1 /*-
2 * Copyright (c) 1991, 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 * 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 #include <stddef.h>
33 #include <stdlib.h>
34 #include <string.h>
35
36 char **environ = (char **)0;
37 static char empty[1];
38 char *__progname = empty;
39 static int fd;
40
41 extern unsigned char etext;
42 extern unsigned char eprol asm ("eprol");
43 extern start() asm("start");
44
45 asm(".text; orb #0,d0"); /* 32 bits of zero at location 0 */
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 /*
56 * ALL REGISTER VARIABLES!!!
57 */
58 register struct kframe *kfp; /* r10 */
59 register char **targv;
60 register char **argv;
61 extern int errno;
62 extern void _mcleanup();
63
64 #ifdef lint
65 kfp = 0;
66 initcode = initcode = 0;
67 #else
68 asm("lea a6@(4),%0" : "=r" (kfp)); /* catch it quick */
69 #endif
70 for (argv = targv = &kfp->kargv[0]; *targv++; /* void */)
71 /* void */ ;
72 if (targv >= (char **)(*argv))
73 --targv;
74 environ = targv;
75 asm("eprol:");
76
77 #ifdef paranoid
78 /*
79 * The standard I/O library assumes that file descriptors 0, 1, and 2
80 * are open. If one of these descriptors is closed prior to the start
81 * of the process, I/O gets very confused. To avoid this problem, we
82 * insure that the first three file descriptors are open before calling
83 * main(). Normally this is undefined, as it adds two unnecessary
84 * system calls.
85 */
86 do {
87 fd = open("/dev/null", 2);
88 } while (fd >= 0 && fd < 3);
89 close(fd);
90 #endif
91
92 #ifdef MCRT0
93 atexit(_mcleanup);
94 monstartup(&eprol, &etext);
95 #endif
96 errno = 0;
97 if (argv[0])
98 if ((__progname = strrchr(argv[0], '/')) == NULL)
99 __progname = argv[0];
100 else
101 ++__progname;
102 exit(main(kfp->kargc, argv, environ));
103 }
104
105 #ifdef CRT0
106 /*
107 * null moncontrol, just in case some routine is compiled for profiling
108 */
moncontrol(val)109 moncontrol(val)
110 int val;
111 {
112
113 }
114 #endif
115