + return; + + gfpu->fpstate = NULL; + vfree(fps); +} +EXPORT_SYMBOL_GPL(fpu_free_guest_fpstate); + +/* + * fpu_enable_guest_xfd_features - Check xfeatures against guest perm and enable + * @guest_fpu: Pointer to the guest FPU container + * @xfeatures: Features requested by guest CPUID + * + * Enable all dynamic xfeatures according to guest perm and requested CPUID. + * + * Return: 0 on success, error code otherwise + */ +int fpu_enable_guest_xfd_features(struct fpu_guest *guest_fpu, u64 xfeatures) +{ + lockdep_assert_preemption_enabled(); + + /* Nothing to do if all requested features are already enabled. */ + xfeatures &= ~guest_fpu->xfeatures; + if (!xfeatures) + return 0; + + return __xfd_enable_feature(xfeatures, guest_fpu); +} +EXPORT_SYMBOL_GPL(fpu_enable_guest_xfd_features); + +#ifdef CONFIG_X86_64 +void fpu_update_guest_xfd(struct fpu_guest *guest_fpu, u64 xfd) +{ + fpregs_lock(); + guest_fpu->fpstate->xfd = xfd; + if (guest_fpu->fpstate->in_use) + xfd_update_state(guest_fpu->fpstate); + fpregs_unlock(); +} +EXPORT_SYMBOL_GPL(fpu_update_guest_xfd); + +/** + * fpu_sync_guest_vmexit_xfd_state - Synchronize XFD MSR and software state + * + * Must be invoked from KVM after a VMEXIT before enabling interrupts when + * XFD write emulation is disabled. This is required because the guest can + * freely modify XFD and the state at VMEXIT is not guaranteed to be the + * same as the state on VMENTER. So software state has to be udpated before + * any operation which depends on it can take place. + * + * Note: It can be invoked unconditionally even when write emulation is + * enabled for the price of a then pointless MSR read. + */ +void fpu_sync_guest_vmexit_xfd_state(void) +{ + struct fpstate *fps = current->thread.fpu.fpstate; + + lockdep_assert_irqs_disabled(); + if (fpu_state_size_dynamic()) { + rdmsrl(MSR_IA32_XFD, fps->xfd); + __this_cpu_write(xfd_state, fps->xfd); + } +} +EXPORT_SYMBOL_GPL(fpu_sync_guest_vmexit_xfd_state); +#endif /* CONFIG_X86_64 */ + +int fpu_swap_kvm_fpstate(struct fpu_guest *guest_fpu, bool enter_guest) +{ + struct fpstate *guest_fps = guest_fpu->fpstate; + struct fpu *fpu = ¤t->thread.fpu; + struct fpstate *cur_fps = fpu->fpstate; + + fpregs_lock(); + if (!cur_fps->is_confidential && !test_thread_flag(TIF_NEED_FPU_LOAD)) + save_fpregs_to_fpstate(fpu); + + /* Swap fpstate */ + if (enter_guest) { + fpu->__task_fpstate = cur_fps; + fpu->fpstate = guest_fps; + guest_fps->in_use = true; + } else { + guest_fps->in_use = false; + fpu->fpstate = fpu->__task_fpstate; + fpu->__task_fpstate = NULL; + } + + cur_fps = fpu->fpstate; + + if (!cur_fps->is_confidential) { + /* Includes XFD update */ + restore_fpregs_from_fpstate(cur_fps, XFEATURE_MASK_FPSTATE); + } else { + /* + * XSTATE is restored by firmware from encrypted + * memory. Make sure XFD state is correct while + * running with guest fpstate + */ + xfd_update_state(cur_fps); + } + + fpregs_mark_activate(); + fpregs_unlock(); + return 0; +} +EXPORT_SYMBOL_GPL(fpu_swap_kvm_fpstate); + +void fpu_copy_guest_fpstate_to_uabi(struct fpu_guest *gfpu, void *buf, + unsigned int size, u64 xfeatures, u32 pkru) +{ + struct fpstate *kstate = gfpu->fpstate; + union fpregs_state *ustate = buf; + struct membuf mb = { .p = buf, .left = size }; + + if (cpu_feature_enabled(X86_FEATURE_XSAVE)) { + __copy_xstate_to_uabi_buf(mb, kstate, xfeatures, pkru, + XSTATE_COPY_XSAVE); + } else { + memcpy(&ustate->fxsave, &kstate->regs.fxsave, + sizeof(ustate->fxsave)); + /* Make it restorable on a XSAVE enabled host */ + ustate->xsave.header.xfeatures = XFEATURE_MASK_FPSSE; + } +} +EXPORT_SYMBOL_GPL(fpu_copy_guest_fpstate_to_uabi); + +int fpu_copy_uabi_to_guest_fpstate(struct fpu_guest *gfpu, const void *buf, + u64 xcr0, u32 *vpkru) +{ + struct fpstate *kstate = gfpu->fpstate; + const union fpregs_state *ustate = buf; + + if (!cpu_feature_enabled(X86_FEATURE_XSAVE)) { + if (ustate->xsave.header.xfeatures & ~XFEATURE_MASK_FPSSE) + return -EINVAL; + if (ustate->fxsave.mxcsr & ~mxcsr_feature_mask) + return -EINVAL; + memcpy(&kstate->regs.fxsave, &ustate->fxsave, sizeof(ustate->fxsave)); + return 0; + } + + if (ustate->xsave.header.xfeatures & ~xcr0) + return -EINVAL; + + /* + * Nullify @vpkru to preserve its current value if PKRU's bit isn't set + * in the header. KVM's odd ABI is to leave PKRU untouched in this + * case (all other components are eventually re-initialized). + */ + if (!(ustate->xsave.header.xfeatures & XFEATURE_MASK_PKRU)) + vpkru = NULL; + + return copy_uabi_from_kernel_to_xstate(kstate, ustate, vpkru); +} +EXPORT_SYMBOL_GPL(fpu_copy_uabi_to_guest_fpstate); +#endif /* CONFIG_KVM */ + +void kernel_fpu_begin_mask(unsigned int kfpu_mask) +{ + preempt_disable(); + + WARN_ON_FPU(!irq_fpu_usable()); + WARN_ON_FPU(this_cpu_read(in_kernel_fpu)); + + this_cpu_write(in_kernel_fpu, true); + + if (!(current->flags & (PF_KTHREAD | PF_IO_WORKER)) && + !test_thread_flag(TIF_NEED_FPU_LOAD)) { + set_thread_flag(TIF_NEED_FPU_LOAD); + save_fpregs_to_fpstate(¤t->thread.fpu); + } + __cpu_invalidate_fpregs_state(); + + /* Put sane initial values into the control registers. */ + if (likely(kfpu_mask & KFPU_MXCSR) && boot_cpu_has(X86_FEATURE_XMM)) + ldmxcsr(MXCSR_DEFAULT); + + if (unlikely(kfpu_mask & KFPU_387) && boot_cpu_has(X86_FEATURE_FPU)) + asm volatile ("fninit"); +} +EXPORT_SYMBOL_GPL(kernel_fpu_begin_mask); + +void kernel_fpu_end(void) +{ + WARN_ON_FPU(!this_cpu_read(in_kernel_fpu)); + + this_cpu_write(in_kernel_fpu, false); + preempt_enable(); +} +EXPORT_SYMBOL_GPL(kernel_fpu_end); + +/* + * Sync the FPU register state to current's memory register state when the + * current task owns the FPU. The hardware register state is preserved. + */ +void fpu_sync_fpstate(struct fpu *fpu) +{ + WARN_ON_FPU(fpu != ¤t->thread.fpu); + + fpregs_lock(); + trace_x86_fpu_before_save(fpu); + + if (!test_thread_flag(TIF_NEED_FPU_LOAD)) + save_fpregs_to_fpstate(fpu); + + trace_x86_fpu_after_save(fpu); + fpregs_unlock(); +} + +static inline unsigned int init_fpstate_copy_size(void) +{ + if (!use_xsave()) + return fpu_kernel_cfg.default_size; + + /* XSAVE(S) just needs the legacy and the xstate header part */ + return sizeof(init_fpstate.regs.xsave); +} + +static inline void fpstate_init_fxstate(struct fpstate *fpstate) +{ + fpstate->regs.fxsave.cwd = 0x37f; + fpstate->regs.fxsave.mxcsr = MXCSR_DEFAULT; +} + +/* + * Legacy x87 fpstate state init: + */ +static inline void fpstate_init_fstate(struct fpstate *fpstate) +{ + fpstate->regs.fsave.cwd = 0xffff037fu; + fpstate->regs.fsave.swd = 0xffff0000u; + fpstate->regs.fsave.twd = 0xffffffffu; + fpstate->regs.fsave.fos = 0xffff0000u; +} + +/* + * Used in two places: + * 1) Early boot to setup init_fpstate for non XSAVE systems + * 2) fpu_init_fpstate_user() which is invoked from KVM + */ +void fpstate_init_user(struct fpstate *fpstate) +{ + if (!cpu_feature_enabled(X86_FEATURE_FPU)) { + fpstate_init_soft(&fpstate->regs.soft); + return; + } + + xstate_init_xcomp_bv(&fpstate->regs.xsave, fpstate->xfeatures); + + if (cpu_feature_enabled(X86_FEATURE_FXSR)) + fpstate_init_fxstate(fpstate); + else + fpstate_init_fstate(fpstate); +} + +static void __fpstate_reset(struct fpstate *fpstate, u64 xfd) +{ + /* Initialize sizes and feature masks */ + fpstate->size = fpu_kernel_cfg.default_size; + fpstate->user_size = fpu_user_cfg.default_size; + fpstate->xfeatures = fpu_kernel_cfg.default_features; + fpstate->user_xfeatures = fpu_user_cfg.default_features; + fpstate->xfd = xfd; +} + +void fpstate_reset(struct fpu *fpu) +{ + /* Set the fpstate pointer to the default fpstate */ + fpu->fpstate = &fpu->__fpstate; + __fpstate_reset(fpu->fpstate, init_fpstate.xfd); + + /* Initialize the permission related info in fpu */ + fpu->perm.__state_perm = fpu_kernel_cfg.default_features; + fpu->perm.__state_size = fpu_kernel_cfg.default_size; + fpu->perm.__user_state_size = fpu_user_cfg.default_size; + /* Same defaults for guests */ + fpu->guest_perm = fpu->perm; +} + +static inline void fpu_inherit_perms(struct fpu *dst_fpu) +{ + if (fpu_state_size_dynamic()) { + struct fpu *src_fpu = ¤t->group_leader->thread.fpu; + + spin_lock_irq(¤t->sighand->siglock); + /* Fork also inherits the permissions of the parent */ + dst_fpu->perm = src_fpu->perm; + dst_fpu->guest_perm = src_fpu->guest_perm; + spin_unlock_irq(¤t->sighand->siglock); + } +} + +/* Clone current's FPU state on fork */ +int fpu_clone(struct task_struct *dst, unsigned long clone_flags, bool minimal) +{ + struct fpu *src_fpu = ¤t->thread.fpu; + struct fpu *dst_fpu = &dst->thread.fpu; + + /* The new task's FPU state cannot be valid in the hardware. */ + dst_fpu->last_cpu = -1; + + fpstate_reset(dst_fpu); + + if (!cpu_feature_enabled(X86_FEATURE_FPU)) + return 0; + + /* + * Enforce reload for user space tasks and prevent kernel threads + * from trying to save the FPU registers on context switch. + */ + set_tsk_thread_flag(dst, TIF_NEED_FPU_LOAD); + + /* + * No FPU state inheritance for kernel threads and IO + * worker threads. + */ + if (minimal) { + /* Clear out the minimal state */ + memcpy(&dst_fpu->fpstate->regs, &init_fpstate.regs, + init_fpstate_copy_size()); + return 0; + } + + /* + * If a new feature is added, ensure all dynamic features are + * caller-saved from here! + */ + BUILD_BUG_ON(XFEATURE_MASK_USER_DYNAMIC != XFEATURE_MASK_XTILE_DATA); + + /* + * Save the default portion of the current FPU state into the + * clone. Assume all dynamic features to be defined as caller- + * saved, which enables skipping both the expansion of fpstate + * and the copying of any dynamic state. + * + * Do not use memcpy() when TIF_NEED_FPU_LOAD is set because + * copying is not valid when current uses non-default states. + */ + fpregs_lock(); + if (test_thread_flag(TIF_NEED_FPU_LOAD)) + fpregs_restore_userregs(); + save_fpregs_to_fpstate(dst_fpu); + fpregs_unlock(); + if (!(clone_flags & CLONE_THREAD)) + fpu_inherit_perms(dst_fpu); + + /* + * Children never inherit PASID state. + * Force it to have its init value: + */ + if (use_xsave()) + dst_fpu->fpstate->regs.xsave.header.xfeatures &= ~XFEATURE_MASK_PASID; + + trace_x86_fpu_copy_src(src_fpu); + trace_x86_fpu_copy_dst(dst_fpu); + + return 0; +} + +/* + * Whitelist the FPU register state embedded into task_struct for hardened + * usercopy. + */ +void fpu_thread_struct_whitelist(unsigned long *offset, unsigned long *size) +{ + *offset = offsetof(struct thread_struct, fpu.__fpstate.regs); + *size = fpu_kernel_cfg.default_size; +} + +/* + * Drops current FPU state: deactivates the fpregs and + * the fpstate. NOTE: it still leaves previous contents + * in the fpregs in the eager-FPU case. + * + * This function can be used in cases where we know that + * a state-restore is coming: either an explicit one, + * or a reschedule. + */ +void fpu__drop(struct fpu *fpu) +{ + preempt_disable(); + + if (fpu == ¤t->thread.fpu) { + /* Ignore delayed exceptions from user space */ + asm volatile("1: fwait\n" + "2:\n" + _ASM_EXTABLE(1b, 2b)); + fpregs_deactivate(fpu); + } + + trace_x86_fpu_dropped(fpu); + + preempt_enable(); +} + +/* + * Clear FPU registers by setting them up from the init fpstate. + * Caller must do fpregs_[un]lock() around it. + */ +static inline void restore_fpregs_from_init_fpstate(u64 features_mask) +{ + if (use_xsave()) + os_xrstor(&init_fpstate, features_mask); + else if (use_fxsr()) + fxrstor(&init_fpstate.regs.fxsave); + else + frstor(&init_fpstate.regs.fsave); + + pkru_write_default(); +} + +/* + * Reset current->fpu memory state to the init values. + */ +static void fpu_reset_fpregs(void) +{ + struct fpu *fpu = ¤t->thread.fpu; + + fpregs_lock(); + __fpu_invalidate_fpregs_state(fpu); + /* + * This does not change the actual hardware registers. It just + * resets the memory image and sets TIF_NEED_FPU_LOAD so a + * subsequent return to usermode will reload the registers from the + * task's memory image. + * + * Do not use fpstate_init() here. Just copy init_fpstate which has + * the correct content already except for PKRU. + * + * PKRU handling does not rely on the xstate when restoring for + * user space as PKRU is eagerly written in switch_to() and + * flush_thread(). + */ + memcpy(&fpu->fpstate->regs, &init_fpstate.regs, init_fpstate_copy_size()); + set_thread_flag(TIF_NEED_FPU_LOAD); + fpregs_unlock(); +} + +/* + * Reset current's user FPU states to the init states. current's + * supervisor states, if any, are not modified by this function. The + * caller guarantees that the XSTATE header in memory is intact. + */ +void fpu__clear_user_states(struct fpu *fpu) +{ + WARN_ON_FPU(fpu != ¤t->thread.fpu); + + fpregs_lock(); + if (!cpu_feature_enabled(X86_FEATURE_FPU)) { + fpu_reset_fpregs(); + fpregs_unlock(); + return; + } + + /* + * Ensure that current's supervisor states are loaded into their + * corresponding registers. + */ + if (xfeatures_mask_supervisor() && + !fpregs_state_valid(fpu, smp_processor_id())) + os_xrstor_supervisor(fpu->fpstate); + + /* Reset user states in registers. */ + restore_fpregs_from_init_fpstate(XFEATURE_MASK_USER_RESTORE); + + /* + * Now all FPU registers have their desired values. Inform the FPU + * state machine that current's FPU registers are in the hardware + * registers. The memory image does not need to be updated because + * any operation relying on it has to save the registers first when + * current's FPU is marked active. + */ + fpregs_mark_activate(); + fpregs_unlock(); +} + +void fpu_flush_thread(void) +{ + fpstate_reset(¤t->thread.fpu); + fpu_reset_fpregs(); +} +/* + * Load FPU context before returning to userspace. + */ +void switch_fpu_return(void) +{ + if (!static_cpu_has(X86_FEATURE_FPU)) + return; + + fpregs_restore_userregs(); +} +EXPORT_SYMBOL_GPL(switch_fpu_return); + +#ifdef CONFIG_X86_DEBUG_FPU +/* + * If current FPU state according to its tracking (loaded FPU context on this + * CPU) is not valid then we must have TIF_NEED_FPU_LOAD set so the context is + * loaded on return to userland. + */ +void fpregs_assert_state_consistent(void) +{ + struct fpu *fpu = ¤t->thread.fpu; + + if (test_thread_flag(TIF_NEED_FPU_LOAD)) + return; + + WARN_ON_FPU(!fpregs_state_valid(fpu, smp_processor_id())); +} +EXPORT_SYMBOL_GPL(fpregs_assert_state_consistent); +#endif + +void fpregs_mark_activate(void) +{ + struct fpu *fpu = ¤t->thread.fpu; + + fpregs_activate(fpu); + fpu->last_cpu = smp_processor_id(); + clear_thread_flag(TIF_NEED_FPU_LOAD); +} + +/* + * x87 math exception handling: + */ + +int fpu__exception_code(struct fpu *fpu, int trap_nr) +{ + int err; + + if (trap_nr == X86_TRAP_MF) { + unsigned short cwd, swd; + /* + * (~cwd & swd) will mask out exceptions that are not set to unmasked + * status. 