tools/include/nolibc/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 char **environ __attribute__((weak));
  11 const unsigned long *_auxv __attribute__((weak));
  12
  13 static void __stack_chk_init(void);
  14 static void exit(int);
  15
  16 extern void (*const __preinit_array_start[])(int, char **, char**) __attribute__((weak));
  17 extern void (*const __preinit_array_end[])(int, char **, char**) __attribute__((weak));
  18
  19 extern void (*const __init_array_start[])(int, char **, char**) __attribute__((weak));
  20 extern void (*const __init_array_end[])(int, char **, char**) __attribute__((weak));
  21
  22 extern void (*const __fini_array_start[])(void) __attribute__((weak));
  23 extern void (*const __fini_array_end[])(void) __attribute__((weak));
  24
  25 __attribute__((weak,used))
  26 void _start_c(long *sp)
  27 {
  28         long argc;
  29         char **argv;
  30         char **envp;
  31         int exitcode;
  32         void (* const *ctor_func)(int, char **, char **);
  33         void (* const *dtor_func)(void);
  34         const unsigned long *auxv;
  35         /* silence potential warning: conflicting types for 'main' */
  36         int _nolibc_main(int, char **, char **) __asm__ ("main");
  37
  38         /* initialize stack protector */
  39         __stack_chk_init();
  40
  41         /*
  42          * sp  :    argc          <-- argument count, required by main()
  43          * argv:    argv[0]       <-- argument vector, required by main()
  44          *          argv[1]
  45          *          ...
  46          *          argv[argc-1]
  47          *          null
  48          * environ: environ[0]    <-- environment variables, required by main() and getenv()
  49          *          environ[1]
  50          *          ...
  51          *          null
  52          * _auxv:   _auxv[0]      <-- auxiliary vector, required by getauxval()
  53          *          _auxv[1]
  54          *          ...
  55          *          null
  56          */
  57
  58         /* assign argc and argv */
  59         argc = *sp;
  60         argv = (void *)(sp + 1);
  61
  62         /* find environ */
  63         environ = envp = argv + argc + 1;
  64
  65         /* find _auxv */
  66         for (auxv = (void *)envp; *auxv++;)
  67                 ;
  68         _auxv = auxv;
  69
  70         for (ctor_func = __preinit_array_start; ctor_func < __preinit_array_end; ctor_func++)
  71                 (*ctor_func)(argc, argv, envp);
  72         for (ctor_func = __init_array_start; ctor_func < __init_array_end; ctor_func++)
  73                 (*ctor_func)(argc, argv, envp);
  74
  75         /* go to application */
  76         exitcode = _nolibc_main(argc, argv, envp);
  77
  78         for (dtor_func = __fini_array_end; dtor_func > __fini_array_start;)
  79                 (*--dtor_func)();
  80
  81         exit(exitcode);
  82 }
  83
  84 #endif /* _NOLIBC_CRT_H */