sysfile.c

在x86平台上运行不可信任代码的sandbox。

	lock(&c->ref.lk);
	c->devoffset += nn;
	c->offset += nnn;
	unlock(&c->ref.lk);

	poperror();
	cclose(c);

	return nnn;
}

long
sys_read(ulong *arg)
{
	return doread(arg, nil);
}

long
syspread(ulong *arg)
{
	vlong v;

	// Plan 9 VX replaced dodgy varargs code
	v = *(vlong*)&arg[3];

	if(v == ~0ULL)
		return doread(arg, nil);

	return doread(arg, &v);
}

static long
dowrite(ulong *arg, vlong *offp)
{
	Chan *c;
	long m, n;
	vlong off;
	uchar *p;

	p = uvalidaddr(arg[1], arg[2], 0);
	n = 0;
	c = fdtochan(arg[0], OWRITE, 1, 1);
	if(waserror()) {
		if(offp == nil){
			lock(&c->ref.lk);
			c->offset -= n;
			unlock(&c->ref.lk);
		}
		cclose(c);
		nexterror();
	}

	if(c->qid.type & QTDIR)
		error(Eisdir);

	n = arg[2];

	if(offp == nil){	/* use and maintain channel's offset */
		lock(&c->ref.lk);
		off = c->offset;
		c->offset += n;
		unlock(&c->ref.lk);
	}else
		off = *offp;

	if(off < 0)
		error(Enegoff);

	m = devtab[c->type]->write(c, p, n, off);

	if(offp == nil && m < n){
		lock(&c->ref.lk);
		c->offset -= n - m;
		unlock(&c->ref.lk);
	}

	poperror();
	cclose(c);

	return m;
}

long
sys_write(ulong *arg)
{
	return dowrite(arg, nil);
}

long
syspwrite(ulong *arg)
{
	vlong v;

	// Plan 9 VX replaced dodgy varargs code
	v = *(vlong*)&arg[3];

	if(v == ~0ULL)
		return dowrite(arg, nil);

	return dowrite(arg, &v);
}

static void
sseek(ulong *arg)
{
	Chan *c;
	uchar buf[sizeof(Dir)+100];
	Dir dir;
	int n;
	vlong off;
	union {
		vlong v;
		ulong u[2];
	} o;

	c = fdtochan(arg[1], -1, 1, 1);
	if(waserror()){
		cclose(c);
		nexterror();
	}
	if(devtab[c->type]->dc == '|')
		error(Eisstream);

	off = 0;
	o.u[0] = arg[2];
	o.u[1] = arg[3];
	switch(arg[4]){
	case 0:
		off = o.v;
		if((c->qid.type & QTDIR) && off != 0)
			error(Eisdir);
		if(off < 0)
			error(Enegoff);
		c->offset = off;
		break;

	case 1:
		if(c->qid.type & QTDIR)
			error(Eisdir);
		lock(&c->ref.lk);	/* lock for read/write update */
		off = o.v + c->offset;
		if(off < 0){
			unlock(&c->ref.lk);
			error(Enegoff);
		}
		c->offset = off;
		unlock(&c->ref.lk);
		break;

	case 2:
		if(c->qid.type & QTDIR)
			error(Eisdir);
		n = devtab[c->type]->stat(c, buf, sizeof buf);
		if(convM2D(buf, n, &dir, nil) == 0)
			error("internal error: stat error in seek");
		off = dir.length + o.v;
		if(off < 0)
			error(Enegoff);
		c->offset = off;
		break;

	default:
		error(Ebadarg);
	}
	*(vlong*)arg[0] = off;	/* caller translated arg[0] already */
	c->uri = 0;
	c->dri = 0;
	cclose(c);
	poperror();
}

long
sysseek(ulong *arg)
{
	arg[0] = (ulong)uvalidaddr(arg[0], BY2V, 1);
	sseek(arg);
	return 0;
}

long
sysoseek(ulong *arg)
{
	union {
		vlong v;
		ulong u[2];
	} o;
	ulong a[5];

