ext4 utils: Refactor read_ext, and expose some of the functions
Make read_ext an externally useable function. Use case is to
enable fast encryption by being able to look at whether each block
is in use or not.
Bug: 11985952
Change-Id: Ief71f408a55db7261c75ebe974620415ed8cfd29
diff --git a/ext4_utils/ext4_utils.c b/ext4_utils/ext4_utils.c
index d4fbc7c..1b70afe 100644
--- a/ext4_utils/ext4_utils.c
+++ b/ext4_utils/ext4_utils.c
@@ -62,6 +62,21 @@
return (a == b) ? 1 : 0;
}
+int bitmap_get_bit(u8 *bitmap, u32 bit)
+{
+ if (bitmap[bit / 8] & (1 << (bit % 8)))
+ return 1;
+
+ return 0;
+}
+
+void bitmap_clear_bit(u8 *bitmap, u32 bit)
+{
+ bitmap[bit / 8] &= ~(1 << (bit % 8));
+
+ return;
+}
+
/* Returns 1 if the bg contains a backup superblock. On filesystems with
the sparse_super feature, only block groups 0, 1, and powers of 3, 5,
and 7 have backup superblocks. Otherwise, all block groups have backup
@@ -81,6 +96,38 @@
return 0;
}
+/* Function to read the primary superblock */
+void read_sb(int fd, struct ext4_super_block *sb)
+{
+ off64_t ret;
+
+ ret = lseek64(fd, 1024, SEEK_SET);
+ if (ret < 0)
+ critical_error_errno("failed to seek to superblock");
+
+ ret = read(fd, sb, sizeof(*sb));
+ if (ret < 0)
+ critical_error_errno("failed to read superblock");
+ if (ret != sizeof(*sb))
+ critical_error("failed to read all of superblock");
+}
+
+/* Function to write a primary or backup superblock at a given offset */
+void write_sb(int fd, unsigned long long offset, struct ext4_super_block *sb)
+{
+ off64_t ret;
+
+ ret = lseek64(fd, offset, SEEK_SET);
+ if (ret < 0)
+ critical_error_errno("failed to seek to superblock");
+
+ ret = write(fd, sb, sizeof(*sb));
+ if (ret < 0)
+ critical_error_errno("failed to write superblock");
+ if (ret != sizeof(*sb))
+ critical_error("failed to write all of superblock");
+}
+
/* Write the filesystem image to a file */
void write_ext4_image(int fd, int gz, int sparse, int crc)
{
@@ -450,3 +497,48 @@
return num;
}
+
+int read_ext(int fd, int verbose)
+{
+ off64_t ret;
+ struct ext4_super_block sb;
+
+ read_sb(fd, &sb);
+
+ ext4_parse_sb(&sb);
+
+ ret = lseek64(fd, info.len, SEEK_SET);
+ if (ret < 0)
+ critical_error_errno("failed to seek to end of input image");
+
+ ret = lseek64(fd, info.block_size * (aux_info.first_data_block + 1), SEEK_SET);
+ if (ret < 0)
+ critical_error_errno("failed to seek to block group descriptors");
+
+ ret = read(fd, aux_info.bg_desc, info.block_size * aux_info.bg_desc_blocks);
+ if (ret < 0)
+ critical_error_errno("failed to read block group descriptors");
+ if (ret != (int)info.block_size * (int)aux_info.bg_desc_blocks)
+ critical_error("failed to read all of block group descriptors");
+
+ if (verbose) {
+ printf("Found filesystem with parameters:\n");
+ printf(" Size: %llu\n", info.len);
+ printf(" Block size: %d\n", info.block_size);
+ printf(" Blocks per group: %d\n", info.blocks_per_group);
+ printf(" Inodes per group: %d\n", info.inodes_per_group);
+ printf(" Inode size: %d\n", info.inode_size);
+ printf(" Label: %s\n", info.label);
+ printf(" Blocks: %llu\n", aux_info.len_blocks);
+ printf(" Block groups: %d\n", aux_info.groups);
+ printf(" Reserved block group size: %d\n", info.bg_desc_reserve_blocks);
+ printf(" Used %d/%d inodes and %d/%d blocks\n",
+ aux_info.sb->s_inodes_count - aux_info.sb->s_free_inodes_count,
+ aux_info.sb->s_inodes_count,
+ aux_info.sb->s_blocks_count_lo - aux_info.sb->s_free_blocks_count_lo,
+ aux_info.sb->s_blocks_count_lo);
+ }
+
+ return 0;
+}
+