1 files changed, 325 insertions, 0 deletions
diff --git a/libblkid/src/evaluate.c b/libblkid/src/evaluate.c
new file mode 100644
index 000000000..3d9a76b0a
--- /dev/null
+++ b/libblkid/src/evaluate.c
@@ -0,0 +1,325 @@
+/*
+ * evaluate.c - very high-level API to evaluate LABELs or UUIDs
+ *
+ * Copyright (C) 2009 Karel Zak <kzak@redhat.com>
+ *
+ * This file may be redistributed under the terms of the
+ * GNU Lesser General Public License.
+ */
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <ctype.h>
+#include <sys/sysmacros.h>
+#include <sys/types.h>
+#ifdef HAVE_SYS_STAT_H
+#include <sys/stat.h>
+#endif
+#ifdef HAVE_ERRNO_H
+#include <errno.h>
+#endif
+#include <stdint.h>
+#include <stdarg.h>
+
+#include "pathnames.h"
+#include "canonicalize.h"
+#include "closestream.h"
+
+#include "blkidP.h"
+
+/**
+ * SECTION:evaluate
+ * @title: Tags and Spec evaluation
+ * @short_description: top-level API for LABEL and UUID evaluation.
+ *
+ * This API provides very simple and portable way how evaluate LABEL and UUID
+ * tags.  The blkid_evaluate_tag() and blkid_evaluate_spec() work on 2.4 and
+ * 2.6 systems and on systems with or without udev. Currently, the libblkid
+ * library supports "udev" and "scan" methods. The "udev" method uses udev
+ * /dev/disk/by-* symlinks and the "scan" method scans all block devices from
+ * the /proc/partitions file. The evaluation could be controlled by the
+ * /etc/blkid.conf config file. The default is to try "udev" and then "scan"
+ * method.
+ *
+ * The blkid_evaluate_tag() also automatically informs udevd when an obsolete
+ * /dev/disk/by-* symlink is detected.
+ *
+ * If you are not sure how translate LABEL or UUID to the device name use this
+ * API.
+ */
+
+#ifdef CONFIG_BLKID_VERIFY_UDEV
+/* returns zero when the device has NAME=value (LABEL/UUID) */
+static int verify_tag(const char *devname, const char *name, const char *value)
+{
+	blkid_probe pr;
+	int fd = -1, rc = -1;
+	size_t len;
+	const char *data;
+	int errsv = 0;
+
+	pr = blkid_new_probe();
+	if (!pr)
+		return -1;
+
+	blkid_probe_enable_superblocks(pr, TRUE);
+	blkid_probe_set_superblocks_flags(pr,
+			BLKID_SUBLKS_LABEL | BLKID_SUBLKS_UUID);
+
+	blkid_probe_enable_partitions(pr, TRUE);
+	blkid_probe_set_partitions_flags(pr, BLKID_PARTS_ENTRY_DETAILS);
+
+	fd = open(devname, O_RDONLY|O_CLOEXEC);
+	if (fd < 0) {
+		errsv = errno;
+		goto done;
+	}
+	if (blkid_probe_set_device(pr, fd, 0, 0))
+		goto done;
+	rc = blkid_do_safeprobe(pr);
+	if (rc)
+		goto done;
+	rc = blkid_probe_lookup_value(pr, name, &data, &len);
+	if (!rc)
+		rc = memcmp(value, data, len);
+done:
+	DBG(EVALUATE, ul_debug("%s: %s verification %s",
+			devname, name, rc == 0 ? "PASS" : "FAILED"));
+	if (fd >= 0)
+		close(fd);
+	blkid_free_probe(pr);
+
+	/* for non-root users we use unverified udev links */
+	return errsv == EACCES ? 0 : rc;
+}
+#endif /* CONFIG_BLKID_VERIFY_UDEV*/
+
+/**
+ * blkid_send_uevent:
+ * @devname: absolute path to the device
+ * @action: event string
+ *
+ * Returns: -1 in case of failure, or 0 on success.
