c742b31c03
The extract cpu time instruction (ectg) instruction allows the user process to get the current thread cputime without calling into the kernel. The code that uses the instruction needs to switch to the access registers mode to get access to the per-cpu info page that contains the two base values that are needed to calculate the current cputime from the CPU timer with the ectg instruction. Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
44 lines
1.1 KiB
ArmAsm
44 lines
1.1 KiB
ArmAsm
/*
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* Userland implementation of clock_getres() for 64 bits processes in a
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* s390 kernel for use in the vDSO
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*
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* Copyright IBM Corp. 2008
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* Author(s): Martin Schwidefsky (schwidefsky@de.ibm.com)
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License (version 2 only)
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* as published by the Free Software Foundation.
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*/
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#include <asm/vdso.h>
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#include <asm/asm-offsets.h>
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#include <asm/unistd.h>
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.text
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.align 4
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.globl __kernel_clock_getres
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.type __kernel_clock_getres,@function
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__kernel_clock_getres:
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.cfi_startproc
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cghi %r2,CLOCK_REALTIME
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je 0f
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cghi %r2,CLOCK_MONOTONIC
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je 0f
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cghi %r2,-2 /* CLOCK_THREAD_CPUTIME_ID for this thread */
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jne 2f
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larl %r5,_vdso_data
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icm %r0,15,__LC_ECTG_OK(%r5)
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jz 2f
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0: ltgr %r3,%r3
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jz 1f /* res == NULL */
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larl %r1,3f
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lg %r0,0(%r1)
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xc 0(8,%r3),0(%r3) /* set tp->tv_sec to zero */
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stg %r0,8(%r3) /* store tp->tv_usec */
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1: lghi %r2,0
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br %r14
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2: lghi %r1,__NR_clock_getres /* fallback to svc */
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svc 0
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br %r14
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3: .quad CLOCK_REALTIME_RES
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.cfi_endproc
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.size __kernel_clock_getres,.-__kernel_clock_getres
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