[Qemu-devel] [PATCH V12 05/15] hw/9pfs: Support for opening a file in chroot environment

["M. Mohan Kumar" <mohan@in.ibm.com>]

This patch adds both chroot worker and qemu side support to open a file/
directory in the chroot environment

Signed-off-by: M. Mohan Kumar <mohan@in.ibm.com>
---
 hw/9pfs/virtio-9p-chroot.c |   29 ++++++++++++----
 hw/9pfs/virtio-9p-chroot.h |    2 +-
 hw/9pfs/virtio-9p-local.c  |   79 ++++++++++++++++++++++++++++++++++++++++++--
 3 files changed, 98 insertions(+), 12 deletions(-)

diff --git a/hw/9pfs/virtio-9p-chroot.c b/hw/9pfs/virtio-9p-chroot.c
index 63de410..f5b3abc 100644
--- a/hw/9pfs/virtio-9p-chroot.c
+++ b/hw/9pfs/virtio-9p-chroot.c
@@ -91,13 +91,26 @@ static int v9fs_write_request(int sockfd, V9fsFileObjectRequest *request)
     return 0;
 }
 
-/*
- * This patch adds v9fs_receivefd and v9fs_write_request functions,
- * but there is no caller. To avoid compiler warning message,
- * refer these two functions
- */
-void chroot_dummy(void)
+/* Return opened file descriptor on success or -errno on error */
+int v9fs_request(FsContext *fs_ctx, V9fsFileObjectRequest *request)
 {
-    (void)v9fs_receivefd;
-    (void)v9fs_write_request;
+    int fd, sock_error;
+    qemu_mutex_lock(&fs_ctx->chroot_mutex);
+    if (fs_ctx->chroot_socket == -1) {
+        goto error;
+    }
+    if (v9fs_write_request(fs_ctx->chroot_socket, request) < 0) {
+        goto error;
+    }
+    fd = v9fs_receivefd(fs_ctx->chroot_socket, &sock_error);
+    if (fd < 0 && sock_error) {
+        goto error;
+    }
+    qemu_mutex_unlock(&fs_ctx->chroot_mutex);
+    return fd;
+error:
+    close(fs_ctx->chroot_socket);
+    fs_ctx->chroot_socket = -1;
+    qemu_mutex_unlock(&fs_ctx->chroot_mutex);
+    return -EIO;
 }
diff --git a/hw/9pfs/virtio-9p-chroot.h b/hw/9pfs/virtio-9p-chroot.h
index a817bcf..326238d 100644
--- a/hw/9pfs/virtio-9p-chroot.h
+++ b/hw/9pfs/virtio-9p-chroot.h
@@ -35,6 +35,6 @@ typedef struct V9fsFileObjectRequest
 } V9fsFileObjectRequest;
 
 int v9fs_chroot(FsContext *fs_ctx);
-void chroot_dummy(void);
+int v9fs_request(FsContext *fs_ctx, V9fsFileObjectRequest *or);
 
 #endif /* _QEMU_VIRTIO_9P_CHROOT_H */
diff --git a/hw/9pfs/virtio-9p-local.c b/hw/9pfs/virtio-9p-local.c
index 7a46e93..a91adb8 100644
--- a/hw/9pfs/virtio-9p-local.c
+++ b/hw/9pfs/virtio-9p-local.c
@@ -14,6 +14,9 @@
 #include "hw/virtio.h"
 #include "virtio-9p.h"
 #include "virtio-9p-xattr.h"
+#include "qemu_socket.h"
+#include "fsdev/qemu-fsdev.h"
+#include "virtio-9p-chroot.h"
 #include <arpa/inet.h>
 #include <pwd.h>
 #include <grp.h>
@@ -24,6 +27,63 @@
 #include <linux/magic.h>
 #include <sys/ioctl.h>
 
+/* Helper routine to fill V9fsFileObjectRequest structure */
+static int fill_fileobjectrequest(V9fsFileObjectRequest *request,
+                const char *oldpath, const char *path, int flags,
+                FsCred *credp, int type)
+{
+    if (oldpath && strlen(oldpath) >= PATH_MAX) {
+        return -ENAMETOOLONG;
+    }
+    /* path can't be NULL */
+    if (!path) {
+        return -EFAULT;
+    }
+
+    if (strlen(path) >= PATH_MAX) {
+        return -ENAMETOOLONG;
+    }
+    strcpy(request->path.path, path);
+    if (oldpath) {
+        strcpy(request->path.old_path, oldpath);
+    } else {
+        request->path.old_path[0] = '\0';
+    }
+
+    memset(&request->data, 0, sizeof(request->data));
+    if (credp) {
+        request->data.mode = credp->fc_mode;
+        request->data.uid = credp->fc_uid;
+        request->data.gid = credp->fc_gid;
+        request->data.dev = credp->fc_rdev;
+    }
+
+    request->data.flags = flags;
+    request->data.type = type;
+    return 0;
+}
+
+static int passthrough_request(FsContext *fs_ctx, const char *old_path,
+                const char *path, int flags, FsCred *credp, int type)
+{
+    V9fsFileObjectRequest request;
+    int retval;
+
+    retval = fill_fileobjectrequest(&request, old_path, path, flags, credp,
+                    type);
+    if (retval < 0) {
+        errno = -retval;
+        return -1;
+    }
+
+    retval = v9fs_request(fs_ctx, &request);
+    if (retval < 0) {
+        errno = -retval;
+        retval = -1;
+    }
+    return retval;
+}
+
 static int local_lstat(FsContext *fs_ctx, V9fsPath *fs_path, struct stat *stbuf)
 {
     int err;
@@ -157,7 +217,11 @@ static int local_open(FsContext *ctx, V9fsPath *fs_path,
     char buffer[PATH_MAX];
     char *path = fs_path->data;
 
-    fs->fd = open(rpath(ctx, path, buffer), flags);
+    if (ctx->fs_sm == SM_PASSTHROUGH) {
+        fs->fd = passthrough_request(ctx, NULL, path, flags, NULL, T_OPEN);
+    } else {
+        fs->fd = open(rpath(ctx, path, buffer), flags);
+    }
     return fs->fd;
 }
 
@@ -167,7 +231,17 @@ static int local_opendir(FsContext *ctx,
     char buffer[PATH_MAX];
     char *path = fs_path->data;
 
-    fs->dir = opendir(rpath(ctx, path, buffer));
+    if (ctx->fs_sm == SM_PASSTHROUGH) {
+        int fd;
+        fd = passthrough_request(ctx, NULL, path, O_DIRECTORY, NULL, T_OPEN);
+        if (fd < 0) {
+            return -1;
+        }
+        fs->dir = fdopendir(fd);
+    } else {
+        fs->dir = opendir(rpath(ctx, path, buffer));
+    }
+
     if (!fs->dir) {
         return -1;
     }
@@ -426,7 +500,6 @@ out:
     return err;
 }
 
-
 static int local_symlink(FsContext *fs_ctx, const char *oldpath,
                          V9fsPath *dir_path, const char *name, FsCred *credp)
 {
-- 
1.7.6