sysdeps/unix/sparc/start.c

   1 /* Copyright (C) 1991,92,93,94,95,96,97,2004 Free Software Foundation, Inc.
   2    This file is part of the GNU C Library.
   3
   4    The GNU C Library is free software; you can redistribute it and/or
   5    modify it under the terms of the GNU Lesser General Public
   6    License as published by the Free Software Foundation; either
   7    version 2.1 of the License, or (at your option) any later version.
   8
   9    In addition to the permissions in the GNU Lesser General Public
  10    License, the Free Software Foundation gives you unlimited
  11    permission to link the compiled version of this file with other
  12    programs, and to distribute those programs without any restriction
  13    coming from the use of this file. (The GNU Lesser General Public
  14    License restrictions do apply in other respects; for example, they
  15    cover modification of the file, and distribution when not linked
  16    into another program.)
  17
  18    Note that people who make modified versions of this file are not
  19    obligated to grant this special exception for their modified
  20    versions; it is their choice whether to do so. The GNU Lesser
  21    General Public License gives permission to release a modified
  22    version without this exception; this exception also makes it
  23    possible to release a modified version which carries forward this
  24    exception.
  25
  26    The GNU C Library is distributed in the hope that it will be useful,
  27    but WITHOUT ANY WARRANTY; without even the implied warranty of
  28    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  29    Lesser General Public License for more details.
  30
  31    You should have received a copy of the GNU Lesser General Public
  32    License along with the GNU C Library; if not, write to the Free
  33    Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA
  34    02111-1307 USA.  */
  35
  36 #include <errno.h>
  37 #include <stdlib.h>
  38 #include <unistd.h>
  39 #include <fcntl.h>
  40
  41 #ifndef NO_SHLIB
  42 #include <sys/exec.h>
  43 #include <sys/types.h>
  44 #include <sys/mman.h>
  45 #include <link.h>
  46 #include <syscall.h>
  47 #endif
  48
  49 #if !defined (__GNUC__) || __GNUC__ < 2
  50   #error This file uses GNU C extensions; you must compile with GCC version 2.
  51 #endif
  52
  53 /* The first piece of initialized data.  */
  54 int __data_start = 0;
  55 #ifdef HAVE_WEAK_SYMBOLS
  56 weak_alias (__data_start, data_start)
  57 #endif
  58
  59 extern void __libc_init (int argc, char **argv, char **envp) __THROW;
  60 extern int main (int argc, char **argv, char **envp) __THROW;
  61
  62 register long int sp asm("%sp"), fp asm("%fp");
  63
  64 #ifndef NO_SHLIB
  65 static void init_shlib (void) __THROW;
  66 #endif
  67
  68 #ifndef NO_EXPLICIT_START
  69 /* Declare _start with an explicit assembly symbol name of `start'
  70    (note no leading underscore).  This is the name Sun's crt0.o uses,
  71    and programs are often linked with `ld -e start'.  */
  72 void _start (void) asm ("start");
  73 #endif
  74
  75 void
  76 _start (void)
  77 {
  78   /* It is important that these be declared `register'.
  79      Otherwise, when compiled without optimization, they are put on the
  80      stack, which loses completely after we zero the FP.  */
  81   register int argc;
  82   register char **argv, **envp;
  83
  84   /* Unwind the frame built when we entered the function.  */
  85   asm("restore");
  86
  87   /* And clear the frame pointer.  */
  88   fp = 0;
  89
  90   /* The argument info starts after one register
  91      window (64 bytes) past the SP.  */
  92   argc = ((int *) sp)[16];
  93   argv = (char **) &((int *) sp)[17];
  94   envp = &argv[argc + 1];
  95   __environ = envp;
  96
  97 #ifndef NO_SHLIB
  98   init_shlib ();
  99 #endif
 100
 101   /* Allocate 24 bytes of stack space for the register save area.  */
 102   sp -= 24;
 103   __libc_init (argc, argv, envp);
 104
 105   exit (main (argc, argv, envp));
 106 }
 107 \f
 108 #ifndef NO_SHLIB
 109
 110 /* System calls for use by the bootstrap routine.
 111    These are defined here since the usual calls may be dynamically linked.  */
 112
 113 int syscall (int sysno, ...) asm ("init_syscall");
 114 asm ("init_syscall:\n"
 115      "  clr %g1\n"
 116      "  ta 0\n"
 117      "  bcc 1f\n"
 118      "  sethi %hi(_errno), %g1\n"
 119      "  st %o0, [%g1 + %lo(_errno)]\n"
 120      "  sub %g0, 1, %o0\n"
 121      "1:retl\n"
 122      "  nop");
 123
 124 static void
 125 init_shlib ()
 126 {
 127   extern struct link_dynamic _DYNAMIC;
 128   int so, zf;
 129   caddr_t somap;
 130   caddr_t sodmap;
 131   caddr_t sobssmap;
 132   void (*ldstart) (int, int);
 133   struct exec soexec;
 134   struct
 135     {
 136       caddr_t crt_ba;
 137       int crt_dzfd;
 138       int crt_ldfd;
 139       struct link_dynamic *crt_dp;
 140       char **crt_ep;
 141       caddr_t crt_bp;
 142     } soarg;
 143
 144   /* If not dynamically linked, do nothing.  */
 145   if (&_DYNAMIC == 0)
 146     return;
 147
 148   /* Map in the dynamic linker.  */
 149   so = syscall (SYS_open, "/usr/lib/ld.so", O_RDONLY);
 150   if (syscall (SYS_read, so, &soexec, sizeof (soexec)) != sizeof (soexec)
 151       || soexec.a_magic != ZMAGIC)
 152     {
 153       static const char emsg[] = "crt0: no /usr/lib/ld.so\n";
 154
 155       syscall (SYS_write, 2, emsg, sizeof (emsg) - 1);
 156       syscall (SYS_exit, 127);
 157     }
 158   somap = (caddr_t) syscall (SYS_mmap, 0,
 159                              soexec.a_text + soexec.a_data + soexec.a_bss,
 160                              PROT_READ | PROT_EXEC, _MAP_NEW | MAP_PRIVATE,
 161                              so, 0);
 162   sodmap = (caddr_t) syscall (SYS_mmap, somap + soexec.a_text, soexec.a_data,
 163                               PROT_READ | PROT_WRITE | PROT_EXEC,
 164                               _MAP_NEW | MAP_FIXED | MAP_PRIVATE,
 165                               so, soexec.a_text);
 166   zf = syscall (SYS_open, "/dev/zero", O_RDONLY);
 167   if (soexec.a_bss != 0)
 168     sobssmap = (caddr_t) syscall (SYS_mmap,
 169                                   somap + soexec.a_text + soexec.a_data,
 170                                   soexec.a_bss,
 171                                   PROT_READ | PROT_WRITE | PROT_EXEC,
 172                                   _MAP_NEW | MAP_FIXED | MAP_PRIVATE,
 173                                   zf, 0);
 174
 175   /* Call the entry point of the dynamic linker.  */
 176   soarg.crt_ba = somap;
 177   soarg.crt_dzfd = zf;
 178   soarg.crt_ldfd = so;
 179   soarg.crt_dp = &_DYNAMIC;
 180   soarg.crt_ep = __environ;
 181   soarg.crt_bp = (caddr_t) &&retaddr;
 182
 183   ldstart = (__typeof (ldstart)) (somap + soexec.a_entry);
 184   (*ldstart) (1, (char *) &soarg - (char *) sp);
 185
 186  retaddr:
 187 }
 188
 189 #endif