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Subject[RFC PATCH v2 6/6] crypto: ccp - provide in-kernel API to submit TEE commands
Date
Extend the functionality of AMD Secure Processor (SP) driver by
providing an in-kernel API to submit commands to TEE ring buffer for
processing by Trusted OS running on AMD Secure Processor.

Following TEE commands are supported by Trusted OS:

* TEE_CMD_ID_LOAD_TA : Load Trusted Application (TA) binary into
TEE environment
* TEE_CMD_ID_UNLOAD_TA : Unload TA binary from TEE environment
* TEE_CMD_ID_OPEN_SESSION : Open session with loaded TA
* TEE_CMD_ID_CLOSE_SESSION : Close session with loaded TA
* TEE_CMD_ID_INVOKE_CMD : Invoke a command with loaded TA
* TEE_CMD_ID_MAP_SHARED_MEM : Map shared memory
* TEE_CMD_ID_UNMAP_SHARED_MEM : Unmap shared memory

Linux AMD-TEE driver will use this API to submit command buffers
for processing in Trusted Execution Environment. The AMD-TEE driver
shall be introduced in a separate patch.

Cc: Jens Wiklander <jens.wiklander@linaro.org>
Cc: Tom Lendacky <thomas.lendacky@amd.com>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Co-developed-by: Devaraj Rangasamy <Devaraj.Rangasamy@amd.com>
Signed-off-by: Devaraj Rangasamy <Devaraj.Rangasamy@amd.com>
Signed-off-by: Rijo Thomas <Rijo-john.Thomas@amd.com>
---
drivers/crypto/ccp/tee-dev.c | 126 +++++++++++++++++++++++++++++++++++++++++++
drivers/crypto/ccp/tee-dev.h | 1 +
include/linux/psp-tee.h | 73 +++++++++++++++++++++++++
3 files changed, 200 insertions(+)
create mode 100644 include/linux/psp-tee.h

diff --git a/drivers/crypto/ccp/tee-dev.c b/drivers/crypto/ccp/tee-dev.c
index ccbc2ce..555c8a7 100644
--- a/drivers/crypto/ccp/tee-dev.c
+++ b/drivers/crypto/ccp/tee-dev.c
@@ -14,6 +14,7 @@
#include <linux/slab.h>
#include <linux/gfp.h>
#include <linux/psp-sev.h>
+#include <linux/psp-tee.h>

#include "psp-dev.h"
#include "tee-dev.h"
@@ -38,6 +39,7 @@ static int tee_alloc_ring(struct psp_tee_device *tee, int ring_size)
rb_mgr->ring_start = start_addr;
rb_mgr->ring_size = ring_size;
rb_mgr->ring_pa = __psp_pa(start_addr);
+ mutex_init(&rb_mgr->mutex);

return 0;
}
@@ -55,6 +57,7 @@ static void tee_free_ring(struct psp_tee_device *tee)
rb_mgr->ring_start = NULL;
rb_mgr->ring_size = 0;
rb_mgr->ring_pa = 0;
+ mutex_destroy(&rb_mgr->mutex);
}

static int tee_wait_cmd_poll(struct psp_tee_device *tee, unsigned int timeout,
@@ -236,3 +239,126 @@ void tee_dev_destroy(struct psp_device *psp)

