volume_id: add squashfs detection

function                                             old     new   delta
volume_id_probe_squashfs                               -      74     +74
fs1                                                   12      16      +4

Signed-off-by: Sven-Göran Bergh <sgb@systemasis.org>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

util-linux/Config.src

@@ -841,6 +841,16 @@ config FEATURE_VOLUMEID_ROMFS
 	help
 	  TODO
 
+config FEATURE_VOLUMEID_SQUASHFS
+	bool "SquashFS filesystem"
+	default y
+	depends on VOLUMEID && FEATURE_BLKID_TYPE
+	help
+	  Squashfs is a compressed read-only filesystem for Linux. Squashfs is
+	  intended for general read-only filesystem use and in constrained block
+	  device/memory systems (e.g. embedded systems) where low overhead is
+	  needed.
+
 config FEATURE_VOLUMEID_SYSV
 	bool "sysv filesystem"
 	default y

util-linux/volume_id/squashfs.c

@@ -0,0 +1,59 @@
+/*
+ * volume_id - reads filesystem label and uuid
+ *
+ * Copyright (C) 2012 S-G Bergh <sgb@systemasis.org>
+ *
+ * Licensed under GPLv2, see file LICENSE in this source tree.
+ */
+
+//config:config FEATURE_VOLUMEID_SQUASHFS
+//config:	bool "SquashFS filesystem"
+//config:	default y
+//config:	depends on VOLUMEID && FEATURE_BLKID_TYPE
+//config:	help
+//config:	  Squashfs is a compressed read-only filesystem for Linux. Squashfs is
+//config:	  intended for general read-only filesystem use and in constrained block
+//config:	  device/memory systems (e.g. embedded systems) where low overhead is
+//config:	  needed.
+
+//kbuild:lib-$(CONFIG_FEATURE_VOLUMEID_SQUASHFS) += squashfs.o
+
+#include "volume_id_internal.h"
+
+struct squashfs_superblock {
+	uint32_t	magic;
+/*
+	uint32_t	dummy[6];
+	uint16_t        major;
+	uint16_t        minor;
+*/
+} PACKED;
+
+int FAST_FUNC volume_id_probe_squashfs(struct volume_id *id /*,uint64_t off*/)
+{
+#define off ((uint64_t)0)
+	struct squashfs_superblock *sb;
+
+	dbg("SquashFS: probing at offset 0x%llx", (unsigned long long) off);
+	sb = volume_id_get_buffer(id, off, 0x200);
+	if (!sb)
+		return -1;
+
+	// Old SquashFS (pre 4.0) can be both big and little endian, so test for both.
+	// Likewise, it is commonly used in firwmare with some non-standard signatures.
+#define pack(a,b,c,d) ( (uint32_t)((a * 256 + b) * 256 + c) * 256 + d )
+#define SIG1 pack('s','q','s','h')
+#define SIG2 pack('h','s','q','s')
+#define SIG3 pack('s','h','s','q')
+#define SIG4 pack('q','s','h','s')
+	if (sb->magic == SIG1
+	 || sb->magic == SIG2
+	 || sb->magic == SIG3
+	 || sb->magic == SIG4
+	) {
+		IF_FEATURE_BLKID_TYPE(id->type = "squashfs";)
+		return 0;
+	}
+
+	return -1;
+}

util-linux/volume_id/volume_id.c

@@ -99,6 +99,9 @@ static const probe_fptr fs1[] = {
 #if ENABLE_FEATURE_VOLUMEID_MAC
 	volume_id_probe_mac_partition_map,
 #endif
+#if ENABLE_FEATURE_VOLUMEID_SQUASHFS
+	volume_id_probe_squashfs,
+#endif
 #if ENABLE_FEATURE_VOLUMEID_XFS
 	volume_id_probe_xfs,
 #endif

util-linux/volume_id/volume_id_internal.h

@@ -227,6 +227,8 @@ int FAST_FUNC volume_id_probe_reiserfs(struct volume_id *id /*,uint64_t off*/);
 
 int FAST_FUNC volume_id_probe_romfs(struct volume_id *id /*,uint64_t off*/);
 
+int FAST_FUNC volume_id_probe_squashfs(struct volume_id *id /*,uint64_t off*/);
+
 int FAST_FUNC volume_id_probe_sysv(struct volume_id *id /*,uint64_t off*/);
 
 int FAST_FUNC volume_id_probe_udf(struct volume_id *id /*,uint64_t off*/);