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#include <u.h>

#include <libc.h>

#include <auth.h>

#include <fcall.h>

/*

 * Rather than reading /adm/users, which is a lot of work for

 * a toy program, we assume all groups have the form

 *	NNN:user:user:

 * meaning that each user is the leader of his own group.

 */

enum

{

	OPERM	= 0x3,		/* mask of all permission types in open mode */

	Nram	= 4096,

	Maxsize	= 768*1024*1024,

	Maxfdata	= 8192,

	Maxulong= (1ULL << 32) - 1,

};

typedef struct Fid Fid;

typedef struct Ram Ram;

struct Fid

{

	short	busy;

	short	open;

	short	rclose;

	int	fid;

	Fid	*next;

	char	*user;

	Ram	*ram;

};

struct Ram

{

	short	busy;

	short	open;

	long	parent;		/* index in Ram array */

	Qid	qid;

	long	perm;

	char	*name;

	ulong	atime;

	ulong	mtime;

	char	*user;

	char	*group;

	char	*muid;

	char	*data;

	long	ndata;

};

enum

{

	Pexec =		1,

	Pwrite = 	2,

	Pread = 	4,

	Pother = 	1,

	Pgroup = 	8,

	Powner =	64,

};

ulong	path;		/* incremented for each new file */

Fid	*fids;

Ram	ram[Nram];

int	nram;

int	mfd[2];

char	*user;

uchar	mdata[IOHDRSZ+Maxfdata];

uchar	rdata[Maxfdata];	/* buffer for data in reply */

uchar statbuf[STATMAX];

Fcall thdr;

Fcall	rhdr;

int	messagesize = sizeof mdata;

Fid *	newfid(int);

uint	ramstat(Ram*, uchar*, uint);

void	error(char*);

void	io(void);

void	*erealloc(void*, ulong);

void	*emalloc(ulong);

char	*estrdup(char*);

void	usage(void);

int	perm(Fid*, Ram*, int);

char	*rflush(Fid*), *rversion(Fid*), *rauth(Fid*),

	*rattach(Fid*), *rwalk(Fid*),

	*ropen(Fid*), *rcreate(Fid*),

	*rread(Fid*), *rwrite(Fid*), *rclunk(Fid*),

	*rremove(Fid*), *rstat(Fid*), *rwstat(Fid*);

int needfid[] = {

	[Tversion] 0,

	[Tflush] 0,

	[Tauth] 0,

	[Tattach] 0,

	[Twalk] 1,

	[Topen] 1,

	[Tcreate] 1,

	[Tread] 1,

	[Twrite] 1,

	[Tclunk] 1,

	[Tremove] 1,

	[Tstat] 1,

	[Twstat] 1,

};

char 	*(*fcalls[])(Fid*) = {

	[Tversion]	rversion,

	[Tflush]	rflush,

	[Tauth]	rauth,

	[Tattach]	rattach,

	[Twalk]		rwalk,

	[Topen]		ropen,

	[Tcreate]	rcreate,

	[Tread]		rread,

	[Twrite]	rwrite,

	[Tclunk]	rclunk,

	[Tremove]	rremove,

	[Tstat]		rstat,

	[Twstat]	rwstat,

};

char	Eperm[] =	"permission denied";

char	Enotdir[] =	"not a directory";

char	Enoauth[] =	"ramfs: authentication not required";

char	Enotexist[] =	"file does not exist";

char	Einuse[] =	"file in use";

char	Eexist[] =	"file exists";

char	Eisdir[] =	"file is a directory";

char	Enotowner[] =	"not owner";

char	Eisopen[] = 	"file already open for I/O";

char	Excl[] = 	"exclusive use file already open";

char	Ename[] = 	"illegal name";

char	Eversion[] =	"unknown 9P version";

char	Enotempty[] =	"directory not empty";

int debug;

int private;

static int memlim = 1;

void

notifyf(void *a, char *s)

{

	USED(a);

	if(strncmp(s, "interrupt", 9) == 0)

		noted(NCONT);

	noted(NDFLT);

}

void

main(int argc, char *argv[])

{

	Ram *r;

	char *defmnt, *service;

	int p[2];

	int fd;

	int stdio = 0;

	service = "ramfs";

	defmnt = "/tmp";

	ARGBEGIN{

	case 'i':

		defmnt = 0;

		stdio = 1;

		mfd[0] = 0;

		mfd[1] = 1;

		break;

	case 'm':

		defmnt = EARGF(usage());

		break;

	case 'p':

		private++;

		break;

	case 's':

		defmnt = 0;

		break;

	case 'u':

		memlim = 0;		/* unlimited memory consumption */

		break;

	case 'D':

		debug = 1;

		break;

	case 'S':

		defmnt = 0;

		service = EARGF(usage());

		break;

	default:

		usage();

