diff options
| -rw-r--r-- | arch/x86/include/asm/i387.h | 54 | ||||
| -rw-r--r-- | arch/x86/kernel/traps.c | 1 |
2 files changed, 47 insertions, 8 deletions
diff --git a/arch/x86/include/asm/i387.h b/arch/x86/include/asm/i387.h index a5c7ae504176..a29571821b99 100644 --- a/arch/x86/include/asm/i387.h +++ b/arch/x86/include/asm/i387.h @@ -307,9 +307,54 @@ static inline void __clear_fpu(struct task_struct *tsk) } } +/* + * Were we in an interrupt that interrupted kernel mode? + * + * We can do a kernel_fpu_begin/end() pair *ONLY* if that + * pair does nothing at all: TS_USEDFPU must be clear (so + * that we don't try to save the FPU state), and TS must + * be set (so that the clts/stts pair does nothing that is + * visible in the interrupted kernel thread). + */ +static inline bool interrupted_kernel_fpu_idle(void) +{ + return !(current_thread_info()->status & TS_USEDFPU) && + (read_cr0() & X86_CR0_TS); +} + +/* + * Were we in user mode (or vm86 mode) when we were + * interrupted? + * + * Doing kernel_fpu_begin/end() is ok if we are running + * in an interrupt context from user mode - we'll just + * save the FPU state as required. + */ +static inline bool interrupted_user_mode(void) +{ + struct pt_regs *regs = get_irq_regs(); + return regs && user_mode_vm(regs); +} + +/* + * Can we use the FPU in kernel mode with the + * whole "kernel_fpu_begin/end()" sequence? + * + * It's always ok in process context (ie "not interrupt") + * but it is sometimes ok even from an irq. + */ +static inline bool irq_fpu_usable(void) +{ + return !in_interrupt() || + interrupted_user_mode() || + interrupted_kernel_fpu_idle(); +} + static inline void kernel_fpu_begin(void) { struct thread_info *me = current_thread_info(); + + WARN_ON_ONCE(!irq_fpu_usable()); preempt_disable(); if (me->status & TS_USEDFPU) __save_init_fpu(me->task); @@ -323,14 +368,6 @@ static inline void kernel_fpu_end(void) preempt_enable(); } -static inline bool irq_fpu_usable(void) -{ - struct pt_regs *regs; - - return !in_interrupt() || !(regs = get_irq_regs()) || \ - user_mode(regs) || (read_cr0() & X86_CR0_TS); -} - /* * Some instructions like VIA's padlock instructions generate a spurious * DNA fault but don't modify SSE registers. And these instructions @@ -367,6 +404,7 @@ static inline void irq_ts_restore(int TS_state) */ static inline void save_init_fpu(struct task_struct *tsk) { + WARN_ON_ONCE(task_thread_info(tsk)->status & TS_USEDFPU); preempt_disable(); __save_init_fpu(tsk); stts(); diff --git a/arch/x86/kernel/traps.c b/arch/x86/kernel/traps.c index 982433b5da30..8ba27dbc107a 100644 --- a/arch/x86/kernel/traps.c +++ b/arch/x86/kernel/traps.c @@ -631,6 +631,7 @@ EXPORT_SYMBOL_GPL(math_state_restore); dotraplinkage void __kprobes do_device_not_available(struct pt_regs *regs, long error_code) { + WARN_ON_ONCE(!user_mode_vm(regs)); #ifdef CONFIG_MATH_EMULATION if (read_cr0() & X86_CR0_EM) { struct math_emu_info info = { }; |