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Diffstat (limited to 'sysdeps/arm/elf/start.S')
| -rw-r--r-- | sysdeps/arm/elf/start.S | 109 |
1 files changed, 109 insertions, 0 deletions
diff --git a/sysdeps/arm/elf/start.S b/sysdeps/arm/elf/start.S new file mode 100644 index 0000000000..e0964a1e38 --- /dev/null +++ b/sysdeps/arm/elf/start.S @@ -0,0 +1,109 @@ +/* Startup code for ARM & ELF + 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. + + Note that the code in the .init section has already been run. + This includes _init and _libc_init + + + At this entry point, most registers' values are unspecified, except for: + + r0 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. + + sp 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 Intel ABI suggests this be done, + to mark the outermost frame obviously. This seems like a + sensible thing to do */ + mov fp, #0 + + /* r0 contains the address of the shared library termination + function, which we will register with `atexit' to be called by + `exit'. I suspect that on some systems, and when statically + linked, this will not be set by anything to any function + pointer; hopefully it will be zero so we don't try to call + random pointers. */ + cmp r0,#0 + blne atexit(PLT) + + /* Do essential libc initialization. In statically linked + programs under the GNU Hurd, this is what sets up the + arguments on the stack for the code below. For dyn-link + programs, this has been run already, in the .init code. */ +#ifndef PIC + bl __libc_init_first + + /* Extract the arguments and environment as encoded on the stack + and set up the arguments for `main': argc, argv, envp. */ + ldr r0,[sp] + add r1,sp,#4 + add r2,r1,r0,lsl #2 + add r2,r2,#4 + /* save a copy of envp while we have it */ + ldr r3,L_environ + str r2,[r3] + + /* Call `_init', which is the entry point to our own `.init' + section; and register with `atexit' to have `exit' call + `_fini', which is the entry point to our own `.fini' section. */ + bl _init + ldr r0,L_fini + bl atexit + b L_pfini + +L_fini: .word _fini +L_environ: .word _environ +L_pfini: +#endif + /* rebuild the arg list for main() */ + ldr r0,[sp] + add r1,sp,#4 + add r2,r1,r0,lsl #2 + add r2,r2,#4 + + /* Call the user's main function, and exit with its value. */ + bl main + bl exit + /* should never get here....*/ + bl abort + + +/* 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 |