1/* Startup code compliant to the ELF m68k ABI.
2 Copyright (C) 1996-2026 Free Software Foundation, Inc.
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
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.
9
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
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.
31
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/>. */
35
36/* This is the canonical entry point, usually the first thing in the text
37 segment. The SVR4/m68k ABI says that when the entry point runs,
38 most registers' values are unspecified, except for:
39
40 %a1 Contains a function pointer to be registered with `atexit'.
41 This is how the dynamic linker arranges to have DT_FINI
42 functions called for shared libraries that have been loaded
43 before this code runs.
44
45 %sp The stack contains the arguments and environment:
46 0(%sp) argc
47 4(%sp) argv[0]
48 ...
49 (4*argc)(%sp) NULL
50 (4*(argc+1))(%sp) envp[0]
51 ...
52 NULL
53*/
54
55#include <sysdep.h>
56
57 .text
58 .globl _start
59 .type _start,@function
60_start:
61 /* Clear the frame pointer. The ABI suggests this be done, to mark
62 the outermost frame obviously. */
63 sub.l %fp, %fp
64
65 /* Extract the arguments as encoded on the stack and set up the
66 arguments for `main': argc, argv. envp will be determined
67 later in __libc_start_main. */
68 move.l (%sp)+, %d0 /* Pop the argument count. */
69 move.l %sp, %a0 /* The argument vector starts just at the
70 current stack top. */
71
72 /* Provide the highest stack address to the user code (for stacks
73 which grow downward). */
74 pea (%sp)
75
76 pea (%a1) /* Push address of the shared library
77 termination function. */
78
79 /* These used to be addresses of the .fini and .init entry points. */
80 clr.l -(%sp)
81 clr.l -(%sp)
82
83#ifdef PIC
84 /* Load PIC register. */
85 LOAD_GOT (%a5)
86
87 pea (%a0) /* Push second argument: argv. */
88 move.l %d0, -(%sp) /* Push first argument: argc. */
89
90 move.l main@GOT(%a5), -(%sp)
91
92 /* Call the user's main function, and exit with its value. But
93 let the libc call main. */
94 jbsr __libc_start_main@PLTPC
95#else
96
97 pea (%a0) /* Push second argument: argv. */
98 move.l %d0, -(%sp) /* Push first argument: argc. */
99
100 pea main
101
102 /* Call the user's main function, and exit with its value. But
103 let the libc call main. */
104 jbsr __libc_start_main
105#endif
106
107 illegal /* Crash if somehow `exit' does return. */
108
109/* Define a symbol for the first piece of initialized data. */
110 .data
111 .globl __data_start
112__data_start:
113 .long 0
114 .weak data_start
115 data_start = __data_start