	}ARGEND

	if(pipe(p) < 0)

		error("pipe failed");

	if(!stdio){

		mfd[0] = p[0];

		mfd[1] = p[0];

		if(defmnt == 0){

			char buf[64];

			snprint(buf, sizeof buf, "#s/%s", service);

			fd = create(buf, OWRITE|ORCLOSE, 0666);

			if(fd < 0)

				error("create failed");

			sprint(buf, "%d", p[1]);

			if(write(fd, buf, strlen(buf)) < 0)

				error("writing service file");

		}

	}

	user = getuser();

	notify(notifyf);

	nram = 1;

	r = &ram[0];

	r->busy = 1;

	r->data = 0;

	r->ndata = 0;

	r->perm = DMDIR | 0775;

	r->qid.type = QTDIR;

	r->qid.path = 0LL;

	r->qid.vers = 0;

	r->parent = 0;

	r->user = user;

	r->group = user;

	r->muid = user;

	r->atime = time(0);

	r->mtime = r->atime;

	r->name = estrdup(".");

	if(debug) {

		fmtinstall('F', fcallfmt);

		fmtinstall('M', dirmodefmt);

	}

	switch(rfork(RFFDG|RFPROC|RFNAMEG|RFNOTEG)){

	case -1:

		error("fork");

	case 0:

		close(p[1]);

		io();

		break;

	default:

		close(p[0]);	/* don't deadlock if child fails */

		if(defmnt && mount(p[1], -1, defmnt, MREPL|MCREATE, "") < 0)

			error("mount failed");

	}

	exits(0);

}

char*

rversion(Fid*)

{

	Fid *f;

	for(f = fids; f; f = f->next)

		if(f->busy)

			rclunk(f);

	if(thdr.msize > sizeof mdata)

		rhdr.msize = sizeof mdata;

	else

		rhdr.msize = thdr.msize;

	messagesize = rhdr.msize;

	if(strncmp(thdr.version, "9P2000", 6) != 0)

		return Eversion;

	rhdr.version = "9P2000";

	return 0;

}

char*

rauth(Fid*)

{

	return "ramfs: no authentication required";

}

char*

rflush(Fid *f)

{

	USED(f);

	return 0;

}

char*

rattach(Fid *f)

{

	/* no authentication! */

	f->busy = 1;

	f->rclose = 0;

	f->ram = &ram[0];

	rhdr.qid = f->ram->qid;

	if(thdr.uname[0])

		f->user = estrdup(thdr.uname);

	else

		f->user = "none";

	if(strcmp(user, "none") == 0)

		user = f->user;

	return 0;

}

char*

clone(Fid *f, Fid **nf)

{

	if(f->open)

		return Eisopen;

	if(f->ram->busy == 0)

		return Enotexist;

	*nf = newfid(thdr.newfid);

	(*nf)->busy = 1;

	(*nf)->open = 0;

	(*nf)->rclose = 0;

	(*nf)->ram = f->ram;

	(*nf)->user = f->user;	/* no ref count; the leakage is minor */

	return 0;

}

char*

rwalk(Fid *f)

{

	Ram *r, *fram;

	char *name;

	Ram *parent;

	Fid *nf;

	char *err;

	ulong t;

	int i;

	err = nil;

	nf = nil;

	rhdr.nwqid = 0;

	if(thdr.newfid != thdr.fid){

		err = clone(f, &nf);

		if(err)

			return err;

		f = nf;	/* walk the new fid */

	}

	fram = f->ram;

	if(thdr.nwname > 0){

		t = time(0);

		for(i=0; i<thdr.nwname && i<MAXWELEM; i++){

			if((fram->qid.type & QTDIR) == 0){

				err = Enotdir;

 				break;

			}

			if(fram->busy == 0){

				err = Enotexist;

				break;

			}

			fram->atime = t;

			name = thdr.wname[i];

			if(strcmp(name, ".") == 0){

    Found:

				rhdr.nwqid++;

				rhdr.wqid[i] = fram->qid;

				continue;

			}

			parent = &ram[fram->parent];

			if(!perm(f, parent, Pexec)){

				err = Eperm;

				break;

			}

			if(strcmp(name, "..") == 0){

				fram = parent;

				goto Found;

			}

			for(r=ram; r < &ram[nram]; r++)

				if(r->busy && r->parent==fram-ram && strcmp(name, r->name)==0){

					fram = r;

					goto Found;

				}

			break;

