unmkinitramfs: Add support for lzma compression

The kernel and mkinitramfs support lzma compression, but for some
reason this was not included in unmkinitramfs.

- Add a format code, magic entry, and decompression command for lzma
  to unmkinitramfs
- Add lzma to the compression commands in the test case

Signed-off-by: Ben Hutchings <benh@debian.org>

debian/tests/unmkinitramfs

@@ -57,7 +57,7 @@ for n_early in 0 1 2; do
 			continue
 		fi
 
-		for compressor in no_compressor gzip bzip2 xz lzop 'lz4 -l' zstd; do
+		for compressor in no_compressor gzip bzip2 lzma xz lzop 'lz4 -l' zstd; do
 			# If last archive is early, it can't be compressed
 			if [ $n_main -eq 0 ] && [ "$compressor" != no_compressor ]; then
 				continue

unmkinitramfs.c

@@ -65,6 +65,7 @@ enum format {
 	FORMAT_CPIO_NEW,
 	FORMAT_GZIP,
 	FORMAT_BZIP2,
+	FORMAT_LZMA,
 	FORMAT_XZ,
 	FORMAT_LZO,
 	FORMAT_LZ4,
@@ -86,6 +87,7 @@ static const struct magic_entry magic_table[] = {
 	MAGIC_ENTRY(CPIO_NEW_CRC_MAGIC,		FORMAT_CPIO_NEW),
 	MAGIC_ENTRY("\x1f\x8b\x08",		FORMAT_GZIP),
 	MAGIC_ENTRY("BZh",			FORMAT_BZIP2),
+	MAGIC_ENTRY("\x5d\0\0",			FORMAT_LZMA),
 	MAGIC_ENTRY("\xfd""7zXZ\0",		FORMAT_XZ),
 	MAGIC_ENTRY("\x89LZO\0\r\n\x1a\n",	FORMAT_LZO),
 	/* lz4 "legacy" format, the only version that the kernel supports */
@@ -97,6 +99,7 @@ static const struct magic_entry magic_table[] = {
 static const char *const decomp_table[][2] = {
 	[FORMAT_GZIP] =		{ "gzip", "-cd" },
 	[FORMAT_BZIP2] =	{ "bzip2", "-cd" },
+	[FORMAT_LZMA] =		{ "lzma", "-cd" },
 	[FORMAT_XZ] =		{ "xzcat" },
 	[FORMAT_LZO] =		{ "lzop", "-cd" },
 	[FORMAT_LZ4] =		{ "lz4cat" },