x86: clean up switch_to()

 * Saving eflags is important. It switches not only IOPL between tasks,

 * it also protects other tasks from NT leaking through sysenter etc.

 */

#define switch_to(prev, next, last) do {				\

#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"				\

									\

	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  */	\

		"1:			\t"				\

		     "popl %%ebp\n\t"					\

		     "popfl"						\

		     :"=m" (prev->thread.sp), "=m" (prev->thread.ip),	\

		      "=a" (last), "=S" (esi), "=D" (edi)		\

		     :"m" (next->thread.sp), "m" (next->thread.ip),	\

		      "2" (prev), "d" (next));				\

		"popl %%ebp		\n\t"	/* restore EBP   */	\

		"popfl			\n"	/* restore flags */	\

									\

		  /* output parameters */				\

		: [prev_sp] "=m" (prev->thread.sp),			\

		  [prev_ip] "=m" (prev->thread.ip),			\

			    "=a" (last),				\

									\

		  /* clobbered output registers: */			\

		  "=S" (esi), "=D" (edi)				\

									\

		  /* input parameters: */				\

		: [next_sp]  "m" (next->thread.sp),			\

		  [next_ip]  "m" (next->thread.ip),			\

									\

		  /* regparm parameters for __switch_to(): */		\

		  [prev]     "a" (prev),				\

		  [next]     "d" (next)					\

	);								\

} while (0)

/*