Date: Wed, 22 Aug 2001 15:23:22 -0400 (EDT) From: Andrew Gallatin <gallatin@cs.duke.edu> To: marcel@freebsd.org Cc: freebsd-emulation@freebsd.org Subject: please review- linulator getcwd bugfix Message-ID: <15236.1706.531042.974240@grasshopper.cs.duke.edu>
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Currently, linux_getcwd() is broken. It calls __getcwd(). __getcwd()
is essentially an optimiziation on FreeBSD. If the cwd is in the
namei cache, then it returns it & saves libc a lot of trouble.
However, linux expects it to always succeed. When it fails, linux
apps end up with an error condition they don't expect, and strange and
bizzare things can happen (like trying to open files in / rather than
in /some/path/name). This happens often when running programs
compiled by the compaq linux/alpha Fortran compiler.
See kern/24315 for a concise description of the problem.
I've appended a fix using an in-kernel getcwd obtained from NetBSD by
way of OpenBSD. I try the old __getdents() way first, and then try
the more heavy-handed approach.
Please review.
Thanks,
Drew
Index: modules/linux/Makefile
===================================================================
RCS file: /home/ncvs/src/sys/modules/linux/Makefile,v
retrieving revision 1.51
diff -u -r1.51 Makefile
--- modules/linux/Makefile 2001/02/04 10:52:24 1.51
+++ modules/linux/Makefile 2001/08/22 17:25:49
@@ -5,8 +5,8 @@
.PATH: ${.CURDIR}/../../compat/linux ${.CURDIR}/../../${MACHINE_ARCH}/linux
KMOD= linux
-SRCS= linux_file.c linux_ioctl.c linux_ipc.c linux_machdep.c linux_misc.c \
- linux_signal.c linux_socket.c linux_stats.c linux_mib.c \
+SRCS= linux_file.c linux_getcwd.c linux_ioctl.c linux_ipc.c linux_machdep.c \
+ linux_misc.c linux_signal.c linux_socket.c linux_stats.c linux_mib.c \
linux_dummy.c linux_sysent.c linux_sysvec.c linux_util.c \
opt_compat.h opt_linux.h opt_vmpage.h vnode_if.h
OBJS= linux_locore.o
Index: conf/files.alpha
===================================================================
RCS file: /home/ncvs/src/sys/conf/files.alpha,v
retrieving revision 1.69
diff -u -r1.69 files.alpha
--- conf/files.alpha 2001/08/02 13:22:28 1.69
+++ conf/files.alpha 2001/08/22 19:10:06
@@ -170,6 +170,7 @@
alpha/tlsb/tlsbmem.c optional dec_kn8ae
alpha/tlsb/zs_tlsb.c optional dec_kn8ae
compat/linux/linux_file.c optional compat_linux
+compat/linux/linux_getcwd.c optional compat_linux
compat/linux/linux_ioctl.c optional compat_linux
compat/linux/linux_ipc.c optional compat_linux
compat/linux/linux_mib.c optional compat_linux
Index: conf/files.i386
===================================================================
RCS file: /home/ncvs/src/sys/conf/files.i386,v
retrieving revision 1.369
diff -u -r1.369 files.i386
--- conf/files.i386 2001/08/09 00:02:30 1.369
+++ conf/files.i386 2001/08/22 19:10:34
@@ -57,6 +57,7 @@
no-implicit-rule
#
compat/linux/linux_file.c optional compat_linux
+compat/linux/linux_getcwd.c optional compat_linux
compat/linux/linux_ioctl.c optional compat_linux
compat/linux/linux_ipc.c optional compat_linux
compat/linux/linux_mib.c optional compat_linux
Index: compat/linux/linux_file.c
===================================================================
RCS file: /home/ncvs/src/sys/compat/linux/linux_file.c,v
retrieving revision 1.53
diff -u -r1.53 linux_file.c
--- compat/linux/linux_file.c 2001/05/01 08:11:51 1.53
+++ compat/linux/linux_file.c 2001/08/22 17:04:10
@@ -830,34 +830,6 @@
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)
--- /dev/null Wed Aug 22 15:03:56 2001
+++ compat/linux/linux_getcwd.c Wed Aug 22 13:07:21 2001
@@ -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);
+}
+
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