diff mbox series

fstools: add support of mapped rootfs

Message ID 20230616084709.3630672-1-paul.henrys_ext@softathome.com
State New
Headers show
Series fstools: add support of mapped rootfs | expand

Commit Message

Paul HENRYS (EXT) June 16, 2023, 8:47 a.m. UTC 
From: Paul HENRYS <paul.henrys_ext@softathome.com>

When the rootfs is signed and/or ciphered and dmsetup is used, virtual
block devices are created and mapped to the physical block device where
the rootfs is actually stored.
Inside mount_root.c, when volume_find("rootfs_data") is called in start(),
the implementation iterates over the registered drivers and eventually
when the rootfs is mapped, when calling rootdisk_volume_find(), the
virtual device is pointed by rootdev instead of the physical device which
should be used.

Hereafter is an example of mapped rootfs (signed and ciphered) stored in a
UBI device:

   / # dmsetup ls --tree
   vrootfs_crypt (253:1)
    `-vrootfs_linear (253:0)
       `- (254:0)
   / # cat /sys/class/block/dm-1/dev
   253:1
   / # cat /sys/class/block/dm-0/dev
   253:0
   / # cat /sys/class/block/ubiblock0_5/dev
   254:0
   / # cat /sys/class/ubi/ubi0_5/name
   rootfs
   / # ls -lrt /sys/class/block/dm-1/slaves/
   lrwxrwxrwx 1 root root 0 Jan  1 00:01 dm-0 -> ../../dm-0
   / # ls -lrt /sys/class/block/dm-1/slaves/dm-0/slaves/
   lrwxrwxrwx 1 root root 0 Jan  1 00:01 ubiblock0_5 -> ../../ubiblock0_5
   / # ls -lrt /sys/class/block/dm-1/slaves/dm-0/slaves/ubiblock0_5/slaves

In such a case, the previous implementation failed to detect the rootfs is
stored in a UBI and did not mount an overlayfs.

The fix looks for slave devices in /sys/class/block to find the physical
block device.

Signed-off-by: Paul HENRYS <paul.henrys_ext@softathome.com>
---
 libfstools/common.c   | 36 ++++++++++++++++++++++++++++++++++++
 libfstools/common.h   | 13 +++++++++++++
 libfstools/rootdisk.c |  8 ++++++++
 3 files changed, 57 insertions(+)

--
2.25.1

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diff mbox series

Patch

diff --git a/libfstools/common.c b/libfstools/common.c
index e5b7bc3..07cf39d 100644
--- a/libfstools/common.c
+++ b/libfstools/common.c
@@ -176,3 +176,39 @@  do_format:

        return ret;
 }
+
+char *block_get_slave(const char *bdev)
+{
+       int fd = -1;
+       DIR *dirp = NULL;
+       struct dirent *d;
+       char path[256] = {0};
+       static char slave[256];
+       int slaves = 0;
+
+       if (!bdev)
+               goto out;
+
+       snprintf(path, sizeof(path), "/sys/class/block/%s/slaves", bdev);
+       fd = open(path, O_RDONLY|O_CLOEXEC);
+       if (fd < 0)
+               goto out;
+
+       dirp = fdopendir(fd);
+       if (!dirp)
+               goto out;
+
+       while ((d = xreaddir(dirp))) {
+               if (++slaves > 1)
+                       goto out;       /* more than one slave */
+               strncpy(slave, d->d_name, sizeof(slave));
+               slave[sizeof(slave) - 1] = '\0'; /* make sure slave is always NULL terminated */
+       }
+
+ out:
+       if (dirp)
+               closedir(dirp);
+       if  (fd >= 0)
+               close(fd);
+       return slaves == 1 ? slave : NULL;
+}
diff --git a/libfstools/common.h b/libfstools/common.h
index b5cc692..4330ecd 100644
--- a/libfstools/common.h
+++ b/libfstools/common.h
@@ -21,7 +21,20 @@ 

 #define F2FS_MINSIZE           (100ULL * 1024ULL * 1024ULL)

+/* Look for directories but skip "." and ".." */
+static inline struct dirent *xreaddir(DIR *dirp)
+{
+       struct dirent *d;
+
+       while ((d = readdir(dirp)) &&
+              (!strcmp(d->d_name, ".") || !strcmp(d->d_name, "..")))
+               ;
+
+       return d;
+}
+
 int read_uint_from_file(char *dirname, char *filename, unsigned int *i);
 char *read_string_from_file(const char *dirname, const char *filename, char *buf, size_t bufsz);
 int block_file_identify(FILE *f, uint64_t offset);
 int block_volume_format(struct volume *v, uint64_t offset, const char *bdev);
+char *block_get_slave(const char *bdev);
diff --git a/libfstools/rootdisk.c b/libfstools/rootdisk.c
index 9f2317f..ef6f29e 100644
--- a/libfstools/rootdisk.c
+++ b/libfstools/rootdisk.c
@@ -97,6 +97,8 @@  static struct volume *rootdisk_volume_find(char *name)
 {
        struct squashfs_super_block sb;
        struct rootdev_volume *p;
+       static char slave[256] = {0};
+       char *tmp = NULL;

        if (strcmp(name, "rootfs_data") != 0)
                return NULL;
@@ -108,6 +110,12 @@  static struct volume *rootdisk_volume_find(char *name)
        if (!rootdev)
                return NULL;

+       /* Check for slaves to reach the initial block device */
+       while ((tmp = block_get_slave(basename((char *)rootdev)))) {
+               strncpy(slave, tmp, sizeof(slave));
+               rootdev = slave;
+       }
+
        if (strstr(rootdev, "mtdblock") ||
            strstr(rootdev, "ubiblock"))
                return NULL;