0x3f is the exception bits in these regs, 0x200 is the + * C1 reg you need in case of a stack fault, 0x040 is the stack + * fault bit. We should only be taking one exception at a time, + * so if this combination doesn't produce any single exception, + * then we have a bad program that isn't synchronizing its FPU usage + * and it will suffer the consequences since we won't be able to + * fully reproduce the context of the exception. + */ + if (boot_cpu_has(X86_FEATURE_FXSR)) { + cwd = fpu->fpstate->regs.fxsave.cwd; + swd = fpu->fpstate->regs.fxsave.swd; + } else { + cwd = (unsigned short)fpu->fpstate->regs.fsave.cwd; + swd = (unsigned short)fpu->fpstate->regs.fsave.swd; + } + + err = swd & ~cwd; + } else { + /* + * The SIMD FPU exceptions are handled a little differently, as there + * is only a single status/control register. Thus, to determine which + * unmasked exception was caught we must mask the exception mask bits + * at 0x1f80, and then use these to mask the exception bits at 0x3f. + */ + unsigned short mxcsr = MXCSR_DEFAULT; + + if (boot_cpu_has(X86_FEATURE_XMM)) + mxcsr = fpu->fpstate->regs.fxsave.mxcsr; + + err = ~(mxcsr >> 7) & mxcsr; + } + + if (err & 0x001) { /* Invalid op */ + /* + * swd & 0x240 == 0x040: Stack Underflow + * swd & 0x240 == 0x240: Stack Overflow + * User must clear the SF bit (0x40) if set + */ + return FPE_FLTINV; + } else if (err & 0x004) { /* Divide by Zero */ + return FPE_FLTDIV; + } else if (err & 0x008) { /* Overflow */ + return FPE_FLTOVF; + } else if (err & 0x012) { /* Denormal, Underflow */ + return FPE_FLTUND; + } else if (err & 0x020) { /* Precision */ + return FPE_FLTRES; + } + + /* + * If we're using IRQ 13, or supposedly even some trap + * X86_TRAP_MF implementations, it's possible + * we get a spurious trap, which is not an error. + */ + return 0; +} + +/* + * Initialize register state that may prevent from entering low-power idle. + * This function will be invoked from the cpuidle driver only when needed. + */ +noinstr void fpu_idle_fpregs(void) +{ + /* Note: AMX_TILE being enabled implies XGETBV1 support */ + if (cpu_feature_enabled(X86_FEATURE_AMX_TILE) && + (xfeatures_in_use() & XFEATURE_MASK_XTILE)) { + tile_release(); + __this_cpu_write(fpu_fpregs_owner_ctx, NULL); + } +} diff --git a/arch/x86/kernel/fpu/init.c b/arch/x86/kernel/fpu/init.c new file mode 100644 index 000000000..998a08f17 --- /dev/null +++ b/arch/x86/kernel/fpu/init.c @@ -0,0 +1,229 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * x86 FPU boot time init code: + */ +#include <asm/fpu/api.h> +#include <asm/tlbflush.h> +#include <asm/setup.h> + +#include <linux/sched.h> +#include <linux/sched/task.h> +#include <linux/init.h> + +#include "internal.h" +#include "legacy.h" +#include "xstate.h" + +/* + * Initialize the registers found in all CPUs, CR0 and CR4: + */ +static void fpu__init_cpu_generic(void) +{ + unsigned long cr0; + unsigned long cr4_mask = 0; + + if (boot_cpu_has(X86_FEATURE_FXSR)) + cr4_mask |= X86_CR4_OSFXSR; + if (boot_cpu_has(X86_FEATURE_XMM)) + cr4_mask |= X86_CR4_OSXMMEXCPT; + if (cr4_mask) + cr4_set_bits(cr4_mask); + + cr0 = read_cr0(); + cr0 &= ~(X86_CR0_TS|X86_CR0_EM); /* clear TS and EM */ + if (!boot_cpu_has(X86_FEATURE_FPU)) + cr0 |= X86_CR0_EM; + write_cr0(cr0); + + /* Flush out any pending x87 state: */ +#ifdef CONFIG_MATH_EMULATION + if (!boot_cpu_has(X86_FEATURE_FPU)) + fpstate_init_soft(¤t->thread.fpu.fpstate->regs.soft); + else +#endif + asm volatile ("fninit"); +} + +/* + * Enable all supported FPU features. Called when a CPU is brought online: + */ +void fpu__init_cpu(void) +{ + fpu__init_cpu_generic(); + fpu__init_cpu_xstate(); +} + +static bool __init fpu__probe_without_cpuid(void) +{ + unsigned long cr0; + u16 fsw, fcw; + + fsw = fcw = 0xffff; + + cr0 = read_cr0(); + cr0 &= ~(X86_CR0_TS | X86_CR0_EM); + write_cr0(cr0); + + asm volatile("fninit ; fnstsw %0 ; fnstcw %1" : "+m" (fsw), "+m" (fcw)); + + pr_info("x86/fpu: Probing for FPU: FSW=0x%04hx FCW=0x%04hx\n", fsw, fcw); + + return fsw == 0 && (fcw & 0x103f) == 0x003f; +} + +static void __init fpu__init_system_early_generic(void) +{ + if (!boot_cpu_has(X86_FEATURE_CPUID) && + !test_bit(X86_FEATURE_FPU, (unsigned long *)cpu_caps_cleared)) { + if (fpu__probe_without_cpuid()) + setup_force_cpu_cap(X86_FEATURE_FPU); + else + setup_clear_cpu_cap(X86_FEATURE_FPU); + } + +#ifndef CONFIG_MATH_EMULATION + if (!test_cpu_cap(&boot_cpu_data, X86_FEATURE_FPU)) { + pr_emerg("x86/fpu: Giving up, no FPU found and no math emulation present\n"); + for (;;) + asm volatile("hlt"); + } +#endif +} + +/* + * Boot time FPU feature detection code: + */ +unsigned int mxcsr_feature_mask __ro_after_init = 0xffffffffu; +EXPORT_SYMBOL_GPL(mxcsr_feature_mask); + +static void __init fpu__init_system_mxcsr(void) +{ + unsigned int mask = 0; + + if (boot_cpu_has(X86_FEATURE_FXSR)) { + /* Static because GCC does not get 16-byte stack alignment right: */ + static struct fxregs_state fxregs __initdata; + + asm volatile("fxsave %0" : "+m" (fxregs)); + + mask = fxregs.mxcsr_mask; + + /* + * If zero then use the default features mask, + * which has all features set, except the + * denormals-are-zero feature bit: + */ + if (mask == 0) + mask = 0x0000ffbf; + } + mxcsr_feature_mask &= mask; +} + +/* + * Once per bootup FPU initialization sequences that will run on most x86 CPUs: + */ +static void __init fpu__init_system_generic(void) +{ + /* + * Set up the legacy init FPU context. Will be updated when the + * CPU supports XSAVE[S]. + */ + fpstate_init_user(&init_fpstate); + + fpu__init_system_mxcsr(); +} + +/* + * Enforce that 'MEMBER' is the last field of 'TYPE'. + * + * Align the computed size with alignment of the TYPE, + * because that's how C aligns structs. + */ +#define CHECK_MEMBER_AT_END_OF(TYPE, MEMBER) \ + BUILD_BUG_ON(sizeof(TYPE) != \ + ALIGN(offsetofend(TYPE, MEMBER), _Alignof(TYPE))) + +/* + * We append the 'struct fpu' to the task_struct: + */ +static void __init fpu__init_task_struct_size(void) +{ + int task_size = sizeof(struct task_struct); + + /* + * Subtract off the static size of the register state. + * It potentially has a bunch of padding. + */ + task_size -= sizeof(current->thread.fpu.__fpstate.regs); + + /* + * Add back the dynamically-calculated register state + * size. + */ + task_size += fpu_kernel_cfg.default_size; + + /* + * We dynamically size 'struct fpu', so we require that + * it be at the end of 'thread_struct' and that + * 'thread_struct' be at the end of 'task_struct'. If + * you hit a compile error here, check the structure to + * see if something got added to the end. + */ + CHECK_MEMBER_AT_END_OF(struct fpu, __fpstate); + CHECK_MEMBER_AT_END_OF(struct thread_struct, fpu); + CHECK_MEMBER_AT_END_OF(struct task_struct, thread); + + arch_task_struct_size = task_size; +} + +/* + * Set up the user and kernel xstate sizes based on the legacy FPU context size. + * + * We set this up first, and later it will be overwritten by + * fpu__init_system_xstate() if the CPU knows about xstates. + */ +static void __init fpu__init_system_xstate_size_legacy(void) +{ + unsigned int size; + + /* + * Note that the size configuration might be overwritten later + * during fpu__init_system_xstate(). + */ + if (!cpu_feature_enabled(X86_FEATURE_FPU)) { + size = sizeof(struct swregs_state); + } else if (cpu_feature_enabled(X86_FEATURE_FXSR)) { + size = sizeof(struct fxregs_state); + fpu_user_cfg.legacy_features = XFEATURE_MASK_FPSSE; + } else { + size = sizeof(struct fregs_state); + fpu_user_cfg.legacy_features = XFEATURE_MASK_FP; + } + + fpu_kernel_cfg.max_size = size; + fpu_kernel_cfg.default_size = size; + fpu_user_cfg.max_size = size; + fpu_user_cfg.default_size = size; + fpstate_reset(¤t->thread.fpu); +} + +/* + * Called on the boot CPU once per system bootup, to set up the initial + * FPU state that is later cloned into all processes: + */ +void __init fpu__init_system(void) +{ + fpstate_reset(¤t->thread.fpu); + fpu__init_system_early_generic(); + + /* + * The FPU has to be operational for some of the + * later FPU init activities: + */ + fpu__init_cpu(); + + fpu__init_system_generic(); + fpu__init_system_xstate_size_legacy(); + fpu__init_system_xstate(fpu_kernel_cfg.max_size); + fpu__init_task_struct_size(); +} diff --git a/arch/x86/kernel/fpu/internal.h b/arch/x86/kernel/fpu/internal.h new file mode 100644 index 000000000..dbdb31f55 --- /dev/null +++ b/arch/x86/kernel/fpu/internal.h @@ -0,0 +1,28 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef __X86_KERNEL_FPU_INTERNAL_H +#define __X86_KERNEL_FPU_INTERNAL_H + +extern struct fpstate init_fpstate; + +/* CPU feature check wrappers */ +static __always_inline __pure bool use_xsave(void) +{ + return cpu_feature_enabled(X86_FEATURE_XSAVE); +} + +static __always_inline __pure bool use_fxsr(void) +{ + return cpu_feature_enabled(X86_FEATURE_FXSR); +} + +#ifdef CONFIG_X86_DEBUG_FPU +# define WARN_ON_FPU(x) WARN_ON_ONCE(x) +#else +# define WARN_ON_FPU(x) ({ (void)(x); 0; }) +#endif + +/* Used in init.c */ +extern void fpstate_init_user(struct fpstate *fpstate); +extern void fpstate_reset(struct fpu *fpu); + +#endif diff --git a/arch/x86/kernel/fpu/legacy.h b/arch/x86/kernel/fpu/legacy.h new file mode 100644 index 000000000..098f367bb --- /dev/null +++ b/arch/x86/kernel/fpu/legacy.h @@ -0,0 +1,111 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef __X86_KERNEL_FPU_LEGACY_H +#define __X86_KERNEL_FPU_LEGACY_H + +#include <asm/fpu/types.h> + +extern unsigned int mxcsr_feature_mask; + +static inline void ldmxcsr(u32 mxcsr) +{ + asm volatile("ldmxcsr %0" :: "m" (mxcsr)); +} + +/* + * Returns 0 on success or the trap number when the operation raises an + * exception. + */ +#define user_insn(insn, output, input...) \ +({ \ + int err; \ + \ + might_fault(); \ + \ + asm volatile(ASM_STAC "\n" \ + "1: " #insn "\n" \ + "2: " ASM_CLAC "\n" \ + _ASM_EXTABLE_TYPE(1b, 2b, EX_TYPE_FAULT_MCE_SAFE) \ + : [err] "=a" (err), output \ + : "0"(0), input); \ + err; \ +}) + +#define kernel_insn_err(insn, output, input...) \ +({ \ + int err; \ + asm volatile("1:" #insn "\n\t" \ + "2:\n" \ + _ASM_EXTABLE_TYPE_REG(1b, 2b, EX_TYPE_EFAULT_REG, %[err]) \ + : [err] "=r" (err), output \ + : "0"(0), input); \ + err; \ +}) + +#define kernel_insn(insn, output, input...) \ + asm volatile("1:" #insn "\n\t" \ + "2:\n" \ + _ASM_EXTABLE_TYPE(1b, 2b, EX_TYPE_FPU_RESTORE) \ + : output : input) + +static inline int fnsave_to_user_sigframe(struct fregs_state __user *fx) +{ + return user_insn(fnsave %[fx]; fwait, [fx] "=m" (*fx), "m" (*fx)); +} + +static inline int fxsave_to_user_sigframe(struct fxregs_state __user *fx) +{ + if (IS_ENABLED(CONFIG_X86_32)) + return user_insn(fxsave %[fx], [fx] "=m" (*fx), "m" (*fx)); + else + return user_insn(fxsaveq %[fx], [fx] "=m" (*fx), "m" (*fx)); + +} + +static inline void fxrstor(struct fxregs_state *fx) +{ + if (IS_ENABLED(CONFIG_X86_32)) + kernel_insn(fxrstor %[fx], "=m" (*fx), [fx] "m" (*fx)); + else + kernel_insn(fxrstorq %[fx], "=m" (*fx), [fx] "m" (*fx)); +} + +static inline int fxrstor_safe(struct fxregs_state *fx) +{ + if (IS_ENABLED(CONFIG_X86_32)) + return kernel_insn_err(fxrstor %[fx], "=m" (*fx), [fx] "m" (*fx)); + else + return kernel_insn_err(fxrstorq %[fx], "=m" (*fx), [fx] "m" (*fx)); +} + +static inline int fxrstor_from_user_sigframe(struct fxregs_state __user *fx) +{ + if (IS_ENABLED(CONFIG_X86_32)) + return user_insn(fxrstor %[fx], "=m" (*fx), [fx] "m" (*fx)); + else + return user_insn(fxrstorq %[fx], "=m" (*fx), [fx] "m" (*fx)); +} + +static inline void frstor(struct fregs_state *fx) +{ + kernel_insn(frstor %[fx], "=m" (*fx), [fx] "m" (*fx)); +} + +static inline int frstor_safe(struct fregs_state *fx) +{ + return kernel_insn_err(frstor %[fx], "=m" (*fx), [fx] "m" (*fx)); +} + +static inline int frstor_from_user_sigframe(struct fregs_state __user *fx) +{ + return user_insn(frstor %[fx], "=m" (*fx), [fx] "m" (*fx)); +} + +static inline void fxsave(struct fxregs_state *fx) +{ + if (IS_ENABLED(CONFIG_X86_32)) + asm volatile( "fxsave %[fx]" : [fx] "=m" (*fx)); + else + asm volatile("fxsaveq %[fx]" : [fx] "=m" (*fx)); +} + +#endif diff --git a/arch/x86/kernel/fpu/regset.c b/arch/x86/kernel/fpu/regset.c new file mode 100644 index 000000000..6d056b68f --- /dev/null +++ b/arch/x86/kernel/fpu/regset.c @@ -0,0 +1,386 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * FPU register's regset abstraction, for ptrace, core dumps, etc. + */ +#include <linux/sched/task_stack.h> +#include <linux/vmalloc.h> + +#include <asm/fpu/api.h> +#include <asm/fpu/signal.h> +#include <asm/fpu/regset.h> + +#include "context.h" +#include "internal.h" +#include "legacy.h" +#include "xstate.h" + +/* + * The xstateregs_active() routine is the same as the regset_fpregs_active() routine, + * as the "regset->n" for the xstate regset will be updated based on the feature + * capabilities supported by the xsave. + */ +int regset_fpregs_active(struct task_struct *target, const struct user_regset *regset) +{ + return regset->n; +} + +int regset_xregset_fpregs_active(struct task_struct *target, const struct user_regset *regset) +{ + if (boot_cpu_has(X86_FEATURE_FXSR)) + return regset->n; + else + return 0; +} + +/* + * The regset get() functions are invoked from: + * + * - coredump to dump the current task's fpstate. If the current task + * owns the FPU then the memory state has to be synchronized and the + * FPU register state preserved. Otherwise fpstate is already in sync. + * + * - ptrace to dump fpstate of a stopped task, in which case the registers + * have already been saved to fpstate on context switch. + */ +static void sync_fpstate(struct fpu *fpu) +{ + if (fpu == ¤t->thread.fpu) + fpu_sync_fpstate(fpu); +} + +/* + * Invalidate cached FPU registers before modifying the stopped target + * task's fpstate. + * + * This forces the target task on resume to restore the FPU registers from + * modified fpstate. Otherwise the task might skip the restore and operate + * with the cached FPU registers which discards the modifications. + */ +static void fpu_force_restore(struct fpu *fpu) +{ + /* + * Only stopped child tasks can be used to modify the FPU + * state in the fpstate buffer: + */ + WARN_ON_FPU(fpu == ¤t->thread.fpu); + + __fpu_invalidate_fpregs_state(fpu); +} + +int xfpregs_get(struct task_struct *target, const struct user_regset *regset, + struct membuf to) +{ + struct fpu *fpu = &target->thread.fpu; + + if (!cpu_feature_enabled(X86_FEATURE_FXSR)) + return -ENODEV; + + sync_fpstate(fpu); + + if (!use_xsave()) { + return membuf_write(&to, &fpu->fpstate->regs.fxsave, + sizeof(fpu->fpstate->regs.fxsave)); + } + + copy_xstate_to_uabi_buf(to, target, XSTATE_COPY_FX); + return 0; +} + +int xfpregs_set(struct task_struct *target, const struct user_regset *regset, + unsigned int pos, unsigned int count, + const void *kbuf, const void __user *ubuf) +{ + struct fpu *fpu = &target->thread.fpu; + struct fxregs_state newstate; + int ret; + + if (!cpu_feature_enabled(X86_FEATURE_FXSR)) + return -ENODEV; + + /* No funny business with partial or oversized writes is permitted. */ + if (pos != 0 || count != sizeof(newstate)) + return -EINVAL; + + ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &newstate, 0, -1); + if (ret) + return ret; + + /* Do not allow an invalid MXCSR value. */ + if (newstate.mxcsr & ~mxcsr_feature_mask) + return -EINVAL; + + fpu_force_restore(fpu); + + /* Copy the state */ + memcpy(&fpu->fpstate->regs.fxsave, &newstate, sizeof(newstate)); + + /* Clear xmm8..15 for 32-bit callers */ + BUILD_BUG_ON(sizeof(fpu->__fpstate.regs.fxsave.xmm_space) != 16 * 16); + if (in_ia32_syscall()) + memset(&fpu->fpstate->regs.fxsave.xmm_space[8*4], 0, 8 * 16); + + /* Mark FP and SSE as in use when XSAVE is enabled */ + if (use_xsave()) + fpu->fpstate->regs.xsave.header.xfeatures |= XFEATURE_MASK_FPSSE; + + return 0; +} + +int xstateregs_get(struct task_struct *target, const struct user_regset *regset, + struct membuf to) +{ + if (!cpu_feature_enabled(X86_FEATURE_XSAVE)) + return -ENODEV; + + sync_fpstate(&target->thread.fpu); + + copy_xstate_to_uabi_buf(to, target, XSTATE_COPY_XSAVE); + return 0; +} + +int xstateregs_set(struct task_struct *target, const struct user_regset *regset, + unsigned int pos, unsigned int count, + const void *kbuf, const void __user *ubuf) +{ + struct fpu *fpu = &target->thread.fpu; + struct xregs_state *tmpbuf = NULL; + int ret; + + if (!cpu_feature_enabled(X86_FEATURE_XSAVE)) + return -ENODEV; + + /* + * A whole standard-format XSAVE buffer is needed: + */ + if (pos != 0 || count != fpu_user_cfg.max_size) + return -EFAULT; + + if (!kbuf) { + tmpbuf = vmalloc(count); + if (!tmpbuf) + return -ENOMEM; + + if (copy_from_user(tmpbuf, ubuf, count)) { + ret = -EFAULT; + goto out; + } + } + + fpu_force_restore(fpu); + ret = copy_uabi_from_kernel_to_xstate(fpu->fpstate, kbuf ?: tmpbuf, &target->thread.pkru); + +out: + vfree(tmpbuf); + return ret; +} + +#if defined CONFIG_X86_32 || defined CONFIG_IA32_EMULATION + +/* + * FPU tag word conversions. + */ + +static inline unsigned short twd_i387_to_fxsr(unsigned short twd) +{ + unsigned int tmp; /* to avoid 16 bit prefixes in the code */ + + /* Transform each pair of bits into 01 (valid) or 00 (empty) */ + tmp = ~twd; + tmp = (tmp | (tmp>>1)) & 0x5555; /* 0V0V0V0V0V0V0V0V */ + /* and move the valid bits to the lower byte. */ + tmp = (tmp | (tmp >> 1)) & 0x3333; /* 00VV00VV00VV00VV */ + tmp = (tmp | (tmp >> 2)) & 0x0f0f; /* 0000VVVV0000VVVV */ + tmp = (tmp | (tmp >> 4)) & 0x00ff; /* 00000000VVVVVVVV */ + + return tmp; +} + +#define FPREG_ADDR(f, n) ((void *)&(f)->st_space + (n) * 16) +#define FP_EXP_TAG_VALID 0 +#define FP_EXP_TAG_ZERO 1 +#define FP_EXP_TAG_SPECIAL 2 +#define FP_EXP_TAG_EMPTY 3 + +static inline u32 twd_fxsr_to_i387(struct fxregs_state *fxsave) +{ + struct _fpxreg *st; + u32 tos = (fxsave->swd >> 11) & 7; + u32 twd = (unsigned long) fxsave->twd; + u32 tag; + u32 ret = 0xffff0000u; + int i; + + for (i = 0; i < 8; i++, twd >>= 1) { + if (twd & 0x1) { + st = FPREG_ADDR(fxsave, (i - tos) & 7); + + switch (st->exponent & 0x7fff) { + case 0x7fff: + tag = FP_EXP_TAG_SPECIAL; + break; + case 0x0000: + if (!st->significand[0] && + !st->significand[1] && + !st->significand[2] && + !st->significand[3]) + tag = FP_EXP_TAG_ZERO; + else + tag = FP_EXP_TAG_SPECIAL; + break; + default: + if (st->significand[3] & 0x8000) + tag = FP_EXP_TAG_VALID; + else + tag = FP_EXP_TAG_SPECIAL; + break; + } + } else { + tag = FP_EXP_TAG_EMPTY; + } + ret |= tag << (2 * i); + } + return ret; +} + +/* + * FXSR floating point environment conversions. + */ + +static void __convert_from_fxsr(struct user_i387_ia32_struct *env, + struct task_struct *tsk, + struct fxregs_state *fxsave) +{ + struct _fpreg *to = (struct _fpreg *) &env->st_space[0]; + struct _fpxreg *from = (struct _fpxreg *) &fxsave->st_space[0]; + int i; + + env->cwd = fxsave->cwd | 0xffff0000u; + env->swd = fxsave->swd | 0xffff0000u; + env->twd = twd_fxsr_to_i387(fxsave); + +#ifdef CONFIG_X86_64 + env->fip = fxsave->rip; + env->foo = fxsave->rdp; + /* + * should be actually ds/cs at fpu exception time, but + * that information is not available in 64bit mode. + */ + env->fcs = task_pt_regs(tsk)->cs; + if (tsk == current) { + savesegment(ds, env->fos); + } else { + env->fos = tsk->thread.ds; + } + env->fos |= 0xffff0000; +#else + env->fip = fxsave->fip; + env->fcs = (u16) fxsave->fcs | ((u32) fxsave->fop << 16); + env->foo = fxsave->foo; + env->fos = fxsave->fos; +#endif + + for (i = 0; i < 8; ++i) + memcpy(&to[i], &from[i], sizeof(to[0])); +} + +void +convert_from_fxsr(struct user_i387_ia32_struct *env, struct task_struct *tsk) +{ + __convert_from_fxsr(env, tsk, &tsk->thread.fpu.fpstate->regs.fxsave); +} + +void convert_to_fxsr(struct fxregs_state *fxsave, + const struct user_i387_ia32_struct *env) + +{ + struct _fpreg *from = (struct _fpreg *) &env->st_space[0]; + struct _fpxreg *to = (struct _fpxreg *) &fxsave->st_space[0]; + int i; + + fxsave->cwd = env->cwd; + fxsave->swd = env->swd; + fxsave->twd = twd_i387_to_fxsr(env->twd); + fxsave->fop = (u16) ((u32) env->fcs >> 16); +#ifdef CONFIG_X86_64 + fxsave->rip = env->fip; + fxsave->rdp = env->foo; + /* cs and ds ignored */ +#else + fxsave->fip = env->fip; + fxsave->fcs = (env->fcs & 0xffff); + fxsave->foo = env->foo; + fxsave->fos = env->fos; +#endif + + for (i = 0; i < 8; ++i) + memcpy(&to[i], &from[i], sizeof(from[0])); +} + +int fpregs_get(struct task_struct *target, const struct user_regset *regset, + struct membuf to) +{ + struct fpu *fpu = &target->thread.fpu; + struct user_i387_ia32_struct env; + struct fxregs_state fxsave, *fx; + + sync_fpstate(fpu); + + if (!cpu_feature_enabled(X86_FEATURE_FPU)) + return fpregs_soft_get(target, regset, to); + + if (!cpu_feature_enabled(X86_FEATURE_FXSR)) { + return membuf_write(&to, &fpu->fpstate->regs.fsave, + sizeof(struct fregs_state)); + } + + if (use_xsave()) { + struct membuf mb = { .p = &fxsave, .left = sizeof(fxsave) }; + + /* Handle init state optimized xstate correctly */ + copy_xstate_to_uabi_buf(mb, target, XSTATE_COPY_FP); + fx = &fxsave; + } else { + fx = &fpu->fpstate->regs.fxsave; + } + + __convert_from_fxsr(&env, target, fx); + return membuf_write(&to, &env, sizeof(env)); +} + +int fpregs_set(struct task_struct *target, const struct user_regset *regset, + unsigned int pos, unsigned int count, + const void *kbuf, const void __user *ubuf) +{ + struct fpu *fpu = &target->thread.fpu; + struct user_i387_ia32_struct env; + int ret; + + /* No funny business with partial or oversized writes is permitted. */ + if (pos != 0 || count != sizeof(struct user_i387_ia32_struct)) + return -EINVAL; + + if (!cpu_feature_enabled(X86_FEATURE_FPU)) + return fpregs_soft_set(target, regset, pos, count, kbuf, ubuf); + + ret = user_regset_copyin(&pos, &count, &kbuf, &ubuf, &env, 0, -1); + if (ret) + return ret; + + fpu_force_restore(fpu); + + if (cpu_feature_enabled(X86_FEATURE_FXSR)) + convert_to_fxsr(&fpu->fpstate->regs.fxsave, &env); + else + memcpy(&fpu->fpstate->regs.fsave, &env, sizeof(env)); + + /* + * Update the header bit in the xsave header, indicating the + * presence of FP. + */ + if (cpu_feature_enabled(X86_FEATURE_XSAVE)) + fpu->fpstate->regs.xsave.header.xfeatures |= XFEATURE_MASK_FP; + + return 0; +} + +#endif /* CONFIG_X86_32 || CONFIG_IA32_EMULATION */ diff --git a/arch/x86/kernel/fpu/signal.c b/arch/x86/kernel/fpu/signal.c new file mode 100644 index 000000000..558076dbd --- /dev/null +++ b/arch/x86/kernel/fpu/signal.c @@ -0,0 +1,542 @@ +// SPDX-License-Identifier: GPL-2.0 +/* + * FPU signal frame handling routines. + */ + +#include <linux/compat.h> +#include <linux/cpu.h> +#include <linux/pagemap.h> + +#include <asm/fpu/signal.h> +#include <asm/fpu/regset.h> +#include <asm/fpu/xstate.h> + +#include <asm/sigframe.h> +#include <asm/trapnr.h> +#include <asm/trace/fpu.h> + +#include "context.h" +#include "internal.h" +#include "legacy.h" +#include "xstate.h" + +/* + * Check for the presence of extended state information in the + * user fpstate pointer in the sigcontext. + */ +static inline bool check_xstate_in_sigframe(struct fxregs_state __user *fxbuf, + struct _fpx_sw_bytes *fx_sw) +{ + int min_xstate_size = sizeof(struct fxregs_state) + + sizeof(struct xstate_header); + void __user *fpstate = fxbuf; + unsigned int magic2; + + if (__copy_from_user(fx_sw, &fxbuf->sw_reserved[0], sizeof(*fx_sw))) + return false; + + /* Check for the first magic field and other error scenarios. */ + if (fx_sw->magic1 != FP_XSTATE_MAGIC1 || + fx_sw->xstate_size < min_xstate_size || + fx_sw->xstate_size > current->thread.fpu.fpstate->user_size || + fx_sw->xstate_size > fx_sw->extended_size) + goto setfx; + + /* + * Check for the presence of second magic word at the end of memory + * layout. This detects the case where the user just copied the legacy + * fpstate layout with out copying the extended state information + * in the memory layout. + */ + if (__get_user(magic2, (__u32 __user *)(fpstate + fx_sw->xstate_size))) + return false; + + if (likely(magic2 == FP_XSTATE_MAGIC2)) + return true; +setfx: + trace_x86_fpu_xstate_check_failed(¤t->thread.fpu); + + /* Set the parameters for fx only state */ + fx_sw->magic1 = 0; + fx_sw->xstate_size = sizeof(struct fxregs_state); + fx_sw->xfeatures = XFEATURE_MASK_FPSSE; + return true; +} + +/* + * Signal frame handlers. + */ +static inline bool save_fsave_header(struct task_struct *tsk, void __user *buf) +{ + if (use_fxsr()) { + struct xregs_state *xsave = &tsk->thread.fpu.fpstate->regs.xsave; + struct user_i387_ia32_struct env; + struct _fpstate_32 __user *fp = buf; + + fpregs_lock(); + if (!test_thread_flag(TIF_NEED_FPU_LOAD)) + fxsave(&tsk->thread.fpu.fpstate->regs.fxsave); + fpregs_unlock(); + + convert_from_fxsr(&env, tsk); + + if (__copy_to_user(buf, &env, sizeof(env)) || + __put_user(xsave->i387.swd, &fp->status) || + __put_user(X86_FXSR_MAGIC, &fp->magic)) + return false; + } else { + struct fregs_state __user *fp = buf; + u32 swd; + + if (__get_user(swd, &fp->swd) || __put_user(swd, &fp->status)) + return false; + } + + return