crt1.S 8.3 KB

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  1. /* Startup code for ARM & ELF
  2. Copyright (C) 1995, 1996, 1997, 1998, 2001, 2002, 2005
  3. Free Software Foundation, Inc.
  4. This file is part of the GNU C Library.
  5. The GNU C Library is free software; you can redistribute it and/or
  6. modify it under the terms of the GNU Lesser General Public
  7. License as published by the Free Software Foundation; either
  8. version 2.1 of the License, or (at your option) any later version.
  9. In addition to the permissions in the GNU Lesser General Public
  10. License, the Free Software Foundation gives you unlimited
  11. permission to link the compiled version of this file with other
  12. programs, and to distribute those programs without any restriction
  13. coming from the use of this file. (The GNU Lesser General Public
  14. License restrictions do apply in other respects; for example, they
  15. cover modification of the file, and distribution when not linked
  16. into another program.)
  17. Note that people who make modified versions of this file are not
  18. obligated to grant this special exception for their modified
  19. versions; it is their choice whether to do so. The GNU Lesser
  20. General Public License gives permission to release a modified
  21. version without this exception; this exception also makes it
  22. possible to release a modified version which carries forward this
  23. exception.
  24. The GNU C Library is distributed in the hope that it will be useful,
  25. but WITHOUT ANY WARRANTY; without even the implied warranty of
  26. MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
  27. Lesser General Public License for more details.
  28. You should have received a copy of the GNU Lesser General Public
  29. License along with the GNU C Library; if not, see
  30. <http://www.gnu.org/licenses/>. */
  31. /* This is the canonical entry point, usually the first thing in the text
  32. segment.
  33. Note that the code in the .init section has already been run.
  34. This includes _init and _libc_init
  35. At this entry point, most registers' values are unspecified, except:
  36. a1 Contains a function pointer to be registered with `atexit'.
  37. This is how the dynamic linker arranges to have DT_FINI
  38. functions called for shared libraries that have been loaded
  39. before this code runs.
  40. sp The stack contains the arguments and environment:
  41. 0(sp) argc
  42. 4(sp) argv[0]
  43. ...
  44. (4*argc)(sp) NULL
  45. (4*(argc+1))(sp) envp[0]
  46. ...
  47. NULL
  48. */
  49. /*
  50. For uClinux it looks like this:
  51. argc argument counter (integer)
  52. argv char *argv[]
  53. envp char *envp[]
  54. argv[0] program name (pointer)
  55. argv[1...N] program args (pointers)
  56. argv[argc-1] end of args (integer)
  57. NULL
  58. env[0...N] environment variables (pointers)
  59. NULL
  60. ARM register quick reference:
  61. Name Number ARM Procedure Calling Standard Role
  62. a1 r0 argument 1 / integer result / scratch register / argc
  63. a2 r1 argument 2 / scratch register / argv
  64. a3 r2 argument 3 / scratch register / envp
  65. a4 r3 argument 4 / scratch register
  66. v1 r4 register variable
  67. v2 r5 register variable
  68. v3 r6 register variable
  69. v4 r7 register variable
  70. v5 r8 register variable
  71. sb/v6 r9 static base / register variable
  72. sl/v7 r10 stack limit / stack chunk handle / reg. variable
  73. fp r11 frame pointer
  74. ip r12 scratch register / new-sb in inter-link-unit calls
  75. sp r13 lower end of current stack frame
  76. lr r14 link address / scratch register
  77. pc r15 program counter
  78. */
  79. #include <features.h>
  80. #include <bits/arm_asm.h>
  81. #if defined(__FDPIC__)
  82. .text
  83. .arm
  84. .globl _start
  85. _start:
  86. /* Start by self relocation. */
  87. sub r4, pc, #8
  88. ldr r1, .L__ROFIXUP_LIST__
  89. add r1, r1, r4
  90. ldr r2, .L__ROFIXUP_END__
  91. add r2, r2, r4
  92. mov r0, r7
  93. push {r9, r10}
  94. bl __self_reloc
  95. pop {r9, r10}
  96. mov r9, r0
  97. /* Clear the frame pointer since this is the outermost frame. */
  98. mov r3, #0
  99. mov fp, r3
  100. /* Now fill __uClibc_main arguments. */
  101. sub sp, sp, #16 /* Reserve space for 3 args (keep aligment) */
  102. ldr r0, .L_main_got_funcdesc /* r0 GOT FUNCDESC of main */
  103. ldr r0, [r9, r0]
  104. ldr r1, [sp, #16] /* argc */
  105. add r2, sp, #20 /* argv */
  106. ldr r3, .L_init_got_funcdesc /* r3 GOT init */
  107. ldr r3, [r9, r3]
  108. ldr r4, .L_fini_got_funcdesc
  109. ldr r4, [r9, r4]
  110. str r4, [sp, #0] /* sp + 0 GOT fini */
  111. movs r4, r8 /* Test if static binary (r8 is 0 as there is no interpreter). */
  112. movne r4, r10
