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  */
  26 V_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
  60 1:      mtlr    r12
  61         blr
  62
  63 2:      mr      r3,r10
  64         mr      r4,r11
  65         li      r0,__NR_gettimeofday
  66         sc
  67         b       1b
  68   .cfi_endproc
  69 V_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          */
  81 1:      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 */
  92 2:      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          */
 138 3:      blr
 139   .cfi_endproc