/arch/ppc64/kernel/vdso32/gettimeofday.S

  1/*
  2 * Userland implementation of gettimeofday() for 32 bits processes in a
  3 * ppc64 kernel for use in the vDSO
  4 *
  5 * Copyright (C) 2004 Benjamin Herrenschmuidt (benh@kernel.crashing.org), IBM Corp.
  6 *
  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.
 11 */
 12#include <linux/config.h>
 13#include <asm/processor.h>
 14#include <asm/ppc_asm.h>
 15#include <asm/vdso.h>
 16#include <asm/offsets.h>
 17#include <asm/unistd.h>
 18
 19	.text
 20/*
 21 * Exact prototype of gettimeofday
 22 *
 23 * int __kernel_gettimeofday(struct timeval *tv, struct timezone *tz);
 24 *
 25 */
 26V_FUNCTION_BEGIN(__kernel_gettimeofday)
 27  .cfi_startproc
 28	mflr	r12
 29  .cfi_register lr,r12
 30
 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 */
 37
 38	/* seconds are xsec >> 20 */
 39	rlwinm	r5,r4,12,20,31
 40	rlwimi	r5,r3,12,0,19
 41	stw	r5,TVAL32_TV_SEC(r10)
 42
 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
 46	 */
 47	rlwinm	r5,r4,12,0,19
 48	lis	r6,1000000@h
 49	ori	r6,r6,1000000@l
 50	mulhwu	r5,r5,r6
 51	stw	r5,TVAL32_TV_USEC(r10)
 52
 53	cmpli	cr0,r11,0		/* check if tz is NULL */
 54	beq	1f
 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)
 59
 601:	mtlr	r12
 61	blr
 62
 632:	mr	r3,r10
 64	mr	r4,r11
 65	li	r0,__NR_gettimeofday
 66	sc
 67	b	1b
 68  .cfi_endproc
 69V_FUNCTION_END(__kernel_gettimeofday)
 70
 71/*
 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
 75*/
 76__do_get_xsec:
 77  .cfi_startproc
 78	/* Check for update count & load values. We use the low
 79	 * order 32 bits of the update count
 80	 */
 811:	lwz	r8,(CFG_TB_UPDATE_COUNT+4)(r9)
 82	andi.	r0,r8,1			/* pending update ? loop */
 83	bne-	1b
 84	xor	r0,r8,r8		/* create dependency */
 85	add	r9,r9,r0
 86
 87	/* Load orig stamp (offset to TB) */
 88	lwz	r5,CFG_TB_ORIG_STAMP(r9)
 89	lwz	r6,(CFG_TB_ORIG_STAMP+4)(r9)
 90
 91	/* Get a stable TB value */
 922:	mftbu	r3
 93	mftbl	r4
 94	mftbu	r0
 95	cmpl	cr0,r3,r0
 96	bne-	2b
 97
 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
101	 */
102	subfc	r7,r6,r4
103	subfe.	r0,r5,r3
104	bne-	3f
105
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)
109	mulhwu	r4,r7,r5
110	mulhwu	r6,r7,r6
111	mullw	r6,r7,r5
112	addc	r6,r6,r0
113
114	/* At this point, we have the scaled xsec value in r4 + XER:CA
115	 * we load & add the stamp since epoch
116	 */
117	lwz	r5,CFG_STAMP_XSEC(r9)
118	lwz	r6,(CFG_STAMP_XSEC+4)(r9)
119	adde	r4,r4,r6
120	addze	r3,r5
121
122	/* We now have our result in r3,r4. We create a fake dependency
123	 * on that result and re-check the counter
124	 */
125	xor	r0,r4,r4
126	add	r9,r9,r0
127	lwz	r0,(CFG_TB_UPDATE_COUNT+4)(r9)
128        cmpl    cr0,r8,r0		/* check if updated */
129	bne-	1b
130
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.
137	 */
1383:	blr
139  .cfi_endproc