hw/9pfs: Add new proxy filesystem driver

Add new proxy filesystem driver to add root privilege to qemu process.
It needs a helper process to be started by root user.

Following command line can be used to utilize proxy filesystem driver
-virtfs proxy,id=<id>,mount_tag=<tag>,socket_fd=<socket-fd>

Signed-off-by: M. Mohan Kumar <mohan@in.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>

Makefile.objs

@@ -311,6 +311,7 @@ hw-obj-$(CONFIG_SOUND) += $(sound-obj-y)
 9pfs-nested-$(CONFIG_VIRTFS) += virtio-9p-coth.o cofs.o codir.o cofile.o
 9pfs-nested-$(CONFIG_VIRTFS) += coxattr.o virtio-9p-synth.o
 9pfs-nested-$(CONFIG_OPEN_BY_HANDLE) +=  virtio-9p-handle.o
+9pfs-nested-$(CONFIG_VIRTFS) += virtio-9p-proxy.o
 
 hw-obj-$(CONFIG_REALLY_VIRTFS) += $(addprefix 9pfs/, $(9pfs-nested-y))
 $(addprefix 9pfs/, $(9pfs-nested-y)): QEMU_CFLAGS+=$(GLIB_CFLAGS)

fsdev/qemu-fsdev.c

@@ -27,6 +27,7 @@ static FsDriverTable FsDrivers[] = {
     { .name = "handle", .ops = &handle_ops},
 #endif
     { .name = "synth", .ops = &synth_ops},
+    { .name = "proxy", .ops = &proxy_ops},
 };
 
 int qemu_fsdev_add(QemuOpts *opts)

fsdev/qemu-fsdev.h

@@ -44,4 +44,5 @@ FsDriverEntry *get_fsdev_fsentry(char *id);
 extern FileOperations local_ops;
 extern FileOperations handle_ops;
 extern FileOperations synth_ops;
+extern FileOperations proxy_ops;
 #endif

