--- /dev/null
+/*
+ * net/9p/protocol.c
+ *
+ * 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.
+ *
+ *  This program is free software; you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License version 2
+ *  as published by the Free Software Foundation.
+ *
+ *  This program is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with this program; if not, write to:
+ *  Free Software Foundation
+ *  51 Franklin Street, Fifth Floor
+ *  Boston, MA  02111-1301  USA
+ *
+ */
+
+#include <linux/module.h>
+#include <linux/errno.h>
+#include <net/9p/9p.h>
+#include <net/9p/client.h>
+#include "protocol.h"
+
+#ifndef MIN
+#define MIN(a, b) (((a) < (b)) ? (a) : (b))
+#endif
+
+#ifndef MAX
+#define MAX(a, b) (((a) > (b)) ? (a) : (b))
+#endif
+
+#ifndef offset_of
+#define offset_of(type, memb) \
+       ((unsigned long)(&((type *)0)->memb))
+#endif
+#ifndef container_of
+#define container_of(obj, type, memb) \
+       ((type *)(((char *)obj) - offset_of(type, memb)))
+#endif
+
+static int
+p9pdu_writef(struct p9_fcall *pdu, int optional, const char *fmt, ...);
+
+void p9stat_free(struct p9_wstat *stbuf)
+{
+       kfree(stbuf->name);
+       kfree(stbuf->uid);
+       kfree(stbuf->gid);
+       kfree(stbuf->muid);
+       kfree(stbuf->extension);
+}
+EXPORT_SYMBOL(p9stat_free);
+
+static 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;
+}
+
+/*
+       b - int8_t
+       w - int16_t
+       d - int32_t
+       q - int64_t
+       s - string
+       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)
+       ? - if optional = 1, continue parsing
+*/
+
+static int
+p9pdu_vreadf(struct p9_fcall *pdu, int optional, 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 *);
+                               if (pdu_read(pdu, val, sizeof(*val))) {
+                                       errcode = -EFAULT;
+                                       break;
+                               }
+                               *val = cpu_to_le16(*val);
+                       }
+                       break;
+               case 'd':{
+                               int32_t *val = va_arg(ap, int32_t *);
+                               if (pdu_read(pdu, val, sizeof(*val))) {
+                                       errcode = -EFAULT;
+                                       break;
+                               }
+                               *val = cpu_to_le32(*val);
+                       }
+                       break;
+               case 'q':{
+                               int64_t *val = va_arg(ap, int64_t *);
+                               if (pdu_read(pdu, val, sizeof(*val))) {
+                                       errcode = -EFAULT;
+                                       break;
+                               }
+                               *val = cpu_to_le64(*val);
+                       }
+                       break;
+               case 's':{
+                               char **ptr = va_arg(ap, char **);
+                               int16_t len;
+                               int size;
+
+                               errcode = p9pdu_readf(pdu, optional, "w", &len);
+                               if (errcode)
+                                       break;
+
+                               size = MAX(len, 0);
+
+                               *ptr = kmalloc(size + 1, GFP_KERNEL);
+                               if (*ptr == NULL) {
+                                       errcode = -EFAULT;
+                                       break;
+                               }
+                               if (pdu_read(pdu, *ptr, size)) {
+                                       errcode = -EFAULT;
+                                       kfree(*ptr);
+                                       *ptr = NULL;
+                               } else
+                                       (*ptr)[size] = 0;
+                       }
+                       break;
+               case 'Q':{
+                               struct p9_qid *qid =
+                                   va_arg(ap, struct p9_qid *);
+
+                               errcode = p9pdu_readf(pdu, optional, "bdq",
+                                                     &qid->type, &qid->version,
+                                                     &qid->path);
+                       }
+                       break;
+               case 'S':{
+                               struct p9_wstat *stbuf =
+                                   va_arg(ap, struct p9_wstat *);
+
+                               stbuf->extension = NULL;
+                               stbuf->n_uid = stbuf->n_gid = stbuf->n_muid =
+                                   -1;
+
+                               errcode =
+                                   p9pdu_readf(pdu, optional,
+                                               "wwdQdddqssss?sddd",
+                                               &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':{
+                               int32_t *count = va_arg(ap, int32_t *);
+                               void **data = va_arg(ap, void **);
+
+                               errcode =
+                                   p9pdu_readf(pdu, optional, "d", count);
+                               if (!errcode) {
+                                       *count =
+                                           MIN(*count,
+                                               pdu->size - pdu->offset);
+                                       *data = &pdu->sdata[pdu->offset];
+                               }
+                       }
+                       break;
+               case 'T':{
+                               int16_t *nwname = va_arg(ap, int16_t *);
+                               char ***wnames = va_arg(ap, char ***);
+
+                               errcode =
+                                   p9pdu_readf(pdu, optional, "w", nwname);
+                               if (!errcode) {
+                                       *wnames =
+                                           kmalloc(sizeof(char *) * *nwname,
+                                                   GFP_KERNEL);
+                                       if (!*wnames)
+                                               errcode = -ENOMEM;
+                               }
+
+                               if (!errcode) {
+                                       int i;
+
+                                       for (i = 0; i < *nwname; i++) {
+                                               errcode =
+                                                   p9pdu_readf(pdu, optional,
+                                                               "s",
+                                                               &(*wnames)[i]);
+                                               if (errcode)
+                                                       break;
+                                       }
+                               }
+
+                               if (errcode) {
+                                       if (*wnames) {
+                                               int i;
+
+                                               for (i = 0; i < *nwname; i++)
+                                                       kfree((*wnames)[i]);
+                                       }
+                                       kfree(*wnames);
+                                       *wnames = NULL;
+                               }
