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df27fae1 | 1 | /* Startup code for ARM & ELF |
b168057a | 2 | Copyright (C) 1995-2015 Free Software Foundation, Inc. |
df27fae1 UD |
3 | This file is part of the GNU C Library. |
4 | ||
5 | The GNU C Library is free software; you can redistribute it and/or | |
3214b89b AJ |
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. | |
df27fae1 | 9 | |
0bec0145 RM |
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.) | |
18 | ||
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 | |
25 | exception. | |
26 | ||
df27fae1 UD |
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 | |
3214b89b | 30 | Lesser General Public License for more details. |
df27fae1 | 31 | |
3214b89b | 32 | You should have received a copy of the GNU Lesser General Public |
ab84e3ff PE |
33 | License along with the GNU C Library. If not, see |
34 | <http://www.gnu.org/licenses/>. */ | |
df27fae1 UD |
35 | |
36 | /* This is the canonical entry point, usually the first thing in the text | |
37 | segment. | |
38 | ||
39 | Note that the code in the .init section has already been run. | |
40 | This includes _init and _libc_init | |
41 | ||
42 | ||
e7304fce | 43 | At this entry point, most registers' values are unspecified, except: |
df27fae1 | 44 | |
e7304fce | 45 | a1 Contains a function pointer to be registered with `atexit'. |
13906e12 | 46 | This is how the dynamic linker arranges to have DT_FINI |
df27fae1 UD |
47 | functions called for shared libraries that have been loaded |
48 | before this code runs. | |
49 | ||
50 | sp The stack contains the arguments and environment: | |
13906e12 | 51 | 0(sp) argc |
e7304fce | 52 | 4(sp) argv[0] |
df27fae1 | 53 | ... |
e7304fce UD |
54 | (4*argc)(sp) NULL |
55 | (4*(argc+1))(sp) envp[0] | |
df27fae1 UD |
56 | ... |
57 | NULL | |
58 | */ | |
27489557 | 59 | |
27489557 DG |
60 | /* Tag_ABI_align8_preserved: This code preserves 8-byte |
61 | alignment in any callee. */ | |
62 | .eabi_attribute 25, 1 | |
63 | /* Tag_ABI_align8_needed: This code may require 8-byte alignment from | |
64 | the caller. */ | |
65 | .eabi_attribute 24, 1 | |
27489557 | 66 | |
5631abde JM |
67 | #if defined(__thumb2__) |
68 | .thumb | |
69 | .syntax unified | |
70 | #endif | |
df27fae1 UD |
71 | |
72 | .text | |
73 | .globl _start | |
791746df | 74 | .type _start,#function |
df27fae1 | 75 | _start: |
f10eff58 DJ |
76 | /* Protect against unhandled exceptions. */ |
77 | .fnstart | |
856cb777 | 78 | /* Clear the frame pointer and link register since this is the outermost frame. */ |
df27fae1 | 79 | mov fp, #0 |
856cb777 | 80 | mov lr, #0 |
df27fae1 | 81 | |
e7304fce | 82 | /* Pop argc off the stack and save a pointer to argv */ |
55668624 | 83 | pop { a2 } |
e7304fce UD |
84 | mov a3, sp |
85 | ||
a16ce997 | 86 | /* Push stack limit */ |
55668624 | 87 | push { a3 } |
a16ce997 UD |
88 | |
89 | /* Push rtld_fini */ | |
55668624 | 90 | push { a1 } |
e7304fce | 91 | |
856cb777 DJ |
92 | #ifdef SHARED |
93 | ldr sl, .L_GOT | |
b5c2620b JB |
94 | adr a4, .L_GOT |
95 | add sl, sl, a4 | |
856cb777 DJ |
96 | |
97 | ldr ip, .L_GOT+4 /* __libc_csu_fini */ | |
98 | ldr ip, [sl, ip] | |
99 | ||
55668624 | 100 | push { ip } /* Push __libc_csu_fini */ |
856cb777 DJ |
101 | |
102 | ldr a4, .L_GOT+8 /* __libc_csu_init */ | |
103 | ldr a4, [sl, a4] | |
104 | ||
105 | ldr a1, .L_GOT+12 /* main */ | |
106 | ldr a1, [sl, a1] | |
107 | ||
108 | /* __libc_start_main (main, argc, argv, init, fini, rtld_fini, stack_end) */ | |
109 | /* Let the libc call main and exit with its return code. */ | |
110 | bl __libc_start_main(PLT) | |
111 | #else | |
112 | /* Fetch address of __libc_csu_fini */ | |
113 | ldr ip, =__libc_csu_fini | |
114 | ||
115 | /* Push __libc_csu_fini */ | |
55668624 | 116 | push { ip } |
856cb777 | 117 | |
a16ce997 | 118 | /* Set up the other arguments in registers */ |
e7304fce | 119 | ldr a1, =main |
f8a26bed | 120 | ldr a4, =__libc_csu_init |
e7304fce | 121 | |
a16ce997 | 122 | /* __libc_start_main (main, argc, argv, init, fini, rtld_fini, stack_end) */ |
e7304fce UD |
123 | /* Let the libc call main and exit with its return code. */ |
124 | bl __libc_start_main | |
856cb777 | 125 | #endif |
a16ce997 | 126 | |
df27fae1 UD |
127 | /* should never get here....*/ |
128 | bl abort | |
129 | ||
856cb777 | 130 | #ifdef SHARED |
e5cd24d4 | 131 | .align 2 |
856cb777 | 132 | .L_GOT: |
b5c2620b | 133 | .word _GLOBAL_OFFSET_TABLE_ - .L_GOT |
856cb777 DJ |
134 | .word __libc_csu_fini(GOT) |
135 | .word __libc_csu_init(GOT) | |
136 | .word main(GOT) | |
137 | #endif | |
138 | ||
f10eff58 DJ |
139 | .cantunwind |
140 | .fnend | |
f10eff58 | 141 | |
df27fae1 UD |
142 | /* Define a symbol for the first piece of initialized data. */ |
143 | .data | |
144 | .globl __data_start | |
145 | __data_start: | |
146 | .long 0 | |
147 | .weak data_start | |
148 | data_start = __data_start |