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| author |   Martin Schwidefsky <schwidefsky@de.ibm.com> | 2016-01-05 13:29:38 +0100 |
|---|---|---|
| committer | Martin Schwidefsky <schwidefsky@de.ibm.com> | 2016-01-11 13:01:24 +0100 |
| commit | 249c543b97e1409b13fb9539b2f880e58ddd87cf (patch) | |
| tree | 956a0719238b56b8dffa3877d3fe3eb5c27df9f4 /arch/s390/kernel/vdso32/getcpu.S | |
| parent | s390: drop smp_mb in vdso_init (diff) | |
| download | wireguard-linux-249c543b97e1409b13fb9539b2f880e58ddd87cf.tar.xz wireguard-linux-249c543b97e1409b13fb9539b2f880e58ddd87cf.zip | |
s390/vdso: optimize getcpu system call
Add the CPU number to the per-cpu vdso data page and add the
__kernel_getcpu function to the vdso object to retrieve the
CPU number in user space.
Suggested-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Reviewed-by: Heiko Carstens <heiko.carstens@de.ibm.com>
Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'arch/s390/kernel/vdso32/getcpu.S')
| -rw-r--r-- | arch/s390/kernel/vdso32/getcpu.S | 43 |
1 files changed, 43 insertions, 0 deletions
diff --git a/arch/s390/kernel/vdso32/getcpu.S b/arch/s390/kernel/vdso32/getcpu.S new file mode 100644 index 000000000000..c1ed0b72030f --- /dev/null +++ b/arch/s390/kernel/vdso32/getcpu.S @@ -0,0 +1,43 @@ +/* + * Userland implementation of getcpu() for 32 bits processes in a + * s390 kernel for use in the vDSO + * + * Copyright IBM Corp. 2016 + * Author(s): Martin Schwidefsky <schwidefsky@de.ibm.com> + */ +#include <asm/vdso.h> +#include <asm/asm-offsets.h> + + .text + .align 4 + .globl __kernel_getcpu + .type __kernel_getcpu,@function +__kernel_getcpu: + .cfi_startproc + ear %r1,%a4 + lhi %r4,1 + sll %r4,24 + sar %a4,%r4 + la %r4,0 + epsw %r0,0 + sacf 512 + l %r5,__VDSO_CPU_NR(%r4) + l %r4,__VDSO_NODE_ID(%r4) + tml %r0,0x4000 + jo 1f + tml %r0,0x8000 + jno 0f + sacf 256 + j 1f +0: sacf 0 +1: sar %a4,%r1 + ltr %r2,%r2 + jz 2f + st %r5,0(%r2) +2: ltr %r3,%r3 + jz 3f + st %r4,0(%r3) +3: lhi %r2,0 + br %r14 + .cfi_endproc + .size __kernel_getcpu,.-__kernel_getcpu |