		}

		if(i==0 && err == nil)

			err = Enotexist;

	}

	if(nf != nil && (err!=nil || rhdr.nwqid<thdr.nwname)){

		/* clunk the new fid, which is the one we walked */

		f->busy = 0;

		f->ram = nil;

	}

	if(rhdr.nwqid > 0)

		err = nil;	/* didn't get everything in 9P2000 right! */

	if(rhdr.nwqid == thdr.nwname)	/* update the fid after a successful walk */

		f->ram = fram;

	return err;

}

char *

ropen(Fid *f)

{

	Ram *r;

	int mode, trunc;

	if(f->open)

		return Eisopen;

	r = f->ram;

	if(r->busy == 0)

		return Enotexist;

	if(r->perm & DMEXCL)

		if(r->open)

			return Excl;

	mode = thdr.mode;

	if(r->qid.type & QTDIR){

		if(mode != OREAD)

			return Eperm;

		rhdr.qid = r->qid;

		return 0;

	}

	if(mode & ORCLOSE){

		/* can't remove root; must be able to write parent */

		if(r->qid.path==0 || !perm(f, &ram[r->parent], Pwrite))

			return Eperm;

		f->rclose = 1;

	}

	trunc = mode & OTRUNC;

	mode &= OPERM;

	if(mode==OWRITE || mode==ORDWR || trunc)

		if(!perm(f, r, Pwrite))

			return Eperm;

	if(mode==OREAD || mode==ORDWR)

		if(!perm(f, r, Pread))

			return Eperm;

	if(mode==OEXEC)

		if(!perm(f, r, Pexec))

			return Eperm;

	if(trunc && (r->perm&DMAPPEND)==0){

		r->ndata = 0;

		if(r->data)

			free(r->data);

		r->data = 0;

		r->qid.vers++;

	}

	rhdr.qid = r->qid;

	rhdr.iounit = messagesize-IOHDRSZ;

	f->open = 1;

	r->open++;

	return 0;

}

char *

rcreate(Fid *f)

{

	Ram *r;

	char *name;

	long parent, prm;

	if(f->open)

		return Eisopen;

	if(f->ram->busy == 0)

		return Enotexist;

	parent = f->ram - ram;

	if((f->ram->qid.type&QTDIR) == 0)

		return Enotdir;

	/* must be able to write parent */

	if(!perm(f, f->ram, Pwrite))

		return Eperm;

	prm = thdr.perm;

	name = thdr.name;

	if(strcmp(name, ".")==0 || strcmp(name, "..")==0)

		return Ename;

	for(r=ram; r<&ram[nram]; r++)

		if(r->busy && parent==r->parent)

		if(strcmp((char*)name, r->name)==0)

			return Einuse;

	for(r=ram; r->busy; r++)

		if(r == &ram[Nram-1])

			return "no free ram resources";

	r->busy = 1;

	r->qid.path = ++path;

	r->qid.vers = 0;

	if(prm & DMDIR)

		r->qid.type |= QTDIR;

	r->parent = parent;

	free(r->name);

	r->name = estrdup(name);

	r->user = f->user;

	r->group = f->ram->group;

	r->muid = f->ram->muid;

	if(prm & DMDIR)

		prm = (prm&~0777) | (f->ram->perm&prm&0777);

	else

		prm = (prm&(~0777|0111)) | (f->ram->perm&prm&0666);

	r->perm = prm;

	r->ndata = 0;

	if(r-ram >= nram)

		nram = r - ram + 1;

	r->atime = time(0);

	r->mtime = r->atime;

	f->ram->mtime = r->atime;

	f->ram = r;

	rhdr.qid = r->qid;

	rhdr.iounit = messagesize-IOHDRSZ;

	f->open = 1;

	if(thdr.mode & ORCLOSE)

		f->rclose = 1;

	r->open++;

	return 0;

}

char*

rread(Fid *f)

{

	Ram *r;

	uchar *buf;

	vlong off;

	int n, m, cnt;

	if(f->ram->busy == 0)

		return Enotexist;

	n = 0;

	rhdr.count = 0;

	rhdr.data = (char*)rdata;

	if (thdr.offset < 0)

		return "negative seek offset";

	off = thdr.offset;

	buf = rdata;

	cnt = thdr.count;

	if(cnt > messagesize)	/* shouldn't happen, anyway */

		cnt = messagesize;

	if(cnt < 0)

		return "negative read count";

	if(f->ram->qid.type & QTDIR){

		for(r=ram+1; off > 0; r++){

			if(r->busy && r->parent==f->ram-ram)

				off -= ramstat(r, statbuf, sizeof statbuf);

			if(r == &ram[nram-1])

				return 0;