true; +} + +/* + * Prepare the SW reserved portion of the fxsave memory layout, indicating + * the presence of the extended state information in the memory layout + * pointed to by the fpstate pointer in the sigcontext. + * This is saved when ever the FP and extended state context is + * saved on the user stack during the signal handler delivery to the user. + */ +static inline void save_sw_bytes(struct _fpx_sw_bytes *sw_bytes, bool ia32_frame, + struct fpstate *fpstate) +{ + sw_bytes->magic1 = FP_XSTATE_MAGIC1; + sw_bytes->extended_size = fpstate->user_size + FP_XSTATE_MAGIC2_SIZE; + sw_bytes->xfeatures = fpstate->user_xfeatures; + sw_bytes->xstate_size = fpstate->user_size; + + if (ia32_frame) + sw_bytes->extended_size += sizeof(struct fregs_state); +} + +static inline bool save_xstate_epilog(void __user *buf, int ia32_frame, + struct fpstate *fpstate) +{ + struct xregs_state __user *x = buf; + struct _fpx_sw_bytes sw_bytes = {}; + u32 xfeatures; + int err; + + /* Setup the bytes not touched by the [f]xsave and reserved for SW. */ + save_sw_bytes(&sw_bytes, ia32_frame, fpstate); + err = __copy_to_user(&x->i387.sw_reserved, &sw_bytes, sizeof(sw_bytes)); + + if (!use_xsave()) + return !err; + + err |= __put_user(FP_XSTATE_MAGIC2, + (__u32 __user *)(buf + fpstate->user_size)); + + /* + * Read the xfeatures which we copied (directly from the cpu or + * from the state in task struct) to the user buffers. + */ + err |= __get_user(xfeatures, (__u32 __user *)&x->header.xfeatures); + + /* + * For legacy compatible, we always set FP/SSE bits in the bit + * vector while saving the state to the user context. This will + * enable us capturing any changes(during sigreturn) to + * the FP/SSE bits by the legacy applications which don't touch + * xfeatures in the xsave header. + * + * xsave aware apps can change the xfeatures in the xsave + * header as well as change any contents in the memory layout. + * xrestore as part of sigreturn will capture all the changes. + */ + xfeatures |= XFEATURE_MASK_FPSSE; + + err |= __put_user(xfeatures, (__u32 __user *)&x->header.xfeatures); + + return !err; +} + +static inline int copy_fpregs_to_sigframe(struct xregs_state __user *buf) +{ + if (use_xsave()) + return xsave_to_user_sigframe(buf); + if (use_fxsr()) + return fxsave_to_user_sigframe((struct fxregs_state __user *) buf); + else + return fnsave_to_user_sigframe((struct fregs_state __user *) buf); +} + +/* + * Save the fpu, extended register state to the user signal frame. + * + * 'buf_fx' is the 64-byte aligned pointer at which the [f|fx|x]save + * state is copied. + * 'buf' points to the 'buf_fx' or to the fsave header followed by 'buf_fx'. + * + * buf == buf_fx for 64-bit frames and 32-bit fsave frame. + * buf != buf_fx for 32-bit frames with fxstate. + * + * Save it directly to the user frame with disabled page fault handler. If + * that faults, try to clear the frame which handles the page fault. + * + * If this is a 32-bit frame with fxstate, put a fsave header before + * the aligned state at 'buf_fx'. + * + * For [f]xsave state, update the SW reserved fields in the [f]xsave frame + * indicating the absence/presence of the extended state to the user. + */ +bool copy_fpstate_to_sigframe(void __user *buf, void __user *buf_fx, int size) +{ + struct task_struct *tsk = current; + struct fpstate *fpstate = tsk->thread.fpu.fpstate; + bool ia32_fxstate = (buf != buf_fx); + int ret; + + ia32_fxstate &= (IS_ENABLED(CONFIG_X86_32) || + IS_ENABLED(CONFIG_IA32_EMULATION)); + + if (!static_cpu_has(X86_FEATURE_FPU)) { + struct user_i387_ia32_struct fp; + + fpregs_soft_get(current, NULL, (struct membuf){.p = &fp, + .left = sizeof(fp)}); + return !copy_to_user(buf, &fp, sizeof(fp)); + } + + if (!access_ok(buf, size)) + return false; + + if (use_xsave()) { + struct xregs_state __user *xbuf = buf_fx; + + /* + * Clear the xsave header first, so that reserved fields are + * initialized to zero. + */ + if (__clear_user(&xbuf->header, sizeof(xbuf->header))) + return false; + } +retry: + /* + * Load the FPU registers if they are not valid for the current task. + * With a valid FPU state we can attempt to save the state directly to + * userland's stack frame which will likely succeed. If it does not, + * resolve the fault in the user memory and try again. + */ + fpregs_lock(); + if (test_thread_flag(TIF_NEED_FPU_LOAD)) + fpregs_restore_userregs(); + + pagefault_disable(); + ret = copy_fpregs_to_sigframe(buf_fx); + pagefault_enable(); + fpregs_unlock(); + + if (ret) { + if (!__clear_user(buf_fx, fpstate->user_size)) + goto retry; + return false; + } + + /* Save the fsave header for the 32-bit frames. */ + if ((ia32_fxstate || !use_fxsr()) && !save_fsave_header(tsk, buf)) + return false; + + if (use_fxsr() && !save_xstate_epilog(buf_fx, ia32_fxstate, fpstate)) + return false; + + return true; +} + +static int __restore_fpregs_from_user(void __user *buf, u64 ufeatures, + u64 xrestore, bool fx_only) +{ + if (use_xsave()) { + u64 init_bv = ufeatures & ~xrestore; + int ret; + + if (likely(!fx_only)) + ret = xrstor_from_user_sigframe(buf, xrestore); + else + ret = fxrstor_from_user_sigframe(buf); + + if (!ret && unlikely(init_bv)) + os_xrstor(&init_fpstate, init_bv); + return ret; + } else if (use_fxsr()) { + return fxrstor_from_user_sigframe(buf); + } else { + return frstor_from_user_sigframe(buf); + } +} + +/* + * Attempt to restore the FPU registers directly from user memory. + * Pagefaults are handled and any errors returned are fatal. + */ +static bool restore_fpregs_from_user(void __user *buf, u64 xrestore, + bool fx_only, unsigned int size) +{ + struct fpu *fpu = ¤t->thread.fpu; + int ret; + +retry: + fpregs_lock(); + /* Ensure that XFD is up to date */ + xfd_update_state(fpu->fpstate); + pagefault_disable(); + ret = __restore_fpregs_from_user(buf, fpu->fpstate->user_xfeatures, + xrestore, fx_only); + pagefault_enable(); + + if (unlikely(ret)) { + /* + * The above did an FPU restore operation, restricted to + * the user portion of the registers, and failed, but the + * microcode might have modified the FPU registers + * nevertheless. + * + * If the FPU registers do not belong to current, then + * invalidate the FPU register state otherwise the task + * might preempt current and return to user space with + * corrupted FPU registers. + */ + if (test_thread_flag(TIF_NEED_FPU_LOAD)) + __cpu_invalidate_fpregs_state(); + fpregs_unlock(); + + /* Try to handle #PF, but anything else is fatal. */ + if (ret != X86_TRAP_PF) + return false; + + if (!fault_in_readable(buf, size)) + goto retry; + return false; + } + + /* + * Restore supervisor states: previous context switch etc has done + * XSAVES and saved the supervisor states in the kernel buffer from + * which they can be restored now. + * + * It would be optimal to handle this with a single XRSTORS, but + * this does not work because the rest of the FPU registers have + * been restored from a user buffer directly. + */ + if (test_thread_flag(TIF_NEED_FPU_LOAD) && xfeatures_mask_supervisor()) + os_xrstor_supervisor(fpu->fpstate); + + fpregs_mark_activate(); + fpregs_unlock(); + return true; +} + +static bool __fpu_restore_sig(void __user *buf, void __user *buf_fx, + bool ia32_fxstate) +{ + struct task_struct *tsk = current; + struct fpu *fpu = &tsk->thread.fpu; + struct user_i387_ia32_struct env; + bool success, fx_only = false; + union fpregs_state *fpregs; + unsigned int state_size; + u64 user_xfeatures = 0; + + if (use_xsave()) { + struct _fpx_sw_bytes fx_sw_user; + + if (!check_xstate_in_sigframe(buf_fx, &fx_sw_user)) + return false; + + fx_only = !fx_sw_user.magic1; + state_size = fx_sw_user.xstate_size; + user_xfeatures = fx_sw_user.xfeatures; + } else { + user_xfeatures = XFEATURE_MASK_FPSSE; + state_size = fpu->fpstate->user_size; + } + + if (likely(!ia32_fxstate)) { + /* Restore the FPU registers directly from user memory. */ + return restore_fpregs_from_user(buf_fx, user_xfeatures, fx_only, + state_size); + } + + /* + * Copy the legacy state because the FP portion of the FX frame has + * to be ignored for histerical raisins. The legacy state is folded + * in once the larger state has been copied. + */ + if (__copy_from_user(&env, buf, sizeof(env))) + return false; + + /* + * By setting TIF_NEED_FPU_LOAD it is ensured that our xstate is + * not modified on context switch and that the xstate is considered + * to be loaded again on return to userland (overriding last_cpu avoids + * the optimisation). + */ + fpregs_lock(); + if (!test_thread_flag(TIF_NEED_FPU_LOAD)) { + /* + * If supervisor states are available then save the + * hardware state in current's fpstate so that the + * supervisor state is preserved. Save the full state for + * simplicity. There is no point in optimizing this by only + * saving the supervisor states and then shuffle them to + * the right place in memory. It's ia32 mode. Shrug. + */ + if (xfeatures_mask_supervisor()) + os_xsave(fpu->fpstate); + set_thread_flag(TIF_NEED_FPU_LOAD); + } + __fpu_invalidate_fpregs_state(fpu); + __cpu_invalidate_fpregs_state(); + fpregs_unlock(); + + fpregs = &fpu->fpstate->regs; + if (use_xsave() && !fx_only) { + if (copy_sigframe_from_user_to_xstate(tsk, buf_fx)) + return false; + } else { + if (__copy_from_user(&fpregs->fxsave, buf_fx, + sizeof(fpregs->fxsave))) + return false; + + if (IS_ENABLED(CONFIG_X86_64)) { + /* Reject invalid MXCSR values. */ + if (fpregs->fxsave.mxcsr & ~mxcsr_feature_mask) + return false; + } else { + /* Mask invalid bits out for historical reasons (broken hardware). */ + fpregs->fxsave.mxcsr &= mxcsr_feature_mask; + } + + /* Enforce XFEATURE_MASK_FPSSE when XSAVE is enabled */ + if (use_xsave()) + fpregs->xsave.header.xfeatures |= XFEATURE_MASK_FPSSE; + } + + /* Fold the legacy FP storage */ + convert_to_fxsr(&fpregs->fxsave, &env); + + fpregs_lock(); + if (use_xsave()) { + /* + * Remove all UABI feature bits not set in user_xfeatures + * from the memory xstate header which makes the full + * restore below bring them into init state. This works for + * fx_only mode as well because that has only FP and SSE + * set in user_xfeatures. + * + * Preserve supervisor states! + */ + u64 mask = user_xfeatures | xfeatures_mask_supervisor(); + + fpregs->xsave.header.xfeatures &= mask; + success = !os_xrstor_safe(fpu->fpstate, + fpu_kernel_cfg.max_features); + } else { + success = !fxrstor_safe(&fpregs->fxsave); + } + + if (likely(success)) + fpregs_mark_activate(); + + fpregs_unlock(); + return success; +} + +static inline unsigned int xstate_sigframe_size(struct fpstate *fpstate) +{ + unsigned int size = fpstate->user_size; + + return use_xsave() ? size + FP_XSTATE_MAGIC2_SIZE : size; +} + +/* + * Restore FPU state from a sigframe: + */ +bool fpu__restore_sig(void __user *buf, int ia32_frame) +{ + struct fpu *fpu = ¤t->thread.fpu; + void __user *buf_fx = buf; + bool ia32_fxstate = false; + bool success = false; + unsigned int size; + + if (unlikely(!buf)) { + fpu__clear_user_states(fpu); + return true; + } + + size = xstate_sigframe_size(fpu->fpstate); + + ia32_frame &= (IS_ENABLED(CONFIG_X86_32) || + IS_ENABLED(CONFIG_IA32_EMULATION)); + + /* + * Only FXSR enabled systems need the FX state quirk. + * FRSTOR does not need it and can use the fast path. + */ + if (ia32_frame && use_fxsr()) { + buf_fx = buf + sizeof(struct fregs_state); + size += sizeof(struct fregs_state); + ia32_fxstate = true; + } + + if (!access_ok(buf, size)) + goto out; + + if (!IS_ENABLED(CONFIG_X86_64) && !cpu_feature_enabled(X86_FEATURE_FPU)) { + success = !fpregs_soft_set(current, NULL, 0, + sizeof(struct user_i387_ia32_struct), + NULL, buf); + } else { + success = __fpu_restore_sig(buf, buf_fx, ia32_fxstate); + } + +out: + if (unlikely(!success)) + fpu__clear_user_states(fpu); + return success; +} + +unsigned long +fpu__alloc_mathframe(unsigned long sp, int ia32_frame, + unsigned long *buf_fx, unsigned long *size) +{ + unsigned long frame_size = xstate_sigframe_size(current->thread.fpu.fpstate); + + *buf_fx = sp = round_down(sp - frame_size, 64); + if (ia32_frame && use_fxsr()) { + frame_size += sizeof(struct fregs_state); + sp -= sizeof(struct fregs_state); + } + + *size = frame_size; + + return sp; +} + +unsigned long __init fpu__get_fpstate_size(void) +{ + unsigned long ret = fpu_user_cfg.max_size; + + if (use_xsave()) + ret += FP_XSTATE_MAGIC2_SIZE; + + /* + * This space is needed on (most) 32-bit kernels, or when a 32-bit + * app is running on a 64-bit kernel. To keep things simple, just + * assume the worst case and always include space for 'freg_state', + * even for 64-bit apps on 64-bit kernels. This wastes a bit of + * space, but keeps the code simple. + */ + if ((IS_ENABLED(CONFIG_IA32_EMULATION) || + IS_ENABLED(CONFIG_X86_32)) && use_fxsr()) + ret += sizeof(struct fregs_state); + + return ret; +} + diff --git a/arch/x86/kernel/fpu/xstate.c b/arch/x86/kernel/fpu/xstate.c new file mode 100644 index 000000000..ebe698f8a --- /dev/null +++ b/arch/x86/kernel/fpu/xstate.c @@ -0,0 +1,1843 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * xsave/xrstor support. + * + * Author: Suresh Siddha <suresh.b.siddha@intel.com> + */ +#include <linux/bitops.h> +#include <linux/compat.h> +#include <linux/cpu.h> +#include <linux/mman.h> +#include <linux/nospec.h> +#include <linux/pkeys.h> +#include <linux/seq_file.h> +#include <linux/proc_fs.h> +#include <linux/vmalloc.h> + +#include <asm/fpu/api.h> +#include <asm/fpu/regset.h> +#include <asm/fpu/signal.h> +#include <asm/fpu/xcr.h> + +#include <asm/tlbflush.h> +#include <asm/prctl.h> +#include <asm/elf.h> + +#include "context.h" +#include "internal.h" +#include "legacy.h" +#include "xstate.h" + +#define for_each_extended_xfeature(bit, mask) \ + (bit) = FIRST_EXTENDED_XFEATURE; \ + for_each_set_bit_from(bit, (unsigned long *)&(mask), 8 * sizeof(mask)) + +/* + * Although we spell it out in here, the Processor Trace + * xfeature is completely unused. We use other mechanisms + * to save/restore PT state in Linux. + */ +static const char *xfeature_names[] = +{ + "x87 floating point registers" , + "SSE registers" , + "AVX registers" , + "MPX bounds registers" , + "MPX CSR" , + "AVX-512 opmask" , + "AVX-512 Hi256" , + "AVX-512 ZMM_Hi256" , + "Processor Trace (unused)" , + "Protection Keys User registers", + "PASID state", + "unknown xstate feature" , + "unknown xstate feature" , + "unknown xstate feature" , + "unknown xstate feature" , + "unknown xstate feature" , + "unknown xstate feature" , + "AMX Tile config" , + "AMX Tile data" , + "unknown xstate feature" , +}; + +static unsigned short xsave_cpuid_features[] __initdata = { + [XFEATURE_FP] = X86_FEATURE_FPU, + [XFEATURE_SSE] = X86_FEATURE_XMM, + [XFEATURE_YMM] = X86_FEATURE_AVX, + [XFEATURE_BNDREGS] = X86_FEATURE_MPX, + [XFEATURE_BNDCSR] = X86_FEATURE_MPX, + [XFEATURE_OPMASK] = X86_FEATURE_AVX512F, + [XFEATURE_ZMM_Hi256] = X86_FEATURE_AVX512F, + [XFEATURE_Hi16_ZMM] = X86_FEATURE_AVX512F, + [XFEATURE_PT_UNIMPLEMENTED_SO_FAR] = X86_FEATURE_INTEL_PT, + [XFEATURE_PKRU] = X86_FEATURE_PKU, + [XFEATURE_PASID] = X86_FEATURE_ENQCMD, + [XFEATURE_XTILE_CFG] = X86_FEATURE_AMX_TILE, + [XFEATURE_XTILE_DATA] = X86_FEATURE_AMX_TILE, +}; + +static unsigned int xstate_offsets[XFEATURE_MAX] __ro_after_init = + { [ 0 ... XFEATURE_MAX - 1] = -1}; +static unsigned int xstate_sizes[XFEATURE_MAX] __ro_after_init = + { [ 0 ... XFEATURE_MAX - 1] = -1}; +static unsigned int xstate_flags[XFEATURE_MAX] __ro_after_init; + +#define XSTATE_FLAG_SUPERVISOR BIT(0) +#define XSTATE_FLAG_ALIGNED64 BIT(1) + +/* + * Return whether the system supports a given xfeature. + * + * Also return the name of the (most advanced) feature that the caller requested: + */ +int cpu_has_xfeatures(u64 xfeatures_needed, const char **feature_name) +{ + u64 xfeatures_missing = xfeatures_needed & ~fpu_kernel_cfg.max_features; + + if (unlikely(feature_name)) { + long xfeature_idx, max_idx; + u64 xfeatures_print; + /* + * So we use FLS here to be able to print the most advanced + * feature that was requested but is missing. So if a driver + * asks about "XFEATURE_MASK_SSE | XFEATURE_MASK_YMM" we'll print the + * missing AVX feature - this is the most informative message + * to users: + */ + if (xfeatures_missing) + xfeatures_print = xfeatures_missing; + else + xfeatures_print = xfeatures_needed; + + xfeature_idx = fls64(xfeatures_print)-1; + max_idx = ARRAY_SIZE(xfeature_names)-1; + xfeature_idx = min(xfeature_idx, max_idx); + + *feature_name = xfeature_names[xfeature_idx]; + } + + if (xfeatures_missing) + return 0; + + return 1; +} +EXPORT_SYMBOL_GPL(cpu_has_xfeatures); + +static bool xfeature_is_aligned64(int xfeature_nr) +{ + return xstate_flags[xfeature_nr] & XSTATE_FLAG_ALIGNED64; +} + +static bool xfeature_is_supervisor(int xfeature_nr) +{ + return xstate_flags[xfeature_nr] & XSTATE_FLAG_SUPERVISOR; +} + +static unsigned int xfeature_get_offset(u64 xcomp_bv, int xfeature) +{ + unsigned int offs, i; + + /* + * Non-compacted format and legacy features use the cached fixed + * offsets. + */ + if (!cpu_feature_enabled(X86_FEATURE_XCOMPACTED) || + xfeature <= XFEATURE_SSE) + return xstate_offsets[xfeature]; + + /* + * Compacted format offsets depend on the actual content of the + * compacted xsave area which is determined by the xcomp_bv header + * field. + */ + offs = FXSAVE_SIZE + XSAVE_HDR_SIZE; + for_each_extended_xfeature(i, xcomp_bv) { + if (xfeature_is_aligned64(i)) + offs = ALIGN(offs, 64); + if (i == xfeature) + break; + offs += xstate_sizes[i]; + } + return offs; +} + +/* + * Enable the extended processor state save/restore feature. + * Called once per CPU onlining. + */ +void fpu__init_cpu_xstate(void) +{ + if (!boot_cpu_has(X86_FEATURE_XSAVE) || !fpu_kernel_cfg.max_features) + return; + + cr4_set_bits(X86_CR4_OSXSAVE); + + /* + * Must happen after CR4 setup and before xsetbv() to allow KVM + * lazy passthrough. Write independent of the dynamic state static + * key as that does not work on the boot CPU. This also ensures + * that any stale state is wiped out from XFD. + */ + if (cpu_feature_enabled(X86_FEATURE_XFD)) + wrmsrl(MSR_IA32_XFD, init_fpstate.xfd); + + /* + * XCR_XFEATURE_ENABLED_MASK (aka. XCR0) sets user features + * managed by XSAVE{C, OPT, S} and XRSTOR{S}. Only XSAVE user + * states can be set here. + */ + xsetbv(XCR_XFEATURE_ENABLED_MASK, fpu_user_cfg.max_features); + + /* + * MSR_IA32_XSS sets supervisor states managed by XSAVES. + */ + if (boot_cpu_has(X86_FEATURE_XSAVES)) { + wrmsrl(MSR_IA32_XSS, xfeatures_mask_supervisor() | + xfeatures_mask_independent()); + } +} + +static bool xfeature_enabled(enum xfeature xfeature) +{ + return fpu_kernel_cfg.max_features & BIT_ULL(xfeature); +} + +/* + * Record the offsets and sizes of various xstates contained + * in the XSAVE state memory layout. + */ +static void __init setup_xstate_cache(void) +{ + u32 eax, ebx, ecx, edx, i; + /* start at the beginning of the "extended state" */ + unsigned int last_good_offset = offsetof(struct xregs_state, + extended_state_area); + /* + * The FP xstates and SSE xstates are legacy states. They are always + * in the fixed offsets in the xsave area in either compacted form + * or standard form. + */ + xstate_offsets[XFEATURE_FP] = 0; + xstate_sizes[XFEATURE_FP] = offsetof(struct fxregs_state, + xmm_space); + + xstate_offsets[XFEATURE_SSE] = xstate_sizes[XFEATURE_FP]; + xstate_sizes[XFEATURE_SSE] = sizeof_field(struct fxregs_state, + xmm_space); + + for_each_extended_xfeature(i, fpu_kernel_cfg.max_features) { + cpuid_count(XSTATE_CPUID, i, &eax, &ebx, &ecx, &edx); + + xstate_sizes[i] = eax; + xstate_flags[i] = ecx; + + /* + * If an xfeature is supervisor state, the offset in EBX is + * invalid, leave it to -1. + */ + if (xfeature_is_supervisor(i)) + continue; + + xstate_offsets[i] = ebx; + + /* + * In our xstate size checks, we assume that the highest-numbered + * xstate feature has the highest offset in the buffer. Ensure + * it does. + */ + WARN_ONCE(last_good_offset > xstate_offsets[i], + "x86/fpu: misordered xstate at %d\n", last_good_offset); + + last_good_offset = xstate_offsets[i]; + } +} + +static void __init print_xstate_feature(u64 xstate_mask) +{ + const char *feature_name; + + if (cpu_has_xfeatures(xstate_mask, &feature_name)) + pr_info("x86/fpu: Supporting XSAVE feature 0x%03Lx: '%s'\n", xstate_mask, feature_name); +} + +/* + * Print out all the supported xstate features: + */ +static void __init print_xstate_features(void) +{ + print_xstate_feature(XFEATURE_MASK_FP); + print_xstate_feature(XFEATURE_MASK_SSE); + print_xstate_feature(XFEATURE_MASK_YMM); + print_xstate_feature(XFEATURE_MASK_BNDREGS); + print_xstate_feature(XFEATURE_MASK_BNDCSR); + print_xstate_feature(XFEATURE_MASK_OPMASK); + print_xstate_feature(XFEATURE_MASK_ZMM_Hi256); + print_xstate_feature(XFEATURE_MASK_Hi16_ZMM); + print_xstate_feature(XFEATURE_MASK_PKRU); + print_xstate_feature(XFEATURE_MASK_PASID); + print_xstate_feature(XFEATURE_MASK_XTILE_CFG); + print_xstate_feature(XFEATURE_MASK_XTILE_DATA); +} + +/* + * This check is important because it is easy to get XSTATE_* + * confused with XSTATE_BIT_*. + */ +#define CHECK_XFEATURE(nr) do { \ + WARN_ON(nr < FIRST_EXTENDED_XFEATURE); \ + WARN_ON(nr >= XFEATURE_MAX); \ +} while (0) + +/* + * Print out xstate component offsets and sizes + */ +static void __init print_xstate_offset_size(void) +{ + int i; + + for_each_extended_xfeature(i, fpu_kernel_cfg.max_features) { + pr_info("x86/fpu: xstate_offset[%d]: %4d, xstate_sizes[%d]: %4d\n", + i, xfeature_get_offset(fpu_kernel_cfg.max_features, i), + i, xstate_sizes[i]); + } +} + +/* + * This function is called only during boot time when x86 caps are not set + * up and alternative can not be used yet. + */ +static __init void os_xrstor_booting(struct xregs_state *xstate) +{ + u64 mask = fpu_kernel_cfg.max_features & XFEATURE_MASK_FPSTATE; + u32 lmask = mask; + u32 hmask = mask >> 32; + int err; + + if (cpu_feature_enabled(X86_FEATURE_XSAVES)) + XSTATE_OP(XRSTORS, xstate, lmask, hmask, err); + else + XSTATE_OP(XRSTOR, xstate, lmask, hmask, err); + + /* + * We should never fault when copying from a kernel buffer, and the FPU + * state we set at boot time should be valid. + */ + WARN_ON_FPU(err); +} + +/* + * All supported features have either init state all zeros or are + * handled in setup_init_fpu() individually. This is an explicit + * feature list and does not use XFEATURE_MASK*SUPPORTED to catch + * newly added supported features at build time and make people + * actually look at the init state for the new feature. + */ +#define XFEATURES_INIT_FPSTATE_HANDLED \ + (XFEATURE_MASK_FP | \ + XFEATURE_MASK_SSE | \ + XFEATURE_MASK_YMM | \ + XFEATURE_MASK_OPMASK | \ + XFEATURE_MASK_ZMM_Hi256 | \ + XFEATURE_MASK_Hi16_ZMM | \ + XFEATURE_MASK_PKRU | \ + XFEATURE_MASK_BNDREGS | \ + XFEATURE_MASK_BNDCSR | \ + XFEATURE_MASK_PASID | \ + XFEATURE_MASK_XTILE) + +/* + * setup the xstate image representing the init state + */ +static void __init setup_init_fpu_buf(void) +{ + BUILD_BUG_ON((XFEATURE_MASK_USER_SUPPORTED | + XFEATURE_MASK_SUPERVISOR_SUPPORTED) != + XFEATURES_INIT_FPSTATE_HANDLED); + + if (!boot_cpu_has(X86_FEATURE_XSAVE)) + return; + + print_xstate_features(); + + xstate_init_xcomp_bv(&init_fpstate.regs.xsave, init_fpstate.xfeatures); + + /* + * Init all the features state with header.xfeatures being 0x0 + */ + os_xrstor_booting(&init_fpstate.regs.xsave); + + /* + * All components are now in init state. Read the state back so + * that init_fpstate contains all non-zero init state. This only + * works with XSAVE, but not with XSAVEOPT and XSAVEC/S because + * those use the init optimization which skips writing data for + * components in init state. + * + * XSAVE could be used, but that would require to reshuffle the + * data when XSAVEC/S is available because XSAVEC/S uses xstate + * compaction. But doing so is a pointless exercise because most + * components have an all zeros init state except for the legacy + * ones (FP and SSE). Those can be saved with FXSAVE into the + * legacy area. Adding new features requires to ensure that init + * state is all zeroes or if not to add the necessary handling + * here. + */ + fxsave(&init_fpstate.regs.fxsave); +} + +int xfeature_size(int xfeature_nr) +{ + u32 eax, ebx, ecx, edx; + + CHECK_XFEATURE(xfeature_nr); + cpuid_count(XSTATE_CPUID, xfeature_nr, &eax, &ebx, &ecx, &edx); + return eax; +} + +/* Validate an xstate header supplied by userspace (ptrace or sigreturn) */ +static int validate_user_xstate_header(const struct xstate_header *hdr, + struct fpstate *fpstate) +{ + /* No unknown or supervisor features may be set */ + if (hdr->xfeatures & ~fpstate->user_xfeatures) + return -EINVAL; + + /* Userspace must use the uncompacted format */ + if (hdr->xcomp_bv) + return -EINVAL; + + /* + * If 'reserved' is shrunken to add a new field, make sure to validate + * that new field here! + */ + BUILD_BUG_ON(sizeof(hdr->reserved) != 48); + + /* No reserved bits may be set */ + if (memchr_inv(hdr->reserved, 0, sizeof(hdr->reserved))) + return -EINVAL; + + return 0; +} + +static void __init __xstate_dump_leaves(void) +{ + int i; + u32 eax, ebx, ecx, edx; + static int should_dump = 1; + + if (!should_dump) + return; + should_dump = 0; + /* + * Dump out a few leaves past the ones that we support + * just in case there are some goodies up there + */ + for (i = 0; i < XFEATURE_MAX + 10; i++) { + cpuid_count(XSTATE_CPUID, i, &eax, &ebx, &ecx, &edx); + pr_warn("CPUID[%02x, %02x]: eax=%08x ebx=%08x ecx=%08x edx=%08x\n", + XSTATE_CPUID, i, eax, ebx, ecx, edx); + } +} + +#define XSTATE_WARN_ON(x, fmt, ...) do { \ + if (WARN_ONCE(x, "XSAVE consistency problem: " fmt, ##__VA_ARGS__)) { \ + __xstate_dump_leaves(); \ + } \ +} while (0) + +#define XCHECK_SZ(sz, nr, nr_macro, __struct) do { \ + if ((nr == nr_macro) && \ + WARN_ONCE(sz != sizeof(__struct), \ + "%s: struct is %zu bytes, cpu state %d bytes\n", \ + __stringify(nr_macro), sizeof(__struct), sz)) { \ + __xstate_dump_leaves(); \ + } \ +} while (0) + +/** + * check_xtile_data_against_struct - Check tile data state size. + * + * Calculate the state size by multiplying the single tile size which is + * recorded in a C struct, and the number of tiles that the CPU informs. + * Compare the provided size with the calculation. + * + * @size: The tile data state size + * + * Returns: 0 on success, -EINVAL on mismatch. + */ +static int __init check_xtile_data_against_struct(int size) +{ + u32 max_palid, palid, state_size; + u32 eax, ebx, ecx, edx; + u16 