Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 801 insertions, 0 deletions

diff --git a/net/9p/protocol.c b/net/9p/protocol.c
new file mode 100644
index 000000000..0e6603b1e
--- /dev/null
+++ b/net/9p/protocol.c
@@ -0,0 +1,801 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * 9P Protocol Support Code
+ *
+ *  Copyright (C) 2008 by Eric Van Hensbergen <ericvh@gmail.com>
+ *
+ *  Base on code from Anthony Liguori <aliguori@us.ibm.com>
+ *  Copyright (C) 2008 by IBM, Corp.
+ */
+
+#include <linux/module.h>
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/uaccess.h>
+#include <linux/slab.h>
+#include <linux/sched.h>
+#include <linux/stddef.h>
+#include <linux/types.h>
+#include <linux/uio.h>
+#include <net/9p/9p.h>
+#include <net/9p/client.h>
+#include "protocol.h"
+
+#include <trace/events/9p.h>
+
+/* len[2] text[len] */
+#define P9_STRLEN(s) \
+	(2 + min_t(size_t, s ? strlen(s) : 0, USHRT_MAX))
+
+/**
+ * p9_msg_buf_size - Returns a buffer size sufficiently large to hold the
+ * intended 9p message.
+ * @c: client
+ * @type: message type
+ * @fmt: format template for assembling request message
+ * (see p9pdu_vwritef)
+ * @ap: variable arguments to be fed to passed format template
+ * (see p9pdu_vwritef)
+ *
+ * Note: Even for response types (P9_R*) the format template and variable
+ * arguments must always be for the originating request type (P9_T*).
+ */
+size_t p9_msg_buf_size(struct p9_client *c, enum p9_msg_t type,
+			const char *fmt, va_list ap)
+{
+	/* size[4] type[1] tag[2] */
+	const int hdr = 4 + 1 + 2;
+	/* ename[s] errno[4] */
+	const int rerror_size = hdr + P9_ERRMAX + 4;
+	/* ecode[4] */
+	const int rlerror_size = hdr + 4;
+	const int err_size =
+		c->proto_version == p9_proto_2000L ? rlerror_size : rerror_size;
+
+	static_assert(NAME_MAX <= 4*1024, "p9_msg_buf_size() currently assumes "
+				  "a max. allowed directory entry name length of 4k");
+
+	switch (type) {
+
+	/* message types not used at all */
+	case P9_TERROR:
+	case P9_TLERROR:
+	case P9_TAUTH:
+	case P9_RAUTH:
+		BUG();
+
+	/* variable length & potentially large message types */
+	case P9_TATTACH:
+		BUG_ON(strcmp("ddss?u", fmt));
+		va_arg(ap, int32_t);
+		va_arg(ap, int32_t);
+		{
+			const char *uname = va_arg(ap, const char *);
+			const char *aname = va_arg(ap, const char *);
+			/* fid[4] afid[4] uname[s] aname[s] n_uname[4] */
+			return hdr + 4 + 4 + P9_STRLEN(uname) + P9_STRLEN(aname) + 4;
+		}
+	case P9_TWALK:
+		BUG_ON(strcmp("ddT", fmt));
+		va_arg(ap, int32_t);
+		va_arg(ap, int32_t);
+		{
+			uint i, nwname = va_arg(ap, int);
+			size_t wname_all;
+			const char **wnames = va_arg(ap, const char **);
+			for (i = 0, wname_all = 0; i < nwname; ++i) {
+				wname_all += P9_STRLEN(wnames[i]);
+			}
+			/* fid[4] newfid[4] nwname[2] nwname*(wname[s]) */
+			return hdr + 4 + 4 + 2 + wname_all;
+		}
+	case P9_RWALK:
+		BUG_ON(strcmp("ddT", fmt));
+		va_arg(ap, int32_t);
+		va_arg(ap, int32_t);
+		{
+			uint nwname = va_arg(ap, int);
+			/* nwqid[2] nwqid*(wqid[13]) */
+			return max_t(size_t, hdr + 2 + nwname * 13, err_size);
+		}
+	case P9_TCREATE:
+		BUG_ON(strcmp("dsdb?s", fmt));
+		va_arg(ap, int32_t);
+		{
+			const char *name = va_arg(ap, const char *);
+			if (c->proto_version == p9_proto_legacy) {
+				/* fid[4] name[s] perm[4] mode[1] */
+				return hdr + 4 + P9_STRLEN(name) + 4 + 1;
+			} else {