hw/9pfs/virtio-9p-proxy.c

@@ -0,0 +1,388 @@
+/*
+ * Virtio 9p Proxy callback
+ *
+ * Copyright IBM, Corp. 2011
+ *
+ * Authors:
+ * M. Mohan Kumar <mohan@in.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ */
+#include <sys/socket.h>
+#include <sys/un.h>
+#include "hw/virtio.h"
+#include "virtio-9p.h"
+#include "fsdev/qemu-fsdev.h"
+#include "virtio-9p-proxy.h"
+
+typedef struct V9fsProxy {
+    int sockfd;
+    QemuMutex mutex;
+    struct iovec iovec;
+} V9fsProxy;
+
+static int proxy_lstat(FsContext *fs_ctx, V9fsPath *fs_path, struct stat *stbuf)
+{
+    errno = EOPNOTSUPP;
+    return -1;
+}
+
+static ssize_t proxy_readlink(FsContext *fs_ctx, V9fsPath *fs_path,
+                              char *buf, size_t bufsz)
+{
+    errno = EOPNOTSUPP;
+    return -1;
+}
+
+static int proxy_close(FsContext *ctx, V9fsFidOpenState *fs)
+{
+    return close(fs->fd);
+}
+
+static int proxy_closedir(FsContext *ctx, V9fsFidOpenState *fs)
+{
+    return closedir(fs->dir);
+}
+
+static int proxy_open(FsContext *ctx, V9fsPath *fs_path,
+                      int flags, V9fsFidOpenState *fs)
+{
+    fs->fd = -1;
+    return fs->fd;
+}
+
+static int proxy_opendir(FsContext *ctx,
+                         V9fsPath *fs_path, V9fsFidOpenState *fs)
+{
+    fs->dir = NULL;
+    errno = EOPNOTSUPP;
+    return -1;
+}
+
+static void proxy_rewinddir(FsContext *ctx, V9fsFidOpenState *fs)
+{
+    return rewinddir(fs->dir);
+}
+
+static off_t proxy_telldir(FsContext *ctx, V9fsFidOpenState *fs)
+{
+    return telldir(fs->dir);
+}
+
+static int proxy_readdir_r(FsContext *ctx, V9fsFidOpenState *fs,
+                           struct dirent *entry,
+                           struct dirent **result)
+{
+    return readdir_r(fs->dir, entry, result);
+}
+
+static void proxy_seekdir(FsContext *ctx, V9fsFidOpenState *fs, off_t off)
+{
+    return seekdir(fs->dir, off);
+}
+
+static ssize_t proxy_preadv(FsContext *ctx, V9fsFidOpenState *fs,
+                            const struct iovec *iov,
+                            int iovcnt, off_t offset)
+{
+#ifdef CONFIG_PREADV
+    return preadv(fs->fd, iov, iovcnt, offset);
+#else
+    int err = lseek(fs->fd, offset, SEEK_SET);
+    if (err == -1) {
+        return err;
+    } else {
+        return readv(fs->fd, iov, iovcnt);
+    }
+#endif
+}
+
+static ssize_t proxy_pwritev(FsContext *ctx, V9fsFidOpenState *fs,
+                             const struct iovec *iov,
+                             int iovcnt, off_t offset)
+{
+    ssize_t ret;
+
+#ifdef CONFIG_PREADV
+    ret = pwritev(fs->fd, iov, iovcnt, offset);
+#else
+    int err = lseek(fs->fd, offset, SEEK_SET);
+    if (err == -1) {
+        return err;
+    } else {
+        ret = writev(fs->fd, iov, iovcnt);
+    }
+#endif
+#ifdef CONFIG_SYNC_FILE_RANGE
+    if (ret > 0 && ctx->export_flags & V9FS_IMMEDIATE_WRITEOUT) {
+        /*
+         * Initiate a writeback. This is not a data integrity sync.
+         * We want to ensure that we don't leave dirty pages in the cache
+         * after write when writeout=immediate is sepcified.
+         */
+        sync_file_range(fs->fd, offset, ret,
+                        SYNC_FILE_RANGE_WAIT_BEFORE | SYNC_FILE_RANGE_WRITE);
+    }
+#endif
+    return ret;
+}
+
+static int proxy_chmod(FsContext *fs_ctx, V9fsPath *fs_path, FsCred *credp)
+{
+    errno = EOPNOTSUPP;
+    return -1;
+}
+
+static int proxy_mknod(FsContext *fs_ctx, V9fsPath *dir_path,
+                       const char *name, FsCred *credp)
+{
+    errno = EOPNOTSUPP;
+    return -1;
+}
+
+static int proxy_mkdir(FsContext *fs_ctx, V9fsPath *dir_path,
+                       const char *name, FsCred *credp)
+{
+    errno = EOPNOTSUPP;
+    return -1;
+}
+
+static int proxy_fstat(FsContext *fs_ctx, int fid_type,
+                       V9fsFidOpenState *fs, struct stat *stbuf)
+{
+    int fd;
+
+    if (fid_type == P9_FID_DIR) {
+        fd = dirfd(fs->dir);
+    } else {
+        fd = fs->fd;
+    }
+    return fstat(fd, stbuf);
+}
+
+static int proxy_open2(FsContext *fs_ctx, V9fsPath *dir_path, const char *name,
+                       int flags, FsCred *credp, V9fsFidOpenState *fs)
+{
+    fs->fd = -1;
+    errno = EOPNOTSUPP;
+    return -1;
+}
+
+
+static int proxy_symlink(FsContext *fs_ctx, const char *oldpath,
+                         V9fsPath *dir_path, const char *name, FsCred *credp)
+{
+    errno = EOPNOTSUPP;
+    return -1;
+}
+
+static int proxy_link(FsContext *ctx, V9fsPath *oldpath,
+                      V9fsPath *dirpath, const char *name)
+{
+    errno = EOPNOTSUPP;
+    return -1;
+}
+
+static int proxy_truncate(FsContext *ctx, V9fsPath *fs_path, off_t size)
+{
+    errno = EOPNOTSUPP;
+    return -1;
+}
+
+static int proxy_rename(FsContext *ctx, const char *oldpath,
+                        const char *newpath)
+{
+    errno = EOPNOTSUPP;
+    return -1;
+}
+
+static int proxy_chown(FsContext *fs_ctx, V9fsPath *fs_path, FsCred *credp)
+{
+    errno = EOPNOTSUPP;
+    return -1;
+}
+
+static int proxy_utimensat(FsContext *s, V9fsPath *fs_path,
