rootdev: fix -d, add -c and -r. ifdefs for so use
Multiple changes:
- Ensure the -d flag trims off all of the partition info and only if there is a partition
- Add -c, device node creation for platform-agnostic /dev/ROOT, /dev/ROOT0 and /dev/ROOT1
- Add -r, resolve the first slave if the device is a device-mapper device
- Add -s, create a symlink from the found device to /dev/ACTIVE_ROOT
- Adds short-circuiting if /dev/ACTIVE_ROOT exists to both dm resolution and
normal lookups
- Add support for building a library with a reusable header and interfaces
I'll follow this up with a change to install <rootdev/rootdev.h> and the .so in
the ebuild if the interface is at all interesting. If prefered, I can just add:
rootdev -s -r to chromeos_startup, then AU can just rely on readlink(/dev/ACTIVE_ROOT).
BUG=chromium-os:5988
TEST=built for x86-generic testing with vroot: -r, -s, -c, -d and combos
switching to non-vroot to test now
can someone test arm for me?
Change-Id: Ibab8072afb012ea77d457517f1849e0917d02892
Review URL: http://codereview.chromium.org/3141038
diff --git a/rootdev.c b/rootdev.c
index c3dc175..867974f 100644
--- a/rootdev.c
+++ b/rootdev.c
@@ -1,100 +1,389 @@
-/* Taken from util-linux source. GPLv2.
- * Emits the current rootfs device.
- * Works by searching /dev recursively for a BLK device with the same device
- * number as '/'.
+/* Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ *
+ * Implements root device discovery via sysfs with optional bells and whistles.
*/
-#include <stdio.h>
-#include <err.h>
-#include <sys/types.h>
+#include "rootdev.h"
+
+#include <ctype.h>
#include <dirent.h>
-#include <sys/stat.h>
+#include <err.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <stdbool.h>
+#include <stddef.h>
+#include <stdio.h>
+#include <stdlib.h>
#include <string.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+#include <unistd.h>
+static const char *kDefaultSearchPath = "/sys/block";
+static const char *kDefaultDevPath = "/dev";
-static int
-find_dev_recursive(char *dirnamebuf, int number, int deviceOnly) {
- DIR *dp;
- struct dirent *dir;
- struct stat s;
- int dirnamelen = 0;
+/* Encode the root device structuring here for Chromium OS */
+static const char kActiveRoot[] = "/dev/ACTIVE_ROOT";
+static const char kRootDev[] = "/dev/ROOT";
+static const char kRootA[] = "/dev/ROOT0";
+static const char kRootB[] = "/dev/ROOT1";
- if ((dp = opendir(dirnamebuf)) == NULL)
- err(1, "can't read directory %s", dirnamebuf);
- dirnamelen = strlen(dirnamebuf);
- while ((dir = readdir(dp)) != NULL) {
- if (!strcmp(dir->d_name, ".") || !strcmp(dir->d_name, ".."))