+				va_arg(ap, int32_t);
+				va_arg(ap, int);
+				{
+					const char *ext = va_arg(ap, const char *);
+					/* fid[4] name[s] perm[4] mode[1] extension[s] */
+					return hdr + 4 + P9_STRLEN(name) + 4 + 1 + P9_STRLEN(ext);
+				}
+			}
+		}
+	case P9_TLCREATE:
+		BUG_ON(strcmp("dsddg", fmt));
+		va_arg(ap, int32_t);
+		{
+			const char *name = va_arg(ap, const char *);
+			/* fid[4] name[s] flags[4] mode[4] gid[4] */
+			return hdr + 4 + P9_STRLEN(name) + 4 + 4 + 4;
+		}
+	case P9_RREAD:
+	case P9_RREADDIR:
+		BUG_ON(strcmp("dqd", fmt));
+		va_arg(ap, int32_t);
+		va_arg(ap, int64_t);
+		{
+			const int32_t count = va_arg(ap, int32_t);
+			/* count[4] data[count] */
+			return max_t(size_t, hdr + 4 + count, err_size);
+		}
+	case P9_TWRITE:
+		BUG_ON(strcmp("dqV", fmt));
+		va_arg(ap, int32_t);
+		va_arg(ap, int64_t);
+		{
+			const int32_t count = va_arg(ap, int32_t);
+			/* fid[4] offset[8] count[4] data[count] */
+			return hdr + 4 + 8 + 4 + count;
+		}
+	case P9_TRENAMEAT:
+		BUG_ON(strcmp("dsds", fmt));
+		va_arg(ap, int32_t);
+		{
+			const char *oldname, *newname;
+			oldname = va_arg(ap, const char *);
+			va_arg(ap, int32_t);
+			newname = va_arg(ap, const char *);
+			/* olddirfid[4] oldname[s] newdirfid[4] newname[s] */
+			return hdr + 4 + P9_STRLEN(oldname) + 4 + P9_STRLEN(newname);
+		}
+	case P9_TSYMLINK:
+		BUG_ON(strcmp("dssg", fmt));
+		va_arg(ap, int32_t);
+		{
+			const char *name = va_arg(ap, const char *);
+			const char *symtgt = va_arg(ap, const char *);
+			/* fid[4] name[s] symtgt[s] gid[4] */
+			return hdr + 4 + P9_STRLEN(name) + P9_STRLEN(symtgt) + 4;
+		}
+
+	case P9_RERROR:
+		return rerror_size;
+	case P9_RLERROR:
+		return rlerror_size;
+
+	/* small message types */
+	case P9_TWSTAT:
+	case P9_RSTAT:
+	case P9_RREADLINK:
+	case P9_TXATTRWALK:
+	case P9_TXATTRCREATE:
+	case P9_TLINK:
+	case P9_TMKDIR:
+	case P9_TMKNOD:
+	case P9_TRENAME:
+	case P9_TUNLINKAT:
+	case P9_TLOCK:
+		return 8 * 1024;
+
+	/* tiny message types */
+	default:
+		return 4 * 1024;
+
+	}
+}
+
+static int
+p9pdu_writef(struct p9_fcall *pdu, int proto_version, const char *fmt, ...);
+
+void p9stat_free(struct p9_wstat *stbuf)
+{
+	kfree(stbuf->name);
+	stbuf->name = NULL;
+	kfree(stbuf->uid);
+	stbuf->uid = NULL;
+	kfree(stbuf->gid);
+	stbuf->gid = NULL;
+	kfree(stbuf->muid);
+	stbuf->muid = NULL;
+	kfree(stbuf->extension);
+	stbuf->extension = NULL;
+}
+EXPORT_SYMBOL(p9stat_free);
+
+size_t pdu_read(struct p9_fcall *pdu, void *data, size_t size)
+{
+	size_t len = min(pdu->size - pdu->offset, size);
+
+	memcpy(data, &pdu->sdata[pdu->offset], len);
+	pdu->offset += len;
+	return size - len;
+}
+
+static size_t pdu_write(struct p9_fcall *pdu, const void *data, size_t size)
+{
+	size_t len = min(pdu->capacity - pdu->size, size);
+
+	memcpy(&pdu->sdata[pdu->size], data, len);
+	pdu->size += len;
+	return size - len;
+}
+
+static size_t
+pdu_write_u(struct p9_fcall *pdu, struct iov_iter *from, size_t size)
+{
+	size_t len = min(pdu->capacity - pdu->size, size);
+
+	if (!copy_from_iter_full(&pdu->sdata[pdu->size], len, from))
+		len = 0;
+
+	pdu->size += len;
+	return size - len;
+}
+
+/*	b - int8_t
+ *	w - int16_t
+ *	d - int32_t
+ *	q - int64_t
+ *	s - string
+ *	u - numeric uid
+ *	g - numeric gid
+ *	S - stat
+ *	Q - qid
+ *	D - data blob (int32_t size followed by void *, results are not freed)