	o.v = (long)arg[1];
	a[0] = (ulong)&o.v;
	a[1] = arg[0];
	a[2] = o.u[0];
	a[3] = o.u[1];
	a[4] = arg[2];
	sseek(a);
	return o.v;
}

void
validstat(uchar *s, int n)
{
	int m;
	char buf[64];

	if(statcheck(s, n) < 0)
		error(Ebadstat);
	/* verify that name entry is acceptable */
	s += STATFIXLEN - 4*BIT16SZ;	/* location of first string */
	/*
	 * s now points at count for first string.
	 * if it's too long, let the server decide; this is
	 * only for his protection anyway. otherwise
	 * we'd have to allocate and waserror.
	 */
	m = GBIT16(s);
	s += BIT16SZ;
	if(m+1 > sizeof buf)
		return;
	memmove(buf, s, m);
	buf[m] = '\0';
	/* name could be '/' */
	if(strcmp(buf, "/") != 0)
		validname(buf, 0);
}

static char*
pathlast(Path *p)
{
	char *s;

	if(p == nil)
		return nil;
	if(p->len == 0)
		return nil;
	s = strrchr(p->s, '/');
	if(s)
		return s+1;
	return p->s;
}

long
sysfstat(ulong *arg)
{
	Chan *c;
	uint l;
	uchar *p;

	l = arg[2];
	p = uvalidaddr(arg[1], l, 1);
	c = fdtochan(arg[0], -1, 0, 1);
	if(waserror()) {
		cclose(c);
		nexterror();
	}
	l = devtab[c->type]->stat(c, p, l);
	poperror();
	cclose(c);
	return l;
}

long
sysstat(ulong *arg)
{
	char *name;
	Chan *c;
	uint l;
	uchar *p;

	l = arg[2];
	p = uvalidaddr(arg[1], l, 1);
	name = uvalidaddr(arg[0], 1, 0);
	c = namec(name, Aaccess, 0, 0);
	if(waserror()){
		cclose(c);
		nexterror();
	}
	l = devtab[c->type]->stat(c, p, l);
	name = pathlast(c->path);
	if(name)
		l = dirsetname(name, strlen(name), p, l, arg[2]);

	poperror();
	cclose(c);
	return l;
}

long
syschdir(ulong *arg)
{
	Chan *c;
	char *name;

	name = uvalidaddr(arg[0], 1, 0);

	c = namec(name, Atodir, 0, 0);
	cclose(up->dot);
	up->dot = c;
	return 0;
}

long
bindmount(int ismount, int fd, int afd, char* arg0, char* arg1, ulong flag, char* spec)
{
	int ret;
	Chan *c0, *c1, *ac, *bc;
	struct{
		Chan	*chan;
		Chan	*authchan;
		char	*spec;
		int	flags;
	}bogus;

	if((flag&~MMASK) || (flag&MORDER)==(MBEFORE|MAFTER))
		error(Ebadarg);

	bogus.flags = flag & MCACHE;

	if(ismount){
		if(up->pgrp->noattach)
			error(Enoattach);

		ac = nil;
		bc = fdtochan(fd, ORDWR, 0, 1);
		if(waserror()) {
			if(ac)
				cclose(ac);
			cclose(bc);
			nexterror();
		}

		if(afd >= 0)
			ac = fdtochan(afd, ORDWR, 0, 1);

		bogus.chan = bc;
		bogus.authchan = ac;

		bogus.spec = spec;
		if(waserror())
			error(Ebadspec);
		spec = validnamedup(spec, 1);
		poperror();
		
		if(waserror()){
			free(spec);
			nexterror();
		}

		ret = devno('M', 0);
		c0 = devtab[ret]->attach((char*)&bogus);

		poperror();	/* spec */
		free(spec);
		poperror();	/* ac bc */
		if(ac)
			cclose(ac);
		cclose(bc);
	}else{
		bogus.spec = 0;
		c0 = namec(arg0, Abind, 0, 0);
	}

