x86, xsave: Sync xsave memory layout with its header for user handling

With xsaveopt, if a processor implementation discern that a processor state
component is in its initialized state it may modify the corresponding bit in
the xsave_hdr.xstate_bv as '0', with out modifying the corresponding memory
layout. Hence wHile presenting the xstate information to the user, we always
ensure that the memory layout of a feature will be in the init state if the
corresponding header bit is zero. This ensures the consistency and avoids the
condition of the user seeing some some stale state in the memory layout during
signal handling, debugging etc.

Signed-off-by: Suresh Siddha <suresh.b.siddha@intel.com>
LKML-Reference: <20100719230205.351459480@sbs-t61.sc.intel.com>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

2 files changed, 24 insertions, 0 deletions

diff --git a/arch/x86/include/asm/i387.h b/arch/x86/include/asm/i387.h
index c991b3a7b904..bb370fd0a1c2 100644
--- a/arch/x86/include/asm/i387.h
+++ b/arch/x86/include/asm/i387.h
@@ -58,11 +58,25 @@ extern int restore_i387_xstate_ia32(void __user *buf);
 
 #define X87_FSW_ES (1 << 7)     /* Exception Summary */
 
+static __always_inline __pure bool use_xsaveopt(void)
+{
+        return 0;
+}
+
 static __always_inline __pure bool use_xsave(void)
 {
         return static_cpu_has(X86_FEATURE_XSAVE);
 }
 
+extern void __sanitize_i387_state(struct task_struct *);
+
+static inline void sanitize_i387_state(struct task_struct *tsk)
+{
+        if (!use_xsaveopt())
+                return;
+        __sanitize_i387_state(tsk);
+}
+
 #ifdef CONFIG_X86_64
 
 /* Ignore delayed exceptions from user space */
diff --git a/arch/x86/include/asm/xsave.h b/arch/x86/include/asm/xsave.h
index 2c4390cae228..0c72adc0cb15 100644
--- a/arch/x86/include/asm/xsave.h
+++ b/arch/x86/include/asm/xsave.h
@@ -111,6 +111,16 @@ static inline void xrstor_state(struct xsave_struct *fx, u64 mask)
                      :   "memory");
 }
 
+static inline void xsave_state(struct xsave_struct *fx, u64 mask)
+{
+        u32 lmask = mask;
+        u32 hmask = mask >> 32;
+
+        asm volatile(".byte " REX_PREFIX "0x0f,0xae,0x27\n\t"
+                     : : "D" (fx), "m" (*fx), "a" (lmask), "d" (hmask)
+                     :   "memory");
+}
+
 static inline void fpu_xsave(struct fpu *fpu)
 {
         /* This, however, we can work around by forcing the compiler to select