[Qemu-devel] [V3 PATCH 4/8] virtio-9p: Add support to open a file in chroot environment

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

This patch adds both server and client 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 |   45 +++++++++++++++++++++++++++++++------
 hw/9pfs/virtio-9p-chroot.h |    1 +
 hw/9pfs/virtio-9p-local.c  |   52 ++++++++++++++++++++++++++++++++++++++++---
 3 files changed, 86 insertions(+), 12 deletions(-)

diff --git a/hw/9pfs/virtio-9p-chroot.c b/hw/9pfs/virtio-9p-chroot.c
index 25a7fab..b599e23 100644
--- a/hw/9pfs/virtio-9p-chroot.c
+++ b/hw/9pfs/virtio-9p-chroot.c
@@ -167,6 +167,32 @@ static void v9fs_write_request(int sockfd, V9fsFileObjectRequest *request)
     }
 }
 
+/* Return opened file descriptor on success or -1 on error */
+int v9fs_request(FsContext *fs_ctx, V9fsFileObjectRequest *request,
+                        int *error)
+{
+    int fd;
+    pthread_mutex_lock(&fs_ctx->chroot_mutex);
+    v9fs_write_request(fs_ctx->chroot_socket, request);
+    fd = v9fs_receivefd(fs_ctx->chroot_socket, error);
+    pthread_mutex_unlock(&fs_ctx->chroot_mutex);
+    return fd;
+}
+
+/*
+ * Helper routine to open a file and return fd and error status in
+ * FdInfo structure
+ */
+static void chroot_do_open(V9fsFileObjectRequest *request, FdInfo *fd_info)
+{
+    fd_info->fi_fd = open(request->path.path, request->data.flags);
+    if (fd_info->fi_fd < 0) {
+        fd_info->fi_error = errno;
+    } else {
+        fd_info->fi_error = 0;
+    }
+}
+
 static int chroot_daemonize(int chroot_sock)
 {
     sigset_t sigset;
@@ -195,13 +221,6 @@ static int chroot_daemonize(int chroot_sock)
     return 0;
 }
 
-static void chroot_dummy(void)
-{
-    (void)chroot_sendfd;
-    (void)v9fs_receivefd;
-    (void)v9fs_write_request;
-}
-
 /*
  * Fork a process and chroot into the share path. Communication
  * between qemu process and chroot process happens via socket
@@ -210,6 +229,7 @@ int v9fs_chroot(FsContext *fs_ctx)
 {
     int fd_pair[2], pid, chroot_sock, error;
     V9fsFileObjectRequest request;
+    FdInfo fd_info;
 
     if (socketpair(PF_UNIX, SOCK_STREAM, 0, fd_pair) < 0) {
         error_report("socketpair %s", strerror(errno));
@@ -234,7 +254,6 @@ int v9fs_chroot(FsContext *fs_ctx)
         return -1;
     }
 
-    chroot_dummy();
     if (chroot_daemonize(chroot_sock) < 0) {
         _exit(-1);
     }
@@ -250,6 +269,16 @@ int v9fs_chroot(FsContext *fs_ctx)
     /* get the request from the socket */
     while (1) {
         chroot_read_request(chroot_sock, &request);
+        switch (request.data.type) {
+        case T_OPEN:
+            chroot_do_open(&request, &fd_info);
+            if (chroot_sendfd(chroot_sock, &fd_info) <= 0) {
+                error = -2;
+            }
+            break;
+        default:
+            break;
+        }
         qemu_free(request.path.path);
         if (request.data.oldpath_len) {
             qemu_free(request.path.old_path);
diff --git a/hw/9pfs/virtio-9p-chroot.h b/hw/9pfs/virtio-9p-chroot.h
index 3bee5e3..f5a2ca0 100644
--- a/hw/9pfs/virtio-9p-chroot.h
+++ b/hw/9pfs/virtio-9p-chroot.h
@@ -35,5 +35,6 @@ typedef struct V9fsFileObjectRequest
 
 
 int v9fs_chroot(FsContext *fs_ctx);
+int v9fs_request(FsContext *fs_ctx, V9fsFileObjectRequest *or, int *error);
 
 #endif /* _QEMU_VIRTIO_9P_CHROOT_H */
diff --git a/hw/9pfs/virtio-9p-local.c b/hw/9pfs/virtio-9p-local.c
index a8e7525..2376ec2 100644
--- a/hw/9pfs/virtio-9p-local.c
+++ b/hw/9pfs/virtio-9p-local.c
@@ -13,6 +13,7 @@
 #include "virtio.h"
 #include "virtio-9p.h"
 #include "virtio-9p-xattr.h"
+#include "virtio-9p-chroot.h"
 #include <arpa/inet.h>
 #include <pwd.h>
 #include <grp.h>
@@ -20,6 +21,36 @@
 #include <sys/un.h>
 #include <attr/xattr.h>
 
+/* Helper routine to fill V9fsFileObjectRequest structure */
+static void fill_request(V9fsFileObjectRequest *request, const char *path,
+                FsCred *credp)
+{
+    memset(request, 0, sizeof(*request));
+    request->data.path_len = strlen(path);
+    request->path.path = qemu_strdup(path);
+    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;
+    }
+}
+
+static int __open(FsContext *fs_ctx, const char *path, int flags)
+{
+    V9fsFileObjectRequest request;
+    int fd, error = 0;
+
+    fill_request(&request, path, NULL);
+    request.data.flags = flags;
+    request.data.type = T_OPEN;
+    fd = v9fs_request(fs_ctx, &request, &error);
+    if (fd < 0) {
+        errno = error;
+    }
+    qemu_free(request.path.path);
+    return fd;
+}
 
 static int local_lstat(FsContext *fs_ctx, const char *path, struct stat *stbuf)
 {
@@ -138,14 +169,27 @@ static int local_closedir(FsContext *ctx, DIR *dir)
     return closedir(dir);
 }
 
-static int local_open(FsContext *ctx, const char *path, int flags)
+static int local_open(FsContext *fs_ctx, const char *path, int flags)
 {
-    return open(rpath(ctx, path), flags);
+    if (fs_ctx->fs_sm == SM_PASSTHROUGH) {
+        return __open(fs_ctx, path, flags);
+    } else {
+        return open(rpath(fs_ctx, path), flags);
+    }
 }
 
-static DIR *local_opendir(FsContext *ctx, const char *path)
+static DIR *local_opendir(FsContext *fs_ctx, const char *path)
 {
-    return opendir(rpath(ctx, path));
+    if (fs_ctx->fs_sm == SM_PASSTHROUGH) {
+        int fd;
+        fd = __open(fs_ctx, path, O_DIRECTORY);
+        if (fd < 0) {
+            return NULL;
+        }
+        return fdopendir(fd);
+    } else {
+        return opendir(rpath(fs_ctx, path));
+    }
 }
 
 static void local_rewinddir(FsContext *ctx, DIR *dir)
-- 
1.7.3.4