1 /*- 2 * Copyright (c) 1982 The Regents of the University of California. 3 * All rights reserved. 4 * 5 * %sccs.include.proprietary.c% 6 */ 7 8 #if defined(LIBC_SCCS) && !defined(lint) 9 static char sccsid[] = "@(#)crt0.c 5.5 (Berkeley) 04/12/91"; 10 #endif /* LIBC_SCCS and 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 * 3) We can allocate as many register variables as we want, 25 * and don't have to save them for anybody. 26 * 4) Because of the ways that asm's work, we can't have 27 * any automatic variables allocated on the stack, because 28 * we must catch the value of sp before any automatics are 29 * allocated. 30 */ 31 32 char **environ = (char **)0; 33 static int fd; 34 35 asm("#define _start start"); 36 asm("#define _eprol eprol"); 37 extern unsigned char etext; 38 extern unsigned char eprol; 39 start() 40 { 41 struct kframe { 42 int kargc; 43 char *kargv[1]; /* size depends on kargc */ 44 char kargstr[1]; /* size varies */ 45 char kenvstr[1]; /* size varies */ 46 }; 47 /* 48 * ALL REGISTER VARIABLES!!! 49 */ 50 register int r11; /* needed for init */ 51 register struct kframe *kfp; /* r10 */ 52 register char **targv; 53 register char **argv; 54 extern int errno; 55 56 #ifdef lint 57 kfp = 0; 58 initcode = initcode = 0; 59 #else not lint 60 asm(" movl sp,r10"); /* catch it quick */ 61 #endif not lint 62 for (argv = targv = &kfp->kargv[0]; *targv++; /* void */) 63 /* void */ ; 64 if (targv >= (char **)(*argv)) 65 --targv; 66 environ = targv; 67 asm("eprol:"); 68 69 #ifdef paranoid 70 /* 71 * The standard I/O library assumes that file descriptors 0, 1, and 2 72 * are open. If one of these descriptors is closed prior to the start 73 * of the process, I/O gets very confused. To avoid this problem, we 74 * insure that the first three file descriptors are open before calling 75 * main(). Normally this is undefined, as it adds two unnecessary 76 * system calls. 77 */ 78 do { 79 fd = open("/dev/null", 2); 80 } while (fd >= 0 && fd < 3); 81 close(fd); 82 #endif paranoid 83 84 #ifdef MCRT0 85 monstartup(&eprol, &etext); 86 #endif MCRT0 87 errno = 0; 88 exit(main(kfp->kargc, argv, environ)); 89 } 90 asm("#undef _start"); 91 asm("#undef _eprol"); 92 93 #ifdef MCRT0 94 /*ARGSUSED*/ 95 exit(code) 96 register int code; /* r11 */ 97 { 98 monitor(0); 99 _cleanup(); 100 _exit(code); 101 } 102 #endif MCRT0 103 104 #ifdef CRT0 105 /* 106 * null mcount and moncontrol, 107 * just in case some routine is compiled for profiling 108 */ 109 moncontrol(val) 110 int val; 111 { 112 113 } 114 asm(" .globl mcount"); 115 asm("mcount: rsb"); 116 #endif CRT0 117