diff options
Diffstat (limited to 'libc/sysdeps/linux/i386/crt1.S')
| -rw-r--r-- | libc/sysdeps/linux/i386/crt1.S | 125 |
1 files changed, 125 insertions, 0 deletions
diff --git a/libc/sysdeps/linux/i386/crt1.S b/libc/sysdeps/linux/i386/crt1.S new file mode 100644 index 000000000..76e71be56 --- /dev/null +++ b/libc/sysdeps/linux/i386/crt1.S @@ -0,0 +1,125 @@ +/* Copyright (C) 1991, 1992 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., 675 Mass Ave, +Cambridge, MA 02139, USA. */ + + +/* Based on the code from GNU libc, but hacked up by John Beppu and Erik Andersen */ +/* adapted by PaX Team for ET_DYN/PIE binaries */ + +/* + When we enter this piece of code, the program stack looks like this: + argc argument counter (integer) + argv[0] program name (pointer) + argv[1...N] program args (pointers) + argv[argc-1] end of args (integer) + NULL + env[0...N] environment variables (pointers) + NULL +*/ + +#include <features.h> + +.text + .align 4 + + .global _start + .type _start,%function + .weak _init + .weak _fini + .type __uClibc_start_main,%function + +_start: + /* locate the start of the environment variables */ + popl %ecx /* Store argc into %ecx */ + movl %esp,%ebx /* Store argv into ebx */ + movl %esp,%eax /* Store argv into eax as well*/ + movl %edx,%esi /* Store edx(FINI ptr) in %esi */ + movl %ecx,%edx /* Stick argc into %edx so we can do some math in a sec */ + leal 4(%eax,%edx,4),%eax + + /* [ register layout ] + + sizeof(char*) == 4 + %ecx = argc ; 0(esp) + %ebx = argv ; 4(esp) + %eax = env ; argv + (argc * 4) + 4 + */ + xorl %ebp,%ebp /* NULL */ + /* + Before pushing the arguments align the stack to a 16-byte + (SSE needs 16-byte alignment) boundary to avoid penalties from + misaligned accesses. Thanks to Edward Seidl <seidl@janed.com> + for pointing this out. + */ + andl $0xfffffff0, %esp + /* Push NULL to make sure stack ptr + is 16 byte aligned when calling __uClibc_start_main */ + pushl %ebp + pushl %ebp + + /* Set up an invalid (NULL return address, NULL frame pointer) + callers stack frame so anybody unrolling the stack knows where + to stop */ + pushl %ebp /* callers %cs */ + pushl %ebp /* callers %eip (return address) */ + pushl %ebp /* callers %ebp (frame pointer) */ + movl %esp,%ebp /* mark callers stack frame as invalid */ + +#if defined L_Scrt1 + call .L0 +.L0: + pop %edx + addl $_GLOBAL_OFFSET_TABLE_+[.-.L0],%edx +#endif + pushl %esi /* Push FINI pointer */ + + /* Push apps .init, .fini and main arguments to __uClibc_start_main() on the stack */ +#ifdef L_Scrt1 + pushl main@GOT(%edx) + pushl _fini@GOT(%edx) + pushl _init@GOT(%edx) +#else + pushl $main + pushl $_fini + pushl $_init +#endif + + /* Push envp, argc, and argc arguments to __uClibc_start_main() on the stack */ + pushl %eax /* Environment pointer */ + pushl %ebx /* Argument pointer */ + pushl %ecx /* And the argument count */ + + /* Ok, now run uClibc's main() -- shouldn't return */ +#ifdef L_Scrt1 + call *__uClibc_start_main@GOT(%edx) +#else + call __uClibc_start_main +#endif + + /* Crash if somehow `exit' returns anyways. */ + hlt +.size _start,.-_start + + +/* 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 + |