[PATCH] hw/arm/virt: Add DT property /secure-chosen/kaslr-seed

[Jerome Forissier <jerome@forissier.org>]

This commit generates a random seed to be used by the secure OS for
ASLR when the machine is secure. The seed is a 64-bit random value
exported via the DT in /secure-chosen/kaslr-seed. This interface is
used by OP-TEE [1].

[1] https://github.com/OP-TEE/optee_os/commit/ef262691fe0e

Signed-off-by: Jerome Forissier <jerome@forissier.org>
---
 hw/arm/virt.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/hw/arm/virt.c b/hw/arm/virt.c
index 7dc96abf72c..42a6f84086f 100644
--- a/hw/arm/virt.c
+++ b/hw/arm/virt.c
@@ -77,6 +77,7 @@
 #include "hw/acpi/generic_event_device.h"
 #include "hw/virtio/virtio-iommu.h"
 #include "hw/char/pl011.h"
+#include "crypto/random.h"
 
 #define DEFINE_VIRT_MACHINE_LATEST(major, minor, latest) \
     static void virt_##major##_##minor##_class_init(ObjectClass *oc, \
@@ -1635,6 +1636,18 @@ static void finalize_gic_version(VirtMachineState *vms)
     }
 }
 
+static void create_secure_kaslr_seed(VirtMachineState *vms)
+{
+    Error *err = NULL;
+    uint64_t seed;
+
+    if (qcrypto_random_bytes(&seed, sizeof(seed), &err)) {
+        error_free(err);
+        return;
+    }
+    qemu_fdt_setprop_u64(vms->fdt, "/secure-chosen", "kaslr-seed", seed);
+}
+
 static void machvirt_init(MachineState *machine)
 {
     VirtMachineState *vms = VIRT_MACHINE(machine);
@@ -1837,6 +1850,7 @@ static void machvirt_init(MachineState *machine)
     if (vms->secure) {
         create_secure_ram(vms, secure_sysmem);
         create_uart(vms, VIRT_SECURE_UART, secure_sysmem, serial_hd(1));
+        create_secure_kaslr_seed(vms);
     }
 
     vms->highmem_ecam &= vms->highmem && (!firmware_loaded || aarch64);
-- 
2.20.1