1 /* Startup code for ARM & ELF
2 Copyright (C) 1995-2022 Free Software Foundation, Inc.
3 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.
10 In addition to the permissions in the GNU Lesser General Public
11 License, the Free Software Foundation gives you unlimited
12 permission to link the compiled version of this file with other
13 programs, and to distribute those programs without any restriction
14 coming from the use of this file. (The GNU Lesser General Public
15 License restrictions do apply in other respects; for example, they
16 cover modification of the file, and distribution when not linked
17 into another program.)
19 Note that people who make modified versions of this file are not
20 obligated to grant this special exception for their modified
21 versions; it is their choice whether to do so. The GNU Lesser
22 General Public License gives permission to release a modified
23 version without this exception; this exception also makes it
24 possible to release a modified version which carries forward this
27 The GNU C Library is distributed in the hope that it will be useful,
28 but WITHOUT ANY WARRANTY; without even the implied warranty of
29 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
30 Lesser General Public License for more details.
32 You should have received a copy of the GNU Lesser General Public
33 License along with the GNU C Library. If not, see
34 <https://www.gnu.org/licenses/>. */
36 /* This is the canonical entry point, usually the first thing in the text
39 Note that the code in the .init section has already been run.
40 This includes _init and _libc_init
43 At this entry point, most registers' values are unspecified, except:
45 a1 Contains a function pointer to be registered with `atexit'.
46 This is how the dynamic linker arranges to have DT_FINI
47 functions called for shared libraries that have been loaded
48 before this code runs.
50 sp The stack contains the arguments and environment:
55 (4*(argc+1))(sp) envp[0]
60 /* Tag_ABI_align8_preserved: This code preserves 8-byte
61 alignment in any callee. */
63 /* Tag_ABI_align8_needed: This code may require 8-byte alignment from
67 #if defined(__thumb2__)
74 .type _start,#function
76 /* Protect against unhandled exceptions. */
78 /* Clear the frame pointer and link register since this is the outermost frame. */
82 /* Pop argc off the stack and save a pointer to argv */
86 /* Push stack limit */
97 mov a4, #0 /* Used to be init. */
98 push { a4 } /* Used to be fini. */
100 ldr a1, .L_GOT+4 /* main */
103 /* __libc_start_main (main, argc, argv, init, fini, rtld_fini, stack_end) */
104 /* Let the libc call main and exit with its return code. */
105 bl __libc_start_main(PLT)
108 mov a4, #0 /* Used to init. */
109 push { a4 } /* Used to fini. */
112 /* __libc_start_main (main, argc, argv, init, fini, rtld_fini, stack_end) */
113 /* Let the libc call main and exit with its return code. */
117 /* should never get here....*/
123 .word _GLOBAL_OFFSET_TABLE_ - .L_GOT
130 /* Define a symbol for the first piece of initialized data. */
136 data_start = __data_start