osfmk/i386/mcount.s

   1 /*
   2  * Copyright (c) 2003 Apple Computer, Inc. All rights reserved.
   3  *
   4  * @APPLE_LICENSE_HEADER_START@
   5  *
   6  * Copyright (c) 1999-2003 Apple Computer, Inc.  All Rights Reserved.
   7  *
   8  * This file contains Original Code and/or Modifications of Original Code
   9  * as defined in and that are subject to the Apple Public Source License
  10  * Version 2.0 (the 'License'). You may not use this file except in
  11  * compliance with the License. Please obtain a copy of the License at
  12  * http://www.opensource.apple.com/apsl/ and read it before using this
  13  * file.
  14  *
  15  * The Original Code and all software distributed under the License are
  16  * distributed on an 'AS IS' basis, WITHOUT WARRANTY OF ANY KIND, EITHER
  17  * EXPRESS OR IMPLIED, AND APPLE HEREBY DISCLAIMS ALL SUCH WARRANTIES,
  18  * INCLUDING WITHOUT LIMITATION, ANY WARRANTIES OF MERCHANTABILITY,
  19  * FITNESS FOR A PARTICULAR PURPOSE, QUIET ENJOYMENT OR NON-INFRINGEMENT.
  20  * Please see the License for the specific language governing rights and
  21  * limitations under the License.
  22  *
  23  * @APPLE_LICENSE_HEADER_END@
  24  */
  25
  26 #define __NO_UNDERSCORES__
  27 #include <i386/asm.h>
  28 #include <assym.s>
  29
  30 Entry(mcount)
  31         pushl   %ebp                    // setup mcount's frame
  32         movl    %esp,%ebp
  33         pushf                           // save interrupt state
  34         cli                             // disable interrupts
  35
  36         //
  37         // Check that %gs, with segment pointing at the per-cpu data area,
  38         // has been set up. C routines (mp_desc_init() in particular) may
  39         // be called very early before this happens.
  40         //
  41         mov     %gs,%ax
  42         test    %ax,%ax
  43         jz      1f
  44
  45         //
  46         // Check that this cpu is ready.
  47         // This delays the start of mcounting until a cpu is really prepared.
  48         //
  49         movl    %gs:CPD_CPU_STATUS,%eax
  50         testl   %eax,%eax
  51         jz      1f
  52
  53         //
  54         // Test for recursion as indicated by a per-cpu flag.
  55         // Skip if nested, otherwise set the flag and call the C mount().
  56         //
  57         movl    %gs:CPD_MCOUNT_OFF,%eax
  58         testl   %eax,%eax               // test for recursion
  59         jnz     1f
  60         incl    %gs:CPD_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:CPD_MCOUNT_OFF      // turn off recursion flag
  70 1:
  71         popf                            // restore interrupt state
  72         movl    %ebp,%esp               // tear down mcount's frame
  73         popl    %ebp
  74         ret