+                       }
+                       break;
+               case 'R':{
+                               int16_t *nwqid = va_arg(ap, int16_t *);
+                               struct p9_qid **wqids =
+                                   va_arg(ap, struct p9_qid **);
+
+                               *wqids = NULL;
+
+                               errcode =
+                                   p9pdu_readf(pdu, optional, "w", nwqid);
+                               if (!errcode) {
+                                       *wqids =
+                                           kmalloc(*nwqid *
+                                                   sizeof(struct p9_qid),
+                                                   GFP_KERNEL);
+                                       if (*wqids == NULL)
+                                               errcode = -ENOMEM;
+                               }
+
+                               if (!errcode) {
+                                       int i;
+
+                                       for (i = 0; i < *nwqid; i++) {
+                                               errcode =
+                                                   p9pdu_readf(pdu, optional,
+                                                               "Q",
+                                                               &(*wqids)[i]);
+                                               if (errcode)
+                                                       break;
+                                       }
+                               }
+
+                               if (errcode) {
+                                       kfree(*wqids);
+                                       *wqids = NULL;
+                               }
+                       }
+                       break;
+               case '?':
+                       if (!optional)
+                               return 0;
+                       break;
+               default:
+                       BUG();
+                       break;
+               }
+
+               if (errcode)
+                       break;
+       }
+
+       return errcode;
+}
+
+int
+p9pdu_vwritef(struct p9_fcall *pdu, int optional, 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':{
+                               int16_t val = va_arg(ap, int);
+                               if (pdu_write(pdu, &val, sizeof(val)))
+                                       errcode = -EFAULT;
+                       }
+                       break;
+               case 'd':{
+                               int32_t val = va_arg(ap, int32_t);
+                               if (pdu_write(pdu, &val, sizeof(val)))
+                                       errcode = -EFAULT;
+                       }
+                       break;
+               case 'q':{
+                               int64_t val = va_arg(ap, int64_t);
+                               if (pdu_write(pdu, &val, sizeof(val)))
+                                       errcode = -EFAULT;
+                       }
+                       break;
+               case 's':{
+                               const char *ptr = va_arg(ap, const char *);
+                               int16_t len = 0;
+
+                               if (ptr)
+                                       len = MIN(strlen(ptr), USHORT_MAX);
+
+                               errcode = p9pdu_writef(pdu, optional, "w", len);
+                               if (!errcode && pdu_write(pdu, ptr, len))
+                                       errcode = -EFAULT;
+                       }
+                       break;
+               case 'Q':{
+                               const struct p9_qid *qid =
+                                   va_arg(ap, const struct p9_qid *);
+                               errcode =
+                                   p9pdu_writef(pdu, optional, "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, optional,
+                                                "wwdQdddqssss?sddd",
+                                                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 'D':{
+                               int32_t count = va_arg(ap, int32_t);
+                               const void *data = va_arg(ap, const void *);
+
+                               errcode =
+                                   p9pdu_writef(pdu, optional, "d", count);
+                               if (!errcode && pdu_write(pdu, data, count))
+                                       errcode = -EFAULT;
+                       }
+                       break;
+               case 'T':{
+                               int16_t nwname = va_arg(ap, int);
+                               const char **wnames = va_arg(ap, const char **);
+
+                               errcode =
+                                   p9pdu_writef(pdu, optional, "w", nwname);
+                               if (!errcode) {
+                                       int i;
+
+                                       for (i = 0; i < nwname; i++) {
+                                               errcode =
+                                                   p9pdu_writef(pdu, optional,
+                                                                "s",
+                                                                wnames[i]);
+                                               if (errcode)
+                                                       break;
+                                       }
+                               }
+                       }
+                       break;
+               case 'R':{
+                               int16_t nwqid = va_arg(ap, int);
+                               struct p9_qid *wqids =
+                                   va_arg(ap, struct p9_qid *);
+
+                               errcode =
+                                   p9pdu_writef(pdu, optional, "w", nwqid);
+                               if (!errcode) {
+                                       int i;
+
+                                       for (i = 0; i < nwqid; i++) {
+                                               errcode =
+                                                   p9pdu_writef(pdu, optional,
+                                                                "Q",
+                                                                &wqids[i]);
+                                               if (errcode)
+                                                       break;
+                                       }
+                               }
+                       }
+                       break;
+               case '?':
+                       if (!optional)
+                               return 0;
+                       break;
+               default:
+                       BUG();
+                       break;
+               }
+
+               if (errcode)
+                       break;
+       }
+
+       return errcode;
+}
+
+int p9pdu_readf(struct p9_fcall *pdu, int optional, const char *fmt, ...)
+{
+       va_list ap;
+       int ret;
+
+       va_start(ap, fmt);
+       ret = p9pdu_vreadf(pdu, optional, fmt, ap);
+       va_end(ap);
+
+       return ret;
+}
+
+static int
+p9pdu_writef(struct p9_fcall *pdu, int optional, const char *fmt, ...)
+{
+       va_list ap;
+       int ret;
+
+       va_start(ap, fmt);
+       ret = p9pdu_vwritef(pdu, optional, fmt, ap);
+       va_end(ap);
+
+       return ret;
+}