debugfs: add the hexdump_block command

Signed-off-by: Theodore Ts'o <tytso@mit.edu>

debugfs/debug_cmds.ct

@@ -145,6 +145,9 @@ request do_set_block_group_descriptor, "Set block group descriptor field",
 request do_logdump, "Dump the contents of the journal",
 	logdump;
 
+request do_hexdump_block, "Dump the contents of a block",
+	hexdump_block, hexdump;
+
 request do_htree_dump, "Dump a hash-indexed directory",
 	htree_dump, htree;
 

debugfs/debugfs.8.in

@@ -392,6 +392,11 @@ is specified, also clear num-1 inodes after the specified inode.
 Print a list of commands understood by
 .BR debugfs .
 .TP
+.BI hexdump_block " block"
+Dump the contents of
+.I block
+in hex and ASCII.
+.TP
 .BI htree_dump " filespec"
 Dump the hash-indexed directory
 .IR filespec ,

debugfs/debugfs.h

@@ -103,6 +103,7 @@ extern void do_dirsearch(int argc, char **argv);
 
 /* logdump.c */
 extern void do_logdump(int argc, char **argv);
+extern void do_hexdump_block(int argc, char **argv);
 
 /* lsdel.c */
 extern void do_lsdel(int argc, char **argv);

debugfs/logdump.c

@@ -714,3 +714,38 @@ static void do_hexdump (FILE *out_file, char *buf, int blocksize)
 	}
 }
 
+void do_hexdump_block(int argc, char **argv)
+{
+	blk64_t block;
+	char *buf;
+	errcode_t errcode;
+	FILE *out;
+
+	if (common_args_process(argc, argv, 2, 2, argv[0],
+				"<block>", 0))
+		return;
+
+	if (strtoblk(argv[0], argv[1], "block number", &block))
+		return;
+
+	buf = malloc(current_fs->blocksize);
+	if (!buf) {
+		fprintf(stderr, "Couldn't allocate block buffer.\n");
+		return;
+	}
+	out = open_pager();
+
+	errcode = io_channel_read_blk64(current_fs->io, block, 1, buf);
+	if (errcode) {
+		com_err("hexdump_block", errcode,
+			"while reading block %llu\n", block);
+		goto errout;
+	}
+
+	do_hexdump(out, buf, current_fs->blocksize);
+
+errout:
+	free(buf);
+	close_pager(out);
+}
+