Fix linux_getcwd() so that if the cwd isn't cached (__getcwd() fails),

the cwd is looked up inside the kernel. The native getcwd() in libc
handles this in userland if __getcwd() fails.

Obtained from: NetBSD via OpenBSD
Tested by: Chris Casey <chriss@phys.ksu.edu>, Markus Holmberg <markush@acc.umu.se>
Reviewed by: Darrell Anderson <anderson@cs.duke.edu>
PR: kern/24315

2 files changed, 466 insertions, 28 deletions

diff --git a/sys/compat/linux/linux_file.c b/sys/compat/linux/linux_file.c
index 0f68ab5..2a5d673 100644
--- a/sys/compat/linux/linux_file.c
+++ b/sys/compat/linux/linux_file.c
@@ -830,34 +830,6 @@ linux_link(struct proc *p, struct linux_link_args *args)
     return link(p, &bsd);
 }
 
-int
-linux_getcwd(struct proc *p, struct linux_getcwd_args *args)
-{
-	struct __getcwd_args bsd;
-	caddr_t sg;
-	int error, len;
-
-#ifdef DEBUG
-	if (ldebug(getcwd))
-		printf(ARGS(getcwd, "%p, %ld"), args->buf, args->bufsize);
-#endif
-
-	sg = stackgap_init();
-	bsd.buf = stackgap_alloc(&sg, SPARE_USRSPACE);
-	bsd.buflen = SPARE_USRSPACE;
-	error = __getcwd(p, &bsd);
-	if (!error) {
-		len = strlen(bsd.buf) + 1;
-		if (len <= args->bufsize) {
-			p->p_retval[0] = len;
-			error = copyout(bsd.buf, args->buf, len);
-		}
-		else
-			error = ERANGE;
-	}
-	return (error);
-}
-
 #ifndef __alpha__
 int
 linux_fdatasync(p, uap)
diff --git a/sys/compat/linux/linux_getcwd.c b/sys/compat/linux/linux_getcwd.c
new file mode 100644
index 0000000..2231f82
--- /dev/null
+++ b/sys/compat/linux/linux_getcwd.c
@@ -0,0 +1,466 @@
+/* $FreeBSD$ */
+/* $OpenBSD: linux_getcwd.c,v 1.2 2001/05/16 12:50:21 ho Exp $ */
+/* $NetBSD: vfs_getcwd.c,v 1.3.2.3 1999/07/11 10:24:09 sommerfeld Exp $ */
+
+/*-
+ * Copyright (c) 1999 The NetBSD Foundation, Inc.
+ * All rights reserved.
+ *
+ * This code is derived from software contributed to The NetBSD Foundation
+ * by Bill Sommerfeld.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ * 3. All advertising materials mentioning features or use of this software
+ *    must display the following acknowledgement:
+ *        This product includes software developed by the NetBSD
+ *        Foundation, Inc. and its contributors.
+ * 4. Neither the name of The NetBSD Foundation nor the names of its
+ *    contributors may be used to endorse or promote products derived
+ *    from this software without specific prior written permission.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
+ * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
+ * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
+ * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
+ * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+ * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+ * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+ * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+ * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+ * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+ * POSSIBILITY OF SUCH DAMAGE.
+ */
+#include "opt_compat.h"
+
+#include <sys/param.h>
+#include <sys/systm.h>
+#include <sys/sysproto.h>
+#include <sys/namei.h>
+#include <sys/filedesc.h>
+#include <sys/kernel.h>
+#include <sys/file.h>
+#include <sys/stat.h>
+#include <sys/vnode.h>
+#include <sys/mount.h>
+#include <sys/proc.h>
+#include <sys/uio.h>
+#include <sys/malloc.h>
+#include <sys/dirent.h>
+#include <ufs/ufs/dir.h>	/* XXX only for DIRBLKSIZ */
+
+#include <machine/../linux/linux.h>
+#include <machine/../linux/linux_proto.h>
+#include <compat/linux/linux_util.h>
+
+static int
+linux_getcwd_scandir __P((struct vnode **, struct vnode **,
+    char **, char *, struct proc *));
+static int
+linux_getcwd_common __P((struct vnode *, struct vnode *,
+		   char **, char *, int, int, struct proc *));
+
+#define DIRENT_MINSIZE (sizeof(struct dirent) - (MAXNAMLEN+1) + 4)
+
+/*
+ * Vnode variable naming conventions in this file:
+ *
+ * rvp: the current root we're aiming towards.
