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! gcrt1.s for Solaris 2, x86

!   Copyright (C) 1993, 2008, 2009 Free Software Foundation, Inc.
!   Written By Fred Fish, Nov 1992
! 
! This file is free software; you can redistribute it and/or modify it
! under the terms of the GNU General Public License as published by the
! Free Software Foundation; either version 3, or (at your option) any
! later version.
! 
! This file is distributed in the hope that it will be useful, but
! WITHOUT ANY WARRANTY; without even the implied warranty of
! MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
! General Public License for more details.
! 
! Under Section 7 of GPL version 3, you are granted additional
! permissions described in the GCC Runtime Library Exception, version
! 3.1, as published by the Free Software Foundation.
!
! You should have received a copy of the GNU General Public License and
! a copy of the GCC Runtime Library Exception along with this program;
! see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
! <http://www.gnu.org/licenses/>.


! This file takes control of the process from the kernel, as specified
! in section 3 of the System V Application Binary Interface, Intel386
! Processor Supplement.  It has been constructed from information obtained
! from the ABI, information obtained from single stepping existing
! Solaris executables through their startup code with gdb, and from
! information obtained by single stepping executables on other i386 SVR4
! implementations.  This file is the first thing linked into any executable.

! This is a modified crt1.s by J.W.Hawtin <oolon@ankh.org> 15/8/96, 
! to allow program profiling, by calling monstartup on entry and _mcleanup 
! on exit

        .ident  "GNU C gcrt1.s"
        .weak   _DYNAMIC
        .text

! Start creating the initial frame by pushing a NULL value for the return
! address of the initial frame, and mark the end of the stack frame chain
! (the innermost stack frame) with a NULL value, per page 3-32 of the ABI.
! Initialize the first stack frame pointer in %ebp (the contents of which
! are unspecified at process initialization).

        .globl  _start
_start:
        pushl   $0x0
        pushl   $0x0
        movl    %esp,%ebp

! As specified per page 3-32 of the ABI, %edx contains a function 
! pointer that should be registered with atexit(), for proper
! shared object termination.  Just push it onto the stack for now
! to preserve it.  We want to register _cleanup() first.

        pushl   %edx

! Check to see if there is an _cleanup() function linked in, and if
! so, register it with atexit() as the last thing to be run by
! atexit().

        movl    $_mcleanup,%eax
        testl   %eax,%eax
        je      .L1
        pushl   $_mcleanup
        call    atexit
        addl    $0x4,%esp
.L1:

! Now check to see if we have an _DYNAMIC table, and if so then
! we need to register the function pointer previously in %edx, but
! now conveniently saved on the stack as the argument to pass to
! atexit().

        movl    $_DYNAMIC,%eax
        testl   %eax,%eax
        je      .L2
        call    atexit
.L2:

! Register _fini() with atexit().  We will take care of calling _init()
! directly.

        pushl   $_fini
        call    atexit

! Start profiling

        pushl %ebp
        movl %esp,%ebp
        pushl $_etext
        pushl $_start
        call monstartup
        addl $8,%esp
        popl %ebp

! Compute the address of the environment vector on the stack and load
! it into the global variable _environ.  Currently argc is at 8 off
! the frame pointer.  Fetch the argument count into %eax, scale by the
! size of each arg (4 bytes) and compute the address of the environment
! vector which is 16 bytes (the two zero words we pushed, plus argc,
! plus the null word terminating the arg vector) further up the stack,
! off the frame pointer (whew!).

        movl    8(%ebp),%eax
        leal    16(%ebp,%eax,4),%edx
        movl    %edx,_environ

! Push the environment vector pointer, the argument vector pointer,
! and the argument count on to the stack to set up the arguments
! for _init(), _fpstart(), and main().  Note that the environment
! vector pointer and the arg count were previously loaded into
! %edx and %eax respectively.  The only new value we need to compute
! is the argument vector pointer, which is at a fixed address off
! the initial frame pointer.

!
! Make sure the stack is properly aligned.
!
        andl $0xfffffff0,%esp
        subl $4,%esp

        pushl   %edx
        leal    12(%ebp),%edx
        pushl   %edx
        pushl   %eax

! Call _init(argc, argv, environ), _fpstart(argc, argv, environ), and
! main(argc, argv, environ).

        call    _init
        call    __fpstart
        call    main

! Pop the argc, argv, and environ arguments off the stack, push the
! value returned from main(), and call exit().

        addl    $12,%esp
        pushl   %eax
        call    exit

! An inline equivalent of _exit, as specified in Figure 3-26 of the ABI.

        pushl   $0x0
        movl    $0x1,%eax
        lcall   $7,$0

! If all else fails, just try a halt!

        hlt
        .type   _start,@function
        .size   _start,.-_start