executor: reserve fds that will belong to kcov

As now kcov instances may get set up during fuzzing, performing dup2 in
cover_open is no longer safe as it may close some important resource.
Prevent that by reserving most of fds that belong to the kcov fds range.

Unfortunately we must duplicate the code because of the way kcov
implementations are organized.

1 files changed, 8 insertions, 0 deletions

diff --git a/executor/executor_darwin.h b/executor/executor_darwin.h
index c16691663..d6efe0063 100644
--- a/executor/executor_darwin.h
+++ b/executor/executor_darwin.h
@@ -121,3 +121,11 @@ static bool use_cover_edges(uint64 pc)
 {
 	return true;
 }
+
+static void cover_reserve_fd(cover_t* cov)
+{
+	int fd = open("/dev/null", O_RDONLY);
+	if (fd < 0)
+		fail("failed to open /dev/null");
+	dup2(fd, cov->fd);
+}