feat(drivers/arm/rss): add RSS communication driver
This commit adds a driver to conduct the AP's communication
with the Runtime Security Subsystem (RSS).
RSS is Arm's reference implementation for the CCA HES [1].
It can be considered as a secure enclave to which, for example,
certain services can be offloaded such as initial attestation.
RSS comms driver:
- Relies on MHU v2.x communication IP, using a generic MHU API,
- Exposes the psa_call(..) API to the upper layers.
[1] https://developer.arm.com/documentation/DEN0096/latest
Signed-off-by: Tamas Ban <tamas.ban@arm.com>
Signed-off-by: David Vincze <david.vincze@arm.com>
Change-Id: Ib174ac7d1858834006bbaf8aad0eb31e3a3ad107
diff --git a/drivers/arm/rss/rss_comms.c b/drivers/arm/rss/rss_comms.c
new file mode 100644
index 0000000..28a4925
--- /dev/null
+++ b/drivers/arm/rss/rss_comms.c
@@ -0,0 +1,225 @@
+/*
+ * Copyright (c) 2022, Arm Limited. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ */
+
+#include <stdint.h>
+#include <string.h>
+
+#include <common/debug.h>
+#include <drivers/arm/mhu.h>
+#include <drivers/arm/rss_comms.h>
+#include <initial_attestation.h>
+#include <psa/client.h>
+
+#include <platform_def.h>
+
+#define TYPE_OFFSET U(16)
+#define TYPE_MASK (0xFFFFUL << TYPE_OFFSET)
+#define IN_LEN_OFFSET U(8)
+#define IN_LEN_MASK (0xFFUL << IN_LEN_OFFSET)
+#define OUT_LEN_OFFSET U(0)
+#define OUT_LEN_MASK (0xFFUL << OUT_LEN_OFFSET)
+
+#define PARAM_PACK(type, in_len, out_len) \
+ (((((uint32_t)type) << TYPE_OFFSET) & TYPE_MASK) | \
+ ((((uint32_t)in_len) << IN_LEN_OFFSET) & IN_LEN_MASK) | \
+ ((((uint32_t)out_len) << OUT_LEN_OFFSET) & OUT_LEN_MASK))
+
+#define PARAM_UNPACK_IN_LEN(ctrl_param) \
+ ((size_t)(((ctrl_param) & IN_LEN_MASK) >> IN_LEN_OFFSET))
+
+/* Message types */
+struct __packed packed_psa_call_t {
+ uint8_t protocol_ver;
+ uint8_t seq_num;
+ uint16_t client_id;
+ psa_handle_t handle;
+ uint32_t ctrl_param; /* type, in_len, out_len */
+ uint16_t io_size[4];
+};
+
+struct __packed packed_psa_reply_t {
+ uint8_t protocol_ver;
+ uint8_t seq_num;
+ uint16_t client_id;
+ int32_t return_val;
+ uint16_t out_size[4];
+};
+
+/*
+ * In the current implementation the RoT Service request that requires the
+ * biggest message buffer is the RSS_ATTEST_GET_TOKEN. The maximum required
+ * buffer size is calculated based on the platform-specific needs of
+ * this request.
+ */
+#define MAX_REQUEST_PAYLOAD_SIZE (PSA_INITIAL_ATTEST_CHALLENGE_SIZE_64 \
+ + PLAT_ATTEST_TOKEN_MAX_SIZE)
+
+/* Buffer to store the messages to be sent/received. */
+static uint8_t message_buf[MAX_REQUEST_PAYLOAD_SIZE] __aligned(4);
+
+static int32_t pack_params(const psa_invec *invecs,
+ size_t in_len,
+ uint8_t *buf,
+ size_t *buf_len)
+{
+ uint32_t i;
+ size_t payload_size = 0U;
+
+ for (i = 0U; i < in_len; ++i) {
+ if (invecs[i].len > *buf_len - payload_size) {
+ return -1;
+ }
+ memcpy(buf + payload_size, invecs[i].base, invecs[i].len);
+ payload_size += invecs[i].len;
+ }
+
+ *buf_len = payload_size;
+ return 0;
+}
+
+static int serialise_message(const struct packed_psa_call_t *msg,
+ const psa_invec *invecs,
+ uint8_t *payload_buf,
+ size_t *payload_len)
+{
+ size_t message_len = 0U;
+ size_t len;
+
+ /* Copy the message header into the payload buffer. */
+ len = sizeof(*msg);
+ if (len > *payload_len) {
+ ERROR("[RSS-COMMS] Message buffer too small.\n");
