pid1: port executor binary pinning to new build path logic

src/basic/build-path.c

@@ -6,6 +6,7 @@
 
 #include "build-path.h"
 #include "errno-list.h"
+#include "errno-util.h"
 #include "macro.h"
 #include "path-util.h"
 #include "process-util.h"
@@ -236,3 +237,31 @@ int invoke_callout_binary(const char *path, char *const argv[]) {
         execv(path, argv);
         return -errno;
 }
+
+int pin_callout_binary(const char *path) {
+        int r;
+
+        assert(path);
+
+        /* Similar to invoke_callout_binary(), but pins (i.e. O_PATH opens) the binary instead of executing it. */
+
+        _cleanup_free_ char *fn = NULL;
+        r = path_extract_filename(path, &fn);
+        if (r < 0)
+                return r;
+        if (r == O_DIRECTORY) /* Uh? */
+                return -EISDIR;
+
+        const char *e;
+        if (find_environment_binary(fn, &e) >= 0)
+                return RET_NERRNO(open(e, O_CLOEXEC|O_PATH));
+
+        _cleanup_free_ char *np = NULL;
+        if (find_build_dir_binary(fn, &np) >= 0) {
+                r = RET_NERRNO(open(np, O_CLOEXEC|O_PATH));
+                if (r >= 0)
+                        return r;
+        }
+
+        return RET_NERRNO(open(path, O_CLOEXEC|O_PATH));
+}

src/basic/build-path.h

@@ -4,3 +4,5 @@
 int get_build_exec_dir(char **ret);
 
 int invoke_callout_binary(const char *path, char *const argv[]);
+
+int pin_callout_binary(const char *path);