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util-linux/libblkid/src/evaluate.c

324 lines
7.4 KiB

/*
* 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/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 ? "SUCCESS" : "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