	if(waserror()){
		cclose(c0);
		nexterror();
	}

	c1 = namec(arg1, Amount, 0, 0);
	if(waserror()){
		cclose(c1);
		nexterror();
	}

	ret = cmount(&c0, c1, flag, bogus.spec);

	poperror();
	cclose(c1);
	poperror();
	cclose(c0);
	if(ismount)
		fdclose(fd, 0);

	return ret;
}

long
sysbind(ulong *arg)
{
	return bindmount(0, -1, -1, uvalidaddr(arg[0], 1, 0), uvalidaddr(arg[1], 1, 0), arg[2], nil);
}

long
sysmount(ulong *arg)
{
	return bindmount(1, arg[0], arg[1], nil, uvalidaddr(arg[2], 1, 0), arg[3], uvalidaddr(arg[4], 1, 0));
}

long
sys_mount(ulong *arg)
{
	return bindmount(1, arg[0], -1, nil, uvalidaddr(arg[1], 1, 0), arg[2], uvalidaddr(arg[3], 1, 0));
}

long
sysunmount(ulong *arg)
{
	Chan *cmount, *cmounted;
	char *mount, *mounted;

	cmounted = 0;

	mount = uvalidaddr(arg[1], 1, 0);
	cmount = namec(mount, Amount, 0, 0);

	if(arg[0]) {
		if(waserror()) {
			cclose(cmount);
			nexterror();
		}
		mounted = uvalidaddr(arg[0], 1, 0);
		/*
		 * This has to be namec(..., Aopen, ...) because
		 * if arg[0] is something like /srv/cs or /fd/0,
		 * opening it is the only way to get at the real
		 * Chan underneath.
		 */
		cmounted = namec(mounted, Aopen, OREAD, 0);
		poperror();
	}

	if(waserror()) {
		cclose(cmount);
		if(cmounted)
			cclose(cmounted);
		nexterror();
	}

	cunmount(cmount, cmounted);
	cclose(cmount);
	if(cmounted)
		cclose(cmounted);
	poperror();
	return 0;
}

long
syscreate(ulong *arg)
{
	int fd;
	Chan *c = 0;
	char *name;

	openmode(arg[1]&~OEXCL);	/* error check only; OEXCL okay here */
	if(waserror()) {
		if(c)
			cclose(c);
		nexterror();
	}
	name = uvalidaddr(arg[0], 1, 0);
	c = namec(name, Acreate, arg[1], arg[2]);
	fd = newfd(c);
	if(fd < 0)
		error(Enofd);
	poperror();
	return fd;
}

long
sysremove(ulong *arg)
{
	Chan *c;
	char *name;

	name = uvalidaddr(arg[0], 1, 0);
	c = namec(name, Aremove, 0, 0);
	/*
	 * Removing mount points is disallowed to avoid surprises
	 * (which should be removed: the mount point or the mounted Chan?).
	 */
	if(c->ismtpt){
		cclose(c);
		error(Eismtpt);
	}
	if(waserror()){
		c->type = 0;	/* see below */
		cclose(c);
		nexterror();
	}
	devtab[c->type]->remove(c);
	/*
	 * Remove clunks the fid, but we need to recover the Chan
	 * so fake it up.  rootclose() is known to be a nop.
	 */
	c->type = 0;
	poperror();
	cclose(c);
	return 0;
}

static long
wstat(Chan *c, uchar *d, int nd)
{
	long l;
	int namelen;

	if(waserror()){
		cclose(c);
		nexterror();
	}
	if(c->ismtpt){
		/*
		 * Renaming mount points is disallowed to avoid surprises
		 * (which should be renamed? the mount point or the mounted Chan?).
		 */
		dirname(d, &namelen);
		if(namelen)
			nameerror(chanpath(c), Eismtpt);
	}
	l = devtab[c->type]->wstat(c, d, nd);
	poperror();
	cclose(c);
	return l;
}

long
syswstat(ulong *arg)
{
	Chan *c;
	uint l;
	char *name;
	uchar *p;

	l = arg[2];
	p = uvalidaddr(arg[1], l, 0);
	validstat(p, l);
	name = uvalidaddr(arg[0], 1, 0);
	c = namec(name, Aaccess, 0, 0);
	return wstat(c, p, l);
}

long
sysfwstat(ulong *arg)
{
	Chan *c;
	uint l;
	uchar *p;

	l = arg[2];
	p = uvalidaddr(arg[1], l, 0);
	validstat(p, l);
	c = fdtochan(arg[0], -1, 1, 1);
	return wstat(c, p, l);
}

static void
packoldstat(uchar *buf, Dir *d)
{
	uchar *p;
	ulong q;

