osfmk/i386/mcount.s

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