+                           const struct timespec *buf)
+{
+    errno = EOPNOTSUPP;
+    return -1;
+}
+
+static int proxy_remove(FsContext *ctx, const char *path)
+{
+    errno = EOPNOTSUPP;
+    return -1;
+}
+
+static int proxy_fsync(FsContext *ctx, int fid_type,
+                       V9fsFidOpenState *fs, int datasync)
+{
+    int fd;
+
+    if (fid_type == P9_FID_DIR) {
+        fd = dirfd(fs->dir);
+    } else {
+        fd = fs->fd;
+    }
+
+    if (datasync) {
+        return qemu_fdatasync(fd);
+    } else {
+        return fsync(fd);
+    }
+}
+
+static int proxy_statfs(FsContext *s, V9fsPath *fs_path, struct statfs *stbuf)
+{
+    errno = EOPNOTSUPP;
+    return -1;
+}
+
+static ssize_t proxy_lgetxattr(FsContext *ctx, V9fsPath *fs_path,
+                               const char *name, void *value, size_t size)
+{
+    errno = EOPNOTSUPP;
+    return -1;
+}
+
+static ssize_t proxy_llistxattr(FsContext *ctx, V9fsPath *fs_path,
+                                void *value, size_t size)
+{
+    errno = EOPNOTSUPP;
+    return -1;
+}
+
+static int proxy_lsetxattr(FsContext *ctx, V9fsPath *fs_path, const char *name,
+                           void *value, size_t size, int flags)
+{
+    errno = EOPNOTSUPP;
+    return -1;
+}
+
+static int proxy_lremovexattr(FsContext *ctx, V9fsPath *fs_path,
+                              const char *name)
+{
+    errno = EOPNOTSUPP;
+    return -1;
+}
+
+static int proxy_name_to_path(FsContext *ctx, V9fsPath *dir_path,
+                              const char *name, V9fsPath *target)
+{
+    if (dir_path) {
+        v9fs_string_sprintf((V9fsString *)target, "%s/%s",
+                            dir_path->data, name);
+    } else {
+        v9fs_string_sprintf((V9fsString *)target, "%s", name);
+    }
+    /* Bump the size for including terminating NULL */
+    target->size++;
+    return 0;
+}
+
+static int proxy_renameat(FsContext *ctx, V9fsPath *olddir,
+                          const char *old_name, V9fsPath *newdir,
+                          const char *new_name)
+{
+    int ret;
+    V9fsString old_full_name, new_full_name;
+
+    v9fs_string_init(&old_full_name);
+    v9fs_string_init(&new_full_name);
+
+    v9fs_string_sprintf(&old_full_name, "%s/%s", olddir->data, old_name);
+    v9fs_string_sprintf(&new_full_name, "%s/%s", newdir->data, new_name);
+
+    ret = proxy_rename(ctx, old_full_name.data, new_full_name.data);
+    v9fs_string_free(&old_full_name);
+    v9fs_string_free(&new_full_name);
+    return ret;
+}
+
+static int proxy_unlinkat(FsContext *ctx, V9fsPath *dir,
+                          const char *name, int flags)
+{
+    int ret;
+    V9fsString fullname;
+    v9fs_string_init(&fullname);
+
+    v9fs_string_sprintf(&fullname, "%s/%s", dir->data, name);
+    ret = proxy_remove(ctx, fullname.data);
+    v9fs_string_free(&fullname);
+
+    return ret;
+}
+
+static int proxy_parse_opts(QemuOpts *opts, struct FsDriverEntry *fs)
+{
+    const char *sock_fd = qemu_opt_get(opts, "sock_fd");
+
+    if (sock_fd) {
+        fprintf(stderr, "sock_fd option not specified\n");
+        return -1;
+    }
+    fs->path = g_strdup(sock_fd);
+    return 0;
+}
+
+static int proxy_init(FsContext *ctx)
+{
+    V9fsProxy *proxy = g_malloc(sizeof(V9fsProxy));
+    int sock_id;
+
+    sock_id = atoi(ctx->fs_root);
+    if (sock_id < 0) {
+        fprintf(stderr, "socket descriptor not initialized\n");
+        return -1;
+    }
+    g_free(ctx->fs_root);
+
+    proxy->iovec.iov_base = g_malloc(PROXY_MAX_IO_SZ + PROXY_HDR_SZ);
+    proxy->iovec.iov_len = PROXY_MAX_IO_SZ + PROXY_HDR_SZ;
+    ctx->private = proxy;
+    proxy->sockfd = sock_id;
+    qemu_mutex_init(&proxy->mutex);
+
+    ctx->export_flags |= V9FS_PATHNAME_FSCONTEXT;
+    return 0;
+}
+
+FileOperations proxy_ops = {
+    .parse_opts   = proxy_parse_opts,
+    .init         = proxy_init,
+    .lstat        = proxy_lstat,
+    .readlink     = proxy_readlink,
+    .close        = proxy_close,
+    .closedir     = proxy_closedir,
+    .open         = proxy_open,
+    .opendir      = proxy_opendir,
+    .rewinddir    = proxy_rewinddir,
+    .telldir      = proxy_telldir,
+    .readdir_r    = proxy_readdir_r,
+    .seekdir      = proxy_seekdir,
+    .preadv       = proxy_preadv,
+    .pwritev      = proxy_pwritev,
+    .chmod        = proxy_chmod,
+    .mknod        = proxy_mknod,
+    .mkdir        = proxy_mkdir,
+    .fstat        = proxy_fstat,
+    .open2        = proxy_open2,
+    .symlink      = proxy_symlink,
+    .link         = proxy_link,
+    .truncate     = proxy_truncate,
+    .rename       = proxy_rename,
+    .chown        = proxy_chown,
+    .utimensat    = proxy_utimensat,
+    .remove       = proxy_remove,
+    .fsync        = proxy_fsync,
+    .statfs       = proxy_statfs,
+    .lgetxattr    = proxy_lgetxattr,
+    .llistxattr   = proxy_llistxattr,
+    .lsetxattr    = proxy_lsetxattr,
+    .lremovexattr = proxy_lremovexattr,
+    .name_to_path = proxy_name_to_path,
+    .renameat     = proxy_renameat,
+    .unlinkat     = proxy_unlinkat,
+};

