began work to add privilege

1 files changed, 53 insertions, 0 deletions

diff --git a/src/svc.c b/src/svc.c
new file mode 100644
index 0000000..4342a95
--- /dev/null
+++ b/src/svc.c
@@ -0,0 +1,53 @@
+/**
+ * @file svc.c
+ * An unused handler for SVC calls
+ * TODO: use SVC calls, possibly allowing for switch to unprivileged mode?
+ *
+ * Copyright (C) 2018 Clyne Sullivan
+ *
+ * This program is free software: you can redistribute it and/or modify
+ * it under the terms of the GNU General Public License as published by
+ * the Free Software Foundation, either version 3 of the License, or
+ * (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program.  If not, see <https://www.gnu.org/licenses/>.
+ */
+
+#include <stdint.h>
+#include <gpio.h>
+#include <clock.h>
+
+extern void gpio_svc(uint32_t *);
+
+void svc_handler(uint32_t *args)
+{
+	uint32_t svc_number = ((char *)args[6])[-2];
+
+	switch (svc_number) {
+	case 1:
+		gpio_svc(args);
+		break;
+	default:
+		break;
+	}
+}
+
+void SVC_Handler(void) {
+	uint32_t *args;
+
+	asm("\
+		tst lr, #4; \
+		ite eq; \
+		mrseq %0, msp; \
+		mrsne %0, psp; \
+	" : "=r" (args));
+
+	svc_handler(args);
+}
+