probe: add full libblkid support

Attempt to dlopen() libblkid.so at runtime and use it for proping
filesystems if available.

Signed-off-by: Jo-Philipp Wich <jo@mein.io>

4 files changed, 131 insertions, 6 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 0d4c763..e7a97db 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -56,12 +56,12 @@ INSTALL(TARGETS mount_root RUNTIME DESTINATION sbin)
 
 find_library(json NAMES json-c json)
 
-ADD_EXECUTABLE(block block.c probe.c)
+ADD_EXECUTABLE(block block.c probe.c probe-libblkid.c)
 IF(DEFINED CMAKE_UBIFS_EXTROOT)
 	ADD_DEFINITIONS(-DUBIFS_EXTROOT)
-	TARGET_LINK_LIBRARIES(block blkid-tiny uci ubox blobmsg_json ubi-utils ${json})
+	TARGET_LINK_LIBRARIES(block blkid-tiny dl uci ubox blobmsg_json ubi-utils ${json})
 ELSE(DEFINED CMAKE_UBIFS_EXTROOT)
-	TARGET_LINK_LIBRARIES(block blkid-tiny uci ubox blobmsg_json ${json})
+	TARGET_LINK_LIBRARIES(block blkid-tiny dl uci ubox blobmsg_json ${json})
 ENDIF(DEFINED CMAKE_UBIFS_EXTROOT)
 INSTALL(TARGETS block RUNTIME DESTINATION sbin)
 
diff --git a/probe-libblkid.c b/probe-libblkid.c
new file mode 100644
index 0000000..c448888
--- /dev/null
+++ b/probe-libblkid.c
@@ -0,0 +1,117 @@
+/*
+ * Copyright (C) 2016 Jo-Philipp Wich <jo@mein.io>
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of the GNU Lesser General Public License version 2.1
+ * as published by the Free Software Foundation
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+
+#include <dlfcn.h>
+#include <string.h>
+#include <stdbool.h>
+#include <blkid/blkid.h>
+#include <libubox/utils.h>
+
+#include "probe.h"
+
+
+static struct {
+	bool loaded;
+	blkid_probe (*alloc)(const char *);
+	int (*probe)(blkid_probe);
+	int (*lookup)(blkid_probe, const char *, const char **, size_t *);
+	void (*free)(blkid_probe);
+} libblkid = { };
+
+
+static bool
+load_libblkid(void)
+{
+	void *lib;
+
+	if (!libblkid.loaded) {
+		lib = dlopen("libblkid.so", RTLD_GLOBAL);
+
+		if (lib) {
+			libblkid.alloc  = dlsym(lib, "blkid_new_probe_from_filename");
+			libblkid.probe  = dlsym(lib, "blkid_do_probe");
+			libblkid.lookup = dlsym(lib, "blkid_probe_lookup_value");
+			libblkid.free   = dlsym(lib, "blkid_free_probe");
+		}
+
+		libblkid.loaded = true;
+	}
+
+	return (libblkid.alloc && libblkid.probe && libblkid.lookup && libblkid.free);
+}
+
+struct probe_info *
+probe_path_libblkid(const char *path)
+{
+	blkid_probe pr;
+	struct probe_info *info = NULL;
+	size_t type_len, uuid_len, label_len, name_len, version_len;
+	char *dev_ptr, *type_ptr, *uuid_ptr, *label_ptr, *name_ptr, *version_ptr;
+	const char *type_val, *uuid_val, *label_val, *name_val, *version_val;
+
+	if (!load_libblkid())
+		return NULL;
+
+	pr = libblkid.alloc(path);
+
+	if (!pr)
+		return NULL;
+
+	if (libblkid.probe(pr) == 0) {
+		if (libblkid.lookup(pr, "TYPE", &type_val, &type_len))
+			type_len = 0;
+
+		if (libblkid.lookup(pr, "UUID", &uuid_val, &uuid_len))
+			uuid_len = 0;
+
+		if (libblkid.lookup(pr, "LABEL", &label_val, &label_len))
+			label_len = 0;
+
+		if (libblkid.lookup(pr, "NAME", &name_val, &name_len))
+			name_len = 0;
+
+		if (libblkid.lookup(pr, "VERSION", &version_val, &version_len))
+			version_len = 0;
+
+		if (type_len) {
+			info = calloc_a(sizeof(*info),
+			                &dev_ptr,     strlen(path) + 1,
+			                &type_ptr,    type_len,
+			                &uuid_ptr,    uuid_len,
+			                &label_ptr,   label_len,
+			                &name_ptr,    name_len,
+			                &version_ptr, version_len);
+
+			if (info) {
+				info->dev = strcpy(dev_ptr, path);
+				info->type = strcpy(type_ptr, type_val);
+
+				if (uuid_len)
+					info->uuid = strcpy(uuid_ptr, uuid_val);
+
+				if (label_len)
+					info->label = strcpy(label_ptr, label_val);
+
+				if (name_len)
+					info->name = strcpy(name_ptr, name_val);
+
+				if (version_len)
+					info->version = strcpy(version_ptr, version_val);
+			}
+		}
+	}
+
+	libblkid.free(pr);
+
+	return info;
+}
diff --git a/probe.c b/probe.c
index 9983a72..1117044 100644
--- a/probe.c
+++ b/probe.c
@@ -35,7 +35,7 @@ probe_path_tiny(const char *path)
 
 		if (info) {
 			info->type = strcpy(type, pr.id->name);
-			
+
 			if (pr.dev[0])
 				info->dev = strcpy(dev, pr.dev);
 
@@ -56,10 +56,17 @@ probe_path_tiny(const char *path)
 	return info;
 }
 
-struct probe_info * 
+struct probe_info *
 probe_path(const char *path)
 {
-	return probe_path_tiny(path);
+	struct probe_info *info;
+
+	info = probe_path_tiny(path);
+
+	if (!info)
+		info = probe_path_libblkid(path);
+
+	return info;
 }
 
 int
diff --git a/probe.h b/probe.h
index bcee3a8..b8557a4 100644
--- a/probe.h
+++ b/probe.h
@@ -28,6 +28,7 @@ struct probe_info {
 };
 
 struct probe_info * probe_path(const char *path);
+struct probe_info * probe_path_libblkid(const char *path);
 
 int make_devs(void);