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 		_threaddebug(DBGEXEC, "procexec bad %r");
20 		if(pidc)
21 			sendul(pidc, ~0);
22 		return;
23 	}
24 
25 	/*
26 	 * We want procexec to behave like exec; if exec succeeds,
27 	 * never return, and if it fails, return with errstr set.
28 	 * Unfortunately, the exec happens in another proc since
29 	 * we have to wait for the exec'ed process to finish.
30 	 * To provide the semantics, we open a pipe with the 
31 	 * write end close-on-exec and hand it to the proc that
32 	 * is doing the exec.  If the exec succeeds, the pipe will
33 	 * close so that our read below fails.  If the exec fails,
34 	 * then the proc doing the exec sends the errstr down the
35 	 * pipe to us.
36 	 */
37 	if(pipe(p->exec.fd) < 0)
38 		goto Bad;
39 	if(fcntl(p->exec.fd[0], F_SETFD, 1) < 0)
40 		goto Bad;
41 	if(fcntl(p->exec.fd[1], F_SETFD, 1) < 0)
42 		goto Bad;
43 
44 	/* exec in parallel via the scheduler */
45 	assert(p->needexec==0);
46 	p->exec.prog = prog;
47 	p->exec.args = args;
48 	p->needexec = 1;
49 	_sched();
50 
51 	close(p->exec.fd[1]);
52 	if((n = read(p->exec.fd[0], p->exitstr, ERRMAX-1)) > 0){	/* exec failed */
53 		p->exitstr[n] = '\0';
54 		errstr(p->exitstr, ERRMAX);
55 		close(p->exec.fd[0]);
56 		goto Bad;
57 	}
58 	close(p->exec.fd[0]);
59 
60 	if(pidc)
61 		sendul(pidc, t->ret);
62 
63 	_threaddebug(DBGEXEC, "procexec schedexecwait");
64 	/* wait for exec'ed program, then exit */
65 	_schedexecwait();
66 }
67 
68 void
69 procexecl(Channel *pidc, char *f, ...)
70 {
71 	procexec(pidc, f, &f+1);
72 }
73 
74 void
75 _schedexecwait(void)
76 {
77 	int pid;
78 	Channel *c;
79 	Proc *p;
80 	Thread *t;
81 	Waitmsg *w;
82 
83 	p = _threadgetproc();
84 	t = p->thread;
85 	pid = t->ret;
86 	_threaddebug(DBGEXEC, "_schedexecwait %d", t->ret);
87 
88 	for(;;){
89 		w = wait();
90 		if(w == nil)
91 			break;
92 		if(w->pid == pid)
93 			break;
94 		free(w);
95 	}
96 	if(w != nil){
97 		if((c = _threadwaitchan) != nil)
98 			sendp(c, w);
99 		else
100 			free(w);
101 	}
102 	threadexits("procexec");
103 }
104 
105 static void
106 efork(void *ve)
107 {
108 	char buf[ERRMAX];
109 	Execargs *e;
110 
111 	e = ve;
112 	_threaddebug(DBGEXEC, "_schedexec %s -- calling execv", e->prog);
113 	execv(e->prog, e->args);
114 	_threaddebug(DBGEXEC, "_schedexec failed: %r");
115 	rerrstr(buf, sizeof buf);
116 	if(buf[0]=='\0')
117 		strcpy(buf, "exec failed");
118 	write(e->fd[1], buf, strlen(buf));
119 	close(e->fd[1]);
120 	_exits(buf);
121 }
122 
123 int
124 _schedexec(Execargs *e)
125 {
126 	int pid;
127 
128 	pid = fork();
129 	if(pid == 0){
130 		efork(e);
131 		_exit(1);
132 	}
133 	return pid;
134 }