2 * Userland implementation of gettimeofday() for 32 bits processes in a
3 * ppc64 kernel for use in the vDSO
5 * Copyright (C) 2004 Benjamin Herrenschmuidt (benh@kernel.crashing.org), IBM Corp.
7 * This program is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU General Public License
9 * as published by the Free Software Foundation; either version
10 * 2 of the License, or (at your option) any later version.
12 #include <linux/config.h>
13 #include <asm/processor.h>
14 #include <asm/ppc_asm.h>
16 #include <asm/offsets.h>
17 #include <asm/unistd.h>
21 * Exact prototype of gettimeofday
23 * int __kernel_gettimeofday(struct timeval *tv, struct timezone *tz);
26 V_FUNCTION_BEGIN(__kernel_gettimeofday)
31 mr r10,r3 /* r10 saves tv */
32 mr r11,r4 /* r11 saves tz */
33 bl __get_datapage@local /* get data page */
34 mr r9, r3 /* datapage ptr in r9 */
35 bl __do_get_xsec@local /* get xsec from tb & kernel */
36 bne- 2f /* out of line -> do syscall */
38 /* seconds are xsec >> 20 */
41 stw r5,TVAL32_TV_SEC(r10)
43 /* get remaining xsec and convert to usec. we scale
44 * up remaining xsec by 12 bits and get the top 32 bits
45 * of the multiplication
51 stw r5,TVAL32_TV_USEC(r10)
53 cmpli cr0,r11,0 /* check if tz is NULL */
55 lwz r4,CFG_TZ_MINUTEWEST(r9)/* fill tz */
56 lwz r5,CFG_TZ_DSTTIME(r9)
57 stw r4,TZONE_TZ_MINWEST(r11)
58 stw r5,TZONE_TZ_DSTTIME(r11)
65 li r0,__NR_gettimeofday
69 V_FUNCTION_END(__kernel_gettimeofday)
72 * This is the core of gettimeofday(), it returns the xsec
73 * value in r3 & r4 and expects the datapage ptr (non clobbered)
74 * in r9. clobbers r0,r4,r5,r6,r7,r8
78 /* Check for update count & load values. We use the low
79 * order 32 bits of the update count
81 1: lwz r8,(CFG_TB_UPDATE_COUNT+4)(r9)
82 andi. r0,r8,1 /* pending update ? loop */
84 xor r0,r8,r8 /* create dependency */
87 /* Load orig stamp (offset to TB) */
88 lwz r5,CFG_TB_ORIG_STAMP(r9)
89 lwz r6,(CFG_TB_ORIG_STAMP+4)(r9)
91 /* Get a stable TB value */
98 /* Substract tb orig stamp. If the high part is non-zero, we jump to the
99 * slow path which call the syscall. If it's ok, then we have our 32 bits
100 * tb_ticks value in r7
106 /* Load scale factor & do multiplication */
107 lwz r5,CFG_TB_TO_XS(r9) /* load values */
108 lwz r6,(CFG_TB_TO_XS+4)(r9)
114 /* At this point, we have the scaled xsec value in r4 + XER:CA
115 * we load & add the stamp since epoch
117 lwz r5,CFG_STAMP_XSEC(r9)
118 lwz r6,(CFG_STAMP_XSEC+4)(r9)
122 /* We now have our result in r3,r4. We create a fake dependency
123 * on that result and re-check the counter
127 lwz r0,(CFG_TB_UPDATE_COUNT+4)(r9)
128 cmpl cr0,r8,r0 /* check if updated */
131 /* Warning ! The caller expects CR:EQ to be set to indicate a
132 * successful calculation (so it won't fallback to the syscall
133 * method). We have overriden that CR bit in the counter check,
134 * but fortunately, the loop exit condition _is_ CR:EQ set, so
135 * we can exit safely here. If you change this code, be careful
136 * of that side effect.