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Diffstat (limited to 'sysdeps/arm/start.S')
| -rw-r--r-- | sysdeps/arm/start.S | 148 |
1 files changed, 148 insertions, 0 deletions
diff --git a/sysdeps/arm/start.S b/sysdeps/arm/start.S new file mode 100644 index 0000000000..adf6531892 --- /dev/null +++ b/sysdeps/arm/start.S @@ -0,0 +1,148 @@ +/* Startup code for ARM & ELF + Copyright (C) 1995-2014 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 Lesser General Public + License as published by the Free Software Foundation; either + version 2.1 of the License, or (at your option) any later version. + + In addition to the permissions in the GNU Lesser General Public + License, the Free Software Foundation gives you unlimited + permission to link the compiled version of this file with other + programs, and to distribute those programs without any restriction + coming from the use of this file. (The GNU Lesser General Public + License restrictions do apply in other respects; for example, they + cover modification of the file, and distribution when not linked + into another program.) + + Note that people who make modified versions of this file are not + obligated to grant this special exception for their modified + versions; it is their choice whether to do so. The GNU Lesser + General Public License gives permission to release a modified + version without this exception; this exception also makes it + possible to release a modified version which carries forward this + exception. + + 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 + Lesser General Public License for more details. + + You should have received a copy of the GNU Lesser General Public + License along with the GNU C Library. If not, see + <http://www.gnu.org/licenses/>. */ + +/* 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: + + a1 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(sp) argc + 4(sp) argv[0] + ... + (4*argc)(sp) NULL + (4*(argc+1))(sp) envp[0] + ... + NULL +*/ + +/* Tag_ABI_align8_preserved: This code preserves 8-byte + alignment in any callee. */ + .eabi_attribute 25, 1 +/* Tag_ABI_align8_needed: This code may require 8-byte alignment from + the caller. */ + .eabi_attribute 24, 1 + +#if defined(__thumb2__) + .thumb + .syntax unified +#endif + + .text + .globl _start + .type _start,#function +_start: + /* Protect against unhandled exceptions. */ + .fnstart + /* Clear the frame pointer and link register since this is the outermost frame. */ + mov fp, #0 + mov lr, #0 + + /* Pop argc off the stack and save a pointer to argv */ + pop { a2 } + mov a3, sp + + /* Push stack limit */ + push { a3 } + + /* Push rtld_fini */ + push { a1 } + +#ifdef SHARED + ldr sl, .L_GOT + adr a4, .L_GOT + add sl, sl, a4 + + ldr ip, .L_GOT+4 /* __libc_csu_fini */ + ldr ip, [sl, ip] + + push { ip } /* Push __libc_csu_fini */ + + ldr a4, .L_GOT+8 /* __libc_csu_init */ + ldr a4, [sl, a4] + + ldr a1, .L_GOT+12 /* main */ + ldr a1, [sl, a1] + + /* __libc_start_main (main, argc, argv, init, fini, rtld_fini, stack_end) */ + /* Let the libc call main and exit with its return code. */ + bl __libc_start_main(PLT) +#else + /* Fetch address of __libc_csu_fini */ + ldr ip, =__libc_csu_fini + + /* Push __libc_csu_fini */ + push { ip } + + /* Set up the other arguments in registers */ + ldr a1, =main + ldr a4, =__libc_csu_init + + /* __libc_start_main (main, argc, argv, init, fini, rtld_fini, stack_end) */ + /* Let the libc call main and exit with its return code. */ + bl __libc_start_main +#endif + + /* should never get here....*/ + bl abort + +#ifdef SHARED + .align 2 +.L_GOT: + .word _GLOBAL_OFFSET_TABLE_ - .L_GOT + .word __libc_csu_fini(GOT) + .word __libc_csu_init(GOT) + .word main(GOT) +#endif + + .cantunwind + .fnend + +/* 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 |