executor: ignore prctl in fallback coverage

Some prctl commands don't respect the normal convention for return values
(e.g. PR_GET_TIMERSLACK, but there are more) and may produce all possible
errno values. This conflicts with fallback coverage.

1 files changed, 7 insertions, 1 deletions

diff --git a/executor/executor_linux.h b/executor/executor_linux.h
index 73005877d..63c900c5a 100644
--- a/executor/executor_linux.h
+++ b/executor/executor_linux.h
@@ -73,7 +73,13 @@ static intptr_t execute_syscall(const call_t* c, intptr_t a[kMaxArgs])
 {
 	if (c->call)
 		return c->call(a[0], a[1], a[2], a[3], a[4], a[5], a[6], a[7], a[8]);
-	return syscall(c->sys_nr, a[0], a[1], a[2], a[3], a[4], a[5]);
+	intptr_t res = syscall(c->sys_nr, a[0], a[1], a[2], a[3], a[4], a[5]);
+	// Some prctl commands don't respect the normal convention for return values
+	// (e.g. PR_GET_TIMERSLACK, but there are more) and may produce all possible
+	// errno values. This conflicts with fallback coverage.
+	if (!flag_coverage && res == -1 && !strcmp(c->name, "prctl"))
+		errno = EINVAL;
+	return res;
 }
 
 static void cover_open(cover_t* cov, bool extra)