+ *	T - array of strings (int16_t count, followed by strings)
+ *	R - array of qids (int16_t count, followed by qids)
+ *	A - stat for 9p2000.L (p9_stat_dotl)
+ *	? - if optional = 1, continue parsing
+ */
+
+static int
+p9pdu_vreadf(struct p9_fcall *pdu, int proto_version, const char *fmt,
+	     va_list ap)
+{
+	const char *ptr;
+	int errcode = 0;
+
+	for (ptr = fmt; *ptr; ptr++) {
+		switch (*ptr) {
+		case 'b':{
+				int8_t *val = va_arg(ap, int8_t *);
+				if (pdu_read(pdu, val, sizeof(*val))) {
+					errcode = -EFAULT;
+					break;
+				}
+			}
+			break;
+		case 'w':{
+				int16_t *val = va_arg(ap, int16_t *);
+				__le16 le_val;
+				if (pdu_read(pdu, &le_val, sizeof(le_val))) {
+					errcode = -EFAULT;
+					break;
+				}
+				*val = le16_to_cpu(le_val);
+			}
+			break;
+		case 'd':{
+				int32_t *val = va_arg(ap, int32_t *);
+				__le32 le_val;
+				if (pdu_read(pdu, &le_val, sizeof(le_val))) {
+					errcode = -EFAULT;
+					break;
+				}
+				*val = le32_to_cpu(le_val);
+			}
+			break;
+		case 'q':{
+				int64_t *val = va_arg(ap, int64_t *);
+				__le64 le_val;
+				if (pdu_read(pdu, &le_val, sizeof(le_val))) {
+					errcode = -EFAULT;
+					break;
+				}
+				*val = le64_to_cpu(le_val);
+			}
+			break;
+		case 's':{
+				char **sptr = va_arg(ap, char **);
+				uint16_t len;
+
+				errcode = p9pdu_readf(pdu, proto_version,
+								"w", &len);
+				if (errcode)
+					break;
+
+				*sptr = kmalloc(len + 1, GFP_NOFS);
+				if (*sptr == NULL) {
+					errcode = -ENOMEM;
+					break;
+				}
+				if (pdu_read(pdu, *sptr, len)) {
+					errcode = -EFAULT;
+					kfree(*sptr);
+					*sptr = NULL;
+				} else
+					(*sptr)[len] = 0;
+			}
+			break;
+		case 'u': {
+				kuid_t *uid = va_arg(ap, kuid_t *);
+				__le32 le_val;
+				if (pdu_read(pdu, &le_val, sizeof(le_val))) {
+					errcode = -EFAULT;
+					break;
+				}
+				*uid = make_kuid(&init_user_ns,
+						 le32_to_cpu(le_val));
+			} break;
+		case 'g': {
+				kgid_t *gid = va_arg(ap, kgid_t *);
+				__le32 le_val;
+				if (pdu_read(pdu, &le_val, sizeof(le_val))) {
+					errcode = -EFAULT;
+					break;
+				}
+				*gid = make_kgid(&init_user_ns,
+						 le32_to_cpu(le_val));
+			} break;
+		case 'Q':{
+				struct p9_qid *qid =
+				    va_arg(ap, struct p9_qid *);
+
+				errcode = p9pdu_readf(pdu, proto_version, "bdq",
+						      &qid->type, &qid->version,
+						      &qid->path);
+			}
+			break;
+		case 'S':{
+				struct p9_wstat *stbuf =
+				    va_arg(ap, struct p9_wstat *);
+
+				memset(stbuf, 0, sizeof(struct p9_wstat));
+				stbuf->n_uid = stbuf->n_muid = INVALID_UID;
+				stbuf->n_gid = INVALID_GID;
+
+				errcode =
+				    p9pdu_readf(pdu, proto_version,
+						"wwdQdddqssss?sugu",
+						&stbuf->size, &stbuf->type,
+						&stbuf->dev, &stbuf->qid,
+						&stbuf->mode, &stbuf->atime,
+						&stbuf->mtime, &stbuf->length,
+						&stbuf->name, &stbuf->uid,
+						&stbuf->gid, &stbuf->muid,
+						&stbuf->extension,
+						&stbuf->n_uid, &stbuf->n_gid,
+						&stbuf->n_muid);
+				if (errcode)
+					p9stat_free(stbuf);
+			}
+			break;
+		case 'D':{
+				uint32_t *count = va_arg(ap, uint32_t *);
+				void **data = va_arg(ap, void **);
+
+				errcode =
+				    p9pdu_readf(pdu, proto_version, "d", count);
+				if (!errcode) {
+					*count =
+					    min_t(uint32_t, *count,
+						  pdu->size - pdu->offset);
+					*data = &pdu->sdata[pdu->offset];
