diff options
Diffstat (limited to 'arch/x86/kernel/fpu/core.c')
| -rw-r--r-- | arch/x86/kernel/fpu/core.c | 277 |
1 files changed, 201 insertions, 76 deletions
diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c index caf33486dc5e..da233f20ae6f 100644 --- a/arch/x86/kernel/fpu/core.c +++ b/arch/x86/kernel/fpu/core.c @@ -11,12 +11,14 @@ #include <asm/fpu/sched.h> #include <asm/fpu/signal.h> #include <asm/fpu/types.h> +#include <asm/msr.h> #include <asm/traps.h> #include <asm/irq_regs.h> #include <uapi/asm/kvm.h> #include <linux/hardirq.h> +#include <linux/kvm_types.h> #include <linux/pkeys.h> #include <linux/vmalloc.h> @@ -36,6 +38,7 @@ DEFINE_PER_CPU(u64, xfd_state); /* 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; +struct vcpu_fpu_config guest_default_cfg __ro_after_init; /* * Represents the initial FPU state. It's mostly (but not completely) zeroes, @@ -43,14 +46,27 @@ struct fpu_state_config fpu_user_cfg __ro_after_init; */ struct fpstate init_fpstate __ro_after_init; -/* Track in-kernel FPU usage */ -static DEFINE_PER_CPU(bool, in_kernel_fpu); +/* + * Track FPU initialization and kernel-mode usage. 'true' means the FPU is + * initialized and is not currently being used by the kernel: + */ +DEFINE_PER_CPU(bool, kernel_fpu_allowed); /* * Track which context is using the FPU on the CPU: */ DEFINE_PER_CPU(struct fpu *, fpu_fpregs_owner_ctx); +#ifdef CONFIG_X86_DEBUG_FPU +struct fpu *x86_task_fpu(struct task_struct *task) +{ + if (WARN_ON_ONCE(task->flags & PF_KTHREAD)) + return NULL; + + return (void *)task + sizeof(*task); +} +#endif + /* * Can we use the FPU in kernel mode with the * whole "kernel_fpu_begin/end()" sequence? @@ -60,8 +76,18 @@ 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 in the following cases: + * + * - FPU is not yet initialized. This can happen only when the call is + * coming from CPU onlining, for example for microcode checksumming. + * - The kernel is already using the FPU, either because of explicit + * nesting (which should never be done), or because of implicit + * nesting when a hardirq interrupted a kernel-mode FPU section. + * + * The single boolean check below handles both cases: + */ + if (!this_cpu_read(kernel_fpu_allowed)) return false; /* @@ -145,8 +171,8 @@ void restore_fpregs_from_fpstate(struct fpstate *fpstate, u64 mask) asm volatile( "fnclex\n\t" "emms\n\t" - "fildl %P[addr]" /* set F?P to defined value */ - : : [addr] "m" (fpstate)); + "fildl %[addr]" /* set F?P to defined value */ + : : [addr] "m" (*fpstate)); } if (use_xsave()) { @@ -193,9 +219,9 @@ void fpu_reset_from_exception_fixup(void) } #if IS_ENABLED(CONFIG_KVM) -static void __fpstate_reset(struct fpstate *fpstate, u64 xfd); +static void __fpstate_reset(struct fpstate *fpstate); -static void fpu_init_guest_permissions(struct fpu_guest *gfpu) +static void fpu_lock_guest_permissions(void) { struct fpu_state_perm *fpuperm; u64 perm; @@ -204,15 +230,13 @@ static void fpu_init_guest_permissions(struct fpu_guest *gfpu) return; spin_lock_irq(¤t->sighand->siglock); - fpuperm = ¤t->group_leader->thread.fpu.guest_perm; + fpuperm = &x86_task_fpu(current->group_leader)->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) @@ -220,20 +244,21 @@ 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); + size = guest_default_cfg.