1 #include <u.h>
2 #include <sys/wait.h>
3 #include <signal.h>
4 #include <libc.h>
5 #undef rfork
6 
7 static void
8 nop(int x)
9 {
10 	USED(x);
11 }
12 
13 int
14 p9rfork(int flags)
15 {
16 	int pid, status;
17 	int p[2];
18 	int n;
19 	char buf[128], *q;
20 	extern char **environ;
21 
22 	if((flags&(RFPROC|RFFDG|RFMEM)) == (RFPROC|RFFDG)){
23 		/* check other flags before we commit */
24 		flags &= ~(RFPROC|RFFDG|RFENVG);
25 		n = (flags & ~(RFNOTEG|RFNAMEG|RFNOWAIT|RFCENVG));
26 		if(n){
27 			werrstr("unknown flags %08ux in rfork", n);
28 			return -1;
29 		}
30 		if(flags&RFNOWAIT){
31 			/*
32 			 * BUG - should put the signal handler back after we
33 			 * finish, but I just don't care.  If a program calls with
34 			 * NOWAIT once, they're not likely to want child notes
35 			 * after that.
36 			 */
37 			signal(SIGCHLD, nop);
38 			if(pipe(p) < 0)
39 				return -1;
40 		}
41 		pid = fork();
42 		if(pid == -1)
43 			return -1;
44 		if(flags&RFNOWAIT){
45 			flags &= ~RFNOWAIT;
46 			if(pid){
47 				/*
48 				 * Parent - wait for child to fork wait-free child.
49 				 * Then read pid from pipe.  Assume pipe buffer can absorb the write.
50 				 */
51 				close(p[1]);
52 				status = 0;
53 				if(wait4(pid, &status, 0, 0) < 0){
54 					werrstr("pipe dance - wait4 - %r");
55 					close(p[0]);
56 					return -1;
57 				}
58 				n = readn(p[0], buf, sizeof buf-1);
59 				close(p[0]);
60 				if(!WIFEXITED(status) || WEXITSTATUS(status)!=0 || n <= 0){
61 					if(!WIFEXITED(status))
62 						werrstr("pipe dance - !exited 0x%ux", status);
63 					else if(WEXITSTATUS(status) != 0)
64 						werrstr("pipe dance - non-zero status 0x%ux", status);
65 					else if(n < 0)
66 						werrstr("pipe dance - pipe read error - %r");
67 					else if(n == 0)
68 						werrstr("pipe dance - pipe read eof");
69 					else
70 						werrstr("pipe dance - unknown failure");
71 					return -1;
72 				}
73 				buf[n] = 0;
74 				if(buf[0] == 'x'){
75 					werrstr("%s", buf+2);
76 					return -1;
77 				}
78 				pid = strtol(buf, &q, 0);
79 			}else{
80 				/*
81 				 * Child - fork a new child whose wait message can't 
82 				 * get back to the parent because we're going to exit!
83 				 */
84 				signal(SIGCHLD, SIG_IGN);
85 				close(p[0]);
86 				pid = fork();
87 				if(pid){
88 					/* Child parent - send status over pipe and exit. */
89 					if(pid > 0)
90 						fprint(p[1], "%d", pid);
91 					else
92 						fprint(p[1], "x %r");
93 					close(p[1]);
94 					_exit(0);
95 				}else{
96 					/* Child child - close pipe. */
97 					close(p[1]);
98 				}
99 			}
100 		}
101 		if(pid != 0)
102 			return pid;
103 		if(flags&RFCENVG)
104 			if(environ)
105 				*environ = nil;
106 	}
107 	if(flags&RFPROC){
108 		werrstr("cannot use rfork for shared memory -- use libthread");
109 		return -1;
110 	}
111 	if(flags&RFNAMEG){
112 		/* XXX set $NAMESPACE to a new directory */
113 		flags &= ~RFNAMEG;
114 	}
115 	if(flags&RFNOTEG){
116 		setpgid(0, getpid());
117 		flags &= ~RFNOTEG;
118 	}
119 	if(flags&RFNOWAIT){
120 		werrstr("cannot use RFNOWAIT without RFPROC");
121 		return -1;
122 	}
123 	if(flags){
124 		werrstr("unknown flags %08ux in rfork", flags);
125 		return -1;
126 	}
127 	return 0;
128 }