implement program loader

1 files changed, 56 insertions, 0 deletions

diff --git a/loader/loader.c b/loader/loader.c
new file mode 100644
index 0000000..f2942a4
--- /dev/null
+++ b/loader/loader.c
@@ -0,0 +1,56 @@
+/*
+ * Copyright (c) 2017 William Pitcock <nenolod@dereferenced.org>
+ *
+ * Permission to use, copy, modify, and/or distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * This software is provided 'as is' and without any warranty, express or
+ * implied.  In no event shall the authors be liable for any damages arising
+ * from the use of this software.
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <limits.h>
+
+#ifndef PATH_MAX
+#define PATH_MAX      16384
+#endif
+
+#ifndef LINKER
+#error LINKER must be defined
+#endif
+
+#ifndef LIBGCOMPAT
+#error LIBGCOMPAT must be defined
+#endif
+
+int main(int argc, char *argv[], char *envp[]) {
+	size_t i = 0;
+	char target[PATH_MAX];
+	char **new_argv = calloc(sizeof(char *), argc + 5);
+
+	memset(target, 0, sizeof(target));
+	if (readlink("/proc/self/exe", target, sizeof(target)) < 0) {
+		perror("readlink");
+		return EXIT_FAILURE;
+	}
+
+	new_argv[0] = argv[0];
+	new_argv[1] = "--preload";
+	new_argv[2] = LIBGCOMPAT;
+	new_argv[3] = target;
+
+	for (i = 1; i < argc; i++) {
+		new_argv[3 + i] = argv[i];
+	}
+
+	execve(LINKER, new_argv, envp);
+
+	/* execve only returns if there is an error. */
+	perror("execve");
+	return EXIT_FAILURE;
+}