1 #include <fcntl.h>
2 #include <unistd.h>
3 #include "threadimpl.h"
4 
5 void
6 procexec(Channel *pidc, char *prog, char *args[])
7 {
8 	int n;
9 	Proc *p;
10 	Thread *t;
11 
12 	_threaddebug(DBGEXEC, "procexec %s", prog);
13 	/* must be only thread in proc */
14 	p = _threadgetproc();
15 	t = p->thread;
16 	if(p->threads.head != t || p->threads.head->nextt != nil){
17 		werrstr("not only thread in proc");
18 	Bad:
19 		if(pidc)
20 			sendul(pidc, ~0);
21 		return;
22 	}
23 
24 	/*
25 	 * We want procexec to behave like exec; if exec succeeds,
26 	 * never return, and if it fails, return with errstr set.
27 	 * Unfortunately, the exec happens in another proc since
28 	 * we have to wait for the exec'ed process to finish.
29 	 * To provide the semantics, we open a pipe with the 
30 	 * write end close-on-exec and hand it to the proc that
31 	 * is doing the exec.  If the exec succeeds, the pipe will
32 	 * close so that our read below fails.  If the exec fails,
33 	 * then the proc doing the exec sends the errstr down the
34 	 * pipe to us.
35 	 */
36 	if(pipe(p->exec.fd) < 0)
37 		goto Bad;
38 	if(fcntl(p->exec.fd[1], F_SETFD, 1) < 0)
39 		goto Bad;
40 
41 	/* exec in parallel via the scheduler */
42 	assert(p->needexec==0);
43 	p->exec.prog = prog;
44 	p->exec.args = args;
45 	p->needexec = 1;
46 	_sched();
47 
48 	close(p->exec.fd[1]);
49 	if((n = read(p->exec.fd[0], p->exitstr, ERRMAX-1)) > 0){	/* exec failed */
50 		p->exitstr[n] = '\0';
51 		errstr(p->exitstr, ERRMAX);
52 		close(p->exec.fd[0]);
53 		goto Bad;
54 	}
55 	close(p->exec.fd[0]);
56 
57 	if(pidc)
58 		sendul(pidc, t->ret);
59 
60 	/* wait for exec'ed program, then exit */
61 	_schedexecwait();
62 }
63 
64 void
65 procexecl(Channel *pidc, char *f, ...)
66 {
67 	procexec(pidc, f, &f+1);
68 }
69 
70 void
71 _schedexecwait(void)
72 {
73 	int pid;
74 	Channel *c;
75 	Proc *p;
76 	Thread *t;
77 	Waitmsg *w;
78 
79 	p = _threadgetproc();
80 	t = p->thread;
81 	pid = t->ret;
82 	_threaddebug(DBGEXEC, "_schedexecwait %d", t->ret);
83 
84 	for(;;){
85 		w = wait();
86 		if(w == nil)
87 			break;
88 		if(w->pid == pid)
89 			break;
90 		free(w);
91 	}
92 	if(w != nil){
93 		if((c = _threadwaitchan) != nil)
94 			sendp(c, w);
95 		else
96 			free(w);
97 	}
98 	threadexits("procexec");
99 }
100 
101 static void
102 efork(void *ve)
103 {
104 	char buf[ERRMAX];
105 	Execargs *e;
106 
107 	e = ve;
108 	_threaddebug(DBGEXEC, "_schedexec %s", e->prog);
109 	close(e->fd[0]);
110 	execv(e->prog, e->args);
111 	_threaddebug(DBGEXEC, "_schedexec failed: %r");
112 	rerrstr(buf, sizeof buf);
113 	if(buf[0]=='\0')
114 		strcpy(buf, "exec failed");
115 	write(e->fd[1], buf, strlen(buf));
116 	close(e->fd[1]);
117 	_exits(buf);
118 }
119 
120 int
121 _schedexec(Execargs *e)
122 {
123 	return ffork(RFFDG|RFPROC|RFMEM, efork, e);
124 }