		}

		for(; r<&ram[nram] && n < cnt; r++){

			if(!r->busy || r->parent!=f->ram-ram)

				continue;

			m = ramstat(r, buf+n, cnt-n);

			if(m == 0)

				break;

			n += m;

		}

		rhdr.data = (char*)rdata;

		rhdr.count = n;

		return 0;

	}

	r = f->ram;

	if(off >= r->ndata)

		return 0;

	r->atime = time(0);

	n = cnt;

	if(off+n > r->ndata)

		n = r->ndata - off;

	rhdr.data = r->data+off;

	rhdr.count = n;

	return 0;

}

char*

rwrite(Fid *f)

{

	Ram *r;

	vlong off;

	int cnt;

	r = f->ram;

	rhdr.count = 0;

	if(r->busy == 0)

		return Enotexist;

	if (thdr.offset < 0)

		return "negative seek offset";

	off = thdr.offset;

	if(r->perm & DMAPPEND)

		off = r->ndata;

	cnt = thdr.count;

	if(cnt < 0)

		return "negative write count";

	if(r->qid.type & QTDIR)

		return Eisdir;

	if(memlim && off+cnt >= Maxsize)		/* sanity check */

		return "write too big";

	if(off+cnt > r->ndata)

		r->data = erealloc(r->data, off+cnt);

	if(off > r->ndata)

		memset(r->data+r->ndata, 0, off-r->ndata);

	if(off+cnt > r->ndata)

		r->ndata = off+cnt;

	memmove(r->data+off, thdr.data, cnt);

	r->qid.vers++;

	r->mtime = time(0);

	rhdr.count = cnt;

	return 0;

}

static int

emptydir(Ram *dr)

{

	long didx = dr - ram;

	Ram *r;

	for(r=ram; r<&ram[nram]; r++)

		if(r->busy && didx==r->parent)

			return 0;

	return 1;

}

char *

realremove(Ram *r)

{

	if(r->qid.type & QTDIR && !emptydir(r))

		return Enotempty;

	r->ndata = 0;

	if(r->data)

		free(r->data);

	r->data = 0;

	r->parent = 0;

	memset(&r->qid, 0, sizeof r->qid);

	free(r->name);

	r->name = nil;

	r->busy = 0;

	return nil;

}

char *

rclunk(Fid *f)

{

	char *e = nil;

	if(f->open)

		f->ram->open--;

	if(f->rclose)

		e = realremove(f->ram);

	f->busy = 0;

	f->open = 0;

	f->ram = 0;

	return e;

}

char *

rremove(Fid *f)

{

	Ram *r;

	if(f->open)

		f->ram->open--;

	f->busy = 0;

	f->open = 0;

	r = f->ram;

	f->ram = 0;

	if(r->qid.path == 0 || !perm(f, &ram[r->parent], Pwrite))

		return Eperm;

	ram[r->parent].mtime = time(0);

	return realremove(r);

}

char *

rstat(Fid *f)

{

	if(f->ram->busy == 0)

		return Enotexist;

	rhdr.nstat = ramstat(f->ram, statbuf, sizeof statbuf);

	rhdr.stat = statbuf;

	return 0;

}

char *

rwstat(Fid *f)

{

	Ram *r, *s;

	Dir dir;

	if(f->ram->busy == 0)

		return Enotexist;

	convM2D(thdr.stat, thdr.nstat, &dir, (char*)statbuf);

	r = f->ram;

	/*

	 * To change length, must have write permission on file.

	 */

	if(dir.length!=~0 && dir.length!=r->ndata){

	 	if(!perm(f, r, Pwrite))

			return Eperm;

	}

	/*

	 * To change name, must have write permission in parent

	 * and name must be unique.

	 */

	if(dir.name[0]!='\0' && strcmp(dir.name, r->name)!=0){

	 	if(!perm(f, &ram[r->parent], Pwrite))

			return Eperm;

		for(s=ram; s<&ram[nram]; s++)

			if(s->busy && s->parent==r->parent)

			if(strcmp(dir.name, s->name)==0)

				return Eexist;

	}

	/*

	 * To change mode, must be owner or group leader.

	 * Because of lack of users file, leader=>group itself.

	 */

	if(dir.mode!=~0 && r->perm!=dir.mode){

		if(strcmp(f->user, r->user) != 0)

		if(strcmp(f->user, r->group) != 0)

			return Enotowner;

	}

	/*

	 * To change group, must be owner and member of new group,

	 * or leader of current group and leader of new group.

	 * Second case cannot happen, but we check anyway.

