-#define switch_to(prev, next, last) do { \
- unsigned long esi, edi; \
- asm volatile("pushfl\n\t" /* Save flags */ \
- "pushl %%ebp\n\t" \
- "movl %%esp,%0\n\t" /* save ESP */ \
- "movl %5,%%esp\n\t" /* restore ESP */ \
- "movl $1f,%1\n\t" /* save EIP */ \
- "pushl %6\n\t" /* restore EIP */ \
- "jmp __switch_to\n" \
+#define switch_to(prev, next, last) \
+do { \
+ /* \
+ * 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 */ \
+ "pushl %%ebp\n\t" /* save EBP */ \
+ "movl %%esp,%[prev_sp]\n\t" /* save ESP */ \
+ "movl %[next_sp],%%esp\n\t" /* restore ESP */ \
+ "movl $1f,%[prev_ip]\n\t" /* save EIP */ \
+ "pushl %[next_ip]\n\t" /* restore EIP */ \
+ "jmp __switch_to\n" /* regparm call */ \