crt.h

 1/* SPDX-License-Identifier: LGPL-2.1 OR MIT */
 2/*
 3 * C Run Time support for NOLIBC
 4 * Copyright (C) 2023 Zhangjin Wu <falcon@tinylab.org>
 5 */
 6
 7#ifndef _NOLIBC_CRT_H
 8#define _NOLIBC_CRT_H
 9
10#ifndef NOLIBC_NO_RUNTIME
11
12#include "compiler.h"
13
14char **environ __attribute__((weak));
15const unsigned long *_auxv __attribute__((weak));
16
17void _start(void);
18static void __stack_chk_init(void);
19static void exit(int);
20
21extern void (*const __preinit_array_start[])(int, char **, char**) __attribute__((weak));
22extern void (*const __preinit_array_end[])(int, char **, char**) __attribute__((weak));
23
24extern void (*const __init_array_start[])(int, char **, char**) __attribute__((weak));
25extern void (*const __init_array_end[])(int, char **, char**) __attribute__((weak));
26
27extern void (*const __fini_array_start[])(void) __attribute__((weak));
28extern void (*const __fini_array_end[])(void) __attribute__((weak));
29
30void _start_c(long *sp);
31__attribute__((weak,used))
32#if __nolibc_has_feature(undefined_behavior_sanitizer)
33	__attribute__((no_sanitize("function")))
34#endif
35void _start_c(long *sp)
36{
37	long argc;
38	char **argv;
39	char **envp;
40	int exitcode;
41	void (* const *ctor_func)(int, char **, char **);
42	void (* const *dtor_func)(void);
43	const unsigned long *auxv;
44	/* silence potential warning: conflicting types for 'main' */
45	int _nolibc_main(int, char **, char **) __asm__ ("main");
46
47	/* initialize stack protector */
48	__stack_chk_init();
49
50	/*
51	 * sp  :    argc          <-- argument count, required by main()
52	 * argv:    argv[0]       <-- argument vector, required by main()
53	 *          argv[1]
54	 *          ...
55	 *          argv[argc-1]
56	 *          null
57	 * environ: environ[0]    <-- environment variables, required by main() and getenv()
58	 *          environ[1]
59	 *          ...
60	 *          null
61	 * _auxv:   _auxv[0]      <-- auxiliary vector, required by getauxval()
62	 *          _auxv[1]
63	 *          ...
64	 *          null
65	 */
66
67	/* assign argc and argv */
68	argc = *sp;
69	argv = (void *)(sp + 1);
70
71	/* find environ */
72	environ = envp = argv + argc + 1;
73
74	/* find _auxv */
75	for (auxv = (void *)envp; *auxv++;)
76		;
77	_auxv = auxv;
78
79	for (ctor_func = __preinit_array_start; ctor_func < __preinit_array_end; ctor_func++)
80		(*ctor_func)(argc, argv, envp);
81	for (ctor_func = __init_array_start; ctor_func < __init_array_end; ctor_func++)
82		(*ctor_func)(argc, argv, envp);
83
84	/* go to application */
85	exitcode = _nolibc_main(argc, argv, envp);
86
87	for (dtor_func = __fini_array_end; dtor_func > __fini_array_start;)
88		(*--dtor_func)();
89
90	exit(exitcode);
91}
92
93#endif /* NOLIBC_NO_RUNTIME */
94#endif /* _NOLIBC_CRT_H */