1 files changed, 138 insertions, 0 deletions
diff --git a/src/basic/devnum-util.c b/src/basic/devnum-util.c
new file mode 100644
index 0000000..bd1b4d6
--- /dev/null
+++ b/src/basic/devnum-util.c
@@ -0,0 +1,138 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <string.h>
+#include <sys/stat.h>
+
+#include "chase-symlinks.h"
+#include "devnum-util.h"
+#include "parse-util.h"
+#include "path-util.h"
+#include "string-util.h"
+
+int parse_devnum(const char *s, dev_t *ret) {
+        const char *major;
+        unsigned x, y;
+        size_t n;
+        int r;
+
+        n = strspn(s, DIGITS);
+        if (n == 0)
+                return -EINVAL;
+        if (n > DECIMAL_STR_MAX(dev_t))
+                return -EINVAL;
+        if (s[n] != ':')
+                return -EINVAL;
+
+        major = strndupa_safe(s, n);
+        r = safe_atou(major, &x);
+        if (r < 0)
+                return r;
+
+        r = safe_atou(s + n + 1, &y);
+        if (r < 0)
+                return r;
+
+        if (!DEVICE_MAJOR_VALID(x) || !DEVICE_MINOR_VALID(y))
+                return -ERANGE;
+
+        *ret = makedev(x, y);
+        return 0;
+}
+
+int device_path_make_major_minor(mode_t mode, dev_t devnum, char **ret) {
+        const char *t;
+
+        /* Generates the /dev/{char|block}/MAJOR:MINOR path for a dev_t */
+
+        if (S_ISCHR(mode))
+                t = "char";
+        else if (S_ISBLK(mode))
+                t = "block";
+        else
+                return -ENODEV;
+
+        if (asprintf(ret, "/dev/%s/" DEVNUM_FORMAT_STR, t, DEVNUM_FORMAT_VAL(devnum)) < 0)
+                return -ENOMEM;
+
+        return 0;
+}
+
+int device_path_make_inaccessible(mode_t mode, char **ret) {
+        char *s;
+
+        assert(ret);
+
+        if (S_ISCHR(mode))
+                s = strdup("/run/systemd/inaccessible/chr");
+        else if (S_ISBLK(mode))
+                s = strdup("/run/systemd/inaccessible/blk");
+        else
+                return -ENODEV;
+        if (!s)
+                return -ENOMEM;
+
+        *ret = s;
+        return 0;
+}
+
+int device_path_make_canonical(mode_t mode, dev_t devnum, char **ret) {
+        _cleanup_free_ char *p = NULL;
+        int r;
+
+        /* Finds the canonical path for a device, i.e. resolves the /dev/{char|block}/MAJOR:MINOR path to the end. */
+
+        assert(ret);
+
+        if (major(devnum) == 0 && minor(devnum) == 0)
+                /* A special hack to make sure our 'inaccessible' device nodes work. They won't have symlinks in
+                 * /dev/block/ and /dev/char/, hence we handle them specially here. */
+                return device_path_make_inaccessible(mode, ret);
+
+        r = device_path_make_major_minor(mode, devnum, &p);
+        if (r < 0)
+                return r;
+
+        return chase_symlinks(p, NULL, 0, ret, NULL);
+}
+
+int device_path_parse_major_minor(const char *path, mode_t *ret_mode, dev_t *ret_devnum) {
+        mode_t mode;
+        dev_t devnum;
+        int r;
+
+        /* Tries to extract the major/minor directly from the device path if we can. Handles /dev/block/ and /dev/char/
+         * paths, as well out synthetic inaccessible device nodes. Never goes to disk. Returns -ENODEV if the device
+         * path cannot be parsed like this.  */
+
+        if (path_equal(path, "/run/systemd/inaccessible/chr")) {
+                mode = S_IFCHR;
+                devnum = makedev(0, 0);
+        } else if (path_equal(path, "/run/systemd/inaccessible/blk")) {
+                mode = S_IFBLK;
+                devnum = makedev(0, 0);
+        } else {
+                const char *w;
+
+                w = path_startswith(path, "/dev/block/");
+                if (w)
+                        mode = S_IFBLK;
+                else {
+                        w = path_startswith(path, "/dev/char/");
+                        if (!w)
+                                return -ENODEV;
+
+                        mode = S_IFCHR;
+                }
+
+                r = parse_devnum(w, &devnum);
+                if (r < 0)
+                        return r;
+        }
+
+        if (ret_mode)
+                *ret_mode = mode;
+        if (ret_devnum)
+                *ret_devnum = devnum;
+
+        return 0;
+}