- continue;
- if (dirnamelen + 1 + strlen(dir->d_name) > PATH_MAX)
- continue;
- dirnamebuf[dirnamelen] = '/';
- strcpy(dirnamebuf+dirnamelen+1, dir->d_name);
- if (lstat(dirnamebuf, &s) < 0)
- continue;
- if ((s.st_mode & S_IFMT) == S_IFBLK && s.st_rdev == number){
- if (deviceOnly) {
- int len = strlen(dirnamebuf);
- char c = 0;
- do {
- c = dirnamebuf[len-1];
- --len;
- }while(c > 0 && c < 9 && len > 0);
- /* arm has "p" for partition */
- if (dirnamebuf[len-1] == 'p')
- --len;
- dirnamebuf[len]='\0';
- }
- return 1;
- }
- if ((s.st_mode & S_IFMT) == S_IFDIR &&
- find_dev_recursive(dirnamebuf, number, deviceOnly))
- return 1;
- }
- dirnamebuf[dirnamelen] = 0;
- closedir(dp);
- return 0;
+struct part_config {
+ const char *name;
+ int offset;
+};
+
+#define CHROMEOS_PRIMARY_PARTITION 3
+static const struct part_config kPrimaryPart[] = { { kRootA, 0 },
+ { kRootDev, -3 },
+ { kRootB, 2 } };
+#define CHROMEOS_SECONDARY_PARTITION 5
+static const struct part_config kSecondaryPart[] = { { kRootB, 0 },
+ { kRootDev, -5 },
+ { kRootA, -2 } };
+
+/* The number of entries in a part_config so we could add RootC easily. */
+static const int kPartitionEntries = 3;
+
+/* Converts a file of %u:%u -> dev_t. */
+static dev_t devt_from_file(const char *file) {
+ char candidate[10]; /* TODO(wad) system-provided constant? */
+ ssize_t bytes = 0;
+ unsigned int major = 0;
+ unsigned int minor = 0;
+ dev_t dev = 0;
+ int fd = -1;
+
+ /* Never hang. Either get the data or return 0. */
+ fd = open(file, O_NONBLOCK | O_RDONLY);
+ if (fd < 0)
+ return 0;
+ bytes = read(fd, candidate, sizeof(candidate));
+ close(fd);
+
+ /* 0:0 should be considered the minimum size. */
+ if (bytes < 3)
+ return 0;
+ candidate[bytes] = 0;
+ if (sscanf(candidate, "%u:%u", &major, &minor) == 2) {
+ /* candidate's size artificially limits the size of the converted
+ * %u to safely convert to a signed int. */
+ dev = makedev(major, minor);
+ }
+ return dev;
}
-void usage(){
- printf ("rootdev \n\t-d (for device only)\n");
+/* Walks sysfs and will recurse into any directory/link that represents
+ * a block device to find sub-devices (partitions).
+ * If dev == 0, the first device in the directory will be returned. */
+static int match_sysfs_device(char *name, size_t name_len,
+ const char *basedir, dev_t *dev) {
+ int found = -1;
+ size_t basedir_len;
+ DIR *dirp = NULL;
+ struct dirent *entry = NULL;
+ struct dirent *next = NULL;
+ char *working_path = NULL;
+ long working_path_size = 0;
+
+ if (!name || !name_len || !basedir || !dev) {
+ warnx("match_sysfs_device: invalid arguments supplied");
+ return -1;
+ }
+ basedir_len = strlen(basedir);
+ if (!basedir_len) {
+ warnx("match_sysfs_device: basedir must not be empty");
+ return -1;
+ }
+
+ errno = 0;
+ dirp = opendir(basedir);
+ if (!dirp) {
+ /* Don't complain if the directory doesn't exist. */
+ if (errno != ENOENT)
+ warn("match_sysfs_device:opendir(%s)", basedir);
+ return found;
+ }
+
+ /* Grab a platform appropriate path to work with.
+ * Ideally, this won't vary under sys/block. */
+ working_path_size = pathconf(basedir, _PC_NAME_MAX) + 1;
+ /* Fallback to PATH_MAX on any pathconf error. */
+ if (working_path_size < 0)
+ working_path_size = PATH_MAX;
+
+ working_path = malloc(working_path_size);
+ if (!working_path) {
+ warn("malloc(dirent)");
+ closedir(dirp);
+ return found;
+ }
+
+ /* Allocate a properly sized entry. */
+ entry = malloc(offsetof(struct dirent, d_name) + working_path_size);
+ if (!entry) {
+ warn("malloc(dirent)");
+ free(working_path);
+ closedir(dirp);
+ return found;
+ }
+
+ while (readdir_r(dirp, entry, &next) == 0 && next) {
+ size_t candidate_len = strlen(entry->d_name);
+ size_t path_len = 0;
+ dev_t found_devt = 0;
+ /* Ignore the usual */
+ if (!strcmp(entry->d_name, ".") || !strcmp(entry->d_name, ".."))