+ * lvp, *lvpp: the "lower" vnode
+ * uvp, *uvpp: the "upper" vnode.
+ *
+ * Since all the vnodes we're dealing with are directories, and the
+ * lookups are going *up* in the filesystem rather than *down*, the
+ * usual "pvp" (parent) or "dvp" (directory) naming conventions are
+ * too confusing.
+ */
+
+/*
+ * XXX Will infinite loop in certain cases if a directory read reliably
+ *	returns EINVAL on last block.
+ * XXX is EINVAL the right thing to return if a directory is malformed?
+ */
+
+/*
+ * XXX Untested vs. mount -o union; probably does the wrong thing.
+ */
+
+/*
+ * Find parent vnode of *lvpp, return in *uvpp
+ *
+ * If we care about the name, scan it looking for name of directory
+ * entry pointing at lvp.
+ *
+ * Place the name in the buffer which starts at bufp, immediately
+ * before *bpp, and move bpp backwards to point at the start of it.
+ *
+ * On entry, *lvpp is a locked vnode reference; on exit, it is vput and NULL'ed
+ * On exit, *uvpp is either NULL or is a locked vnode reference.
+ */
+static int
+linux_getcwd_scandir(lvpp, uvpp, bpp, bufp, p)
+	struct vnode **lvpp;
+	struct vnode **uvpp;
+	char **bpp;
+	char *bufp;
+	struct proc *p;
+{
+	int     error = 0;
+	int     eofflag;
+	off_t   off;
+	int     tries;
+	struct uio uio;
+	struct iovec iov;
+	char   *dirbuf = NULL;
+	int	dirbuflen;
+	ino_t   fileno;
+	struct vattr va;
+	struct vnode *uvp = NULL;
+	struct vnode *lvp = *lvpp;	
+	struct componentname cn;
+	int len, reclen;
+	tries = 0;
+
+	/*
+	 * If we want the filename, get some info we need while the
+	 * current directory is still locked.
+	 */
+	if (bufp != NULL) {
+		error = VOP_GETATTR(lvp, &va, p->p_ucred, p);
+		if (error) {
+			vput(lvp);
+			*lvpp = NULL;
+			*uvpp = NULL;
+			return error;
+		}
+	}
+
+	/*
+	 * Ok, we have to do it the hard way..
+	 * Next, get parent vnode using lookup of ..
+	 */
+	cn.cn_nameiop = LOOKUP;
+	cn.cn_flags = ISLASTCN | ISDOTDOT | RDONLY;
+	cn.cn_proc = p;
+	cn.cn_cred = p->p_ucred;
+	cn.cn_pnbuf = NULL;
+	cn.cn_nameptr = "..";
+	cn.cn_namelen = 2;
+	cn.cn_consume = 0;
+	
+	/*
+	 * At this point, lvp is locked and will be unlocked by the lookup.
+	 * On successful return, *uvpp will be locked
+	 */
+	error = VOP_LOOKUP(lvp, uvpp, &cn);
+	if (error) {
+		vput(lvp);
+		*lvpp = NULL;
+		*uvpp = NULL;
+		return error;
+	}
+	uvp = *uvpp;
+
+	/* If we don't care about the pathname, we're done */
+	if (bufp == NULL) {
+		vrele(lvp);
+		*lvpp = NULL;
+		return 0;
+	}
+	
+	fileno = va.va_fileid;
+
+	dirbuflen = DIRBLKSIZ;
+	if (dirbuflen < va.va_blocksize)
+		dirbuflen = va.va_blocksize;
+	dirbuf = (char *)malloc(dirbuflen, M_TEMP, M_WAITOK);
+
+#if 0
+unionread:
+#endif
+	off = 0;
+	do {
+		/* call VOP_READDIR of parent */
+		iov.iov_base = dirbuf;
+		iov.iov_len = dirbuflen;
+
+		uio.uio_iov = &iov;
+		uio.uio_iovcnt = 1;
+		uio.uio_offset = off;
+		uio.uio_resid = dirbuflen;
+		uio.uio_segflg = UIO_SYSSPACE;
+		uio.uio_rw = UIO_READ;
+		uio.uio_procp = p;
+
+		eofflag = 0;
+
+		error = VOP_READDIR(uvp, &uio, p->p_ucred, &eofflag, 0, 0);
+
+		off = uio.uio_offset;
+
+		/*
+		 * Try again if NFS tosses its cookies.