max_tile; + + /* + * Check the maximum palette id: + * eax: the highest numbered palette subleaf. + */ + cpuid_count(TILE_CPUID, 0, &max_palid, &ebx, &ecx, &edx); + + /* + * Cross-check each tile size and find the maximum number of + * supported tiles. + */ + for (palid = 1, max_tile = 0; palid <= max_palid; palid++) { + u16 tile_size, max; + + /* + * Check the tile size info: + * eax[31:16]: bytes per title + * ebx[31:16]: the max names (or max number of tiles) + */ + cpuid_count(TILE_CPUID, palid, &eax, &ebx, &edx, &edx); + tile_size = eax >> 16; + max = ebx >> 16; + + if (tile_size != sizeof(struct xtile_data)) { + pr_err("%s: struct is %zu bytes, cpu xtile %d bytes\n", + __stringify(XFEATURE_XTILE_DATA), + sizeof(struct xtile_data), tile_size); + __xstate_dump_leaves(); + return -EINVAL; + } + + if (max > max_tile) + max_tile = max; + } + + state_size = sizeof(struct xtile_data) * max_tile; + if (size != state_size) { + pr_err("%s: calculated size is %u bytes, cpu state %d bytes\n", + __stringify(XFEATURE_XTILE_DATA), state_size, size); + __xstate_dump_leaves(); + return -EINVAL; + } + return 0; +} + +/* + * We have a C struct for each 'xstate'. We need to ensure + * that our software representation matches what the CPU + * tells us about the state's size. + */ +static bool __init check_xstate_against_struct(int nr) +{ + /* + * Ask the CPU for the size of the state. + */ + int sz = xfeature_size(nr); + /* + * Match each CPU state with the corresponding software + * structure. + */ + XCHECK_SZ(sz, nr, XFEATURE_YMM, struct ymmh_struct); + XCHECK_SZ(sz, nr, XFEATURE_BNDREGS, struct mpx_bndreg_state); + XCHECK_SZ(sz, nr, XFEATURE_BNDCSR, struct mpx_bndcsr_state); + XCHECK_SZ(sz, nr, XFEATURE_OPMASK, struct avx_512_opmask_state); + XCHECK_SZ(sz, nr, XFEATURE_ZMM_Hi256, struct avx_512_zmm_uppers_state); + XCHECK_SZ(sz, nr, XFEATURE_Hi16_ZMM, struct avx_512_hi16_state); + XCHECK_SZ(sz, nr, XFEATURE_PKRU, struct pkru_state); + XCHECK_SZ(sz, nr, XFEATURE_PASID, struct ia32_pasid_state); + XCHECK_SZ(sz, nr, XFEATURE_XTILE_CFG, struct xtile_cfg); + + /* The tile data size varies between implementations. */ + if (nr == XFEATURE_XTILE_DATA) + check_xtile_data_against_struct(sz); + + /* + * Make *SURE* to add any feature numbers in below if + * there are "holes" in the xsave state component + * numbers. + */ + if ((nr < XFEATURE_YMM) || + (nr >= XFEATURE_MAX) || + (nr == XFEATURE_PT_UNIMPLEMENTED_SO_FAR) || + ((nr >= XFEATURE_RSRVD_COMP_11) && (nr <= XFEATURE_RSRVD_COMP_16))) { + XSTATE_WARN_ON(1, "No structure for xstate: %d\n", nr); + return false; + } + return true; +} + +static unsigned int xstate_calculate_size(u64 xfeatures, bool compacted) +{ + unsigned int topmost = fls64(xfeatures) - 1; + unsigned int offset = xstate_offsets[topmost]; + + if (topmost <= XFEATURE_SSE) + return sizeof(struct xregs_state); + + if (compacted) + offset = xfeature_get_offset(xfeatures, topmost); + return offset + xstate_sizes[topmost]; +} + +/* + * This essentially double-checks what the cpu told us about + * how large the XSAVE buffer needs to be. We are recalculating + * it to be safe. + * + * Independent XSAVE features allocate their own buffers and are not + * covered by these checks. Only the size of the buffer for task->fpu + * is checked here. + */ +static bool __init paranoid_xstate_size_valid(unsigned int kernel_size) +{ + bool compacted = cpu_feature_enabled(X86_FEATURE_XCOMPACTED); + bool xsaves = cpu_feature_enabled(X86_FEATURE_XSAVES); + unsigned int size = FXSAVE_SIZE + XSAVE_HDR_SIZE; + int i; + + for_each_extended_xfeature(i, fpu_kernel_cfg.max_features) { + if (!check_xstate_against_struct(i)) + return false; + /* + * Supervisor state components can be managed only by + * XSAVES. + */ + if (!xsaves && xfeature_is_supervisor(i)) { + XSTATE_WARN_ON(1, "Got supervisor feature %d, but XSAVES not advertised\n", i); + return false; + } + } + size = xstate_calculate_size(fpu_kernel_cfg.max_features, compacted); + XSTATE_WARN_ON(size != kernel_size, + "size %u != kernel_size %u\n", size, kernel_size); + return size == kernel_size; +} + +/* + * Get total size of enabled xstates in XCR0 | IA32_XSS. + * + * Note the SDM's wording here. "sub-function 0" only enumerates + * the size of the *user* states. If we use it to size a buffer + * that we use 'XSAVES' on, we could potentially overflow the + * buffer because 'XSAVES' saves system states too. + * + * This also takes compaction into account. So this works for + * XSAVEC as well. + */ +static unsigned int __init get_compacted_size(void) +{ + unsigned int eax, ebx, ecx, edx; + /* + * - CPUID function 0DH, sub-function 1: + * EBX enumerates the size (in bytes) required by + * the XSAVES instruction for an XSAVE area + * containing all the state components + * corresponding to bits currently set in + * XCR0 | IA32_XSS. + * + * When XSAVES is not available but XSAVEC is (virt), then there + * are no supervisor states, but XSAVEC still uses compacted + * format. + */ + cpuid_count(XSTATE_CPUID, 1, &eax, &ebx, &ecx, &edx); + return ebx; +} + +/* + * Get the total size of the enabled xstates without the independent supervisor + * features. + */ +static unsigned int __init get_xsave_compacted_size(void) +{ + u64 mask = xfeatures_mask_independent(); + unsigned int size; + + if (!mask) + return get_compacted_size(); + + /* Disable independent features. */ + wrmsrl(MSR_IA32_XSS, xfeatures_mask_supervisor()); + + /* + * Ask the hardware what size is required of the buffer. + * This is the size required for the task->fpu buffer. + */ + size = get_compacted_size(); + + /* Re-enable independent features so XSAVES will work on them again. */ + wrmsrl(MSR_IA32_XSS, xfeatures_mask_supervisor() | mask); + + return size; +} + +static unsigned int __init get_xsave_size_user(void) +{ + unsigned int eax, ebx, ecx, edx; + /* + * - CPUID function 0DH, sub-function 0: + * EBX enumerates the size (in bytes) required by + * the XSAVE instruction for an XSAVE area + * containing all the *user* state components + * corresponding to bits currently set in XCR0. + */ + cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx); + return ebx; +} + +static int __init init_xstate_size(void) +{ + /* Recompute the context size for enabled features: */ + unsigned int user_size, kernel_size, kernel_default_size; + bool compacted = cpu_feature_enabled(X86_FEATURE_XCOMPACTED); + + /* Uncompacted user space size */ + user_size = get_xsave_size_user(); + + /* + * XSAVES kernel size includes supervisor states and uses compacted + * format. XSAVEC uses compacted format, but does not save + * supervisor states. + * + * XSAVE[OPT] do not support supervisor states so kernel and user + * size is identical. + */ + if (compacted) + kernel_size = get_xsave_compacted_size(); + else + kernel_size = user_size; + + kernel_default_size = + xstate_calculate_size(fpu_kernel_cfg.default_features, compacted); + + if (!paranoid_xstate_size_valid(kernel_size)) + return -EINVAL; + + fpu_kernel_cfg.max_size = kernel_size; + fpu_user_cfg.max_size = user_size; + + fpu_kernel_cfg.default_size = kernel_default_size; + fpu_user_cfg.default_size = + xstate_calculate_size(fpu_user_cfg.default_features, false); + + return 0; +} + +/* + * We enabled the XSAVE hardware, but something went wrong and + * we can not use it. Disable it. + */ +static void __init fpu__init_disable_system_xstate(unsigned int legacy_size) +{ + fpu_kernel_cfg.max_features = 0; + cr4_clear_bits(X86_CR4_OSXSAVE); + setup_clear_cpu_cap(X86_FEATURE_XSAVE); + + /* Restore the legacy size.*/ + fpu_kernel_cfg.max_size = legacy_size; + fpu_kernel_cfg.default_size = legacy_size; + fpu_user_cfg.max_size = legacy_size; + fpu_user_cfg.default_size = legacy_size; + + /* + * Prevent enabling the static branch which enables writes to the + * XFD MSR. + */ + init_fpstate.xfd = 0; + + fpstate_reset(¤t->thread.fpu); +} + +/* + * Enable and initialize the xsave feature. + * Called once per system bootup. + */ +void __init fpu__init_system_xstate(unsigned int legacy_size) +{ + unsigned int eax, ebx, ecx, edx; + u64 xfeatures; + int err; + int i; + + if (!boot_cpu_has(X86_FEATURE_FPU)) { + pr_info("x86/fpu: No FPU detected\n"); + return; + } + + if (!boot_cpu_has(X86_FEATURE_XSAVE)) { + pr_info("x86/fpu: x87 FPU will use %s\n", + boot_cpu_has(X86_FEATURE_FXSR) ? "FXSAVE" : "FSAVE"); + return; + } + + if (boot_cpu_data.cpuid_level < XSTATE_CPUID) { + WARN_ON_FPU(1); + return; + } + + /* + * Find user xstates supported by the processor. + */ + cpuid_count(XSTATE_CPUID, 0, &eax, &ebx, &ecx, &edx); + fpu_kernel_cfg.max_features = eax + ((u64)edx << 32); + + /* + * Find supervisor xstates supported by the processor. + */ + cpuid_count(XSTATE_CPUID, 1, &eax, &ebx, &ecx, &edx); + fpu_kernel_cfg.max_features |= ecx + ((u64)edx << 32); + + if ((fpu_kernel_cfg.max_features & XFEATURE_MASK_FPSSE) != XFEATURE_MASK_FPSSE) { + /* + * This indicates that something really unexpected happened + * with the enumeration. Disable XSAVE and try to continue + * booting without it. This is too early to BUG(). + */ + pr_err("x86/fpu: FP/SSE not present amongst the CPU's xstate features: 0x%llx.\n", + fpu_kernel_cfg.max_features); + goto out_disable; + } + + /* + * Clear XSAVE features that are disabled in the normal CPUID. + */ + for (i = 0; i < ARRAY_SIZE(xsave_cpuid_features); i++) { + unsigned short cid = xsave_cpuid_features[i]; + + /* Careful: X86_FEATURE_FPU is 0! */ + if ((i != XFEATURE_FP && !cid) || !boot_cpu_has(cid)) + fpu_kernel_cfg.max_features &= ~BIT_ULL(i); + } + + if (!cpu_feature_enabled(X86_FEATURE_XFD)) + fpu_kernel_cfg.max_features &= ~XFEATURE_MASK_USER_DYNAMIC; + + if (!cpu_feature_enabled(X86_FEATURE_XSAVES)) + fpu_kernel_cfg.max_features &= XFEATURE_MASK_USER_SUPPORTED; + else + fpu_kernel_cfg.max_features &= XFEATURE_MASK_USER_SUPPORTED | + XFEATURE_MASK_SUPERVISOR_SUPPORTED; + + fpu_user_cfg.max_features = fpu_kernel_cfg.max_features; + fpu_user_cfg.max_features &= XFEATURE_MASK_USER_SUPPORTED; + + /* Clean out dynamic features from default */ + fpu_kernel_cfg.default_features = fpu_kernel_cfg.max_features; + fpu_kernel_cfg.default_features &= ~XFEATURE_MASK_USER_DYNAMIC; + + fpu_user_cfg.default_features = fpu_user_cfg.max_features; + fpu_user_cfg.default_features &= ~XFEATURE_MASK_USER_DYNAMIC; + + /* Store it for paranoia check at the end */ + xfeatures = fpu_kernel_cfg.max_features; + + /* + * Initialize the default XFD state in initfp_state and enable the + * dynamic sizing mechanism if dynamic states are available. The + * static key cannot be enabled here because this runs before + * jump_label_init(). This is delayed to an initcall. + */ + init_fpstate.xfd = fpu_user_cfg.max_features & XFEATURE_MASK_USER_DYNAMIC; + + /* Set up compaction feature bit */ + if (cpu_feature_enabled(X86_FEATURE_XSAVEC) || + cpu_feature_enabled(X86_FEATURE_XSAVES)) + setup_force_cpu_cap(X86_FEATURE_XCOMPACTED); + + /* Enable xstate instructions to be able to continue with initialization: */ + fpu__init_cpu_xstate(); + + /* Cache size, offset and flags for initialization */ + setup_xstate_cache(); + + err = init_xstate_size(); + if (err) + goto out_disable; + + /* Reset the state for the current task */ + fpstate_reset(¤t->thread.fpu); + + /* + * Update info used for ptrace frames; use standard-format size and no + * supervisor xstates: + */ + update_regset_xstate_info(fpu_user_cfg.max_size, + fpu_user_cfg.max_features); + + /* + * init_fpstate excludes dynamic states as they are large but init + * state is zero. + */ + init_fpstate.size = fpu_kernel_cfg.default_size; + init_fpstate.xfeatures = fpu_kernel_cfg.default_features; + + if (init_fpstate.size > sizeof(init_fpstate.regs)) { + pr_warn("x86/fpu: init_fpstate buffer too small (%zu < %d), disabling XSAVE\n", + sizeof(init_fpstate.regs), init_fpstate.size); + goto out_disable; + } + + setup_init_fpu_buf(); + + /* + * Paranoia check whether something in the setup modified the + * xfeatures mask. + */ + if (xfeatures != fpu_kernel_cfg.max_features) { + pr_err("x86/fpu: xfeatures modified from 0x%016llx to 0x%016llx during init, disabling XSAVE\n", + xfeatures, fpu_kernel_cfg.max_features); + goto out_disable; + } + + /* + * CPU capabilities initialization runs before FPU init. So + * X86_FEATURE_OSXSAVE is not set. Now that XSAVE is completely + * functional, set the feature bit so depending code works. + */ + setup_force_cpu_cap(X86_FEATURE_OSXSAVE); + + print_xstate_offset_size(); + pr_info("x86/fpu: Enabled xstate features 0x%llx, context size is %d bytes, using '%s' format.\n", + fpu_kernel_cfg.max_features, + fpu_kernel_cfg.max_size, + boot_cpu_has(X86_FEATURE_XCOMPACTED) ? "compacted" : "standard"); + return; + +out_disable: + /* something went wrong, try to boot without any XSAVE support */ + fpu__init_disable_system_xstate(legacy_size); +} + +/* + * Restore minimal FPU state after suspend: + */ +void fpu__resume_cpu(void) +{ + /* + * Restore XCR0 on xsave capable CPUs: + */ + if (cpu_feature_enabled(X86_FEATURE_XSAVE)) + xsetbv(XCR_XFEATURE_ENABLED_MASK, fpu_user_cfg.max_features); + + /* + * Restore IA32_XSS. The same CPUID bit enumerates support + * of XSAVES and MSR_IA32_XSS. + */ + if (cpu_feature_enabled(X86_FEATURE_XSAVES)) { + wrmsrl(MSR_IA32_XSS, xfeatures_mask_supervisor() | + xfeatures_mask_independent()); + } + + if (fpu_state_size_dynamic()) + wrmsrl(MSR_IA32_XFD, current->thread.fpu.fpstate->xfd); +} + +/* + * Given an xstate feature nr, calculate where in the xsave + * buffer the state is. Callers should ensure that the buffer + * is valid. + */ +static void *__raw_xsave_addr(struct xregs_state *xsave, int xfeature_nr) +{ + u64 xcomp_bv = xsave->header.xcomp_bv; + + if (WARN_ON_ONCE(!xfeature_enabled(xfeature_nr))) + return NULL; + + if (cpu_feature_enabled(X86_FEATURE_XCOMPACTED)) { + if (WARN_ON_ONCE(!