Commit 65c07e91 authored by Heiko Carstens's avatar Heiko Carstens Committed by Vasily Gorbik
Browse files

s390/current: Implement current with inline assembly 



Implement current with an inline assembly, which makes use of the
ALTERNATIVE macro, to read current from lowcore. Provide an alternative
instruction with a different offset in case lowcore is relocated.

This replaces sequences of two instructions with one instruction.

Before:
 100076:       a5 1e 00 00             llilh   %r1,0
 10007a:       e3 40 13 40 00 04       lg      %r4,832(%r1)

After:
 100076:       e3 10 03 40 00 04       lg      %r1,832

Kernel image size change:
add/remove: 3/17 grow/shrink: 166/2204 up/down: 7122/-24594 (-17472)

Reviewed-by: default avatarAlexander Gordeev <agordeev@linux.ibm.com>
Signed-off-by: default avatarHeiko Carstens <hca@linux.ibm.com>
Signed-off-by: default avatarVasily Gorbik <gor@linux.ibm.com>
parent 430693c8

arch/s390/include/asm/current.h

+17 −1
Original line number Diff line number Diff line
@@ -11,9 +11,25 @@ 
#define _S390_CURRENT_H



#include <asm/lowcore.h>

#include <asm/machine.h>



struct task_struct;



#define current ((struct task_struct *const)get_lowcore()->current_task)

static __always_inline struct task_struct *get_current(void)

{

	unsigned long ptr, lc_current;



	lc_current = offsetof(struct lowcore, current_task);

	asm_inline(

		ALTERNATIVE("	lg	%[ptr],%[offzero](%%r0)\n",

			    "	lg	%[ptr],%[offalt](%%r0)\n",

			    ALT_FEATURE(MFEATURE_LOWCORE))

		: [ptr] "=d" (ptr)

		: [offzero] "i" (lc_current),

		  [offalt] "i" (lc_current + LOWCORE_ALT_ADDRESS));

	return (struct task_struct *)ptr;

}



#define current get_current()



#endif /* !(_S390_CURRENT_H) */