1 files changed, 69 insertions, 0 deletions
diff --git a/arch/um/kernel/skas/stub.c b/arch/um/kernel/skas/stub.c
new file mode 100644
index 000000000000..5d52ffa682dc
--- /dev/null
+++ b/arch/um/kernel/skas/stub.c
@@ -0,0 +1,69 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright (C) 2021 Benjamin Berg <benjamin@sipsolutions.net>
+ */
+
+#include <sysdep/stub.h>
+
+static __always_inline int syscall_handler(struct stub_data *d)
+{
+	int i;
+	unsigned long res;
+
+	for (i = 0; i < d->syscall_data_len; i++) {
+		struct stub_syscall *sc = &d->syscall_data[i];
+
+		switch (sc->syscall) {
+		case STUB_SYSCALL_MMAP:
+			res = stub_syscall6(STUB_MMAP_NR,
+					    sc->mem.addr, sc->mem.length,
+					    sc->mem.prot,
+					    MAP_SHARED | MAP_FIXED,
+					    sc->mem.fd, sc->mem.offset);
+			if (res != sc->mem.addr) {
+				d->err = res;
+				d->syscall_data_len = i;
+				return -1;
+			}
+			break;
+		case STUB_SYSCALL_MUNMAP:
+			res = stub_syscall2(__NR_munmap,
+					    sc->mem.addr, sc->mem.length);
+			if (res) {
+				d->err = res;
+				d->syscall_data_len = i;
+				return -1;
+			}
+			break;
+		case STUB_SYSCALL_MPROTECT:
+			res = stub_syscall3(__NR_mprotect,
+					    sc->mem.addr, sc->mem.length,
+					    sc->mem.prot);
+			if (res) {
+				d->err = res;
+				d->syscall_data_len = i;
+				return -1;
+			}
+			break;
+		default:
+			d->err = -95; /* EOPNOTSUPP */
+			d->syscall_data_len = i;
+			return -1;
+		}
+	}
+
+	d->err = 0;
+	d->syscall_data_len = 0;
+
+	return 0;
+}
+
+void __section(".__syscall_stub")
+stub_syscall_handler(void)
+{
+	struct stub_data *d = get_stub_data();
+
+	syscall_handler(d);
+
+	trap_myself();
+}