osfmk/i386/mcount.s

   1 /*
   2  * Copyright (c) 2003 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_OSREFERENCE_HEADER_START@
   5  *
   6  * This file contains Original Code and/or Modifications of Original Code
   7  * as defined in and that are subject to the Apple Public Source License
   8  * Version 2.0 (the 'License'). You may not use this file except in
   9  * compliance with the License.  The rights granted to you under the
  10  * License may not be used to create, or enable the creation or
  11  * redistribution of, unlawful or unlicensed copies of an Apple operating
  12  * system, or to circumvent, violate, or enable the circumvention or
  13  * violation of, any terms of an Apple operating system software license
  14  * agreement.
  15  *
  16  * Please obtain a copy of the License at
  17  * http://www.opensource.apple.com/apsl/ and read it before using this
  18  * file.
  19  *
  20  * The Original Code and all software distributed under the License are
  21  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  22  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  23  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  24  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  25  * Please see the License for the specific language governing rights and
  26  * limitations under the License.
  27  *
  28  * @APPLE_LICENSE_OSREFERENCE_HEADER_END@
  29  */
  30
  31 #define __NO_UNDERSCORES__
  32 #include <i386/asm.h>
  33 #include <assym.s>
  34
  35 Entry(mcount)
  36         pushl   %ebp                    // setup mcount's frame
  37         movl    %esp,%ebp
  38         pushl   %eax                    // save %eax
  39         pushf                           // save interrupt state
  40         cli                             // disable interrupts
  41
  42         //
  43         // Check that this cpu is ready.
  44         // This delays the start of mcounting until a cpu is really prepared.
  45         //
  46         movl    %gs:CPU_RUNNING,%eax
  47         testl   %eax,%eax
  48         jz      1f
  49
  50         //
  51         // Test for recursion as indicated by a per-cpu flag.
  52         // Skip if nested, otherwise set the flag and call the C mount().
  53         //
  54         movl    %gs:CPU_MCOUNT_OFF,%eax
  55         testl   %eax,%eax               // test for recursion
  56         jnz     1f
  57
  58         incl    %gs:CPU_MCOUNT_OFF      // set recursion flag
  59
  60         movl    (%ebp),%eax             // frame pointer of mcount's caller
  61         movl    4(%eax),%eax            // mcount's caller's return address
  62         pushl   4(%ebp)                 // push selfpc parameter for mcount()
  63         pushl   %eax                    // push frompc parameter for mcount()
  64         call    _mcount                 // call the C mcount
  65         addl    $8,%esp                 // pop args
  66
  67         decl    %gs:CPU_MCOUNT_OFF      // turn off recursion flag
  68 1:
  69         popf                            // restore interrupt state
  70         popl    %eax
  71         movl    %ebp,%esp               // tear down mcount's frame
  72         popl    %ebp
  73         ret