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6507 i386 makecontext(3c) needs to 16-byte align the stack


  23  * Copyright (c) 2001 by Sun Microsystems, Inc.
  24  * All rights reserved.
  25  */
  26 /*
  27  * Copyright (c) 2013, Joyent, Inc.  All rights reserved.
  28  */
  29 
  30 /*
  31  * These crt*.o modules are provided as the bare minimum required
  32  * from a crt*.o for inclusion in building low level system
  33  * libraries.  The are only be to included in libraries which
  34  * contain *no* C++ code and want to avoid the startup code
  35  * that the C++ runtime has introduced into the crt*.o modules.
  36  *
  37  * For further details - see bug#4433015
  38  */
  39 
  40         .file   "crti.s"
  41 
  42 /*
  43  * Note that when _init and _fini are called we have 16-byte alignment per the
  44  * ABI. We need to make sure that our asm leaves it such that subsequent calls
  45  * will be aligned. gcc expects stack alignment before the call instruction is
  46  * executed. Specifically if we call function foo(), the stack pointer will be
  47  * 0xc aligned after executing the call instruction and before executing foo's
  48  * prologue. Note that because 16-byte alignment also ensures 4-byte alignment
  49  * we will not be breaking compatibility with older applications.


  50  */
  51 
  52 /*
  53  * _init function prologue
  54  */
  55         .section        .init,"ax"
  56         .globl  _init
  57         .type   _init,@function
  58         .align  16
  59 _init:
  60         pushl   %ebp
  61         movl    %esp, %ebp
  62         andl    $-16,%esp
  63         subl    $12,%esp
  64         pushl   %ebx
  65         call    .L1
  66 .L1:    popl    %ebx
  67         addl    $_GLOBAL_OFFSET_TABLE_+[.-.L1], %ebx
  68 
  69 /*


  23  * Copyright (c) 2001 by Sun Microsystems, Inc.
  24  * All rights reserved.
  25  */
  26 /*
  27  * Copyright (c) 2013, Joyent, Inc.  All rights reserved.
  28  */
  29 
  30 /*
  31  * These crt*.o modules are provided as the bare minimum required
  32  * from a crt*.o for inclusion in building low level system
  33  * libraries.  The are only be to included in libraries which
  34  * contain *no* C++ code and want to avoid the startup code
  35  * that the C++ runtime has introduced into the crt*.o modules.
  36  *
  37  * For further details - see bug#4433015
  38  */
  39 
  40         .file   "crti.s"
  41 
  42 /*
  43  * Note that when _init and _fini are called the stack needs to be 16-byte
  44  * aligned with a 4-byte bias.  See comment in lib/libc/i386/gen/makectxt.c.
  45  *
  46  * Note: If you change it, you need to change it in the following files as
  47  * well:
  48  *
  49  *  - lib/libc/i386/threads/machdep.c
  50  *  - lib/libc/i386/gen/makectxt.c
  51  *  - lib/common/i386/crt1.s
  52  */
  53 
  54 /*
  55  * _init function prologue
  56  */
  57         .section        .init,"ax"
  58         .globl  _init
  59         .type   _init,@function
  60         .align  16
  61 _init:
  62         pushl   %ebp
  63         movl    %esp, %ebp
  64         andl    $-16,%esp
  65         subl    $12,%esp
  66         pushl   %ebx
  67         call    .L1
  68 .L1:    popl    %ebx
  69         addl    $_GLOBAL_OFFSET_TABLE_+[.-.L1], %ebx
  70 
  71 /*