+ */
+int blkid_send_uevent(const char *devname, const char *action)
+{
+	char uevent[PATH_MAX];
+	struct stat st;
+	FILE *f;
+	int rc = -1;
+
+	DBG(EVALUATE, ul_debug("%s: uevent '%s' requested", devname, action));
+
+	if (!devname || !action)
+		return -1;
+	if (stat(devname, &st) || !S_ISBLK(st.st_mode))
+		return -1;
+
+	snprintf(uevent, sizeof(uevent), "/sys/dev/block/%d:%d/uevent",
+			major(st.st_rdev), minor(st.st_rdev));
+
+	f = fopen(uevent, "w" UL_CLOEXECSTR);
+	if (f) {
+		rc = 0;
+		if (fputs(action, f) >= 0)
+			rc = 0;
+		if (close_stream(f) != 0)
+			DBG(EVALUATE, ul_debug("write failed: %s", uevent));
+	}
+	DBG(EVALUATE, ul_debug("%s: send uevent %s",
+			uevent, rc == 0 ? "SUCCES" : "FAILED"));
+	return rc;
+}
+
+static char *evaluate_by_udev(const char *token, const char *value, int uevent)
+{
+	char dev[PATH_MAX];
+	char *path = NULL;
+	size_t len;
+	struct stat st;
+
+	DBG(EVALUATE, ul_debug("evaluating by udev %s=%s", token, value));
+
+	if (!strcmp(token, "UUID"))
+		strcpy(dev, _PATH_DEV_BYUUID "/");
+	else if (!strcmp(token, "LABEL"))
+		strcpy(dev, _PATH_DEV_BYLABEL "/");
+	else if (!strcmp(token, "PARTLABEL"))
+		strcpy(dev, _PATH_DEV_BYPARTLABEL "/");
+	else if (!strcmp(token, "PARTUUID"))
+		strcpy(dev, _PATH_DEV_BYPARTUUID "/");
+	else {
+		DBG(EVALUATE, ul_debug("unsupported token %s", token));
+		return NULL;	/* unsupported tag */
+	}
+
+	len = strlen(dev);
+	if (blkid_encode_string(value, &dev[len], sizeof(dev) - len) != 0)
+		return NULL;
+
+	DBG(EVALUATE, ul_debug("expected udev link: %s", dev));
+
+	if (stat(dev, &st))
+		goto failed;	/* link or device does not exist */
+
+	if (!S_ISBLK(st.st_mode))
+		return NULL;
+
+	path = canonicalize_path(dev);
+	if (!path)
+		return NULL;
+
+#ifdef CONFIG_BLKID_VERIFY_UDEV
+	if (verify_tag(path, token, value))
+		goto failed;
+#endif
+	return path;
+
+failed:
+	DBG(EVALUATE, ul_debug("failed to evaluate by udev"));
+
+	if (uevent && path)
+		blkid_send_uevent(path, "change");
+	free(path);
+	return NULL;
+}
+
+static char *evaluate_by_scan(const char *token, const char *value,
+		blkid_cache *cache, struct blkid_config *conf)
+{
+	blkid_cache c = cache ? *cache : NULL;
+	char *res;
+
+	DBG(EVALUATE, ul_debug("evaluating by blkid scan %s=%s", token, value));
+
+	if (!c) {
+		char *cachefile = blkid_get_cache_filename(conf);
+		blkid_get_cache(&c, cachefile);
+		free(cachefile);
+	}
+	if (!c)
+		return NULL;
+
+	res = blkid_get_devname(c, token, value);
+
+	if (cache)
+		*cache = c;
+	else
+		blkid_put_cache(c);
+
+	return res;
+}
+
+/**
+ * blkid_evaluate_tag:
+ * @token: token name (e.g "LABEL" or "UUID") or unparsed tag (e.g. "LABEL=foo")
+ * @value: token data (e.g. "foo")
+ * @cache: pointer to cache (or NULL when you don't want to re-use the cache)
+ *
+ * Returns: allocated string with a device name.
+ */
+char *blkid_evaluate_tag(const char *token, const char *value, blkid_cache *cache)
+{
+	struct blkid_config *conf = NULL;
+	char *t = NULL, *v = NULL;
+	char *ret = NULL;
+	int i;
+
+	if (!token)
+		return NULL;
+
+	if (!cache || !*cache)
+		blkid_init_debug(0);
+
+	DBG(EVALUATE, ul_debug("evaluating  %s%s%s", token, value ? "=" : "",
+		   value ? value : ""));
+
+	if (!value) {
+		if (!strchr(token, '=')) {
+			ret = strdup(token);
+			goto out;
+		}
+		blkid_parse_tag_string(token, &t, &v);
+		if (!t || !v)
+			goto out;
+		token = t;
+		value = v;
+	}
+
+	conf = blkid_read_config(NULL);
+	if (!conf)
+		goto out;
+
+	for (i = 0; i < conf->nevals; i++) {
+		if (conf->eval[i] == BLKID_EVAL_UDEV)
+			ret = evaluate_by_udev(token, value, conf->uevent);
+		else if (conf->eval[i] == BLKID_EVAL_SCAN)
+			ret = evaluate_by_scan(token, value, cache, conf);
+		if (ret)
+			break;
+	}
+
+	DBG(EVALUATE, ul_debug("%s=%s evaluated as %s", token, value, ret));
+out:
+	blkid_free_config(conf);
+	free(t);
+	free(v);
+	return ret;
+}
+
+/**
+ * blkid_evaluate_spec:
+ * @spec: unparsed tag (e.g. "LABEL=foo") or path (e.g. /dev/dm-0)
+ * @cache: pointer to cache (or NULL when you don't want to re-use the cache)
+ *
+ * All returned paths are canonicalized, device-mapper paths are converted
+ * to the /dev/mapper/name format.
+ *
+ * Returns: allocated string with a device name.
+ */
+char *blkid_evaluate_spec(const char *spec, blkid_cache *cache)
+{
+	char *t = NULL, *v = NULL, *res;
+
+	if (!spec)
+		return NULL;
+
+	if (strchr(spec, '=') &&
+	    blkid_parse_tag_string(spec, &t, &v) != 0)	/* parse error */
+		return NULL;
+
+	if (v)
+		res = blkid_evaluate_tag(t, v, cache);
+	else
+		res = canonicalize_path(spec);
+
+	free(t);
+	free(v);
+	return res;
+}
+
+
+#ifdef TEST_PROGRAM
+int main(int argc, char *argv[])
+{
+	blkid_cache cache = NULL;
+	char *res;
+
+	if (argc < 2) {
+		fprintf(stderr, "usage: %s <tag> | <spec>\n", argv[0]);
+		return EXIT_FAILURE;
+	}
+
+	blkid_init_debug(0);
+
+	res = blkid_evaluate_spec(argv[1], &cache);
+	if (res)
+		printf("%s\n", res);
+	if (cache)
+		blkid_put_cache(cache);
+
+	return res ? EXIT_SUCCESS : EXIT_FAILURE;
+}
+#endif