From 88672784c8989279f379384ef76ac52682805eab Mon Sep 17 00:00:00 2001
From: kettenis <kettenis@openbsd.org>
Date: Wed, 17 Jan 2018 10:17:33 +0000
Subject: [PATCH] Implement support for the PSCI_VERSION call and export the
 function such that we can use it to defend against branch target injection
 attacks.

ok patrick@, visa@
---
 sys/dev/fdt/files.fdt |  4 ++--
 sys/dev/fdt/psci.c    | 26 +++++++++++++++++++++++---
 sys/dev/fdt/pscivar.h |  8 ++++++++
 3 files changed, 33 insertions(+), 5 deletions(-)
 create mode 100644 sys/dev/fdt/pscivar.h

diff --git a/sys/dev/fdt/files.fdt b/sys/dev/fdt/files.fdt
index f2aee8937b1..65286f96bd3 100644
--- a/sys/dev/fdt/files.fdt
+++ b/sys/dev/fdt/files.fdt
@@ -1,4 +1,4 @@
-#	$OpenBSD: files.fdt,v 1.36 2018/01/06 13:04:47 kettenis Exp $
+#	$OpenBSD: files.fdt,v 1.37 2018/01/17 10:17:33 kettenis Exp $
 #
 # Config file and device description for machine-independent FDT code.
 # Included by ports that need it.
@@ -69,7 +69,7 @@ file	dev/fdt/plrtc.c			plrtc
 # ARM Power State Coordination Interface
 device	psci
 attach	psci at fdt
-file	dev/fdt/psci.c			psci
+file	dev/fdt/psci.c			psci needs-flag
 
 attach	virtio at fdt with virtio_mmio
 file	dev/fdt/virtio_mmio.c		virtio_mmio
diff --git a/sys/dev/fdt/psci.c b/sys/dev/fdt/psci.c
index e5761a8aa33..69d20dddea9 100644
--- a/sys/dev/fdt/psci.c
+++ b/sys/dev/fdt/psci.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: psci.c,v 1.3 2017/12/29 14:45:15 kettenis Exp $	*/
+/*	$OpenBSD: psci.c,v 1.4 2018/01/17 10:17:33 kettenis Exp $	*/
 
 /*
  * Copyright (c) 2016 Jonathan Gray <jsg@openbsd.org>
@@ -26,10 +26,13 @@
 #include <dev/ofw/openfirm.h>
 #include <dev/ofw/fdt.h>
 
+#include <dev/fdt/pscivar.h>
+
 extern void (*cpuresetfn)(void);
 extern void (*powerdownfn)(void);
 extern int (*cpu_on_fn)(register_t, register_t);
 
+#define PSCI_VERSION	0x84000000
 #define SYSTEM_OFF	0x84000008
 #define SYSTEM_RESET	0x84000009
 #ifdef __LP64__
@@ -42,6 +45,7 @@ struct psci_softc {
 	struct device	 sc_dev;
 	register_t	 (*sc_callfn)(register_t, register_t, register_t,
 			     register_t);
+	int		 sc_psci_version; 
 	int		 sc_system_off;
 	int		 sc_system_reset;
 	int		 sc_cpu_on;
@@ -82,6 +86,7 @@ psci_attach(struct device *parent, struct device *self, void *aux)
 	struct psci_softc *sc = (struct psci_softc *)self;
 	struct fdt_attach_args *faa = aux;
 	char method[128];
+	uint32_t version;
 
 	if (OF_getprop(faa->fa_node, "method", method, sizeof(method))) {
 		if (strcmp(method, "hvc") == 0)
@@ -97,6 +102,7 @@ psci_attach(struct device *parent, struct device *self, void *aux)
 	 */
 	if (OF_is_compatible(faa->fa_node, "arm,psci-0.2") ||
 	    OF_is_compatible(faa->fa_node, "arm,psci-1.0")) {
+		sc->sc_psci_version = PSCI_VERSION;
 		sc->sc_system_off = SYSTEM_OFF;
 		sc->sc_system_reset = SYSTEM_RESET;
 		sc->sc_cpu_on = CPU_ON;
@@ -108,9 +114,11 @@ psci_attach(struct device *parent, struct device *self, void *aux)
 		sc->sc_cpu_on = OF_getpropint(faa->fa_node, "cpu_on", 0);
 	}
 
-	printf("\n");
-
 	psci_sc = sc;
+
+	version = psci_version();
+	printf(": PSCI %d.%d\n", version >> 16, version & 0xffff);
+
 	if (sc->sc_system_off != 0)
 		powerdownfn = psci_powerdown;
 	if (sc->sc_system_reset != 0)
@@ -119,6 +127,18 @@ psci_attach(struct device *parent, struct device *self, void *aux)
 		cpu_on_fn = psci_cpu_on;
 }
 
+uint32_t
+psci_version(void)
+{
+	struct psci_softc *sc = psci_sc;
+
+	if (sc && sc->sc_callfn && sc->sc_psci_version != 0)
+		return (*sc->sc_callfn)(sc->sc_psci_version, 0, 0, 0);
+
+	/* No version support; return 0.0. */
+	return 0;
+}
+
 void
 psci_reset(void)
 {
diff --git a/sys/dev/fdt/pscivar.h b/sys/dev/fdt/pscivar.h
new file mode 100644
index 00000000000..77551db3d2a
--- /dev/null
+++ b/sys/dev/fdt/pscivar.h
@@ -0,0 +1,8 @@
+/* Public Domain */
+
+#ifndef _SYS_DEV_FDT_PSCIVAR_H_
+#define _SYS_DEV_FDT_PSCIVAR_H_
+
+uint32_t psci_version(void);
+
+#endif /* _SYS_DEV_FDT_PSCIVAR_H_ */
-- 
2.20.1