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); + /* Initialize indicators to reflect properties of the fpstate */ fpstate->is_valloc = true; fpstate->is_guest = true; + __fpstate_reset(fpstate); + fpstate_init_user(fpstate); + gfpu->fpstate = fpstate; - gfpu->xfeatures = fpu_user_cfg.default_features; - gfpu->perm = fpu_user_cfg.default_features; + gfpu->xfeatures = guest_default_cfg.features; /* * KVM sets the FP+SSE bits in the XSAVE header when copying FPU state @@ -248,26 +273,26 @@ bool fpu_alloc_guest_fpstate(struct fpu_guest *gfpu) 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); + fpu_lock_guest_permissions(); return true; } -EXPORT_SYMBOL_GPL(fpu_alloc_guest_fpstate); +EXPORT_SYMBOL_FOR_KVM(fpu_alloc_guest_fpstate); void fpu_free_guest_fpstate(struct fpu_guest *gfpu) { - struct fpstate *fps = gfpu->fpstate; + struct fpstate *fpstate = gfpu->fpstate; - if (!fps) + if (!fpstate) return; - if (WARN_ON_ONCE(!fps->is_valloc || !fps->is_guest || fps->in_use)) + if (WARN_ON_ONCE(!fpstate->is_valloc || !fpstate->is_guest || fpstate->in_use)) return; gfpu->fpstate = NULL; - vfree(fps); + vfree(fpstate); } -EXPORT_SYMBOL_GPL(fpu_free_guest_fpstate); +EXPORT_SYMBOL_FOR_KVM(fpu_free_guest_fpstate); /* * fpu_enable_guest_xfd_features - Check xfeatures against guest perm and enable @@ -289,7 +314,7 @@ int fpu_enable_guest_xfd_features(struct fpu_guest *guest_fpu, u64 xfeatures) return __xfd_enable_feature(xfeatures, guest_fpu); } -EXPORT_SYMBOL_GPL(fpu_enable_guest_xfd_features); +EXPORT_SYMBOL_FOR_KVM(fpu_enable_guest_xfd_features); #ifdef CONFIG_X86_64 void fpu_update_guest_xfd(struct fpu_guest *guest_fpu, u64 xfd) @@ -300,7 +325,7 @@ void fpu_update_guest_xfd(struct fpu_guest *guest_fpu, u64 xfd) xfd_update_state(guest_fpu->fpstate); fpregs_unlock(); } -EXPORT_SYMBOL_GPL(fpu_update_guest_xfd); +EXPORT_SYMBOL_FOR_KVM(fpu_update_guest_xfd); /** * fpu_sync_guest_vmexit_xfd_state - Synchronize XFD MSR and software state @@ -308,7 +333,7 @@ EXPORT_SYMBOL_GPL(fpu_update_guest_xfd); * 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 + * same as the state on VMENTER. So software state has to be updated before * any operation which depends on it can take place. * * Note: It can be invoked unconditionally even when write emulation is @@ -316,21 +341,21 @@ EXPORT_SYMBOL_GPL(fpu_update_guest_xfd); */ void fpu_sync_guest_vmexit_xfd_state(void) { - struct fpstate *fps = current->thread.fpu.fpstate; + struct fpstate *fpstate = x86_task_fpu(current)->fpstate; lockdep_assert_irqs_disabled(); if (fpu_state_size_dynamic()) { - rdmsrl(MSR_IA32_XFD, fps->xfd); - __this_cpu_write(xfd_state, fps->xfd); + rdmsrq(MSR_IA32_XFD, fpstate->xfd); + __this_cpu_write(xfd_state, fpstate->xfd); } } -EXPORT_SYMBOL_GPL(fpu_sync_guest_vmexit_xfd_state); +EXPORT_SYMBOL_FOR_KVM(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 fpu *fpu = x86_task_fpu(current); struct fpstate *cur_fps = fpu->fpstate; fpregs_lock(); @@ -366,17 +391,18 @@ int fpu_swap_kvm_fpstate(struct fpu_guest *guest_fpu, bool enter_guest) fpregs_unlock(); return 0; } -EXPORT_SYMBOL_GPL(fpu_swap_kvm_fpstate); +EXPORT_SYMBOL_FOR_KVM(fpu_swap_kvm_fpstate); void fpu_copy_guest_fpstate_to_uabi(struct fpu_guest *gfpu, void *buf, - unsigned int size, u32 pkru) + 