crt0.S 2.7 KB

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  1. /* Copyright (C) 1991, 1992 Free Software Foundation, Inc.
  2. This file is part of the GNU C Library.
  3. The GNU C Library is free software; you can redistribute it and/or
  4. modify it under the terms of the GNU Library General Public License as
  5. published by the Free Software Foundation; either version 2 of the
  6. License, or (at your option) any later version.
  7. The GNU C Library is distributed in the hope that it will be useful,
  8. but WITHOUT ANY WARRANTY; without even the implied warranty of
  9. MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  10. Library General Public License for more details.
  11. You should have received a copy of the GNU Library General Public
  12. License along with the GNU C Library; see the file COPYING.LIB. If
  13. not, write to the Free Software Foundation, Inc., 675 Mass Ave,
  14. Cambridge, MA 02139, USA. */
  15. /* Based on the code from GNU libc, but hacked up by John Beppu and Erik Andersen */
  16. /*
  17. When we enter this piece of code, the program stack looks like this:
  18. argc argument counter (integer)
  19. argv[0] program name (pointer)
  20. argv[1...N] program args (pointers)
  21. argv[argc-1] end of args (integer)
  22. NULL
  23. env[0...N] environment variables (pointers)
  24. NULL
  25. */
  26. .text
  27. .align 4
  28. .globl _start
  29. .type _start,@function
  30. _start:
  31. /* First locate the start of the environment variables */
  32. popl %ecx /* Store argc into %ecx */
  33. movl %esp,%ebx /* Store argv into ebx */
  34. movl %esp,%eax /* Store argv into eax as well*/
  35. movl %ecx,%edx /* Stick argc into %edx so we can do some math in a sec */
  36. leal 4(%eax,%edx,4),%eax
  37. /* [ register layout ]
  38. sizeof(char*) == 4
  39. %ecx = argc ; 0(esp)
  40. %ebx = argv ; 4(esp)
  41. %eax = env ; argv + (argc * 4) + 4
  42. */
  43. /* Set up an invalid (NULL return address, NULL frame pointer)
  44. callers stack frame so anybody unrolling the stack knows where
  45. to stop */
  46. xorl %ebp,%ebp /* NULL */
  47. pushl %ebp /* callers %cs */
  48. pushl %ebp /* callers %eip (return address) */
  49. pushl %ebp /* callers %ebp (frame pointer) */
  50. movl %esp,%ebp /* mark callers stack frame as invalid */
  51. /* Now set the environment, argc, and argv where the app can get to them */
  52. pushl %eax /* Environment pointer */
  53. pushl %ebx /* Argument pointer */
  54. pushl %ecx /* And the argument count */
  55. #if 0
  56. /* Make sure we are not using iBCS2 personality. (i.e. force linux). */
  57. movl $136,%eax
  58. sub %ebx,%ebx
  59. int $0x80
  60. #endif
  61. /* Ok, now run uClibc's main() -- shouldn't return */
  62. call __uClibc_main
  63. /* Stick in a dummy reference to main(), so that if an application
  64. * is linking when the main() function is in a static library (.a)
  65. * we can be sure that main() actually gets linked in */
  66. L_dummy_main_reference:
  67. .long main