initial signal implementation

kernel-src/sys/syscalls/sigaltstack.c

@@ -0,0 +1,21 @@
+#include <kernel/syscalls.h>
+#include <arch/cpu.h>
+
+syscallret_t syscall_sigaltstack(context_t *, stack_t *new, stack_t *old) {
+	syscallret_t ret = {
+		.ret = -1
+	};
+
+	stack_t newtmp, oldtmp;
+	if (new)
+		newtmp = *new;
+
+	signal_altstack(_cpu()->thread, new ? &newtmp : NULL, old ? &oldtmp : NULL);
+
+	if (old)
+		*old = oldtmp;
+
+	ret.errno = 0;
+	ret.ret = 0;
+	return ret;
+}