+ continue;
+ /* TODO(wad) determine how to best bubble up this case. */
+ if (candidate_len > name_len)
+ continue;
+ /* Only traverse directories or symlinks (to directories ideally) */
+ switch (entry->d_type) {
+ case DT_UNKNOWN:
+ case DT_DIR:
+ case DT_LNK:
+ break;
+ default:
+ continue;
+ }
+ /* Determine path to block device number */
+ path_len = snprintf(working_path, working_path_size, "%s/%s/dev",
+ basedir, entry->d_name);
+ /* Ignore if truncation occurs. */
+ if (path_len != candidate_len + basedir_len + 5)
+ continue;
+
+ found_devt = devt_from_file(working_path);
+ /* *dev == 0 is a wildcard. */
+ if (!*dev || found_devt == *dev) {
+ snprintf(name, name_len, "%s", entry->d_name);
+ *dev = found_devt;
+ found = 1;
+ break;
+ }
+
+ /* Recurse one level for devices that may have a matching partition. */
+ if (major(found_devt) == major(*dev) && minor(*dev) > minor(found_devt)) {
+ sprintf(working_path, "%s/%s", basedir, entry->d_name);
+ found = match_sysfs_device(name, name_len, working_path, dev);
+ if (found > 0)
+ break;
+ }
+ }
+
+ free(working_path);
+ free(entry);
+ closedir(dirp);
+ return found;
}
-int main(int argc, char *argv[]) {
- struct stat s;
- char *file = "/";
- static char name[PATH_MAX+1];
- int deviceOnly=0;
- int c;
- extern char *optarg;
- extern int optind, optopt;
- while ((c = getopt(argc, argv, "hd")) != -1) {
- switch(c) {
- case 'd':
- deviceOnly=1;
- break;
- case 'h':
- default:
- usage();
- return 1;
- }
- }
- if (argc - optind >= 1)
- file = argv[optind];
+const char *rootdev_get_partition(const char *dst, size_t len) {
+ const char *end = dst + strnlen(dst, len);
+ const char *part = end - 1;
+ if (!len)
+ return NULL;
- if (stat(file, &s) < 0)
- err(1, "unable to stat %s", file);
+ if (!isdigit(*part--))
+ return NULL;
- if (!s.st_dev)
- err(1, "unknown device number 0");
+ while (part > dst && isdigit(*part)) part--;
+ part++;
- strcpy(name, "/dev");
+ if (part >= end)
+ return NULL;
- if (!find_dev_recursive(name, s.st_dev, deviceOnly)) {
- fprintf(stderr, "unable to find match\n");
- return 1;
- }
+ return part;
+}
- printf("%s\n", name);
+void rootdev_strip_partition(char *dst, size_t len) {
+ char *part = (char *)rootdev_get_partition(dst, len);
+ if (!part)
+ return;
+ /* For devices that end with a digit, the kernel uses a 'p'
+ * as a separator. E.g., mmcblk1p2. */
+ if (*(part - 1) == 'p')
+ part--;
+ *part = '\0';
+}
- return 0;
+int rootdev_symlink_active(const char *path) {
+ int ret = 0;
+ /* Don't overwrite an existing link. */
+ errno = 0;
+ if ((symlink(path, kActiveRoot)) && errno != EEXIST) {
+ warn("failed to symlink %s -> %s", kActiveRoot, path);
+ ret = -1;
+ }
+ return ret;
+}
+
+int rootdev_get_device(char *dst, size_t size, dev_t dev,
+ const char *search) {
+ struct stat active_root_statbuf;
+
+ if (search == NULL)
+ search = kDefaultSearchPath;
+
+ /* Check if the -s symlink exists. */
+ if ((stat(kActiveRoot, &active_root_statbuf) == 0) &&
+ active_root_statbuf.st_rdev == dev) {
+ /* Note, if the link is not fully qualified, this won't be
+ * either. */
+ ssize_t len = readlink(kActiveRoot, dst, PATH_MAX);
+ if (len > 0) {
+ dst[len] = 0;
+ return 0;
+ }
+ /* If readlink fails or is empty, fall through */
+ }
+
+ snprintf(dst, size, "%s", search);
+ if (match_sysfs_device(dst, size, dst, &dev) <= 0) {
+ fprintf (stderr, "unable to find match\n");
+ return 1;
+ }
+