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, pkru, XSTATE_COPY_XSAVE); + __copy_xstate_to_uabi_buf(mb, kstate, xfeatures, pkru, + XSTATE_COPY_XSAVE); } else { memcpy(&ustate->fxsave, &kstate->regs.fxsave, sizeof(ustate->fxsave)); @@ -384,7 +410,7 @@ void fpu_copy_guest_fpstate_to_uabi(struct fpu_guest *gfpu, void *buf, ustate->xsave.header.xfeatures = XFEATURE_MASK_FPSSE; } } -EXPORT_SYMBOL_GPL(fpu_copy_guest_fpstate_to_uabi); +EXPORT_SYMBOL_FOR_KVM(fpu_copy_guest_fpstate_to_uabi); int fpu_copy_uabi_to_guest_fpstate(struct fpu_guest *gfpu, const void *buf, u64 xcr0, u32 *vpkru) @@ -414,22 +440,24 @@ int fpu_copy_uabi_to_guest_fpstate(struct fpu_guest *gfpu, const void *buf, return copy_uabi_from_kernel_to_xstate(kstate, ustate, vpkru); } -EXPORT_SYMBOL_GPL(fpu_copy_uabi_to_guest_fpstate); +EXPORT_SYMBOL_FOR_KVM(fpu_copy_uabi_to_guest_fpstate); #endif /* CONFIG_KVM */ void kernel_fpu_begin_mask(unsigned int kfpu_mask) { - preempt_disable(); + if (!irqs_disabled()) + fpregs_lock(); WARN_ON_FPU(!irq_fpu_usable()); - WARN_ON_FPU(this_cpu_read(in_kernel_fpu)); - this_cpu_write(in_kernel_fpu, true); + /* Toggle kernel_fpu_allowed to false: */ + WARN_ON_FPU(!this_cpu_read(kernel_fpu_allowed)); + this_cpu_write(kernel_fpu_allowed, false); - if (!(current->flags & (PF_KTHREAD | PF_IO_WORKER)) && + if (!(current->flags & (PF_KTHREAD | PF_USER_WORKER)) && !test_thread_flag(TIF_NEED_FPU_LOAD)) { set_thread_flag(TIF_NEED_FPU_LOAD); - save_fpregs_to_fpstate(¤t->thread.fpu); + save_fpregs_to_fpstate(x86_task_fpu(current)); } __cpu_invalidate_fpregs_state(); @@ -444,10 +472,12 @@ EXPORT_SYMBOL_GPL(kernel_fpu_begin_mask); void kernel_fpu_end(void) { - WARN_ON_FPU(!this_cpu_read(in_kernel_fpu)); + /* Toggle kernel_fpu_allowed back to true: */ + WARN_ON_FPU(this_cpu_read(kernel_fpu_allowed)); + this_cpu_write(kernel_fpu_allowed, true); - this_cpu_write(in_kernel_fpu, false); - preempt_enable(); + if (!irqs_disabled()) + fpregs_unlock(); } EXPORT_SYMBOL_GPL(kernel_fpu_end); @@ -457,7 +487,7 @@ EXPORT_SYMBOL_GPL(kernel_fpu_end); */ void fpu_sync_fpstate(struct fpu *fpu) { - WARN_ON_FPU(fpu != ¤t->thread.fpu); + WARN_ON_FPU(fpu != x86_task_fpu(current)); fpregs_lock(); trace_x86_fpu_before_save(fpu); @@ -498,7 +528,7 @@ static inline void fpstate_init_fstate(struct fpstate *fpstate) /* * 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 + * 2) fpu_alloc_guest_fpstate() which is invoked from KVM */ void fpstate_init_user(struct fpstate *fpstate) { @@ -515,34 +545,56 @@ void fpstate_init_user(struct fpstate *fpstate) fpstate_init_fstate(fpstate); } -static void __fpstate_reset(struct fpstate *fpstate, u64 xfd) +static void __fpstate_reset(struct fpstate *fpstate) { - /* Initialize sizes and feature masks */ - fpstate->size = fpu_kernel_cfg.default_size; + /* + * Supervisor features (and thus sizes) may diverge between guest + * FPUs and host FPUs, as some supervisor features are supported + * for guests despite not being utilized by the host. User + * features and sizes are always identical, which allows for + * common guest and userspace ABI. + * + * For the host, set XFD to the kernel's desired initialization + * value. For guests, set XFD to its architectural RESET value. + */ + if (fpstate->is_guest) { + fpstate->size = guest_default_cfg.size; + fpstate->xfeatures = guest_default_cfg.features; + fpstate->xfd = 0; + } else { + fpstate->size = fpu_kernel_cfg.default_size; + fpstate->xfeatures = fpu_kernel_cfg.default_features; + fpstate->xfd = init_fpstate.xfd; + } + 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); + __fpstate_reset(fpu->fpstate); /* 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; + + fpu->guest_perm.