binfmt_misc: Skip dumping if it's not virtual

Similar to devtmpfs and devpts, skip binfmt_misc
mount if it's not virtual.
Signed-off-by: Kirill Tkhai <ktkhai@odin.com>
Acked-by: Andrew Vagin <avagin@virtuozzo.com>
Signed-off-by: Pavel Emelyanov <xemul@parallels.com>

include/fs-magic.h

@@ -45,4 +45,8 @@
 #define PROC_SUPER_MAGIC	0x9fa0
 #endif
 
+#ifndef BINFMTFS_MAGIC
+#define BINFMTFS_MAGIC		0x42494e4d
+#endif
+
 #endif /* __CR_FS_MAGIC_H__ */

include/kerndat.h

@@ -32,6 +32,7 @@ extern struct kerndat_s kdat;
 enum {
 	KERNDAT_FS_STAT_DEVPTS,
 	KERNDAT_FS_STAT_DEVTMPFS,
+	KERNDAT_FS_STAT_BINFMT_MISC,
 
 	KERNDAT_FS_STAT_MAX
 };

kerndat.c

@@ -92,6 +92,11 @@ static dev_t get_host_dev(unsigned int which)
 			.path	= "/dev",
 			.magic	= TMPFS_MAGIC,
 		},
+		[KERNDAT_FS_STAT_BINFMT_MISC] = {
+			.name	= "binfmt_misc",
+			.path	= "/proc/sys/fs/binfmt_misc",
+			.magic	= BINFMTFS_MAGIC,
+		},
 	};
 
 	if (which >= KERNDAT_FS_STAT_MAX) {

mount.c

@@ -1291,6 +1291,11 @@ static int devtmpfs_restore(struct mount_info *pm)
 	return ret;
 }
 
+static int binfmt_misc_virtual(struct mount_info *pm)
+{
+	return kerndat_fs_virtualized(KERNDAT_FS_STAT_BINFMT_MISC, pm->s_dev);
+}
+
 static int parse_binfmt_misc_entry(struct bfd *f, BinfmtMiscEntry *bme)
 {
 	while (1) {
@@ -1375,9 +1380,13 @@ err:
 static int binfmt_misc_dump(struct mount_info *pm)
 {
 	struct cr_img *img;
-	int fd, ret = -1;
 	struct dirent *de;
 	DIR *fdir = NULL;
+	int fd, ret;
+
+	ret = binfmt_misc_virtual(pm);
+	if (ret <= 0)
+		return ret;
 
 	fd = open_mountpoint(pm);
 	if (fd < 0)
@@ -1389,6 +1398,7 @@ static int binfmt_misc_dump(struct mount_info *pm)
 		return -1;
 	}
 
+	ret = -1;
 	img = open_image(CR_FD_BINFMT_MISC, O_DUMP, pm->s_dev);
 	if (!img)
 		goto out;