+		 * XXX this can still loop forever if the directory is busted
+		 * such that the second or subsequent page of it always
+		 * returns EINVAL
+		 */
+		if ((error == EINVAL) && (tries < 3)) {
+			off = 0;
+			tries++;
+			continue;	/* once more, with feeling */
+		}
+
+		if (!error) {
+			char   *cpos;
+			struct dirent *dp;
+			
+			cpos = dirbuf;
+			tries = 0;
+				
+			/* scan directory page looking for matching vnode */ 
+			for (len = (dirbuflen - uio.uio_resid); len > 0; len -= reclen) {
+				dp = (struct dirent *) cpos;
+				reclen = dp->d_reclen;
+
+				/* check for malformed directory.. */
+				if (reclen < DIRENT_MINSIZE) {
+					error = EINVAL;
+					goto out;
+				}
+				/*
+				 * XXX should perhaps do VOP_LOOKUP to
+				 * check that we got back to the right place,
+				 * but getting the locking games for that
+				 * right would be heinous.
+				 */
+				if ((dp->d_type != DT_WHT) &&
+				    (dp->d_fileno == fileno)) {
+					char *bp = *bpp;
+					bp -= dp->d_namlen;
+					
+					if (bp <= bufp) {
+						error = ERANGE;
+						goto out;
+					}
+					bcopy(dp->d_name, bp, dp->d_namlen);
+					error = 0;
+					*bpp = bp;
+					goto out;
+				}
+				cpos += reclen;
+			}
+		}
+	} while (!eofflag);
+	error = ENOENT;
+		
+out:
+	vrele(lvp);
+	*lvpp = NULL;
+	free(dirbuf, M_TEMP);
+	return error;
+}
+
+
+/*
+ * common routine shared by sys___getcwd() and linux_vn_isunder()
+ */
+
+#define GETCWD_CHECK_ACCESS 0x0001
+
+static int
+linux_getcwd_common (lvp, rvp, bpp, bufp, limit, flags, p)
+	struct vnode *lvp;
+	struct vnode *rvp;
+	char **bpp;
+	char *bufp;
+	int limit;
+	int flags;
+	struct proc *p;
+{
+	struct filedesc *fdp = p->p_fd;
+	struct vnode *uvp = NULL;
+	char *bp = NULL;
+	int error;
+	int perms = VEXEC;
+
+	if (rvp == NULL) {
+		rvp = fdp->fd_rdir;
+		if (rvp == NULL)
+			rvp = rootvnode;
+	}
+	
+	VREF(rvp);
+	VREF(lvp);
+
+	/*
+	 * Error handling invariant:
+	 * Before a `goto out':
+	 *	lvp is either NULL, or locked and held.
+	 *	uvp is either NULL, or locked and held.
+	 */
+
+	error = vn_lock(lvp, LK_EXCLUSIVE | LK_RETRY, p);
+	if (error) {
+		vrele(lvp);
+		lvp = NULL;
+		goto out;
+	}
+	if (bufp)
+		bp = *bpp;
+	/*
+	 * this loop will terminate when one of the following happens:
+	 *	- we hit the root
+	 *	- getdirentries or lookup fails
+	 *	- we run out of space in the buffer.
+	 */
+	if (lvp == rvp) {
+		if (bp)
+			*(--bp) = '/';
+		goto out;
+	}
+	do {
+		if (lvp->v_type != VDIR) {
+			error = ENOTDIR;
+			goto out;
+		}
+		
+		/*
+		 * access check here is optional, depending on
+		 * whether or not caller cares.
