| Linus Torvalds | 1da177e | 2005-04-16 15:20:36 -0700 | [diff] [blame^] | 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 |