Import sources from 2011-03-30 iso image

sys/src/libthread/exec.c

@@ -0,0 +1,80 @@
+#include <u.h>
+#include <libc.h>
+#include <thread.h>
+#include "threadimpl.h"
+
+#define PIPEMNT	"/mnt/temp"
+
+void
+procexec(Channel *pidc, char *prog, char *args[])
+{
+	int n;
+	Proc *p;
+	Thread *t;
+
+	_threaddebug(DBGEXEC, "procexec %s", prog);
+	/* must be only thread in proc */
+	p = _threadgetproc();
+	t = p->thread;
+	if(p->threads.head != t || p->threads.head->nextt != nil){
+		werrstr("not only thread in proc");
+	Bad:
+		if(pidc)
+			sendul(pidc, ~0);
+		return;
+	}
+
+	/*
+	 * We want procexec to behave like exec; if exec succeeds,
+	 * never return, and if it fails, return with errstr set.
+	 * Unfortunately, the exec happens in another proc since
+	 * we have to wait for the exec'ed process to finish.
+	 * To provide the semantics, we open a pipe with the 
+	 * write end close-on-exec and hand it to the proc that
+	 * is doing the exec.  If the exec succeeds, the pipe will
+	 * close so that our read below fails.  If the exec fails,
+	 * then the proc doing the exec sends the errstr down the
+	 * pipe to us.
+	 */
+	if(bind("#|", PIPEMNT, MREPL) < 0)
+		goto Bad;
+	if((p->exec.fd[0] = open(PIPEMNT "/data", OREAD)) < 0){
+		unmount(nil, PIPEMNT);
+		goto Bad;
+	}
+	if((p->exec.fd[1] = open(PIPEMNT "/data1", OWRITE|OCEXEC)) < 0){
+		close(p->exec.fd[0]);
+		unmount(nil, PIPEMNT);
+		goto Bad;
+	}
+	unmount(nil, PIPEMNT);
+
+	/* exec in parallel via the scheduler */
+	assert(p->needexec==0);
+	p->exec.prog = prog;
+	p->exec.args = args;
+	p->needexec = 1;
+	_sched();
+
+	close(p->exec.fd[1]);
+	if((n = read(p->exec.fd[0], p->exitstr, ERRMAX-1)) > 0){	/* exec failed */
+		p->exitstr[n] = '\0';
+		errstr(p->exitstr, ERRMAX);
+		close(p->exec.fd[0]);
+		goto Bad;
+	}
+	close(p->exec.fd[0]);
+
+	if(pidc)
+		sendul(pidc, t->ret);
+
+	/* wait for exec'ed program, then exit */
+	_schedexecwait();
+}
+
+void
+procexecl(Channel *pidc, char *f, ...)
+{
+	procexec(pidc, f, &f+1);
+}
+