#include	"dat.h"#include	"fns.h"#include	"error.h" extern	void	vstack(void*); /* * all this is for the benefit of devcmd. * i hope it's grateful. */ typedef struct Targ Targ;struct Targ{	int	fd[3];	/* standard input, output and error */	int	wfd;	int*	spin;	char**	args;	char*	dir;	int	pid;	int	nice;}; /* * called by vstack once it has moved to * the unshared stack in the new process. */voidexectramp(Targ *t){	int *fd, i, nfd;	char filename[128], err[ERRMAX], status[2*ERRMAX]; 	t->pid = getpid();	*t->spin = 0;	/* allow parent to proceed: can't just rendezvous: see below */	fd = t->fd; 	snprint(filename, sizeof(filename), "#d/%d", t->wfd);	t->wfd = open(filename, OWRITE|OCEXEC);	/* if it failed, we'll manage */ 	nfd = MAXNFD;	/* TO DO: should read from /fd */	for(i = 0; i < nfd; i++)		if(i != fd[0] && i != fd[1] && i != fd[2] && i != t->wfd)			close(i); 	if(fd[0] != 0){		dup(fd[0], 0);		close(fd[0]);	}	if(fd[1] != 1){		dup(fd[1], 1);		close(fd[1]);	}	if(fd[2] != 2){		dup(fd[2], 2);		close(fd[2]);	} 	if(t->dir != nil && chdir(t->dir) < 0){		if(t->wfd > 0)			fprint(t->wfd, "chdir: %s: %r", t->dir);		_exits("bad dir");	}	if(t->nice)		oslopri(); 	exec(t->args[0], t->args);	err[0] = 0;	errstr(err, sizeof(err));	if(t->args[0][0] != '/' && t->args[0][0] != '#' &&	   strncmp(t->args[0], "../", 3) != 0 && strncmp(t->args[0], "./", 2) != 0 &&	   strlen(t->args[0])+5 < sizeof(filename)){		snprint(filename, sizeof(filename), "/bin/%s", t->args[0]);		exec(filename, t->args);		errstr(err, sizeof(err));	}	snprint(status, sizeof(status), "%s: can't exec: %s", t->args[0], err);	if(t->wfd > 0)		write(t->wfd, status, strlen(status));	_exits(status);} void*oscmd(char **args, int nice, char *dir, int *fd){	Targ *t;	int spin, *spinptr, fd0[2], fd1[2], fd2[2], wfd[2], n;	Dir *d; 	up->genbuf[0] = 0;	t = mallocz(sizeof(*t), 1);	if(t == nil)		return nil;	t->args = args;	t->dir = dir;	t->nice = nice;	fd0[0] = fd0[1] = -1;	fd1[0] = fd1[1] = -1;	fd2[0] = fd2[1] = -1;	wfd[0] = wfd[1] = -1;	if(dir != nil){		d = dirstat(dir);		if(d == nil)			goto Error;		free(d);	}	if(pipe(fd0) < 0 || pipe(fd1) < 0 || pipe(fd2) < 0 || pipe(wfd) < 0)		goto Error; 	spinptr = &spin;	spin = 1; 	t->fd[0] = fd0[0];	t->fd[1] = fd1[1];	t->fd[2] = fd2[1];	t->wfd = wfd[1];	t->spin = spinptr;	switch(rfork(RFPROC|RFMEM|RFREND|RFNOTEG|RFFDG|RFNAMEG|RFENVG)) {	case -1:		goto Error;	case 0:		/* if child returns first from rfork, its call to vstack replaces ... */		vstack(t);		/* ... parent's return address from rfork and parent returns here */	default:		/* if parent returns first from rfork, it comes here */		/* can't call anything: on shared stack until child releases spin in exectramp */		while(*spinptr)			;		break;	} 	close(fd0[0]);	close(fd1[1]);	close(fd2[1]);	close(wfd[1]); 	n = read(wfd[0], up->genbuf, sizeof(up->genbuf)-1);	close(wfd[0]);	if(n > 0){		close(fd0[1]);		close(fd1[0]);		close(fd2[0]);		up->genbuf[n] = 0;		errstr(up->genbuf, sizeof(up->genbuf));		free(t);		return nil;	} 	fd[0] = fd0[1];	fd[1] = fd1[0];	fd[2] = fd2[0];	return t; Error:	errstr(up->genbuf, sizeof(up->genbuf));	/* save the message before close */	close(fd0[0]);	close(fd0[1]);	close(fd1[0]);	close(fd1[1]);	close(fd2[0]);	close(fd2[1]);	close(wfd[0]);	close(wfd[1]);	free(t);	errstr(up->genbuf, sizeof(up->genbuf));	return nil;} intoscmdkill(void *a){	Targ *t = a; 	return postnote(PNGROUP, t->pid, "kill");} intoscmdwait(void*, char *buf, int n){	return await(buf, n);} voidoscmdfree(void *a){	free(a);}