1 /*- 2 * Copyright (c) 1982 The Regents of the University of California. 3 * All rights reserved. 4 * 5 * %sccs.include.redist.c% 6 */ 7 8 #ifndef lint 9 static char sccsid[] = "@(#)crt0.c 5.11 (Berkeley) 07/16/92"; 10 #endif /* not lint */ 11 12 /* 13 * C start up routine. 14 * Robert Henry, UCB, 20 Oct 81 15 * 16 * We make the following (true) assumptions: 17 * 1) when the kernel calls start, it does a jump to location 2, 18 * and thus avoids the register save mask. We are NOT called 19 * with a calls! see sys1.c:setregs(). 20 * 2) The only register variable that we can trust is sp, 21 * which points to the base of the kernel calling frame. 22 * Do NOT believe the documentation in exec(2) regarding the 23 * values of fp and ap. 24 */ 25 26 char **environ = (char **)0; 27 static int fd; 28 29 extern unsigned char etext; 30 extern unsigned char eprol asm ("eprol"); 31 extern start() asm("start"); 32 33 /* 34 * Two kluges: store sp at entry in environ, and 35 * install 16 bits of 0 at location 0 (a zero register save mask). 36 * These two hacks remove limits on the use of local 37 * and register variables in start(). 38 */ 39 asm(".text; .word 0; movl sp,_environ; jbr start+2"); 40 41 start() 42 { 43 struct kframe { 44 int kargc; 45 char *kargv[1]; /* size depends on kargc */ 46 char kargstr[1]; /* size varies */ 47 char kenvstr[1]; /* size varies */ 48 }; 49 register struct kframe *kfp; 50 register char **targv; 51 register char **argv; 52 extern int errno; 53 extern void _mcleanup(); 54 55 #ifdef lint 56 kfp = 0; 57 initcode = initcode = 0; 58 #else not lint 59 kfp = (struct kframe *) environ; 60 #endif not lint 61 for (argv = targv = &kfp->kargv[0]; *targv++; /* void */) 62 /* void */ ; 63 if (targv >= (char **)(*argv)) 64 --targv; 65 environ = targv; 66 asm("eprol:"); 67 68 #ifdef paranoid 69 /* 70 * The standard I/O library assumes that file descriptors 0, 1, and 2 71 * are open. If one of these descriptors is closed prior to the start 72 * of the process, I/O gets very confused. To avoid this problem, we 73 * insure that the first three file descriptors are open before calling 74 * main(). Normally this is undefined, as it adds two unnecessary 75 * system calls. 76 */ 77 do { 78 fd = open("/dev/null", 2); 79 } while (fd >= 0 && fd < 3); 80 close(fd); 81 #endif paranoid 82 83 #ifdef MCRT0 84 atexit(_mcleanup); 85 monstartup(&eprol, &etext); 86 #endif MCRT0 87 errno = 0; 88 exit(main(kfp->kargc, argv, environ)); 89 } 90 91 #ifdef CRT0 92 /* 93 * null moncontrol, just in case some routine is compiled for profiling 94 */ 95 moncontrol(val) 96 int val; 97 { 98 99 } 100 #endif CRT0 101