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d66e34cd | 1 | /* Startup code compliant to the ELF i386 ABI. |
581c785b | 2 | Copyright (C) 1995-2022 Free Software Foundation, Inc. |
19361cb7 | 3 | This file is part of the GNU C Library. |
d66e34cd | 4 | |
19361cb7 | 5 | The GNU C Library is free software; you can redistribute it and/or |
41bdb6e2 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. | |
d66e34cd | 9 | |
92c6ccd1 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 | ||
19361cb7 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 | |
41bdb6e2 | 30 | Lesser General Public License for more details. |
d66e34cd | 31 | |
41bdb6e2 | 32 | You should have received a copy of the GNU Lesser General Public |
59ba27a6 | 33 | License along with the GNU C Library; if not, see |
5a82c748 | 34 | <https://www.gnu.org/licenses/>. */ |
d66e34cd RM |
35 | |
36 | /* This is the canonical entry point, usually the first thing in the text | |
37 | segment. The SVR4/i386 ABI (pages 3-31, 3-32) says that when the entry | |
38 | point runs, most registers' values are unspecified, except for: | |
39 | ||
40 | %edx Contains a function pointer to be registered with `atexit'. | |
a4540639 | 41 | This is how the dynamic linker arranges to have DT_FINI |
d66e34cd RM |
42 | functions called for shared libraries that have been loaded |
43 | before this code runs. | |
44 | ||
45 | %esp The stack contains the arguments and environment: | |
a4540639 | 46 | 0(%esp) argc |
d66e34cd RM |
47 | 4(%esp) argv[0] |
48 | ... | |
49 | (4*argc)(%esp) NULL | |
50 | (4*(argc+1))(%esp) envp[0] | |
51 | ... | |
52 | NULL | |
53 | */ | |
54 | ||
5a274db4 L |
55 | #include <sysdep.h> |
56 | ||
57 | ENTRY (_start) | |
58 | /* Clearing frame pointer is insufficient, use CFI. */ | |
59 | cfi_undefined (eip) | |
d66e34cd RM |
60 | /* Clear the frame pointer. The ABI suggests this be done, to mark |
61 | the outermost frame obviously. */ | |
19361cb7 | 62 | xorl %ebp, %ebp |
d66e34cd | 63 | |
3db52d94 UD |
64 | /* Extract the arguments as encoded on the stack and set up |
65 | the arguments for `main': argc, argv. envp will be determined | |
66 | later in __libc_start_main. */ | |
d66e34cd | 67 | popl %esi /* Pop the argument count. */ |
3db52d94 | 68 | movl %esp, %ecx /* argv starts just at the current stack top.*/ |
19361cb7 | 69 | |
a4540639 AJ |
70 | /* Before pushing the arguments align the stack to a 16-byte |
71 | (SSE needs 16-byte alignment) boundary to avoid penalties from | |
72 | misaligned accesses. Thanks to Edward Seidl <seidl@janed.com> | |
73 | for pointing this out. */ | |
74 | andl $0xfffffff0, %esp | |
3f121ed3 UD |
75 | pushl %eax /* Push garbage because we allocate |
76 | 28 more bytes. */ | |
c0fb8a56 UD |
77 | |
78 | /* Provide the highest stack address to the user code (for stacks | |
79 | which grow downwards). */ | |
80 | pushl %esp | |
81 | ||
3db52d94 UD |
82 | pushl %edx /* Push address of the shared library |
83 | termination function. */ | |
19361cb7 | 84 | |
1e8e527d | 85 | #ifdef PIC |
bc4647a1 UD |
86 | /* Load PIC register. */ |
87 | call 1f | |
88 | addl $_GLOBAL_OFFSET_TABLE_, %ebx | |
89 | ||
035c012e FW |
90 | /* This used to be the addresses of .fini and .init. */ |
91 | pushl $0 | |
92 | pushl $0 | |
bc4647a1 UD |
93 | |
94 | pushl %ecx /* Push second argument: argv. */ | |
95 | pushl %esi /* Push first argument: argc. */ | |
96 | ||
1e8e527d | 97 | # ifdef SHARED |
2366713d | 98 | pushl main@GOT(%ebx) |
1e8e527d L |
99 | # else |
100 | /* Avoid relocation in static PIE since _start is called before | |
95577475 L |
101 | it is relocated. Don't use "leal main@GOTOFF(%ebx), %eax" |
102 | since main may be in a shared object. Linker will convert | |
103 | "movl main@GOT(%ebx), %eax" to "leal main@GOTOFF(%ebx), %eax" | |
104 | if main is defined locally. */ | |
105 | movl main@GOT(%ebx), %eax | |
1e8e527d L |
106 | pushl %eax |
107 | # endif | |
bc4647a1 UD |
108 | |
109 | /* Call the user's main function, and exit with its value. | |
110 | But let the libc call main. */ | |
2366713d | 111 | call __libc_start_main@PLT |
bc4647a1 | 112 | #else |
035c012e FW |
113 | /* This used to be the addresses of .fini and .init. */ |
114 | pushl $0 | |
115 | pushl $0 | |
3db52d94 UD |
116 | |
117 | pushl %ecx /* Push second argument: argv. */ | |
d66e34cd RM |
118 | pushl %esi /* Push first argument: argc. */ |
119 | ||
2366713d | 120 | pushl $main |
d66e34cd | 121 | |
7dea968e UD |
122 | /* Call the user's main function, and exit with its value. |
123 | But let the libc call main. */ | |
2366713d | 124 | call __libc_start_main |
bc4647a1 | 125 | #endif |
3db52d94 | 126 | |
19361cb7 | 127 | hlt /* Crash if somehow `exit' does return. */ |
273d56ce | 128 | |
1e8e527d | 129 | #ifdef PIC |
bc4647a1 UD |
130 | 1: movl (%esp), %ebx |
131 | ret | |
132 | #endif | |
5a274db4 | 133 | END (_start) |
bc4647a1 | 134 | |
dfd2257a UD |
135 | /* To fulfill the System V/i386 ABI we need this symbol. Yuck, it's so |
136 | meaningless since we don't support machines < 80386. */ | |
137 | .section .rodata | |
138 | .globl _fp_hw | |
25d0dd63 | 139 | _fp_hw: .long 3 |
dfd2257a | 140 | .size _fp_hw, 4 |
34912877 | 141 | .type _fp_hw,@object |
dfd2257a | 142 | |
273d56ce RM |
143 | /* Define a symbol for the first piece of initialized data. */ |
144 | .data | |
145 | .globl __data_start | |
146 | __data_start: | |
147 | .long 0 | |
7752137a RM |
148 | .weak data_start |
149 | data_start = __data_start |