__state_perm = guest_default_cfg.features; + fpu->guest_perm.__state_size = guest_default_cfg.size; + /* + * User features and sizes are always identical between host and + * guest FPUs, which allows for common guest and userspace ABI. + */ + fpu->guest_perm.__user_state_size = fpu_user_cfg.default_size; } static inline void fpu_inherit_perms(struct fpu *dst_fpu) { if (fpu_state_size_dynamic()) { - struct fpu *src_fpu = ¤t->group_leader->thread.fpu; + struct fpu *src_fpu = x86_task_fpu(current->group_leader); spin_lock_irq(¤t->sighand->siglock); /* Fork also inherits the permissions of the parent */ @@ -552,11 +604,47 @@ static inline void fpu_inherit_perms(struct fpu *dst_fpu) } } +/* A passed ssp of zero will not cause any update */ +static int update_fpu_shstk(struct task_struct *dst, unsigned long ssp) +{ +#ifdef CONFIG_X86_USER_SHADOW_STACK + struct cet_user_state *xstate; + + /* If ssp update is not needed. */ + if (!ssp) + return 0; + + xstate = get_xsave_addr(&x86_task_fpu(dst)->fpstate->regs.xsave, + XFEATURE_CET_USER); + + /* + * If there is a non-zero ssp, then 'dst' must be configured with a shadow + * stack and the fpu state should be up to date since it was just copied + * from the parent in fpu_clone(). So there must be a valid non-init CET + * state location in the buffer. + */ + if (WARN_ON_ONCE(!xstate)) + return 1; + + xstate->user_ssp = (u64)ssp; +#endif + return 0; +} + /* Clone current's FPU state on fork */ -int fpu_clone(struct task_struct *dst, unsigned long clone_flags, bool minimal) +int fpu_clone(struct task_struct *dst, u64 clone_flags, bool minimal, + unsigned long ssp) { - struct fpu *src_fpu = ¤t->thread.fpu; - struct fpu *dst_fpu = &dst->thread.fpu; + /* + * We allocate the new FPU structure right after the end of the task struct. + * task allocation size already took this into account. + * + * This is safe because task_struct size is a multiple of cacheline size, + * thus x86_task_fpu() will always be cacheline aligned as well. + */ + struct fpu *dst_fpu = (void *)dst + sizeof(*dst); + + BUILD_BUG_ON(sizeof(*dst) % SMP_CACHE_BYTES != 0); /* The new task's FPU state cannot be valid in the hardware. */ dst_fpu->last_cpu = -1; @@ -613,19 +701,28 @@ int fpu_clone(struct task_struct *dst, unsigned long clone_flags, bool minimal) if (use_xsave()) dst_fpu->fpstate->regs.xsave.header.xfeatures &= ~XFEATURE_MASK_PASID; - trace_x86_fpu_copy_src(src_fpu); + /* + * Update shadow stack pointer, in case it changed during clone. + */ + if (update_fpu_shstk(dst, ssp)) + return 1; + trace_x86_fpu_copy_dst(dst_fpu); return 0; } /* - * Whitelist the FPU register state embedded into task_struct for hardened - * usercopy. + * While struct fpu is no longer part of struct thread_struct, it is still + * allocated after struct task_struct in the "task_struct" kmem cache. But + * since FPU is expected to be part of struct thread_struct, we have to + * adjust for it here. */ void fpu_thread_struct_whitelist(unsigned long *offset, unsigned long *size) { - *offset = offsetof(struct thread_struct, fpu.