diff options
Diffstat (limited to 'include/asm-i386/i387.h')
| -rw-r--r-- | include/asm-i386/i387.h | 30 |
1 files changed, 26 insertions, 4 deletions
diff --git a/include/asm-i386/i387.h b/include/asm-i386/i387.h index 152d0baa576..7b1f01191e7 100644 --- a/include/asm-i386/i387.h +++ b/include/asm-i386/i387.h @@ -13,6 +13,7 @@ #include <linux/sched.h> #include <linux/init.h> +#include <linux/kernel_stat.h> #include <asm/processor.h> #include <asm/sigcontext.h> #include <asm/user.h> @@ -38,17 +39,38 @@ extern void init_fpu(struct task_struct *); extern void kernel_fpu_begin(void); #define kernel_fpu_end() do { stts(); preempt_enable(); } while(0) +/* We need a safe address that is cheap to find and that is already + in L1 during context switch. The best choices are unfortunately + different for UP and SMP */ +#ifdef CONFIG_SMP +#define safe_address (__per_cpu_offset[0]) +#else +#define safe_address (kstat_cpu(0).cpustat.user) +#endif + /* * These must be called with preempt disabled */ static inline void __save_init_fpu( struct task_struct *tsk ) { + /* Use more nops than strictly needed in case the compiler + varies code */ alternative_input( - "fnsave %1 ; fwait ;" GENERIC_NOP2, - "fxsave %1 ; fnclex", + "fnsave %[fx] ;fwait;" GENERIC_NOP8 GENERIC_NOP4, + "fxsave %[fx]\n" + "bt $7,%[fsw] ; jc 1f ; fnclex\n1:", X86_FEATURE_FXSR, - "m" (tsk->thread.i387.fxsave) - :"memory"); + [fx] "m" (tsk->thread.i387.fxsave), + [fsw] "m" (tsk->thread.i387.fxsave.swd) : "memory"); + /* AMD K7/K8 CPUs don't save/restore FDP/FIP/FOP unless an exception + is pending. Clear the x87 state here by setting it to fixed + values. __per_cpu_offset[0] is a random variable that should be in L1 */ + alternative_input( + GENERIC_NOP8 GENERIC_NOP2, + "emms\n\t" /* clear stack tags */ + "fildl %[addr]", /* set F?P to defined value */ + X86_FEATURE_FXSAVE_LEAK, + [addr] "m" (safe_address)); task_thread_info(tsk)->status &= ~TS_USEDFPU; } |