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 	struct sigaction oldchld;
22 
23 	memset(&oldchld, 0, sizeof oldchld);
24 
25 	if((flags&(RFPROC|RFFDG|RFMEM)) == (RFPROC|RFFDG)){
26 		/* check other flags before we commit */
27 		flags &= ~(RFPROC|RFFDG|RFENVG);
28 		n = (flags & ~(RFNOTEG|RFNAMEG|RFNOWAIT|RFCENVG));
29 		if(n){
30 			werrstr("unknown flags %08ux in rfork", n);
31 			return -1;
32 		}
33 		if(flags&RFNOWAIT){
34 			sigaction(SIGCHLD, nil, &oldchld);
35 			signal(SIGCHLD, nop);
36 			if(pipe(p) < 0)
37 				return -1;
38 		}
39 		pid = fork();
40 		if(pid == -1)
41 			return -1;
42 		if(flags&RFNOWAIT){
43 			flags &= ~RFNOWAIT;
44 			if(pid){
45 				/*
46 				 * Parent - wait for child to fork wait-free child.
47 				 * Then read pid from pipe.  Assume pipe buffer can absorb the write.
48 				 */
49 				close(p[1]);
50 				status = 0;
51 				if(wait4(pid, &status, 0, 0) < 0){
52 					werrstr("pipe dance - wait4 - %r");
53 					close(p[0]);
54 					return -1;
55 				}
56 				n = readn(p[0], buf, sizeof buf-1);
57 				close(p[0]);
58 				if(!WIFEXITED(status) || WEXITSTATUS(status)!=0 || n <= 0){
59 					if(!WIFEXITED(status))
60 						werrstr("pipe dance - !exited 0x%ux", status);
61 					else if(WEXITSTATUS(status) != 0)
62 						werrstr("pipe dance - non-zero status 0x%ux", status);
63 					else if(n < 0)
64 						werrstr("pipe dance - pipe read error - %r");
65 					else if(n == 0)
66 						werrstr("pipe dance - pipe read eof");
67 					else
68 						werrstr("pipe dance - unknown failure");
69 					return -1;
70 				}
71 				buf[n] = 0;
72 				if(buf[0] == 'x'){
73 					werrstr("%s", buf+2);
74 					return -1;
75 				}
76 				pid = strtol(buf, &q, 0);
77 			}else{
78 				/*
79 				 * Child - fork a new child whose wait message can't
80 				 * get back to the parent because we're going to exit!
81 				 */
82 				signal(SIGCHLD, SIG_IGN);
83 				close(p[0]);
84 				pid = fork();
85 				if(pid){
86 					/* Child parent - send status over pipe and exit. */
87 					if(pid > 0)
88 						fprint(p[1], "%d", pid);
89 					else
90 						fprint(p[1], "x %r");
91 					close(p[1]);
92 					_exit(0);
93 				}else{
94 					/* Child child - close pipe. */
95 					close(p[1]);
96 				}
97 			}
98 			sigaction(SIGCHLD, &oldchld, nil);
99 		}
100 		if(pid != 0)
101 			return pid;
102 		if(flags&RFCENVG)
103 			if(environ)
104 				*environ = nil;
105 	}
106 	if(flags&RFPROC){
107 		werrstr("cannot use rfork for shared memory -- use libthread");
108 		return -1;
109 	}
110 	if(flags&RFNAMEG){
111 		/* XXX set $NAMESPACE to a new directory */
112 		flags &= ~RFNAMEG;
113 	}
114 	if(flags&RFNOTEG){
115 		setpgid(0, getpid());
116 		flags &= ~RFNOTEG;
117 	}
118 	if(flags&RFNOWAIT){
119 		werrstr("cannot use RFNOWAIT without RFPROC");
120 		return -1;
121 	}
122 	if(flags){
123 		werrstr("unknown flags %08ux in rfork", flags);
124 		return -1;
125 	}
126 	return 0;
127 }