__fpstate.regs); + /* The allocation follows struct task_struct. */ + *offset = sizeof(struct task_struct) - offsetof(struct task_struct, thread); + *offset += offsetof(struct fpu, __fpstate.regs); *size = fpu_kernel_cfg.default_size; } @@ -638,11 +735,18 @@ void fpu_thread_struct_whitelist(unsigned long *offset, unsigned long *size) * a state-restore is coming: either an explicit one, * or a reschedule. */ -void fpu__drop(struct fpu *fpu) +void fpu__drop(struct task_struct *tsk) { + struct fpu *fpu; + + if (test_tsk_thread_flag(tsk, TIF_NEED_FPU_LOAD)) + return; + + fpu = x86_task_fpu(tsk); + preempt_disable(); - if (fpu == ¤t->thread.fpu) { + if (fpu == x86_task_fpu(current)) { /* Ignore delayed exceptions from user space */ asm volatile("1: fwait\n" "2:\n" @@ -674,12 +778,12 @@ static inline void restore_fpregs_from_init_fpstate(u64 features_mask) /* * Reset current->fpu memory state to the init values. */ -static void fpu_reset_fpregs(void) +static void fpu_reset_fpstate_regs(void) { - struct fpu *fpu = ¤t->thread.fpu; + struct fpu *fpu = x86_task_fpu(current); fpregs_lock(); - fpu__drop(fpu); + __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 @@ -705,11 +809,11 @@ static void fpu_reset_fpregs(void) */ void fpu__clear_user_states(struct fpu *fpu) { - WARN_ON_FPU(fpu != ¤t->thread.fpu); + WARN_ON_FPU(fpu != x86_task_fpu(current)); fpregs_lock(); if (!cpu_feature_enabled(X86_FEATURE_FPU)) { - fpu_reset_fpregs(); + fpu_reset_fpstate_regs(); fpregs_unlock(); return; } @@ -722,6 +826,9 @@ void fpu__clear_user_states(struct fpu *fpu) !fpregs_state_valid(fpu, smp_processor_id())) os_xrstor_supervisor(fpu->fpstate); + /* Ensure XFD state is in sync before reloading XSTATE */ + xfd_update_state(fpu->fpstate); + /* Reset user states in registers. */ restore_fpregs_from_init_fpstate(XFEATURE_MASK_USER_RESTORE); @@ -738,8 +845,8 @@ void fpu__clear_user_states(struct fpu *fpu) void fpu_flush_thread(void) { - fpstate_reset(¤t->thread.fpu); - fpu_reset_fpregs(); + fpstate_reset(x86_task_fpu(current)); + fpu_reset_fpstate_regs(); } /* * Load FPU context before returning to userspace. @@ -751,7 +858,25 @@ void switch_fpu_return(void) fpregs_restore_userregs(); } -EXPORT_SYMBOL_GPL(switch_fpu_return); +EXPORT_SYMBOL_FOR_KVM(switch_fpu_return); + +void fpregs_lock_and_load(void) +{ + /* + * fpregs_lock() only disables preemption (mostly). So modifying state + * in an interrupt could screw up some in progress fpregs operation. + * Warn about it. + */ + WARN_ON_ONCE(!irq_fpu_usable()); + WARN_ON_ONCE(current->flags & PF_KTHREAD); + + fpregs_lock(); + + fpregs_assert_state_consistent(); + + if (test_thread_flag(TIF_NEED_FPU_LOAD)) + fpregs_restore_userregs(); +} #ifdef CONFIG_X86_DEBUG_FPU /* @@ -761,19 +886,19 @@ EXPORT_SYMBOL_GPL(switch_fpu_return); */ void fpregs_assert_state_consistent(void) { - struct fpu *fpu = ¤t->thread.fpu; + struct fpu *fpu = x86_task_fpu(current); 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); +EXPORT_SYMBOL_FOR_KVM(fpregs_assert_state_consistent); #endif void fpregs_mark_activate(void) { - struct fpu *fpu = ¤t->thread.fpu; + struct fpu *fpu = x86_task_fpu(current); fpregs_activate(fpu); fpu->last_cpu = smp_processor_id(); |