	/* lay down old stat buffer - grotty code but it's temporary */
	p = buf;
	strncpy((char*)p, d->name, 28);
	p += 28;
	strncpy((char*)p, d->uid, 28);
	p += 28;
	strncpy((char*)p, d->gid, 28);
	p += 28;
	q = d->qid.path & ~DMDIR;	/* make sure doesn't accidentally look like directory */
	if(d->qid.type & QTDIR)	/* this is the real test of a new directory */
		q |= DMDIR;
	PBIT32(p, q);
	p += BIT32SZ;
	PBIT32(p, d->qid.vers);
	p += BIT32SZ;
	PBIT32(p, d->mode);
	p += BIT32SZ;
	PBIT32(p, d->atime);
	p += BIT32SZ;
	PBIT32(p, d->mtime);
	p += BIT32SZ;
	PBIT64(p, d->length);
	p += BIT64SZ;
	PBIT16(p, d->type);
	p += BIT16SZ;
	PBIT16(p, d->dev);
}

long
sys_stat(ulong *arg)
{
	Chan *c;
	uint l;
	uchar buf[128];	/* old DIRLEN plus a little should be plenty */
	char strs[128], *name, *elem;
	Dir d;
	char old[] = "old stat system call - recompile";
	uchar *p;

	p = uvalidaddr(arg[1], 116, 1);
	name = uvalidaddr(arg[0], 1, 0);
	c = namec(name, Aaccess, 0, 0);
	if(waserror()){
		cclose(c);
		nexterror();
	}
	l = devtab[c->type]->stat(c, buf, sizeof buf);
	/* buf contains a new stat buf; convert to old. yuck. */
	if(l <= BIT16SZ)	/* buffer too small; time to face reality */
		error(old);
	elem = pathlast(c->path);
	if(elem)
		l = dirsetname(elem, strlen(elem), buf, l, sizeof buf);
	l = convM2D(buf, l, &d, strs);
	if(l == 0)
		error(old);
	packoldstat(p, &d);
	
	poperror();
	cclose(c);
	return 0;
}

long
sys_fstat(ulong *arg)
{
	Chan *c;
	char *name;
	uint l;
	uchar buf[128];	/* old DIRLEN plus a little should be plenty */
	char strs[128];
	Dir d;
	char old[] = "old fstat system call - recompile";
	uchar *p;

	p = uvalidaddr(arg[1], 116, 1);
	c = fdtochan(arg[0], -1, 0, 1);
	if(waserror()){
		cclose(c);
		nexterror();
	}
	l = devtab[c->type]->stat(c, buf, sizeof buf);
	/* buf contains a new stat buf; convert to old. yuck. */
	if(l <= BIT16SZ)	/* buffer too small; time to face reality */
		error(old);
	name = pathlast(c->path);
	if(name)
		l = dirsetname(name, strlen(name), buf, l, sizeof buf);
	l = convM2D(buf, l, &d, strs);
	if(l == 0)
		error(old);
	packoldstat(p, &d);
	
	poperror();
	cclose(c);
	return 0;
}

long
sys_wstat(ulong *u)
{
	error("old wstat system call - recompile");
	return -1;
}

long
sys_fwstat(ulong *u)
{
	error("old fwstat system call - recompile");
	return -1;
}

// Plan 9 VX additions
long
kbind(char *new, char *old, int flag)
{
	return bindmount(0, -1, -1, new, old, flag, nil);
}

long
syspassfd(ulong *u)
{
	error("passfd unimplemented");
	return -1;
}