From b2681e791dbcee6acb1dca7a5076a0285109ac4c Mon Sep 17 00:00:00 2001 From: Thomas Gleixner Date: Wed, 23 Jun 2021 14:02:06 +0200 Subject: [PATCH] x86/fpu: Rename and sanitize fpu__save/copy() Both function names are a misnomer. fpu__save() is actually about synchronizing the hardware register state into the task's memory state so that either coredump or a math exception handler can inspect the state at the time where the problem happens. The function guarantees to preserve the register state, while "save" is a common terminology for saving the current state so it can be modified and restored later. This is clearly not the case here. Rename it to fpu_sync_fpstate(). fpu__copy() is used to clone the current task's FPU state when duplicating task_struct. While the register state is a copy the rest of the FPU state is not. Name it accordingly and remove the really pointless @src argument along with the warning which comes along with it. Nothing can ever copy the FPU state of a non-current task. It's clearly just a consequence of arch_dup_task_struct(), but it makes no sense to proliferate that further. Signed-off-by: Thomas Gleixner Signed-off-by: Borislav Petkov Reviewed-by: Borislav Petkov Link: https://lkml.kernel.org/r/20210623121455.196727450@linutronix.de --- arch/x86/include/asm/fpu/internal.h | 6 ++++-- arch/x86/kernel/fpu/core.c | 17 ++++++++--------- arch/x86/kernel/fpu/regset.c | 2 +- arch/x86/kernel/process.c | 3 +-- arch/x86/kernel/traps.c | 5 +++-- 5 files changed, 17 insertions(+), 16 deletions(-) diff --git a/arch/x86/include/asm/fpu/internal.h b/arch/x86/include/asm/fpu/internal.h index 3558cd0..f5da2e9 100644 --- a/arch/x86/include/asm/fpu/internal.h +++ b/arch/x86/include/asm/fpu/internal.h @@ -26,14 +26,16 @@ /* * High level FPU state handling functions: */ -extern void fpu__save(struct fpu *fpu); extern int fpu__restore_sig(void __user *buf, int ia32_frame); extern void fpu__drop(struct fpu *fpu); -extern int fpu__copy(struct task_struct *dst, struct task_struct *src); extern void fpu__clear_user_states(struct fpu *fpu); extern void fpu__clear_all(struct fpu *fpu); extern int fpu__exception_code(struct fpu *fpu, int trap_nr); +extern void fpu_sync_fpstate(struct fpu *fpu); + +extern int fpu_clone(struct task_struct *dst); + /* * Boot time FPU initialization functions: */ diff --git a/arch/x86/kernel/fpu/core.c b/arch/x86/kernel/fpu/core.c index 4a59e0f..8762b1a 100644 --- a/arch/x86/kernel/fpu/core.c +++ b/arch/x86/kernel/fpu/core.c @@ -159,11 +159,10 @@ void kernel_fpu_end(void) EXPORT_SYMBOL_GPL(kernel_fpu_end); /* - * Save the FPU state (mark it for reload if necessary): - * - * This only ever gets called for the current task. + * 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__save(struct fpu *fpu) +void fpu_sync_fpstate(struct fpu *fpu) { WARN_ON_FPU(fpu != ¤t->thread.fpu); @@ -221,18 +220,18 @@ void fpstate_init(union fpregs_state *state) } EXPORT_SYMBOL_GPL(fpstate_init); -int fpu__copy(struct task_struct *dst, struct task_struct *src) +/* Clone current's FPU state on fork */ +int fpu_clone(struct task_struct *dst) { + struct fpu *src_fpu = ¤t->thread.fpu; struct fpu *dst_fpu = &dst->thread.fpu; - struct fpu *src_fpu = &src->thread.fpu; + /* The new task's FPU state cannot be valid in the hardware. */ dst_fpu->last_cpu = -1; - if (!static_cpu_has(X86_FEATURE_FPU)) + if (!cpu_feature_enabled(X86_FEATURE_FPU)) return 0; - WARN_ON_FPU(src_fpu != ¤t->thread.fpu); - /* * Don't let 'init optimized' areas of the XSAVE area * leak into the child task: diff --git a/arch/x86/kernel/fpu/regset.c b/arch/x86/kernel/fpu/regset.c index 892aec1..4575796 100644 --- a/arch/x86/kernel/fpu/regset.c +++ b/arch/x86/kernel/fpu/regset.c @@ -41,7 +41,7 @@ int regset_xregset_fpregs_active(struct task_struct *target, const struct user_r static void sync_fpstate(struct fpu *fpu) { if (fpu == ¤t->thread.fpu) - fpu__save(fpu); + fpu_sync_fpstate(fpu); } /* diff --git a/arch/x86/kernel/process.c b/arch/x86/kernel/process.c index 5e1f381..af3db53 100644 --- a/arch/x86/kernel/process.c +++ b/arch/x86/kernel/process.c @@ -87,8 +87,7 @@ int arch_dup_task_struct(struct task_struct *dst, struct task_struct *src) #ifdef CONFIG_VM86 dst->thread.vm86 = NULL; #endif - - return fpu__copy(dst, src); + return fpu_clone(dst); } /* diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index 853ea7a..4c9c4aa 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -1046,9 +1046,10 @@ static void math_error(struct pt_regs *regs, int trapnr) } /* - * Save the info for the exception handler and clear the error. + * Synchronize the FPU register state to the memory register state + * if necessary. This allows the exception handler to inspect it. */ - fpu__save(fpu); + fpu_sync_fpstate(fpu); task->thread.trap_nr = trapnr; task->thread.error_code = 0; -- 2.7.4