diff options
Diffstat (limited to 'include/asm-x86_64')
| -rw-r--r-- | include/asm-x86_64/cpufeature.h | 1 | ||||
| -rw-r--r-- | include/asm-x86_64/i387.h | 20 |
2 files changed, 20 insertions, 1 deletions
diff --git a/include/asm-x86_64/cpufeature.h b/include/asm-x86_64/cpufeature.h index 76bb6193ae91..662964b74e34 100644 --- a/include/asm-x86_64/cpufeature.h +++ b/include/asm-x86_64/cpufeature.h @@ -64,6 +64,7 @@ #define X86_FEATURE_REP_GOOD (3*32+ 4) /* rep microcode works well on this CPU */ #define X86_FEATURE_CONSTANT_TSC (3*32+5) /* TSC runs at constant rate */ #define X86_FEATURE_SYNC_RDTSC (3*32+6) /* RDTSC syncs CPU core */ +#define X86_FEATURE_FXSAVE_LEAK (3*32+7) /* FIP/FOP/FDP leaks through FXSAVE */ /* Intel-defined CPU features, CPUID level 0x00000001 (ecx), word 4 */ #define X86_FEATURE_XMM3 (4*32+ 0) /* Streaming SIMD Extensions-3 */ diff --git a/include/asm-x86_64/i387.h b/include/asm-x86_64/i387.h index 876eb9a2fe78..cba8a3b0cded 100644 --- a/include/asm-x86_64/i387.h +++ b/include/asm-x86_64/i387.h @@ -72,6 +72,23 @@ extern int set_fpregs(struct task_struct *tsk, #define set_fpu_swd(t,val) ((t)->thread.i387.fxsave.swd = (val)) #define set_fpu_fxsr_twd(t,val) ((t)->thread.i387.fxsave.twd = (val)) +#define X87_FSW_ES (1 << 7) /* Exception Summary */ + +/* AMD CPUs don't save/restore FDP/FIP/FOP unless an exception + is pending. Clear the x87 state here by setting it to fixed + values. The kernel data segment can be sometimes 0 and sometimes + new user value. Both should be ok. + Use the PDA as safe address because it should be already in L1. */ +static inline void clear_fpu_state(struct i387_fxsave_struct *fx) +{ + if (unlikely(fx->swd & X87_FSW_ES)) + asm volatile("fnclex"); + alternative_input(ASM_NOP8 ASM_NOP2, + " emms\n" /* clear stack tags */ + " fildl %%gs:0", /* load to clear state */ + X86_FEATURE_FXSAVE_LEAK); +} + static inline int restore_fpu_checking(struct i387_fxsave_struct *fx) { int err; @@ -119,6 +136,7 @@ static inline int save_i387_checking(struct i387_fxsave_struct __user *fx) #endif if (unlikely(err)) __clear_user(fx, sizeof(struct i387_fxsave_struct)); + /* No need to clear here because the caller clears USED_MATH */ return err; } @@ -149,7 +167,7 @@ static inline void __fxsave_clear(struct task_struct *tsk) "i" (offsetof(__typeof__(*tsk), thread.i387.fxsave))); #endif - __asm__ __volatile__("fnclex"); + clear_fpu_state(&tsk->thread.i387.fxsave); } static inline void kernel_fpu_begin(void) |