/* Startup code compliant to the ELF i386 ABI. Copyright (C) 1995, 1996, 1997, 1998 Free Software Foundation, Inc. This file is part of the GNU C Library. The GNU C Library is free software; you can redistribute it and/or modify it under the terms of the GNU Library General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. The GNU C Library 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 Library General Public License for more details. You should have received a copy of the GNU Library General Public License along with the GNU C Library; see the file COPYING.LIB. If not, write to the Free Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. */ /* This is the canonical entry point, usually the first thing in the text segment. The SVR4/i386 ABI (pages 3-31, 3-32) says that when the entry point runs, most registers' values are unspecified, except for: %edx Contains a function pointer to be registered with `atexit'. This is how the dynamic linker arranges to have DT_FINI functions called for shared libraries that have been loaded before this code runs. %esp The stack contains the arguments and environment: 0(%esp) argc 4(%esp) argv[0] ... (4*argc)(%esp) NULL (4*(argc+1))(%esp) envp[0] ... NULL */ .text .globl _start _start: /* Clear the frame pointer. The ABI suggests this be done, to mark the outermost frame obviously. */ xorl %ebp, %ebp /* Extract the arguments as encoded on the stack and set up the arguments for `main': argc, argv. envp will be determined later in __libc_start_main. */ popl %esi /* Pop the argument count. */ movl %esp, %ecx /* argv starts just at the current stack top.*/ /* Before pushing the arguments align the stack to a double word boundary to avoid penalties from misaligned accesses. Thanks to Edward Seidl for pointing this out. */ andl $0xfffffff8, %esp pushl %edx /* Push address of the shared library termination function. */ /* Push address of our own entry points to .fini and .init. */ pushl $_fini pushl $_init pushl %ecx /* Push second argument: argv. */ pushl %esi /* Push first argument: argc. */ pushl $main /* Call the user's main function, and exit with its value. But let the libc call main. */ call __libc_start_main hlt /* Crash if somehow `exit' does return. */ /* To fulfill the System V/i386 ABI we need this symbol. Yuck, it's so meaningless since we don't support machines < 80386. */ .section .rodata .globl _fp_hw .long 3 .size _fp_hw, 4 /* Define a symbol for the first piece of initialized data. */ .data .globl __data_start __data_start: .long 0 .weak data_start data_start = __data_start