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On STP sync events the TOD clock will jump in time, either forward or backward. The TOD clocksource claims to be continuous but in case of an STP sync with a negative offset it is not. Subtract the offset injected by the STP sync check from the result of the TOD clocksource to make it continuous again. Add code to drift the offset towards zero with a fixed rate, steering 1 second in ~9 hours. Suggested-by: David Hildenbrand <dahi@linux.vnet.ibm.com> Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
101 lines
2.5 KiB
ArmAsm
101 lines
2.5 KiB
ArmAsm
/*
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* Userland implementation of gettimeofday() for 32 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_gettimeofday
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.type __kernel_gettimeofday,@function
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__kernel_gettimeofday:
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.cfi_startproc
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ahi %r15,-16
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basr %r5,0
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0: al %r5,13f-0b(%r5) /* get &_vdso_data */
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1: ltr %r3,%r3 /* check if tz is NULL */
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je 2f
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mvc 0(8,%r3),__VDSO_TIMEZONE(%r5)
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2: ltr %r2,%r2 /* check if tv is NULL */
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je 10f
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l %r4,__VDSO_UPD_COUNT+4(%r5) /* load update counter */
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tml %r4,0x0001 /* pending update ? loop */
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jnz 1b
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stcke 0(%r15) /* Store TOD clock */
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lm %r0,%r1,__VDSO_TS_END(%r5) /* TOD steering end time */
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s %r0,1(%r15)
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sl %r1,5(%r15)
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brc 3,14f
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ahi %r0,-1
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14: ltr %r0,%r0 /* past end of steering? */
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jm 16f
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srdl %r0,15 /* 1 per 2^16 */
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tm __VDSO_TS_DIR+3(%r5),0x01 /* steering direction? */
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jz 15f
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lcr %r0,%r0 /* negative TOD offset */
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lcr %r1,%r1
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je 15f
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ahi %r0,-1
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15: a %r0,1(%r15) /* add TOD timestamp */
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al %r1,5(%r15)
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brc 12,17f
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ahi %r0,1
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j 17f
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16: lm %r0,%r1,1(%r15) /* load TOD timestamp */
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17: s %r0,__VDSO_XTIME_STAMP(%r5) /* TOD - cycle_last */
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sl %r1,__VDSO_XTIME_STAMP+4(%r5)
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brc 3,3f
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ahi %r0,-1
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3: ms %r0,__VDSO_TK_MULT(%r5) /* * tk->mult */
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st %r0,0(%r15)
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l %r0,__VDSO_TK_MULT(%r5)
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ltr %r1,%r1
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mr %r0,%r0
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jnm 4f
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a %r0,__VDSO_TK_MULT(%r5)
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4: al %r0,0(%r15)
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al %r0,__VDSO_XTIME_NSEC(%r5) /* + xtime */
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al %r1,__VDSO_XTIME_NSEC+4(%r5)
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brc 12,5f
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ahi %r0,1
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5: mvc 0(4,%r15),__VDSO_XTIME_SEC+4(%r5)
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cl %r4,__VDSO_UPD_COUNT+4(%r5) /* check update counter */
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jne 1b
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l %r4,__VDSO_TK_SHIFT(%r5) /* Timekeeper shift */
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srdl %r0,0(%r4) /* >> tk->shift */
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l %r4,0(%r15) /* get tv_sec from stack */
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basr %r5,0
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6: ltr %r0,%r0
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jnz 7f
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cl %r1,11f-6b(%r5)
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jl 8f
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7: ahi %r4,1
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sl %r1,11f-6b(%r5)
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brc 3,6b
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ahi %r0,-1
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j 6b
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8: st %r4,0(%r2) /* store tv->tv_sec */
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ltr %r1,%r1
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m %r0,12f-6b(%r5)
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jnm 9f
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al %r0,12f-6b(%r5)
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9: srl %r0,6
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st %r0,4(%r2) /* store tv->tv_usec */
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10: slr %r2,%r2
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ahi %r15,16
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br %r14
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11: .long 1000000000
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12: .long 274877907
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13: .long _vdso_data - 0b
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.cfi_endproc
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.size __kernel_gettimeofday,.-__kernel_gettimeofday
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