x86: fix switch_to() clobbers

[sfrench/cifs-2.6.git] / include / asm-x86 / system.h

diff --git a/include/asm-x86/system.h b/include/asm-x86/system.h
index 299ae9605cb1631f2a3f871213f2455f5173dd3e..33b0017156a7fae07db3f80a62b3b14afd4e95ec 100644 (file)
--- a/include/asm-x86/system.h
+++ b/include/asm-x86/system.h
@@ -29,7 +29,14 @@ struct task_struct *__switch_to(struct task_struct *prev,
  */
 #define switch_to(prev, next, last)                                    \
 do {                                                                   \
-       unsigned long esi, edi;                                         \
+       /*                                                              \
+        * Context-switching clobbers all registers, so we clobber      \
+        * them explicitly, via unused output variables.                \
+        * (EAX and EBP is not listed because EBP is saved/restored     \
+        * explicitly for wchan access and EAX is the return value of   \
+        * __switch_to())                                               \
+        */                                                             \
+       unsigned long ebx, ecx, edx, esi, edi;                          \
                                                                        \
        asm volatile(                                                   \
                "pushfl                 \n\t"   /* save    flags */     \
@@ -49,6 +56,7 @@ do {                                                                  \
                            "=a" (last),                                \
                                                                        \
                  /* clobbered output registers: */                     \
+                 "=b" (ebx), "=c" (ecx), "=d" (edx),                   \
                  "=S" (esi), "=D" (edi)                                \
                                                                        \
                  /* input parameters: */                               \