hw/9pfs/virtio-9p-proxy.h

@@ -0,0 +1,24 @@
+/*
+ * Virtio 9p Proxy callback
+ *
+ * Copyright IBM, Corp. 2011
+ *
+ * Authors:
+ * M. Mohan Kumar <mohan@in.ibm.com>
+ *
+ * This work is licensed under the terms of the GNU GPL, version 2.  See
+ * the COPYING file in the top-level directory.
+ */
+#ifndef _QEMU_VIRTIO_9P_PROXY_H
+#define _QEMU_VIRTIO_9P_PROXY_H
+
+#define PROXY_MAX_IO_SZ (64 * 1024)
+
+typedef struct {
+    uint32_t type;
+    uint32_t size;
+} ProxyHeader;
+
+#define PROXY_HDR_SZ (sizeof(ProxyHeader))
+
+#endif

qemu-config.c

@@ -211,6 +211,9 @@ QemuOptsList qemu_fsdev_opts = {
         }, {
             .name = "readonly",
             .type = QEMU_OPT_BOOL,
+        }, {
+            .name = "sock_fd",
+            .type = QEMU_OPT_NUMBER,
         },
 
         { /*End of list */ }
@@ -240,6 +243,9 @@ QemuOptsList qemu_virtfs_opts = {
         }, {
             .name = "readonly",
             .type = QEMU_OPT_BOOL,
+        }, {
+            .name = "sock_fd",
+            .type = QEMU_OPT_NUMBER,
         },
 
         { /*End of list */ }

vl.c

@@ -2661,7 +2661,7 @@ int main(int argc, char **argv, char **envp)
             case QEMU_OPTION_virtfs: {
                 QemuOpts *fsdev;
                 QemuOpts *device;
-                const char *writeout;
+                const char *writeout, *sock_fd;
 
                 olist = qemu_find_opts("virtfs");
                 if (!olist) {
@@ -2701,6 +2701,10 @@ int main(int argc, char **argv, char **envp)
                 qemu_opt_set(fsdev, "path", qemu_opt_get(opts, "path"));
                 qemu_opt_set(fsdev, "security_model",
                              qemu_opt_get(opts, "security_model"));
+                sock_fd = qemu_opt_get(opts, "sock_fd");
+                if (sock_fd) {
+                    qemu_opt_set(fsdev, "sock_fd", sock_fd);
+                }
 
                 qemu_opt_set_bool(fsdev, "readonly",
                                 qemu_opt_get_bool(opts, "readonly", 0));