1 #include <u.h>
2 #include <sys/wait.h>
3 #include <signal.h>
4 #include <libc.h>
5 #include "9proc.h"
6 #undef rfork
7 
8 int
9 p9rfork(int flags)
10 {
11 	int pid, status;
12 	int p[2];
13 	int n;
14 	char buf[128], *q;
15 
16 	_p9uproc(0);
17 	if((flags&(RFPROC|RFFDG|RFMEM)) == (RFPROC|RFFDG)){
18 		/* check other flags before we commit */
19 		flags &= ~(RFPROC|RFFDG);
20 		n = (flags & ~(RFNOTEG|RFNAMEG|RFNOWAIT));
21 		if(n){
22 			werrstr("unknown flags %08ux in rfork", n);
23 			return -1;
24 		}
25 		if(flags&RFNOWAIT){
26 			if(pipe(p) < 0)
27 				return -1;
28 		}
29 		pid = fork();
30 		if(pid == -1)
31 			return -1;
32 		if(flags&RFNOWAIT){
33 			flags &= ~RFNOWAIT;
34 			if(pid){
35 				/*
36 				 * Parent - wait for child to fork wait-free child.
37 				 * Then read pid from pipe.  Assume pipe buffer can absorb the write.
38 				 */
39 				close(p[1]);
40 				wait4(pid, &status, 0, 0);
41 				n = readn(p[0], buf, sizeof buf-1);
42 				close(p[0]);
43 				if(!WIFEXITED(status) || WEXITSTATUS(status)!=0 || n <= 0){
44 					werrstr("pipe dance failed in rfork");
45 					return -1;
46 				}
47 				buf[n] = 0;
48 				n = strtol(buf, &q, 0);
49 				if(*q != 0){
50 					werrstr("%s", q);
51 					return -1;
52 				}
53 				pid = n;
54 			}else{
55 				/*
56 				 * Child - fork a new child whose wait message can't 
57 				 * get back to the parent because we're going to exit!
58 				 */
59 				signal(SIGCHLD, SIG_IGN);
60 				close(p[0]);
61 				pid = fork();
62 				if(pid){
63 					/* Child parent - send status over pipe and exit. */
64 					if(pid > 0)
65 						fprint(p[1], "%d", pid);
66 					else
67 						fprint(p[1], " %r");
68 					close(p[1]);
69 					_exit(0);
70 				}else{
71 					/* Child child - close pipe. */
72 					close(p[1]);
73 				}
74 			}
75 		}
76 		_p9uproc(0);
77 		if(pid != 0)
78 			return pid;
79 	}
80 	if(flags&RFPROC){
81 		werrstr("cannot use rfork for shared memory -- use ffork");
82 		return -1;
83 	}
84 	if(flags&RFNAMEG){
85 		/* XXX set $NAMESPACE to a new directory */
86 		flags &= ~RFNAMEG;
87 	}
88 	if(flags&RFNOTEG){
89 		setpgid(0, getpid());
90 		flags &= ~RFNOTEG;
91 	}
92 	if(flags&RFNOWAIT){
93 		werrstr("cannot use RFNOWAIT without RFPROC");
94 		return -1;
95 	}
96 	if(flags){
97 		werrstr("unknown flags %08ux in rfork", flags);
98 		return -1;
99 	}
100 	return 0;
101 }