+				}
+			}
+			break;
+		case 'T':{
+				uint16_t *nwname = va_arg(ap, uint16_t *);
+				char ***wnames = va_arg(ap, char ***);
+
+				*wnames = NULL;
+
+				errcode = p9pdu_readf(pdu, proto_version,
+								"w", nwname);
+				if (!errcode) {
+					*wnames =
+					    kmalloc_array(*nwname,
+							  sizeof(char *),
+							  GFP_NOFS);
+					if (!*wnames)
+						errcode = -ENOMEM;
+					else
+						(*wnames)[0] = NULL;
+				}
+
+				if (!errcode) {
+					int i;
+
+					for (i = 0; i < *nwname; i++) {
+						errcode =
+						    p9pdu_readf(pdu,
+								proto_version,
+								"s",
+								&(*wnames)[i]);
+						if (errcode) {
+							(*wnames)[i] = NULL;
+							break;
+						}
+					}
+				}
+
+				if (errcode) {
+					if (*wnames) {
+						int i;
+
+						for (i = 0; i < *nwname; i++) {
+							if (!(*wnames)[i])
+								break;
+							kfree((*wnames)[i]);
+						}
+						kfree(*wnames);
+						*wnames = NULL;
+					}
+				}
+			}
+			break;
+		case 'R':{
+				uint16_t *nwqid = va_arg(ap, uint16_t *);
+				struct p9_qid **wqids =
+				    va_arg(ap, struct p9_qid **);
+
+				*wqids = NULL;
+
+				errcode =
+				    p9pdu_readf(pdu, proto_version, "w", nwqid);
+				if (!errcode) {
+					*wqids =
+					    kmalloc_array(*nwqid,
+							  sizeof(struct p9_qid),
+							  GFP_NOFS);
+					if (*wqids == NULL)
+						errcode = -ENOMEM;
+				}
+
+				if (!errcode) {
+					int i;
+
+					for (i = 0; i < *nwqid; i++) {
+						errcode =
+						    p9pdu_readf(pdu,
+								proto_version,
+								"Q",
+								&(*wqids)[i]);
+						if (errcode)
+							break;
+					}
+				}
+
+				if (errcode) {
+					kfree(*wqids);
+					*wqids = NULL;
+				}
+			}
+			break;
+		case 'A': {
+				struct p9_stat_dotl *stbuf =
+				    va_arg(ap, struct p9_stat_dotl *);
+
+				memset(stbuf, 0, sizeof(struct p9_stat_dotl));
+				errcode =
+				    p9pdu_readf(pdu, proto_version,
+					"qQdugqqqqqqqqqqqqqqq",
+					&stbuf->st_result_mask,
+					&stbuf->qid,
+					&stbuf->st_mode,
+					&stbuf->st_uid, &stbuf->st_gid,
+					&stbuf->st_nlink,
+					&stbuf->st_rdev, &stbuf->st_size,
+					&stbuf->st_blksize, &stbuf->st_blocks,
+					&stbuf->st_atime_sec,
+					&stbuf->st_atime_nsec,
+					&stbuf->st_mtime_sec,
+					&stbuf->st_mtime_nsec,
+					&stbuf->st_ctime_sec,
+					&stbuf->st_ctime_nsec,
+					&stbuf->st_btime_sec,
+					&stbuf->st_btime_nsec,
+					&stbuf->st_gen,
+					&stbuf->st_data_version);
+			}
+			break;
+		case '?':
+			if ((proto_version != p9_proto_2000u) &&
+				(proto_version != p9_proto_2000L))
+				return 0;
+			break;
+		default:
+			BUG();
+			break;
+		}
+
+		if (errcode)
+			break;
+	}
+
+	return errcode;
+}
+
+int
+p9pdu_vwritef(struct p9_fcall *pdu, int proto_version, const char *fmt,
+	va_list ap)
+{
+	const char *ptr;
+	int errcode = 0;
+
+	for (ptr = fmt; *ptr; ptr++) {
+		switch (*ptr) {
+		case 'b':{
+				int8_t val = va_arg(ap, int);
+				if (pdu_write(pdu, &val, sizeof(val)))
+					errcode = -EFAULT;
+			}
+			break;
+		case 'w':{
+				__le16 val = cpu_to_le16(va_arg(ap, int));
+				if (pdu_write(pdu, &val, sizeof(val)))
+					errcode = -EFAULT;
+			}
+			break;
+		case 'd':{
+				__le32 val = cpu_to_le32(va_arg(ap, int32_t));
+				if (pdu_write(pdu, &val, sizeof(val)))
+					errcode = -EFAULT;
+			}
+			break;
+		case 'q':{
+				__le64 val = cpu_to_le64(va_arg(ap, int64_t));
