Fix runc-dmz error printing

libcontainer/dmz/_dmz.c

@@ -1,4 +1,7 @@
 #ifdef RUNC_USE_STDLIB
+#  include <linux/limits.h>
+#  include <stdio.h>
+#  include <string.h>
 #  include <unistd.h>
 #else
 #  include "xstat.h"
@@ -11,5 +14,14 @@ int main(int argc, char **argv)
 {
 	if (argc < 1)
 		return 127;
-	return execve(argv[0], argv, environ);
+	int ret = execve(argv[0], argv, environ);
+	if (ret) {
+		/* NOTE: This error message format MUST match Go's format. */
+		char err_msg[5 + PATH_MAX + 1] = "exec ";	// "exec " + argv[0] + '\0'
+		strncat(err_msg, argv[0], PATH_MAX);
+		err_msg[sizeof(err_msg) - 1] = '\0';
+
+		perror(err_msg);
+	}
+	return ret;
 }

tests/integration/run.bats

@@ -230,3 +230,20 @@ function teardown() {
 	grep -E '^monotonic\s+7881\s+2718281$' <<<"$output"
 	grep -E '^boottime\s+1337\s+3141519$' <<<"$output"
 }
+
+@test "runc run [exec error]" {
+	cat <<EOF >rootfs/run.sh
+#!/mmnnttbb foo bar
+sh
+EOF
+	chmod +x rootfs/run.sh
+	update_config '.process.args = [ "/run.sh" ]'
+	runc run test_hello
+
+	# Ensure that the output contains the right error message. For runc-dmz, both
+	# nolibc and libc have the same formatting string (but libc will print the
+	# errno description rather than just the number), and for runc_nodmz the error
+	# message from Go starts with the same string.
+	[ "$status" -ne 0 ]
+	[[ "$output" = *"exec /run.sh: "* ]]
+}