(xcomp_bv & BIT_ULL(xfeature_nr)))) + return NULL; + } + + return (void *)xsave + xfeature_get_offset(xcomp_bv, xfeature_nr); +} + +/* + * Given the xsave area and a state inside, this function returns the + * address of the state. + * + * This is the API that is called to get xstate address in either + * standard format or compacted format of xsave area. + * + * Note that if there is no data for the field in the xsave buffer + * this will return NULL. + * + * Inputs: + * xstate: the thread's storage area for all FPU data + * xfeature_nr: state which is defined in xsave.h (e.g. XFEATURE_FP, + * XFEATURE_SSE, etc...) + * Output: + * address of the state in the xsave area, or NULL if the + * field is not present in the xsave buffer. + */ +void *get_xsave_addr(struct xregs_state *xsave, int xfeature_nr) +{ + /* + * Do we even *have* xsave state? + */ + if (!boot_cpu_has(X86_FEATURE_XSAVE)) + return NULL; + + /* + * We should not ever be requesting features that we + * have not enabled. + */ + if (WARN_ON_ONCE(!xfeature_enabled(xfeature_nr))) + return NULL; + + /* + * This assumes the last 'xsave*' instruction to + * have requested that 'xfeature_nr' be saved. + * If it did not, we might be seeing and old value + * of the field in the buffer. + * + * This can happen because the last 'xsave' did not + * request that this feature be saved (unlikely) + * or because the "init optimization" caused it + * to not be saved. + */ + if (!(xsave->header.xfeatures & BIT_ULL(xfeature_nr))) + return NULL; + + return __raw_xsave_addr(xsave, xfeature_nr); +} + +#ifdef CONFIG_ARCH_HAS_PKEYS + +/* + * This will go out and modify PKRU register to set the access + * rights for @pkey to @init_val. + */ +int arch_set_user_pkey_access(struct task_struct *tsk, int pkey, + unsigned long init_val) +{ + u32 old_pkru, new_pkru_bits = 0; + int pkey_shift; + + /* + * This check implies XSAVE support. OSPKE only gets + * set if we enable XSAVE and we enable PKU in XCR0. + */ + if (!cpu_feature_enabled(X86_FEATURE_OSPKE)) + return -EINVAL; + + /* + * This code should only be called with valid 'pkey' + * values originating from in-kernel users. Complain + * if a bad value is observed. + */ + if (WARN_ON_ONCE(pkey >= arch_max_pkey())) + return -EINVAL; + + /* Set the bits we need in PKRU: */ + if (init_val & PKEY_DISABLE_ACCESS) + new_pkru_bits |= PKRU_AD_BIT; + if (init_val & PKEY_DISABLE_WRITE) + new_pkru_bits |= PKRU_WD_BIT; + + /* Shift the bits in to the correct place in PKRU for pkey: */ + pkey_shift = pkey * PKRU_BITS_PER_PKEY; + new_pkru_bits <<= pkey_shift; + + /* Get old PKRU and mask off any old bits in place: */ + old_pkru = read_pkru(); + old_pkru &= ~((PKRU_AD_BIT|PKRU_WD_BIT) << pkey_shift); + + /* Write old part along with new part: */ + write_pkru(old_pkru | new_pkru_bits); + + return 0; +} +#endif /* ! CONFIG_ARCH_HAS_PKEYS */ + +static void copy_feature(bool from_xstate, struct membuf *to, void *xstate, + void *init_xstate, unsigned int size) +{ + membuf_write(to, from_xstate ? xstate : init_xstate, size); +} + +/** + * __copy_xstate_to_uabi_buf - Copy kernel saved xstate to a UABI buffer + * @to: membuf descriptor + * @fpstate: The fpstate buffer from which to copy + * @xfeatures: The mask of xfeatures to save (XSAVE mode only) + * @pkru_val: The PKRU value to store in the PKRU component + * @copy_mode: The requested copy mode + * + * Converts from kernel XSAVE or XSAVES compacted format to UABI conforming + * format, i.e. from the kernel internal hardware dependent storage format + * to the requested @mode. UABI XSTATE is always uncompacted! + * + * It supports partial copy but @to.pos always starts from zero. + */ +void __copy_xstate_to_uabi_buf(struct membuf to, struct fpstate *fpstate, + u64 xfeatures, u32 pkru_val, + enum xstate_copy_mode copy_mode) +{ + const unsigned int off_mxcsr = offsetof(struct fxregs_state, mxcsr); + struct xregs_state *xinit = &init_fpstate.regs.xsave; + struct xregs_state *xsave = &fpstate->regs.xsave; + struct xstate_header header; + unsigned int zerofrom; + u64 mask; + int i; + + memset(&header, 0, sizeof(header)); + header.xfeatures = xsave->header.xfeatures; + + /* Mask out the feature bits depending on copy mode */ + switch (copy_mode) { + case XSTATE_COPY_FP: + header.xfeatures &= XFEATURE_MASK_FP; + break; + + case XSTATE_COPY_FX: + header.xfeatures &= XFEATURE_MASK_FP | XFEATURE_MASK_SSE; + break; + + case XSTATE_COPY_XSAVE: + header.xfeatures &= fpstate->user_xfeatures & xfeatures; + break; + } + + /* Copy FP state up to MXCSR */ + copy_feature(header.xfeatures & XFEATURE_MASK_FP, &to, &xsave->i387, + &xinit->i387, off_mxcsr); + + /* Copy MXCSR when SSE or YMM are set in the feature mask */ + copy_feature(header.xfeatures & (XFEATURE_MASK_SSE | XFEATURE_MASK_YMM), + &to, &xsave->i387.mxcsr, &xinit->i387.mxcsr, + MXCSR_AND_FLAGS_SIZE); + + /* Copy the remaining FP state */ + copy_feature(header.xfeatures & XFEATURE_MASK_FP, + &to, &xsave->i387.st_space, &xinit->i387.st_space, + sizeof(xsave->i387.st_space)); + + /* Copy the SSE state - shared with YMM, but independently managed */ + copy_feature(header.xfeatures & XFEATURE_MASK_SSE, + &to, &xsave->i387.xmm_space, &xinit->i387.xmm_space, + sizeof(xsave->i387.xmm_space)); + + if (copy_mode != XSTATE_COPY_XSAVE) + goto out; + + /* Zero the padding area */ + membuf_zero(&to, sizeof(xsave->i387.padding)); + + /* Copy xsave->i387.sw_reserved */ + membuf_write(&to, xstate_fx_sw_bytes, sizeof(xsave->i387.sw_reserved)); + + /* Copy the user space relevant state of @xsave->header */ + membuf_write(&to, &header, sizeof(header)); + + zerofrom = offsetof(struct xregs_state, extended_state_area); + + /* + * This 'mask' indicates which states to copy from fpstate. + * Those extended states that are not present in fpstate are + * either disabled or initialized: + * + * In non-compacted format, disabled features still occupy + * state space but there is no state to copy from in the + * compacted init_fpstate. The gap tracking will zero these + * states. + * + * The extended features have an all zeroes init state. Thus, + * remove them from 'mask' to zero those features in the user + * buffer instead of retrieving them from init_fpstate. + */ + mask = header.xfeatures; + + for_each_extended_xfeature(i, mask) { + /* + * If there was a feature or alignment gap, zero the space + * in the destination buffer. + */ + if (zerofrom < xstate_offsets[i]) + membuf_zero(&to, xstate_offsets[i] - zerofrom); + + if (i == XFEATURE_PKRU) { + struct pkru_state pkru = {0}; + /* + * PKRU is not necessarily up to date in the + * XSAVE buffer. Use the provided value. + */ + pkru.pkru = pkru_val; + membuf_write(&to, &pkru, sizeof(pkru)); + } else { + membuf_write(&to, + __raw_xsave_addr(xsave, i), + xstate_sizes[i]); + } + /* + * Keep track of the last copied state in the non-compacted + * target buffer for gap zeroing. + */ + zerofrom = xstate_offsets[i] + xstate_sizes[i]; + } + +out: + if (to.left) + membuf_zero(&to, to.left); +} + +/** + * copy_xstate_to_uabi_buf - Copy kernel saved xstate to a UABI buffer + * @to: membuf descriptor + * @tsk: The task from which to copy the saved xstate + * @copy_mode: The requested copy mode + * + * Converts from kernel XSAVE or XSAVES compacted format to UABI conforming + * format, i.e. from the kernel internal hardware dependent storage format + * to the requested @mode. UABI XSTATE is always uncompacted! + * + * It supports partial copy but @to.pos always starts from zero. + */ +void copy_xstate_to_uabi_buf(struct membuf to, struct task_struct *tsk, + enum xstate_copy_mode copy_mode) +{ + __copy_xstate_to_uabi_buf(to, tsk->thread.fpu.fpstate, + tsk->thread.fpu.fpstate->user_xfeatures, + tsk->thread.pkru, copy_mode); +} + +static int copy_from_buffer(void *dst, unsigned int offset, unsigned int size, + const void *kbuf, const void __user *ubuf) +{ + if (kbuf) { + memcpy(dst, kbuf + offset, size); + } else { + if (copy_from_user(dst, ubuf + offset, size)) + return -EFAULT; + } + return 0; +} + + +/** + * copy_uabi_to_xstate - Copy a UABI format buffer to the kernel xstate + * @fpstate: The fpstate buffer to copy to + * @kbuf: The UABI format buffer, if it comes from the kernel + * @ubuf: The UABI format buffer, if it comes from userspace + * @pkru: The location to write the PKRU value to + * + * Converts from the UABI format into the kernel internal hardware + * dependent format. + * + * This function ultimately has three different callers with distinct PKRU + * behavior. + * 1. When called from sigreturn the PKRU register will be restored from + * @fpstate via an XRSTOR. Correctly copying the UABI format buffer to + * @fpstate is sufficient to cover this case, but the caller will also + * pass a pointer to the thread_struct's pkru field in @pkru and updating + * it is harmless. + * 2. When called from ptrace the PKRU register will be restored from the + * thread_struct's pkru field. A pointer to that is passed in @pkru. + * The kernel will restore it manually, so the XRSTOR behavior that resets + * the PKRU register to the hardware init value (0) if the corresponding + * xfeatures bit is not set is emulated here. + * 3. When called from KVM the PKRU register will be restored from the vcpu's + * pkru field. A pointer to that is passed in @pkru. KVM hasn't used + * XRSTOR and hasn't had the PKRU resetting behavior described above. To + * preserve that KVM behavior, it passes NULL for @pkru if the xfeatures + * bit is not set. + */ +static int copy_uabi_to_xstate(struct fpstate *fpstate, const void *kbuf, + const void __user *ubuf, u32 *pkru) +{ + struct xregs_state *xsave = &fpstate->regs.xsave; + unsigned int offset, size; + struct xstate_header hdr; + u64 mask; + int i; + + offset = offsetof(struct xregs_state, header); + if (copy_from_buffer(&hdr, offset, sizeof(hdr), kbuf, ubuf)) + return -EFAULT; + + if (validate_user_xstate_header(&hdr, fpstate)) + return -EINVAL; + + /* Validate MXCSR when any of the related features is in use */ + mask = XFEATURE_MASK_FP | XFEATURE_MASK_SSE | XFEATURE_MASK_YMM; + if (hdr.xfeatures & mask) { + u32 mxcsr[2]; + + offset = offsetof(struct fxregs_state, mxcsr); + if (copy_from_buffer(mxcsr, offset, sizeof(mxcsr), kbuf, ubuf)) + return -EFAULT; + + /* Reserved bits in MXCSR must be zero. */ + if (mxcsr[0] & ~mxcsr_feature_mask) + return -EINVAL; + + /* SSE and YMM require MXCSR even when FP is not in use. */ + if (!(hdr.xfeatures & XFEATURE_MASK_FP)) { + xsave->i387.mxcsr = mxcsr[0]; + xsave->i387.mxcsr_mask = mxcsr[1]; + } + } + + for (i = 0; i < XFEATURE_MAX; i++) { + mask = BIT_ULL(i); + + if (hdr.xfeatures & mask) { + void *dst = __raw_xsave_addr(xsave, i); + + offset = xstate_offsets[i]; + size = xstate_sizes[i]; + + if (copy_from_buffer(dst, offset, size, kbuf, ubuf)) + return -EFAULT; + } + } + + if (hdr.xfeatures & XFEATURE_MASK_PKRU) { + struct pkru_state *xpkru; + + xpkru = __raw_xsave_addr(xsave, XFEATURE_PKRU); + *pkru = xpkru->pkru; + } else { + /* + * KVM may pass NULL here to indicate that it does not need + * PKRU updated. + */ + if (pkru) + *pkru = 0; + } + + /* + * The state that came in from userspace was user-state only. + * Mask all the user states out of 'xfeatures': + */ + xsave->header.xfeatures &= XFEATURE_MASK_SUPERVISOR_ALL; + + /* + * Add back in the features that came in from userspace: + */ + xsave->header.xfeatures |= hdr.xfeatures; + + return 0; +} + +/* + * Convert from a ptrace standard-format kernel buffer to kernel XSAVE[S] + * format and copy to the target thread. Used by ptrace and KVM. + */ +int copy_uabi_from_kernel_to_xstate(struct fpstate *fpstate, const void *kbuf, u32 *pkru) +{ + return copy_uabi_to_xstate(fpstate, kbuf, NULL, pkru); +} + +/* + * Convert from a sigreturn standard-format user-space buffer to kernel + * XSAVE[S] format and copy to the target thread. This is called from the + * sigreturn() and rt_sigreturn() system calls. + */ +int copy_sigframe_from_user_to_xstate(struct task_struct *tsk, + const void __user *ubuf) +{ + return copy_uabi_to_xstate(tsk->thread.fpu.fpstate, NULL, ubuf, &tsk->thread.pkru); +} + +static bool validate_independent_components(u64 mask) +{ + u64 xchk; + + if (WARN_ON_FPU(!cpu_feature_enabled(X86_FEATURE_XSAVES))) + return false; + + xchk = ~xfeatures_mask_independent(); + + if (WARN_ON_ONCE(!mask || mask & xchk)) + return false; + + return true; +} + +/** + * xsaves - Save selected components to a kernel xstate buffer + * @xstate: Pointer to the buffer + * @mask: Feature mask to select the components to save + * + * The @xstate buffer must be 64 byte aligned and correctly initialized as + * XSAVES does not write