+				if (pdu_write(pdu, &val, sizeof(val)))
+					errcode = -EFAULT;
+			}
+			break;
+		case 's':{
+				const char *sptr = va_arg(ap, const char *);
+				uint16_t len = 0;
+				if (sptr)
+					len = min_t(size_t, strlen(sptr),
+								USHRT_MAX);
+
+				errcode = p9pdu_writef(pdu, proto_version,
+								"w", len);
+				if (!errcode && pdu_write(pdu, sptr, len))
+					errcode = -EFAULT;
+			}
+			break;
+		case 'u': {
+				kuid_t uid = va_arg(ap, kuid_t);
+				__le32 val = cpu_to_le32(
+						from_kuid(&init_user_ns, uid));
+				if (pdu_write(pdu, &val, sizeof(val)))
+					errcode = -EFAULT;
+			} break;
+		case 'g': {
+				kgid_t gid = va_arg(ap, kgid_t);
+				__le32 val = cpu_to_le32(
+						from_kgid(&init_user_ns, gid));
+				if (pdu_write(pdu, &val, sizeof(val)))
+					errcode = -EFAULT;
+			} break;
+		case 'Q':{
+				const struct p9_qid *qid =
+				    va_arg(ap, const struct p9_qid *);
+				errcode =
+				    p9pdu_writef(pdu, proto_version, "bdq",
+						 qid->type, qid->version,
+						 qid->path);
+			} break;
+		case 'S':{
+				const struct p9_wstat *stbuf =
+				    va_arg(ap, const struct p9_wstat *);
+				errcode =
+				    p9pdu_writef(pdu, proto_version,
+						 "wwdQdddqssss?sugu",
+						 stbuf->size, stbuf->type,
+						 stbuf->dev, &stbuf->qid,
+						 stbuf->mode, stbuf->atime,
+						 stbuf->mtime, stbuf->length,
+						 stbuf->name, stbuf->uid,
+						 stbuf->gid, stbuf->muid,
+						 stbuf->extension, stbuf->n_uid,
+						 stbuf->n_gid, stbuf->n_muid);
+			} break;
+		case 'V':{
+				uint32_t count = va_arg(ap, uint32_t);
+				struct iov_iter *from =
+						va_arg(ap, struct iov_iter *);
+				errcode = p9pdu_writef(pdu, proto_version, "d",
+									count);
+				if (!errcode && pdu_write_u(pdu, from, count))
+					errcode = -EFAULT;
+			}
+			break;
+		case 'T':{
+				uint16_t nwname = va_arg(ap, int);
+				const char **wnames = va_arg(ap, const char **);
+
+				errcode = p9pdu_writef(pdu, proto_version, "w",
+									nwname);
+				if (!errcode) {
+					int i;
+
+					for (i = 0; i < nwname; i++) {
+						errcode =
+						    p9pdu_writef(pdu,
+								proto_version,
+								 "s",
+								 wnames[i]);
+						if (errcode)
+							break;
+					}
+				}
+			}
+			break;
+		case 'R':{
+				uint16_t nwqid = va_arg(ap, int);
+				struct p9_qid *wqids =
+				    va_arg(ap, struct p9_qid *);
+
+				errcode = p9pdu_writef(pdu, proto_version, "w",
+									nwqid);
+				if (!errcode) {
+					int i;
+
+					for (i = 0; i < nwqid; i++) {
+						errcode =
+						    p9pdu_writef(pdu,
+								proto_version,
+								 "Q",
+								 &wqids[i]);
+						if (errcode)
+							break;
+					}
+				}
+			}
+			break;
+		case 'I':{
+				struct p9_iattr_dotl *p9attr = va_arg(ap,
+							struct p9_iattr_dotl *);
+
+				errcode = p9pdu_writef(pdu, proto_version,
+							"ddugqqqqq",
+							p9attr->valid,
+							p9attr->mode,
+							p9attr->uid,
+							p9attr->gid,
+							p9attr->size,
+							p9attr->atime_sec,
+							p9attr->atime_nsec,
+							p9attr->mtime_sec,
+							p9attr->mtime_nsec);
+			}
+			break;
+		case '?':
+			if ((proto_version != p9_proto_2000u) &&
+				(proto_version != p9_proto_2000L))
+				return 0;
+			break;
+		default:
+			BUG();
+			break;
+		}
+
+		if (errcode)
+			break;
+	}
+
+	return errcode;
+}
+
+int p9pdu_readf(struct p9_fcall *pdu, int proto_version, const char *fmt, ...)