+		 */
+		if (flags & GETCWD_CHECK_ACCESS) {
+			error = VOP_ACCESS(lvp, perms, p->p_ucred, p);
+			if (error)
+				goto out;
+			perms = VEXEC|VREAD;
+		}
+		
+		/*
+		 * step up if we're a covered vnode..
+		 */
+		while (lvp->v_flag & VROOT) {
+			struct vnode *tvp;
+
+			if (lvp == rvp)
+				goto out;
+			
+			tvp = lvp;
+			lvp = lvp->v_mount->mnt_vnodecovered;
+			vput(tvp);
+			/*
+			 * hodie natus est radici frater
+			 */
+			if (lvp == NULL) {
+				error = ENOENT;
+				goto out;
+			}
+			VREF(lvp);
+			error = vn_lock(lvp, LK_EXCLUSIVE | LK_RETRY, p);
+			if (error != 0) {
+				vrele(lvp);
+				lvp = NULL;
+				goto out;
+			}
+		}
+		error = linux_getcwd_scandir(&lvp, &uvp, &bp, bufp, p);
+		if (error)
+			goto out;
+#if DIAGNOSTIC		
+		if (lvp != NULL)
+			panic("getcwd: oops, forgot to null lvp");
+		if (bufp && (bp <= bufp)) {
+			panic("getcwd: oops, went back too far");
+		}
+#endif		
+		if (bp) 
+			*(--bp) = '/';
+		lvp = uvp;
+		uvp = NULL;
+		limit--;
+	} while ((lvp != rvp) && (limit > 0)); 
+
+out:
+	if (bpp)
+		*bpp = bp;
+	if (uvp)
+		vput(uvp);
+	if (lvp)
+		vput(lvp);
+	vrele(rvp);
+	return error;
+}
+
+
+/*
+ * Find pathname of process's current directory.
+ *
+ * Use vfs vnode-to-name reverse cache; if that fails, fall back
+ * to reading directory contents.
+ */
+
+int
+linux_getcwd(struct proc *p, struct linux_getcwd_args *args)
+{
+	struct __getcwd_args bsd;
+	caddr_t sg, bp, bend, path;
+	int error, len, lenused;
+
+#ifdef DEBUG
+	printf("Linux-emul(%ld): getcwd(%p, %ld)\n", (long)p->p_pid,
+	       args->buf, args->bufsize);
+#endif
+
+	sg = stackgap_init();
+	bsd.buf = stackgap_alloc(&sg, SPARE_USRSPACE);
+	bsd.buflen = SPARE_USRSPACE;
+	error = __getcwd(p, &bsd);
+	if (!error) {
+		lenused = strlen(bsd.buf) + 1;
+		if (lenused <= args->bufsize) {
+			p->p_retval[0] = lenused;
+			error = copyout(bsd.buf, args->buf, lenused);
+		}
+		else
+			error = ERANGE;
+	} else {
+		len = args->bufsize;
+
+		if (len > MAXPATHLEN*4)
+			len = MAXPATHLEN*4;
+		else if (len < 2)
+			return ERANGE;
+
+		path = (char *)malloc(len, M_TEMP, M_WAITOK);
+
+		bp = &path[len];
+		bend = bp;
+		*(--bp) = '\0';
+
+		/*
+		 * 5th argument here is "max number of vnodes to traverse".
+		 * Since each entry takes up at least 2 bytes in the output buffer,
+		 * limit it to N/2 vnodes for an N byte buffer.
+		 */
+
+		error = linux_getcwd_common (p->p_fd->fd_cdir, NULL,
+		    &bp, path, len/2, GETCWD_CHECK_ACCESS, p);
+
+		if (error)
+			goto out;
+		lenused = bend - bp;
+		p->p_retval[0] = lenused;
+		/* put the result into user buffer */
+		error = copyout(bp, args->buf, lenused);
+
+out:
+		free(path, M_TEMP);	
+	}
+	return (error);
+}
+