stat-util: add new APIs device_path_make_{major_minor|canonical}() and device_path_parse_major_minor()

device_path_make_{major_minor|canonical)  generate device node paths
given a mode_t and a dev_t. We have similar code all over the place,
let's unify this in one place. The former will generate a "/dev/char/"
or "/dev/block" path, and never go to disk. The latter then goes to disk
and resolves that path to the actual path of the device node.

device_path_parse_major_minor() reverses device_path_make_major_minor(),
also withozut going to disk.

We have similar code doing something like this at various places, let's
unify this in a single set of functions. This also allows us to teach
them special tricks, for example handling of the
/run/systemd/inaccessible/{blk|chr} device nodes, which we use for
masking device nodes, and which do not exist in /dev/char/* and
/dev/block/*

1 files changed, 40 insertions, 0 deletions

diff --git a/src/test/test-stat-util.c b/src/test/test-stat-util.c
index 713fbc9a08..4201edac97 100644
--- a/src/test/test-stat-util.c
+++ b/src/test/test-stat-util.c
@@ -11,6 +11,7 @@
 #include "missing.h"
 #include "mount-util.h"
 #include "stat-util.h"
+#include "path-util.h"
 
 static void test_files_same(void) {
         _cleanup_close_ int fd = -1;
@@ -116,6 +117,44 @@ static void test_device_major_minor_valid(void) {
         assert_se(DEVICE_MINOR_VALID(minor(0)));
 }
 
+static void test_device_path_make_canonical_one(const char *path) {
+        _cleanup_free_ char *resolved = NULL, *raw = NULL;
+        struct stat st;
+        dev_t devno;
+        mode_t mode;
+        int r;
+
+        assert_se(stat(path, &st) >= 0);
+        r = device_path_make_canonical(st.st_mode, st.st_rdev, &resolved);
+        if (r == -ENOENT) /* maybe /dev/char/x:y and /dev/block/x:y are missing in this test environment, because we
+                           * run in a container or so? */
+                return;
+
+        assert_se(r >= 0);
+        assert_se(path_equal(path, resolved));
+
+        assert_se(device_path_make_major_minor(st.st_mode, st.st_rdev, &raw) >= 0);
+        assert_se(device_path_parse_major_minor(raw, &mode, &devno) >= 0);
+
+        assert_se(st.st_rdev == devno);
+        assert_se((st.st_mode & S_IFMT) == (mode & S_IFMT));
+}
+
+static void test_device_path_make_canonical(void) {
+
+        test_device_path_make_canonical_one("/dev/null");
+        test_device_path_make_canonical_one("/dev/zero");
+        test_device_path_make_canonical_one("/dev/full");
+        test_device_path_make_canonical_one("/dev/random");
+        test_device_path_make_canonical_one("/dev/urandom");
+        test_device_path_make_canonical_one("/dev/tty");
+
+        if (is_device_node("/run/systemd/inaccessible/chr") > 0) {
+                test_device_path_make_canonical_one("/run/systemd/inaccessible/chr");
+                test_device_path_make_canonical_one("/run/systemd/inaccessible/blk");
+        }
+}
+
 int main(int argc, char *argv[]) {
         test_files_same();
         test_is_symlink();
@@ -123,6 +162,7 @@ int main(int argc, char *argv[]) {
         test_path_is_temporary_fs();
         test_fd_is_network_ns();
         test_device_major_minor_valid();
+        test_device_path_make_canonical();
 
         return 0;
 }