usr/src/lib/libc/amd64/sys/gettimeofday.s

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21
  22 /*
  23  * Copyright 2008 Sun Microsystems, Inc.  All rights reserved.
  24  * Use is subject to license terms.
  25  */
  26
  27         .file   "gettimeofday.s"
  28
  29 #include "SYS.h"
  30
  31         ANSI_PRAGMA_WEAK(gettimeofday,function)
  32
  33 /*
  34  *  implements int gettimeofday(struct timeval *tp, void *tzp)
  35  *
  36  *      note that tzp is always ignored
  37  */
  38
  39         ENTRY(gettimeofday)
  40 /*
  41  *      use long long gethrestime()
  42  */
  43         pushq   %rdi            /* pointer to timeval */
  44         SYSFASTTRAP(GETHRESTIME)
  45 /*
  46  *      gethrestime trap returns seconds in %eax, nsecs in %edx
  47  *      need to convert nsecs to usecs & store into area pointed
  48  *      to by struct timeval * argument.
  49  */
  50         popq    %rcx            /* pointer to timeval */
  51         jrcxz   1f              /* bail if we get a null pointer */
  52         movq    %rax, (%rcx)    /* store seconds into timeval ptr        */
  53         movl    $274877907, %eax        /* divide by 1000 as impl. by gcc */
  54         imull   %edx            /* See Hacker's Delight pg 162 */
  55         sarl    $6, %edx        /* simplified by 0 <= nsec <= 1e9 */
  56         movq    %rdx, 8(%rcx)   /* store usecs into timeval ptr + 8. */
  57 1:
  58         RETC                    /* return 0 */
  59         SET_SIZE(gettimeofday)
  60