Implement masking and overriding of generators

Sometimes it is necessary to stop a generator from running. Either
because of a bug, or for testing, or some other reason. The only way
to do that would be to rename or chmod the generator binary, which is
inconvenient and does not survive upgrades. Allow masking and
overriding generators similarly to units and other configuration
files.

For the systemd instance, masking would be more common, rather than
overriding generators. For the user instances, it may also be useful
for users to have generators in $XDG_CONFIG_HOME to augment or
override system-wide generators.

Directories are searched according to the usual scheme (/usr/lib,
/usr/local/lib, /run, /etc), and files with the same name in higher
priority directories override files with the same name in lower
priority directories. Empty files and links to /dev/null mask a given
name.

https://bugs.freedesktop.org/show_bug.cgi?id=87230

1 files changed, 16 insertions, 11 deletions

diff --git a/src/test/test-util.c b/src/test/test-util.c
index d862149fa8..1a5997873c 100644
--- a/src/test/test-util.c
+++ b/src/test/test-util.c
@@ -1207,23 +1207,28 @@ static void test_glob_exists(void) {
 }
 
 static void test_execute_directory(void) {
-        char name[] = "/tmp/test-execute_directory/script1";
-        char name2[] = "/tmp/test-execute_directory/script2";
-        char name3[] = "/tmp/test-execute_directory/useless";
-        char tempdir[] = "/tmp/test-execute_directory/";
+        char template[] = "/tmp/test-readlink_and_make_absolute.XXXXXXX";
+        const char const* dirs[] = {template, NULL};
+        const char *name, *name2, *name3;
 
-        assert_se(mkdir_safe(tempdir, 0755, getuid(), getgid()) >= 0);
-        assert_se(write_string_file(name, "#!/bin/sh\necho 'Executing '$0\ntouch /tmp/test-execute_directory/it_works") == 0);
-        assert_se(write_string_file(name2, "#!/bin/sh\necho 'Executing '$0\ntouch /tmp/test-execute_directory/it_works2") == 0);
+        assert_se(mkdtemp(template));
+
+        name = strappenda(template, "/script");
+        name2 = strappenda(template, "/script2");
+        name3 = strappenda(template, "/useless");
+
+        assert_se(write_string_file(name, "#!/bin/sh\necho 'Executing '$0\ntouch $(dirname $0)/it_works") == 0);
+        assert_se(write_string_file(name2, "#!/bin/sh\necho 'Executing '$0\ntouch $(dirname $0)/it_works2") == 0);
         assert_se(chmod(name, 0755) == 0);
         assert_se(chmod(name2, 0755) == 0);
         assert_se(touch(name3) >= 0);
 
-        execute_directory(tempdir, DEFAULT_TIMEOUT_USEC, NULL);
-        assert_se(access("/tmp/test-execute_directory/it_works", F_OK) >= 0);
-        assert_se(access("/tmp/test-execute_directory/it_works2", F_OK) >= 0);
+        assert(chdir(template) == 0);
+        execute_directories(dirs, DEFAULT_TIMEOUT_USEC, NULL);
+        assert_se(access("it_works", F_OK) >= 0);
+        assert_se(access("it_works2", F_OK) >= 0);
 
-        rm_rf_dangerous(tempdir, false, true, false);
+        rm_rf_dangerous(template, false, true, false);
 }
 
 static void test_unquote_first_word(void) {