the full xstate header. Before first use the + * buffer should be zeroed otherwise a consecutive XRSTORS from that buffer + * can #GP. + * + * The feature mask must be a subset of the independent features. + */ +void xsaves(struct xregs_state *xstate, u64 mask) +{ + int err; + + if (!validate_independent_components(mask)) + return; + + XSTATE_OP(XSAVES, xstate, (u32)mask, (u32)(mask >> 32), err); + WARN_ON_ONCE(err); +} + +/** + * xrstors - Restore selected components from a kernel xstate buffer + * @xstate: Pointer to the buffer + * @mask: Feature mask to select the components to restore + * + * The @xstate buffer must be 64 byte aligned and correctly initialized + * otherwise XRSTORS from that buffer can #GP. + * + * Proper usage is to restore the state which was saved with + * xsaves() into @xstate. + * + * The feature mask must be a subset of the independent features. + */ +void xrstors(struct xregs_state *xstate, u64 mask) +{ + int err; + + if (!validate_independent_components(mask)) + return; + + XSTATE_OP(XRSTORS, xstate, (u32)mask, (u32)(mask >> 32), err); + WARN_ON_ONCE(err); +} + +#if IS_ENABLED(CONFIG_KVM) +void fpstate_clear_xstate_component(struct fpstate *fps, unsigned int xfeature) +{ + void *addr = get_xsave_addr(&fps->regs.xsave, xfeature); + + if (addr) + memset(addr, 0, xstate_sizes[xfeature]); +} +EXPORT_SYMBOL_GPL(fpstate_clear_xstate_component); +#endif + +#ifdef CONFIG_X86_64 + +#ifdef CONFIG_X86_DEBUG_FPU +/* + * Ensure that a subsequent XSAVE* or XRSTOR* instruction with RFBM=@mask + * can safely operate on the @fpstate buffer. + */ +static bool xstate_op_valid(struct fpstate *fpstate, u64 mask, bool rstor) +{ + u64 xfd = __this_cpu_read(xfd_state); + + if (fpstate->xfd == xfd) + return true; + + /* + * The XFD MSR does not match fpstate->xfd. That's invalid when + * the passed in fpstate is current's fpstate. + */ + if (fpstate->xfd == current->thread.fpu.fpstate->xfd) + return false; + + /* + * XRSTOR(S) from init_fpstate are always correct as it will just + * bring all components into init state and not read from the + * buffer. XSAVE(S) raises #PF after init. + */ + if (fpstate == &init_fpstate) + return rstor; + + /* + * XSAVE(S): clone(), fpu_swap_kvm_fpu() + * XRSTORS(S): fpu_swap_kvm_fpu() + */ + + /* + * No XSAVE/XRSTOR instructions (except XSAVE itself) touch + * the buffer area for XFD-disabled state components. + */ + mask &= ~xfd; + + /* + * Remove features which are valid in fpstate. They + * have space allocated in fpstate. + */ + mask &= ~fpstate->xfeatures; + + /* + * Any remaining state components in 'mask' might be written + * by XSAVE/XRSTOR. Fail validation it found. + */ + return !mask; +} + +void xfd_validate_state(struct fpstate *fpstate, u64 mask, bool rstor) +{ + WARN_ON_ONCE(!xstate_op_valid(fpstate, mask, rstor)); +} +#endif /* CONFIG_X86_DEBUG_FPU */ + +static int __init xfd_update_static_branch(void) +{ + /* + * If init_fpstate.xfd has bits set then dynamic features are + * available and the dynamic sizing must be enabled. + */ + if (init_fpstate.xfd) + static_branch_enable(&__fpu_state_size_dynamic); + return 0; +} +arch_initcall(xfd_update_static_branch) + +void fpstate_free(struct fpu *fpu) +{ + if (fpu->fpstate && fpu->fpstate != &fpu->__fpstate) + vfree(fpu->fpstate); +} + +/** + * fpstate_realloc - Reallocate struct fpstate for the requested new features + * + * @xfeatures: A bitmap of xstate features which extend the enabled features + * of that task + * @ksize: The required size for the kernel buffer + * @usize: The required size for user space buffers + * @guest_fpu: Pointer to a guest FPU container. NULL for host allocations + * + * Note vs. vmalloc(): If the task with a vzalloc()-allocated buffer + * terminates quickly, vfree()-induced IPIs may be a concern, but tasks + * with large states are likely to live longer. + * + * Returns: 0 on success, -ENOMEM on allocation error. + */ +static int fpstate_realloc(u64 xfeatures, unsigned int ksize, + unsigned int usize, struct fpu_guest *guest_fpu) +{ + struct fpu *fpu = ¤t->thread.fpu; + struct fpstate *curfps, *newfps = NULL; + unsigned int fpsize; + bool in_use; + + fpsize = ksize + ALIGN(offsetof(struct fpstate, regs), 64); + + newfps = vzalloc(fpsize); + if (!newfps) + return -ENOMEM; + newfps->size = ksize; + newfps->user_size = usize; + newfps->is_valloc = true; + + /* + * When a guest FPU is supplied, use @guest_fpu->fpstate + * as reference independent whether it is in use or not. + */ + curfps = guest_fpu ? guest_fpu->fpstate : fpu->fpstate; + + /* Determine whether @curfps is the active fpstate */ + in_use = fpu->fpstate == curfps; + + if (guest_fpu) { + newfps->is_guest = true; + newfps->is_confidential = curfps->is_confidential; + newfps->in_use = curfps->in_use; + guest_fpu->xfeatures |= xfeatures; + guest_fpu->uabi_size = usize; + } + + fpregs_lock(); + /* + * If @curfps is in use, ensure that the current state is in the + * registers before swapping fpstate as that might invalidate it + * due to layout changes. + */ + if (in_use && test_thread_flag(TIF_NEED_FPU_LOAD)) + fpregs_restore_userregs(); + + newfps->xfeatures = curfps->xfeatures | xfeatures; + newfps->user_xfeatures = curfps->user_xfeatures | xfeatures; + newfps->xfd = curfps->xfd & ~xfeatures; + + /* Do the final updates within the locked region */ + xstate_init_xcomp_bv(&newfps->regs.xsave, newfps->xfeatures); + + if (guest_fpu) { + guest_fpu->fpstate = newfps; + /* If curfps is active, update the FPU fpstate pointer */ + if (in_use) + fpu->fpstate = newfps; + } else { + fpu->fpstate = newfps; + } + + if (in_use) + xfd_update_state(fpu->fpstate); + fpregs_unlock(); + + /* Only free valloc'ed state */ + if (curfps && curfps->is_valloc) + vfree(curfps); + + return 0; +} + +static int validate_sigaltstack(unsigned int usize) +{ + struct task_struct *thread, *leader = current->group_leader; + unsigned long framesize = get_sigframe_size(); + + lockdep_assert_held(¤t->sighand->siglock); + + /* get_sigframe_size() is based on fpu_user_cfg.max_size */ + framesize -= fpu_user_cfg.max_size; + framesize += usize; + for_each_thread(leader, thread) { + if (thread->sas_ss_size && thread->sas_ss_size < framesize) + return -ENOSPC; + } + return 0; +} + +static int __xstate_request_perm(u64 permitted, u64 requested, bool guest) +{ + /* + * This deliberately does not exclude !XSAVES as we still might + * decide to optionally context switch XCR0 or talk the silicon + * vendors into extending XFD for the pre AMX states, especially + * AVX512. + */ + bool compacted = cpu_feature_enabled(X86_FEATURE_XCOMPACTED); + struct fpu *fpu = ¤t->group_leader->thread.fpu; + struct fpu_state_perm *perm; + unsigned int ksize, usize; + u64 mask; + int ret = 0; + + /* Check whether fully enabled */ + if ((permitted & requested) == requested) + return 0; + + /* Calculate the resulting kernel state size */ + mask = permitted | requested; + /* Take supervisor states into account on the host */ + if (!guest) + mask |= xfeatures_mask_supervisor(); + ksize = xstate_calculate_size(mask, compacted); + + /* Calculate the resulting user state size */ + mask &= XFEATURE_MASK_USER_SUPPORTED; + usize = xstate_calculate_size(mask, false); + + if (!guest) { + ret = validate_sigaltstack(usize); + if (ret) + return ret; + } + + perm = guest ? &fpu->guest_perm : &fpu->perm; + /* Pairs with the READ_ONCE() in xstate_get_group_perm() */ + WRITE_ONCE(perm->__state_perm, mask); + /* Protected by sighand lock */ + perm->__state_size = ksize; + perm->__user_state_size = usize; + return ret; +} + +/* + * Permissions array to map facilities with more than one component + */ +static const u64 xstate_prctl_req[XFEATURE_MAX] = { + [XFEATURE_XTILE_DATA] = XFEATURE_MASK_XTILE_DATA, +}; + +static int xstate_request_perm(unsigned long idx, bool guest) +{ + u64 permitted, requested; + int ret; + + if (idx >= XFEATURE_MAX) + return -EINVAL; + + /* + * Look up the facility mask which can require more than + * one xstate component. + */ + idx = array_index_nospec(idx, ARRAY_SIZE(xstate_prctl_req)); + requested = xstate_prctl_req[idx]; + if (!requested) + return -EOPNOTSUPP; + + if ((fpu_user_cfg.max_features & requested) != requested) + return -EOPNOTSUPP; + + /* Lockless quick check */ + permitted = xstate_get_group_perm(guest); + if ((permitted & requested) == requested) + return 0; + + /* Protect against concurrent modifications */ + spin_lock_irq(¤t->sighand->siglock); + permitted = xstate_get_group_perm(guest); + + /* First vCPU allocation locks the permissions. */ + if (guest && (permitted & FPU_GUEST_PERM_LOCKED)) + ret = -EBUSY; + else + ret = __xstate_request_perm(permitted, requested, guest); + spin_unlock_irq(¤t->sighand->siglock); + return ret; +} + +int __xfd_enable_feature(u64 xfd_err, struct fpu_guest *guest_fpu) +{ + u64 xfd_event = xfd_err & XFEATURE_MASK_USER_DYNAMIC; + struct fpu_state_perm *perm; + unsigned int ksize, usize; + struct fpu *fpu; + + if (!xfd_event) { + if (!guest_fpu) + pr_err_once("XFD: Invalid xfd error: %016llx\n", xfd_err); + return 0; + } + + /* Protect against concurrent modifications */ + spin_lock_irq(¤t->sighand->siglock); + + /* If not permitted let it die */ + if ((xstate_get_group_perm(!!guest_fpu) & xfd_event) != xfd_event) { + spin_unlock_irq(¤t->sighand->siglock); + return -EPERM; + } + + fpu = ¤t->group_leader->thread.fpu; + perm = guest_fpu ? &fpu->guest_perm : &fpu->perm; + ksize = perm->__state_size; + usize = perm->__user_state_size; + + /* + * The feature is permitted. State size is sufficient. Dropping + * the lock is safe here even if more features are added from + * another task, the retrieved buffer sizes are valid for the + * currently requested feature(s). + */ + spin_unlock_irq(¤t->sighand->siglock); + + /* + * Try to allocate a new fpstate. If that fails there is no way + * out. + */ + if (fpstate_realloc(xfd_event, ksize, usize, guest_fpu)) + return -EFAULT; + return 0; +} + +int xfd_enable_feature(u64 xfd_err) +{ + return __xfd_enable_feature(xfd_err, NULL); +} + +#else /* CONFIG_X86_64 */ +static inline int xstate_request_perm(unsigned long idx, bool guest) +{ + return -EPERM; +} +#endif /* !CONFIG_X86_64 */ + +u64 xstate_get_guest_group_perm(void) +{ + return xstate_get_group_perm(true); +} +EXPORT_SYMBOL_GPL(xstate_get_guest_group_perm); + +/** + * fpu_xstate_prctl - xstate permission operations + * @tsk: Redundant pointer to current + * @option: A subfunction of arch_prctl() + * @arg2: option argument + * Return: 0 if successful; otherwise, an error code + * + * Option arguments: + * + * ARCH_GET_XCOMP_SUPP: Pointer to user space u64 to store the info + * ARCH_GET_XCOMP_PERM: Pointer to user space u64 to store the info + * ARCH_REQ_XCOMP_PERM: Facility number requested + * + * For facilities which require more than one XSTATE component, the request + * must be the highest state component number related to that facility, + * e.g. for AMX which requires XFEATURE_XTILE_CFG(17) and + * XFEATURE_XTILE_DATA(18) this would be XFEATURE_XTILE_DATA(18). + */ +long fpu_xstate_prctl(int option, unsigned long arg2) +{ + u64 __user *uptr = (u64 __user *)arg2; + u64 permitted, supported; + unsigned long idx = arg2; + bool guest = false; + + switch (option) { + case ARCH_GET_XCOMP_SUPP: + supported = fpu_user_cfg.max_features | fpu_user_cfg.legacy_features; + return put_user(supported, uptr); + + case ARCH_GET_XCOMP_PERM: + /* + * Lockless snapshot as it can also change right after the + * dropping the lock. + */ + permitted = xstate_get_host_group_perm(); + permitted &= XFEATURE_MASK_USER_SUPPORTED; + return put_user(permitted, uptr); + + case ARCH_GET_XCOMP_GUEST_PERM: + permitted = xstate_get_guest_group_perm(); + permitted &= XFEATURE_MASK_USER_SUPPORTED; + return put_user(permitted, uptr); + + case ARCH_REQ_XCOMP_GUEST_PERM: + guest = true; + fallthrough; + + case ARCH_REQ_XCOMP_PERM: + if (!IS_ENABLED(CONFIG_X86_64)) + return -EOPNOTSUPP; + + return xstate_request_perm(idx, guest); + + default: + return -EINVAL; + } +} + +#ifdef CONFIG_PROC_PID_ARCH_STATUS +/* + * Report the amount of time elapsed in millisecond since last AVX512 + * use in the task. + */ +static void avx512_status(struct seq_file *m, struct task_struct *task) +{ + unsigned long timestamp = READ_ONCE(task->thread.fpu.avx512_timestamp); + long delta; + + if (!timestamp) { + /* + * Report -1 if no AVX512 usage + */ + delta = -1; + } else { + delta = (long)(jiffies - timestamp); + /* + * Cap to LONG_MAX if time difference > LONG_MAX + */ + if (delta < 0) + delta = LONG_MAX; + delta = jiffies_to_msecs(delta); + } + + seq_put_decimal_ll(m, "AVX512_elapsed_ms:\t", delta); + seq_putc(m, '\n'); +} + +/* + * Report architecture specific information + */ +int proc_pid_arch_status(struct seq_file *m, struct pid_namespace *ns, + struct pid *pid, struct task_struct *task) +{ + /* + * Report AVX512 state if the processor and build option supported. + */ + if (cpu_feature_enabled(X86_FEATURE_AVX512F)) + avx512_status(m, task); + + return 0; +} +#endif /* CONFIG_PROC_PID_ARCH_STATUS */ diff --git a/arch/x86/kernel/fpu/xstate.h b/arch/x86/kernel/fpu/xstate.h new file mode 100644 index 000000000..3518fb26d --- /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 |