1 /*-
2 * Copyright (c) 1982, 1993
3 * The Regents of the University of California. All rights reserved.
4 *
5 * %sccs.include.redist.c%
6 */
7
8 #ifndef lint
9 static char sccsid[] = "@(#)crt0.c 8.1 (Berkeley) 06/01/93";
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 #include <stddef.h>
27 #include <stdlib.h>
28 #include <string.h>
29
30 char **environ = (char **)0;
31 static char empty[1];
32 char *__progname = empty;
33 static int fd;
34
35 extern unsigned char etext;
36 extern unsigned char eprol asm ("eprol");
37 extern start() asm("start");
38
39 /*
40 * Two kluges: store sp at entry in environ, and
41 * install 16 bits of 0 at location 0 (a zero register save mask).
42 * These two hacks remove limits on the use of local
43 * and register variables in start().
44 */
45 asm(".text; .word 0; movl sp,_environ; jbr start+2");
46
start()47 start()
48 {
49 struct kframe {
50 int kargc;
51 char *kargv[1]; /* size depends on kargc */
52 char kargstr[1]; /* size varies */
53 char kenvstr[1]; /* size varies */
54 };
55 register struct kframe *kfp;
56 register char **targv;
57 register char **argv;
58 extern int errno;
59 extern void _mcleanup();
60
61 #ifdef lint
62 kfp = 0;
63 initcode = initcode = 0;
64 #else
65 kfp = (struct kframe *) environ;
66 #endif
67 for (argv = targv = &kfp->kargv[0]; *targv++; /* void */)
68 /* void */ ;
69 if (targv >= (char **)(*argv))
70 --targv;
71 environ = targv;
72 asm("eprol:");
73
74 #ifdef paranoid
75 /*
76 * The standard I/O library assumes that file descriptors 0, 1, and 2
77 * are open. If one of these descriptors is closed prior to the start
78 * of the process, I/O gets very confused. To avoid this problem, we
79 * insure that the first three file descriptors are open before calling
80 * main(). Normally this is undefined, as it adds two unnecessary
81 * system calls.
82 */
83 do {
84 fd = open("/dev/null", 2);
85 } while (fd >= 0 && fd < 3);
86 close(fd);
87 #endif
88
89 #ifdef MCRT0
90 atexit(_mcleanup);
91 monstartup(&eprol, &etext);
92 #endif
93 errno = 0;
94 if (argv[0])
95 if ((__progname = strrchr(argv[0], '/')) == NULL)
96 __progname = argv[0];
97 else
98 ++__progname;
99 exit(main(kfp->kargc, argv, environ));
100 }
101
102 #ifdef CRT0
103 /*
104 * null moncontrol, just in case some routine is compiled for profiling
105 */
moncontrol(val)106 moncontrol(val)
107 int val;
108 {
109
110 }
111 #endif
112