+{
+	va_list ap;
+	int ret;
+
+	va_start(ap, fmt);
+	ret = p9pdu_vreadf(pdu, proto_version, fmt, ap);
+	va_end(ap);
+
+	return ret;
+}
+
+static int
+p9pdu_writef(struct p9_fcall *pdu, int proto_version, const char *fmt, ...)
+{
+	va_list ap;
+	int ret;
+
+	va_start(ap, fmt);
+	ret = p9pdu_vwritef(pdu, proto_version, fmt, ap);
+	va_end(ap);
+
+	return ret;
+}
+
+int p9stat_read(struct p9_client *clnt, char *buf, int len, struct p9_wstat *st)
+{
+	struct p9_fcall fake_pdu;
+	int ret;
+
+	fake_pdu.size = len;
+	fake_pdu.capacity = len;
+	fake_pdu.sdata = buf;
+	fake_pdu.offset = 0;
+
+	ret = p9pdu_readf(&fake_pdu, clnt->proto_version, "S", st);
+	if (ret) {
+		p9_debug(P9_DEBUG_9P, "<<< p9stat_read failed: %d\n", ret);
+		trace_9p_protocol_dump(clnt, &fake_pdu);
+		return ret;
+	}
+
+	return fake_pdu.offset;
+}
+EXPORT_SYMBOL(p9stat_read);
+
+int p9pdu_prepare(struct p9_fcall *pdu, int16_t tag, int8_t type)
+{
+	pdu->id = type;
+	return p9pdu_writef(pdu, 0, "dbw", 0, type, tag);
+}
+
+int p9pdu_finalize(struct p9_client *clnt, struct p9_fcall *pdu)
+{
+	int size = pdu->size;
+	int err;
+
+	pdu->size = 0;
+	err = p9pdu_writef(pdu, 0, "d", size);
+	pdu->size = size;
+
+	trace_9p_protocol_dump(clnt, pdu);
+	p9_debug(P9_DEBUG_9P, ">>> size=%d type: %d tag: %d\n",
+		 pdu->size, pdu->id, pdu->tag);
+
+	return err;
+}
+
+void p9pdu_reset(struct p9_fcall *pdu)
+{
+	pdu->offset = 0;
+	pdu->size = 0;
+}
+
+int p9dirent_read(struct p9_client *clnt, char *buf, int len,
+		  struct p9_dirent *dirent)
+{
+	struct p9_fcall fake_pdu;
+	int ret;
+	char *nameptr;
+
+	fake_pdu.size = len;
+	fake_pdu.capacity = len;
+	fake_pdu.sdata = buf;
+	fake_pdu.offset = 0;
+
+	ret = p9pdu_readf(&fake_pdu, clnt->proto_version, "Qqbs", &dirent->qid,
+			  &dirent->d_off, &dirent->d_type, &nameptr);
+	if (ret) {
+		p9_debug(P9_DEBUG_9P, "<<< p9dirent_read failed: %d\n", ret);
+		trace_9p_protocol_dump(clnt, &fake_pdu);
+		return ret;
+	}
+
+	ret = strscpy(dirent->d_name, nameptr, sizeof(dirent->d_name));
+	if (ret < 0) {
+		p9_debug(P9_DEBUG_ERROR,
+			 "On the wire dirent name too long: %s\n",
+			 nameptr);
+		kfree(nameptr);
+		return ret;
+	}
+	kfree(nameptr);
+
+	return fake_pdu.offset;
+}
+EXPORT_SYMBOL(p9dirent_read);