	 */

	if(dir.gid[0]!='\0' && strcmp(r->group, dir.gid)!=0){

		if(strcmp(f->user, r->user) == 0)

	//	if(strcmp(f->user, dir.gid) == 0)

			goto ok;

		if(strcmp(f->user, r->group) == 0)

		if(strcmp(f->user, dir.gid) == 0)

			goto ok;

		return Enotowner;

		ok:;

	}

	/* all ok; do it */

	if(dir.mode != ~0){

		dir.mode &= ~DMDIR;	/* cannot change dir bit */

		dir.mode |= r->perm&DMDIR;

		r->perm = dir.mode;

	}

	if(dir.name[0] != '\0'){

		free(r->name);

		r->name = estrdup(dir.name);

	}

	if(dir.gid[0] != '\0')

		r->group = estrdup(dir.gid);

	if(dir.length!=~0 && dir.length!=r->ndata){

		r->data = erealloc(r->data, dir.length);

		if(r->ndata < dir.length)

			memset(r->data+r->ndata, 0, dir.length-r->ndata);

		r->ndata = dir.length;

	}

	ram[r->parent].mtime = time(0);

	return 0;

}

uint

ramstat(Ram *r, uchar *buf, uint nbuf)

{

	int n;

	Dir dir;

	dir.name = r->name;

	dir.qid = r->qid;

	dir.mode = r->perm;

	dir.length = r->ndata;

	dir.uid = r->user;

	dir.gid = r->group;

	dir.muid = r->muid;

	dir.atime = r->atime;

	dir.mtime = r->mtime;

	n = convD2M(&dir, buf, nbuf);

	if(n > 2)

		return n;

	return 0;

}

Fid *

newfid(int fid)

{

	Fid *f, *ff;

	ff = 0;

	for(f = fids; f; f = f->next)

		if(f->fid == fid)

			return f;

		else if(!ff && !f->busy)

			ff = f;

	if(ff){

		ff->fid = fid;

		return ff;

	}

	f = emalloc(sizeof *f);

	f->ram = nil;

	f->fid = fid;

	f->next = fids;

	fids = f;

	return f;

}

void

io(void)

{

	char *err, buf[40];

	int n, pid, ctl;

	Fid *fid;

	pid = getpid();

	if(private){

		snprint(buf, sizeof buf, "/proc/%d/ctl", pid);

		ctl = open(buf, OWRITE);

		if(ctl < 0){

			fprint(2, "can't protect ramfs\n");

		}else{

			fprint(ctl, "noswap\n");

			fprint(ctl, "private\n");

			close(ctl);

		}

	}

	for(;;){

		/*

		 * reading from a pipe or a network device

		 * will give an error after a few eof reads.

		 * however, we cannot tell the difference

		 * between a zero-length read and an interrupt

		 * on the processes writing to us,

		 * so we wait for the error.

		 */

		n = read9pmsg(mfd[0], mdata, messagesize);

		if(n < 0){

			rerrstr(buf, sizeof buf);

			if(buf[0]=='\0' || strstr(buf, "hungup"))

				exits("");

			error("mount read");

		}

		if(n == 0)

			continue;

		if(convM2S(mdata, n, &thdr) == 0)

			continue;

		if(debug)

			fprint(2, "ramfs %d:<-%F\n", pid, &thdr);

		if(thdr.type<0 || thdr.type>=nelem(fcalls) || !fcalls[thdr.type])

			err = "bad fcall type";

		else if(((fid=newfid(thdr.fid))==nil || !fid->ram) && needfid[thdr.type])

			err = "fid not in use";

		else

			err = (*fcalls[thdr.type])(fid);

		if(err){

			rhdr.type = Rerror;

			rhdr.ename = err;

		}else{

			rhdr.type = thdr.type + 1;

			rhdr.fid = thdr.fid;

		}

		rhdr.tag = thdr.tag;

		if(debug)

			fprint(2, "ramfs %d:->%F\n", pid, &rhdr);/**/

		n = convS2M(&rhdr, mdata, messagesize);

		if(n == 0)

			error("convS2M error on write");

		if(write(mfd[1], mdata, n) != n)

			error("mount write");

	}

}

int

perm(Fid *f, Ram *r, int p)

{

	if((p*Pother) & r->perm)

		return 1;

	if(strcmp(f->user, r->group)==0 && ((p*Pgroup) & r->perm))

		return 1;

	if(strcmp(f->user, r->user)==0 && ((p*Powner) & r->perm))

		return 1;

	return 0;

}

void

error(char *s)

{

	fprint(2, "%s: %s: %r\n", argv0, s);

	exits(s);

}