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Diffstat (limited to 'include/asm-i386/i387.h')
-rw-r--r--include/asm-i386/i387.h30
1 files changed, 26 insertions, 4 deletions
diff --git a/include/asm-i386/i387.h b/include/asm-i386/i387.h
index 152d0baa576..bc1d6edae1e 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] ; jnc 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. safe_address 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;
}