+ return -1;
+ }
+ memcpy(payload_buf, (const void *)msg, len);
+ message_len += len;
+
+ /* The input data will follow the message header in the payload buffer. */
+ len = *payload_len - message_len;
+ if (pack_params(invecs, PARAM_UNPACK_IN_LEN(msg->ctrl_param),
+ payload_buf + message_len, &len) != 0) {
+ ERROR("[RSS-COMMS] Message buffer too small.\n");
+ return -1;
+ }
+ message_len += len;
+
+ *payload_len = message_len;
+ return 0;
+}
+
+static void unpack_params(const uint8_t *buf,
+ psa_outvec *outvecs,
+ size_t out_len)
+{
+ size_t i;
+
+ for (i = 0U; i < out_len; ++i) {
+ memcpy(outvecs[i].base, buf, outvecs[i].len);
+ buf += outvecs[i].len;
+ }
+}
+
+static void deserialise_reply(struct packed_psa_reply_t *reply,
+ psa_outvec *outvecs,
+ size_t outlen,
+ const uint8_t *message,
+ size_t message_len)
+{
+ uint32_t i;
+
+ memcpy(reply, message, sizeof(*reply));
+
+ /* Outvecs */
+ for (i = 0U; i < outlen; ++i) {
+ outvecs[i].len = reply->out_size[i];
+ }
+
+ unpack_params(message + sizeof(*reply), outvecs, outlen);
+}
+
+psa_status_t psa_call(psa_handle_t handle, int32_t type,
+ const psa_invec *in_vec, size_t in_len,
+ psa_outvec *out_vec, size_t out_len)
+{
+ enum mhu_error_t err;
+ static uint32_t seq_num = 1U;
+ struct packed_psa_call_t msg = {
+ .protocol_ver = 0U,
+ .seq_num = seq_num,
+ /* No need to distinguish callers (currently concurrent calls are not supported). */
+ .client_id = 1U,
+ .handle = handle,
+ .ctrl_param = PARAM_PACK(type, in_len, out_len),
+ };
+
+ struct packed_psa_reply_t reply = {0};
+ size_t message_size;
+ uint32_t i;
+
+ /* Fill msg iovec lengths */
+ for (i = 0U; i < in_len; ++i) {
+ msg.io_size[i] = in_vec[i].len;
+ }
+ for (i = 0U; i < out_len; ++i) {
+ msg.io_size[in_len + i] = out_vec[i].len;
+ }
+
+ message_size = sizeof(message_buf);
+ if (serialise_message(&msg, in_vec, message_buf, &message_size)) {
+ /* Local buffer is probably too small. */
+ return PSA_ERROR_INSUFFICIENT_MEMORY;
+ }
+
+ err = mhu_send_data(message_buf, message_size);
+ if (err != MHU_ERR_NONE) {
+ return PSA_ERROR_COMMUNICATION_FAILURE;
+ }
+
+ message_size = sizeof(message_buf);
+#if DEBUG
+ /*
+ * Poisoning the message buffer (with a known pattern).
+ * Helps in detecting hypothetical RSS communication bugs.
+ */
+ memset(message_buf, 0xA5, message_size);
+#endif
+ err = mhu_receive_data(message_buf, &message_size);
+ if (err != MHU_ERR_NONE) {
+ return PSA_ERROR_COMMUNICATION_FAILURE;
+ }
+
+ deserialise_reply(&reply, out_vec, out_len, message_buf, message_size);
+
+ seq_num++;
+
+ VERBOSE("[RSS-COMMS] Received reply\n");
+ VERBOSE("protocol_ver=%d\n", reply.protocol_ver);
+ VERBOSE("seq_num=%d\n", reply.seq_num);
+ VERBOSE("client_id=%d\n", reply.client_id);
+ VERBOSE("return_val=%d\n", reply.return_val);
+ VERBOSE("out_size[0]=%d\n", reply.out_size[0]);
+
+ return reply.return_val;
+}
+
+int rss_comms_init(uintptr_t mhu_sender_base, uintptr_t mhu_receiver_base)
+{
+ enum mhu_error_t err;
+
+ err = mhu_init_sender(mhu_sender_base);
+ if (err != MHU_ERR_NONE) {
+ ERROR("[RSS-COMMS] Host to RSS MHU driver initialization failed: %d\n", err);
+ return -1;
+ }
+
+ err = mhu_init_receiver(mhu_receiver_base);
+ if (err != MHU_ERR_NONE) {
+ ERROR("[RSS-COMMS] RSS to Host MHU driver initialization failed: %d\n", err);
+ return -1;
+ }
+
+ return 0;
+}