virtio-9p: Add minimal set of FileOperations

Add minimal set of FileOperations and the corresponding implementations for
local fstype. These will be required for the FID management patches later on.

[aneesh.kumar@linux.vnet.ibm.com: rpath fix ]
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>
Signed-off-by: Aneesh Kumar K.V <aneesh.kumar@linux.vnet.ibm.com>
Signed-off-by: Anthony Liguori <aliguori@us.ibm.com>

hw/file-op-9p.h

@@ -27,6 +27,11 @@ typedef struct FsContext
 
 typedef struct FileOperations
 {
+    int (*lstat)(FsContext *, const char *, struct stat *);
+    ssize_t (*readlink)(FsContext *, const char *, char *, size_t);
+    int (*setuid)(FsContext *, uid_t);
+    int (*close)(FsContext *, int);
+    int (*closedir)(FsContext *, DIR *);
     void *opaque;
 } FileOperations;
 #endif

hw/virtio-9p-local.c

@@ -12,6 +12,84 @@
  */
 #include "virtio.h"
 #include "virtio-9p.h"
+#include <pwd.h>
+#include <grp.h>
+
+static const char *rpath(FsContext *ctx, const char *path)
+{
+    /* FIXME: so wrong... */
+    static char buffer[4096];
+    snprintf(buffer, sizeof(buffer), "%s/%s", ctx->fs_root, path);
+    return buffer;
+}
+
+static int local_lstat(FsContext *ctx, const char *path, struct stat *stbuf)
+{
+    return lstat(rpath(ctx, path), stbuf);
+}
+
+static int local_setuid(FsContext *ctx, uid_t uid)
+{
+    struct passwd *pw;
+    gid_t groups[33];
+    int ngroups;
+    static uid_t cur_uid = -1;
+
+    if (cur_uid == uid) {
+        return 0;
+    }
+
+    if (setreuid(0, 0)) {
+        return -1;
+    }
+
+    pw = getpwuid(uid);
+    if (pw == NULL) {
+        return -1;
+    }
+
+    ngroups = 33;
+    if (getgrouplist(pw->pw_name, pw->pw_gid, groups, &ngroups) == -1) {
+        return -1;
+    }
+
+    if (setgroups(ngroups, groups)) {
+        return -1;
+    }
+
+    if (setregid(-1, pw->pw_gid)) {
+        return -1;
+    }
+
+    if (setreuid(-1, uid)) {
+        return -1;
+    }
+
+    cur_uid = uid;
+
+    return 0;
+}
+
+static ssize_t local_readlink(FsContext *ctx, const char *path,
+                                char *buf, size_t bufsz)
+{
+    return readlink(rpath(ctx, path), buf, bufsz);
+}
+
+static int local_close(FsContext *ctx, int fd)
+{
+    return close(fd);
+}
+
+static int local_closedir(FsContext *ctx, DIR *dir)
+{
+    return closedir(dir);
+}
 
 FileOperations local_ops = {
+    .lstat = local_lstat,
+    .setuid = local_setuid,
+    .readlink = local_readlink,
+    .close = local_close,
+    .closedir = local_closedir,
 };

hw/virtio-9p.c

@@ -21,6 +21,41 @@
 int dotu = 1;
 int debug_9p_pdu;
 
+static int v9fs_do_lstat(V9fsState *s, V9fsString *path, struct stat *stbuf)
+{
+    return s->ops->lstat(&s->ctx, path->data, stbuf);
+}
+
+static int v9fs_do_setuid(V9fsState *s, uid_t uid)
+{
+    return s->ops->setuid(&s->ctx, uid);
+}
+
+static ssize_t v9fs_do_readlink(V9fsState *s, V9fsString *path, V9fsString *buf)
+{
+    ssize_t len;
+
+    buf->data = qemu_malloc(1024);
+
+    len = s->ops->readlink(&s->ctx, path->data, buf->data, 1024 - 1);
+    if (len > -1) {
+        buf->size = len;
+        buf->data[len] = 0;
+    }
+
+    return len;
+}
+
+static int v9fs_do_close(V9fsState *s, int fd)
+{
+    return s->ops->close(&s->ctx, fd);
+}
+
+static int v9fs_do_closedir(V9fsState *s, DIR *dir)
+{
+    return s->ops->closedir(&s->ctx, dir);
+}
+
 static void v9fs_string_init(V9fsString *str)
 {
     str->data = NULL;
@@ -437,9 +472,13 @@ static void v9fs_dummy(V9fsState *s, V9fsPDU *pdu)
     (void) v9fs_string_sprintf;
     (void) v9fs_string_copy;
     (void) v9fs_string_size;
-
-
+    (void) v9fs_do_lstat;
+    (void) v9fs_do_setuid;
+    (void) v9fs_do_readlink;
+    (void) v9fs_do_close;
+    (void) v9fs_do_closedir;
 }
+
 static void v9fs_version(V9fsState *s, V9fsPDU *pdu)
 {
     if (debug_9p_pdu) {