  113. moveq r4, #0
  114. str r4, [sp, #4] /* sp + 4 got rtld_fini */
  115. mov r4, r2 /* stack_end is unused.... */
  116. str r4, [sp, #8] /* sp + 8 got stack_end */
  117. bl __uClibc_main
  118. /* We should never get here.... */
  119. bl abort
  120. .L__ROFIXUP_LIST__:
  121. .word __ROFIXUP_LIST__ - _start
  122. .L__ROFIXUP_END__:
  123. .word __ROFIXUP_END__ - _start
  124. .L_main_got_funcdesc:
  125. .word main(GOTFUNCDESC)
  126. .L_init_got_funcdesc:
  127. .word _init(GOTFUNCDESC)
  128. .L_fini_got_funcdesc:
  129. .word _fini(GOTFUNCDESC)
  130. /* Define a symbol for the first piece of initialized data. */
  131. .data
  132. .globl __data_start
  133. __data_start:
  134. .long 0
  135. .weak data_start
  136. data_start = __data_start
  137. #else /* defined(__FDPIC__) */
  138. .text
  139. .globl _start
  140. .type _start,%function
  141. .type _init,%function
  142. .type _fini,%function
  143. #ifndef __UCLIBC_CTOR_DTOR__
  144. .weak _init
  145. .weak _fini
  146. #endif
  147. #if defined(THUMB1_ONLY)
  148. .thumb_func
  149. _start:
  150. /* Clear the frame pointer since this is the outermost frame. */
  151. mov r3, #0
  152. mov fp, r3
  153. #ifdef __ARCH_USE_MMU__
  154. /* Pop argc off the stack and save a pointer to argv */
  155. pop {a2}
  156. mov a3, sp
  157. #else
  158. /*
  159. * uClinux/arm stacks look a little different from normal
  160. * MMU-full Linux/arm stacks (for no good reason)
  161. */
  162. /* pull argc and argv off the stack. We are going to push 3
  163. * arguments, so pop one here to maintain doubleword alignment. */
  164. pop {a2}
  165. ldr a3, [sp]
  166. #endif
  167. /* Push stack limit and rtld_fini */
  168. push {a1, a3}
  169. #ifdef __PIC__
  170. ldr r4, .L_GOT
  171. adr r5, .L_GOT
  172. add r4, r5, r4
  173. ldr r5, .L_GOT+4 /* _fini */
  174. ldr a1, [r4, r5]
  175. push {a1} /* Push _fini */
  176. ldr r5, .L_GOT+8 /* _init */
  177. ldr a4, [r4, r5]
  178. ldr r5, .L_GOT+12 /* main */
  179. ldr a1, [r4, r5]
  180. #else
  181. /* Fetch address of fini */
  182. ldr r4, =_fini
  183. /* Push fini */
  184. push {r4}
  185. /* Set up the other arguments in registers */
  186. ldr a1, =main
  187. ldr a4, =_init
  188. #endif
  189. /* __uClibc_main (main, argc, argv, init, fini, rtld_fini, stack_end) */
  190. /* Let the libc call main and exit with its return code. */
  191. bl __uClibc_main
  192. /* should never get here....*/
  193. bl abort
  194. .pool
  195. #ifdef __PIC__
  196. .L_GOT:
  197. .word _GLOBAL_OFFSET_TABLE_-.L_GOT
  198. .word _fini(GOT)
  199. .word _init(GOT)
  200. .word main(GOT)
  201. #endif
  202. #else /* !THUMB1_ONLY */
  203. _start:
  204. /* Clear the frame pointer and link register since this is the outermost frame. */
  205. mov fp, #0
  206. mov lr, #0
  207. #ifdef __ARCH_USE_MMU__
  208. /* Pop argc off the stack and save a pointer to argv */
  209. ldr a2, [sp], #4
  210. mov a3, sp
  211. #else
  212. /*
  213. * uClinux/arm stacks look a little different from normal
  214. * MMU-full Linux/arm stacks (for no good reason)
  215. */
  216. /* pull argc and argv off the stack. We are going to push 3
  217. * arguments, so pop one here to maintain doubleword alignment. */
  218. ldr a2, [sp], #4
  219. ldr a3, [sp]
  220. #endif
  221. /* Push stack limit */
  222. str a3, [sp, #-4]!
  223. /* Push rtld_fini */
  224. str a1, [sp, #-4]!
  225. #ifdef __PIC__
  226. ldr sl, .L_GOT
  227. adr a4, .L_GOT
  228. add sl, sl, a4
  229. ldr ip, .L_GOT+4 /* _fini */
  230. ldr a1, [sl, ip]
  231. str a1, [sp, #-4]! /* Push _fini */
  232. ldr ip, .L_GOT+8 /* _init */
  233. ldr a4, [sl, ip]
  234. ldr ip, .L_GOT+12 /* main */
  235. ldr a1, [sl, ip]
  236. /* __uClibc_main (main, argc, argv, init, fini, rtld_fini, stack_end) */
  237. /* Let the libc call main and exit with its return code. */
  238. b __uClibc_main(PLT)
  239. #else
  240. /* Fetch address of fini */
  241. ldr ip, =_fini
  242. /* Push fini */
  243. str ip, [sp, #-4]!
  244. /* Set up the other arguments in registers */
  245. ldr a1, =main
  246. ldr a4, =_init
  247. /* __uClibc_main (main, argc, argv, init, fini, rtld_fini, stack_end) */
  248. /* Let the libc call main and exit with its return code. */
  249. b __uClibc_main
  250. #endif
  251. /* should never get here....*/
  252. bl abort
  253. #ifdef __PIC__
  254. .L_GOT:
  255. .word _GLOBAL_OFFSET_TABLE_ - .L_GOT
  256. .word _fini(GOT)
  257. .word _init(GOT)
  258. .word main(GOT)
  259. #endif
  260. #endif
  261. /* Define a symbol for the first piece of initialized data. */
  262. .data
  263. .globl __data_start
  264. __data_start:
  265. .long 0
  266. .weak data_start
  267. data_start = __data_start
  268. #endif /* defined(__FDPIC__) */