From b935b0202ffeafcf775be96c95c8a67b62241a12 Mon Sep 17 00:00:00 2001
From: dzwdz
Date: Wed, 6 Jul 2022 19:52:34 +0200
Subject: kernel: don't panic on nonexistent syscalls

---
 src/init/tests/main.c | 5 +++++
 src/kernel/syscalls.c | 4 ++--
 2 files changed, 7 insertions(+), 2 deletions(-)

diff --git a/src/init/tests/main.c b/src/init/tests/main.c
index c59b390..0ac399b 100644
--- a/src/init/tests/main.c
+++ b/src/init/tests/main.c
@@ -133,6 +133,10 @@ static void test_malloc(void) {
 	free(p1);
 }
 
+static void test_misc(void) {
+	assert(_syscall(~0, 0, 0, 0, 0) < 0); /* try making an invalid syscall */
+}
+
 static void stress_fork(void) {
 	/* run a lot of processes */
 	for (size_t i = 0; i < 2048; i++) {
@@ -150,5 +154,6 @@ void test_all(void) {
 	run_forked(test_memflag);
 	run_forked(test_malloc);
 	run_forked(test_pipe);
+	run_forked(test_misc);
 	run_forked(stress_fork);
 }
diff --git a/src/kernel/syscalls.c b/src/kernel/syscalls.c
index 05616a3..ae8b0e5 100644
--- a/src/kernel/syscalls.c
+++ b/src/kernel/syscalls.c
@@ -365,8 +365,8 @@ int _syscall(int num, int a, int b, int c, int d) {
 			_syscall_debug_klog((userptr_t)a, b);
 			break;
 		default:
-			kprintf("unknown syscall ");
-			panic_unimplemented(); // TODO fail gracefully
+			regs_savereturn(&process_current->regs, -1);
+			break;
 	}
 
 	/* return value is unused. execution continues in sysenter_stage2 */
-- 
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