4 files changed, 47 insertions, 5 deletions

diff --git a/include/asm-i386/cpufeature.h b/include/asm-i386/cpufeature.h
index 5c0b5876b931..b44bfc6239cb 100644
--- a/include/asm-i386/cpufeature.h
+++ b/include/asm-i386/cpufeature.h
@@ -71,6 +71,7 @@
 #define X86_FEATURE_P4          (3*32+ 7) /* P4 */
 #define X86_FEATURE_CONSTANT_TSC (3*32+ 8) /* TSC ticks at a constant rate */
 #define X86_FEATURE_UP          (3*32+ 9) /* smp kernel running on up */
+#define X86_FEATURE_FXSAVE_LEAK (3*32+10) /* FXSAVE leaks FOP/FIP/FOP */
 
 /* 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-i386/i387.h b/include/asm-i386/i387.h
index 152d0baa576a..7b1f01191e70 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;
 }
 
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)