+ return 0;
+}
+
+int rootdev_get_device_slave(char *slave, size_t size, dev_t *dev,
+ const char *device, const char *search) {
+ char dst[PATH_MAX];
+ int len = 0;
+
+ if (search == NULL)
+ search = kDefaultSearchPath;
+
+ /* So far, I've only seen top-level block devices with slaves. */
+ len = snprintf(dst, sizeof(dst), "%s/%s/slaves", search, device);
+ if (len < 0 || len != strlen(device) + strlen(search) + 8) {
+ warnx("rootdev_get_device_slave: device name too long");
+ return -1;
+ }
+ *dev = 0;
+ if (match_sysfs_device(slave, size, dst, dev) <= 0)
+ return -1;
+
+ return 0;
+}
+
+int rootdev_create_devices(const char *name, dev_t dev, bool symlink) {
+ int ret = 0;
+ unsigned int major = major(dev);
+ unsigned int minor = minor(dev);
+ int i;
+ const struct part_config *config;
+ const char *part_s = rootdev_get_partition(name, strlen(name));
+
+ if (part_s == NULL) {
+ warnx("create_devices: unable to determine partition");
+ return -1;
+ }
+
+ switch (atoi(part_s)) {
+ case CHROMEOS_PRIMARY_PARTITION:
+ config = kPrimaryPart;
+ break;
+ case CHROMEOS_SECONDARY_PARTITION:
+ config = kSecondaryPart;
+ break;
+ default:
+ warnx("create_devices: unable to determine partition: %s",
+ part_s);
+ return -1;
+ }
+
+ for (i = 0; i < kPartitionEntries; ++i) {
+ dev = makedev(major, minor + config[i].offset);
+ errno = 0;
+ if (mknod(config[i].name,
+ S_IFBLK | S_IRUSR | S_IWUSR | S_IRGRP | S_IROTH,
+ dev) && errno != EEXIST) {
+ warn("failed to create %s", config[i].name);
+ return -1;
+ }
+ }
+
+ if (symlink)
+ ret = rootdev_symlink_active(config[0].name);
+ return ret;
+}
+
+int rootdev_get_path(char *path, size_t size, const char *device,
+ dev_t dev, const char *dev_path) {
+ int path_len;
+ struct stat dev_statbuf;
+
+ if (!dev_path)
+ dev_path = kDefaultDevPath;
+
+ if (!path || !size || !device)
+ return -1;
+
+ path_len = snprintf(path, size, "%s/%s", dev_path, device);
+ if (path_len != strlen(dev_path) + 1 + strlen(device))
+ return -1;
+
+ if (stat(path, &dev_statbuf) != 0)
+ return 1;
+
+ if (dev && dev != dev_statbuf.st_rdev)
+ return 2;
+
+ return 0;
+}
+
+int rootdev_wrapper(char *path, size_t size,
+ bool full, bool strip,
+ dev_t *dev,
+ const char *search, const char *dev_path) {
+ int res = 0;
+ char devname[PATH_MAX];
+ if (!search)
+ search = kDefaultSearchPath;
+ if (!dev_path)
+ dev_path = kDefaultDevPath;
+ if (!dev)
+ return -1;
+
+ res = rootdev_get_device(devname, sizeof(devname), *dev, search);
+ if (res != 0)
+ return res;
+
+ if (full)
+ res = rootdev_get_device_slave(devname, sizeof(devname), dev, devname,
+ search);
+
+ /* TODO(wad) we should really just track the block dev, partition number, and
+ * dev path. When we rewrite this, we can track all the sysfs info
+ * in the class. */
+ if (strip) {
+ /* When we strip the partition, we don't want get_path to return non-zero
+ * because of dev mismatch. Passing in 0 tells it to not test. */
+ *dev = 0;
+ rootdev_strip_partition(devname, size);
+ }
+
+ res = rootdev_get_path(path, size, devname, *dev, dev_path);
+
+ return res;
+}
+
+int rootdev(char *path, size_t size, bool full, bool strip) {
+ struct stat root_statbuf;
+
+ /* Yields the containing dev_t in st_dev. */
+ if (stat("/", &root_statbuf) != 0)
+ return -1;
+
+ return rootdev_wrapper(path,
+ size,
+ full,
+ strip,
+ &root_statbuf.st_dev,
+ NULL, /* default /sys dir */
+ NULL); /* default /dev dir */
}