use LD_LIBRARY_PATH for glibc instead of calling its loader

Calling the loader fails on non ELF executables. Exec, formerly run_cmd,
now takes two options: -l LD_LIBRARY_PATH, -p LD_PRELOAD.
-p sets LD_PRELOAD and -l LD_LIBRARY_PATH before executing the rest of argv.

glibc no longer uses cmd_prefix in favor of LD_LIBRARY_PATH.

1 files changed, 32 insertions, 0 deletions

diff --git a/src/exec.c b/src/exec.c
new file mode 100644
index 0000000..37ef5b6
--- /dev/null
+++ b/src/exec.c
@@ -0,0 +1,32 @@
+#define _GNU_SOURCE
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+
+int main(int argc, char* argv[]) {
+	if (argc < 3) {
+		printf("Usage: %s [-p LD_PRELOAD] [-l LD_LIBRARY_PATH] <cmd> [cmd args]\n");
+		printf("\tset LD_PRELOAD to ld_preload and call execvp <cmd> [cmd args]\n");
+		return 1;
+	}
+
+	int i = 1;
+	for (; i < argc; i++) {
+		// Overwrite LD_PRELOAD.
+		if (strncmp(argv[i], "-p", 2) == 0) {
+			setenv("LD_PRELOAD", argv[i+1], 1);
+			i++;
+		// Overwrite LD_LIBRARY_PATH.
+		} else if (strncmp(argv[i], "-l", 2) == 0) {
+			setenv("LD_LIBRARY_PATH", argv[i+1], 1);
+			i++;
+		} else {
+			break;
+		}
+	}
+
+
+	// Run cmd.
+	execvp(argv[i], &argv[i]);
+}