tee_destroy_ring(tee);
}
+
+static int tee_submit_cmd(struct psp_tee_device *tee, enum tee_cmd_id cmd_id,
+ void *buf, size_t len, struct tee_ring_cmd **resp)
+{
+ struct tee_ring_cmd *cmd;
+ u32 rptr, wptr;
+ int nloop = 1000, ret = 0;
+
+ *resp = NULL;
+
+ mutex_lock(&tee->rb_mgr.mutex);
+
+ wptr = tee->rb_mgr.wptr;
+
+ /* Check if ring buffer is full */
+ do {
+ rptr = ioread32(tee->io_regs + tee->vdata->ring_rptr_reg);
+
+ if (!(wptr + sizeof(struct tee_ring_cmd) == rptr))
+ break;
+
+ dev_info(tee->dev, "tee: ring buffer full. rptr = %u wptr = %u\n",
+ rptr, wptr);
+
+ /* Wait if ring buffer is full */
+ mutex_unlock(&tee->rb_mgr.mutex);
+ schedule_timeout_interruptible(msecs_to_jiffies(10));
+ mutex_lock(&tee->rb_mgr.mutex);
+
+ } while (--nloop);
+
+ if (!nloop && (wptr + sizeof(struct tee_ring_cmd) == rptr)) {
+ dev_err(tee->dev, "tee: ring buffer full. rptr = %u wptr = %u\n",
+ rptr, wptr);
+ ret = -EBUSY;
+ goto unlock;
+ }
+
+ /* Pointer to empty data entry in ring buffer */
+ cmd = (struct tee_ring_cmd *)(tee->rb_mgr.ring_start + wptr);
+
+ /* Write command data into ring buffer */
+ cmd->cmd_id = cmd_id;
+ cmd->cmd_state = TEE_CMD_STATE_INIT;
+ memset(&cmd->buf[0], 0, sizeof(cmd->buf));
+ memcpy(&cmd->buf[0], buf, len);
+
+ /* Update local copy of write pointer */
+ tee->rb_mgr.wptr += sizeof(struct tee_ring_cmd);
+ if (tee->rb_mgr.wptr >= tee->rb_mgr.ring_size)
+ tee->rb_mgr.wptr = 0;
+
+ /* Trigger interrupt to Trusted OS */
+ iowrite32(tee->rb_mgr.wptr, tee->io_regs + tee->vdata->ring_wptr_reg);
+
+ /* The response is provided by Trusted OS in same
+ * location as submitted data entry within ring buffer.
+ */
+ *resp = cmd;
+
+unlock:
+ mutex_unlock(&tee->rb_mgr.mutex);
+
+ return ret;
+}
+
+static int tee_wait_cmd_completion(struct psp_tee_device *tee,
+ struct tee_ring_cmd *resp,
+ unsigned int timeout)
+{
+ /* ~5ms sleep per loop => nloop = timeout * 200 */
+ int nloop = timeout * 200;
+
+ while (--nloop) {
+ if (resp->cmd_state == TEE_CMD_STATE_COMPLETED)
+ return 0;
+
+ usleep_range(5000, 5100);
+ }
+
+ dev_err(tee->dev, "tee: command 0x%x timed out, disabling PSP\n",
+ resp->cmd_id);
+
+ psp_dead = true;
+
+ return -ETIMEDOUT;
+}
+
+int psp_tee_process_cmd(enum tee_cmd_id cmd_id, void *buf, size_t len,
+ u32 *status)
+{
+ struct psp_device *psp = psp_get_master_device();
+ struct psp_tee_device *tee;
+ struct tee_ring_cmd *resp;
+ int ret;
+
+ if (!buf || !status || !len || len > sizeof(resp->buf))
+ return -EINVAL;
+
+ *status = 0;
+
+ if (!psp || !psp->tee_data)
+ return -ENODEV;
+
+ if (psp_dead)
+ return -EBUSY;
+
+ tee = psp->tee_data;
+
+ ret = tee_submit_cmd(tee, cmd_id, buf, len, &resp);
+ if (ret)
+ return ret;
+
+ ret = tee_wait_cmd_completion(tee, resp, TEE_DEFAULT_TIMEOUT);
+ if (ret)
+ return ret;
+
+ memcpy(buf, &resp->buf[0], len);
+ *status = resp->status;
+
+ return 0;
+}
+EXPORT_SYMBOL(psp_tee_process_cmd);
diff --git a/drivers/crypto/ccp/tee-dev.h b/drivers/crypto/ccp/tee-dev.h
index b3db0fc..f099601 100644
--- a/drivers/crypto/ccp/tee-dev.h
+++ b/drivers/crypto/ccp/tee-dev.h
@@ -54,6 +54,7 @@ struct tee_init_ring_cmd {
* @wptr: index to the last written entry in ring buffer
*/
struct ring_buf_manager {
+ struct mutex mutex; /* synchronizes access to ring buffer */
void *ring_start;
u32 ring_size;
phys_addr_t ring_pa;
diff --git a/include/linux/psp-tee.h b/include/linux/psp-tee.h
new file mode 100644
index 0000000..63bb221
--- /dev/null
+++ b/include/linux/psp-tee.h
@@ -0,0 +1,73 @@
+/* SPDX-License-Identifier: MIT */
+/*
+ * AMD Trusted Execution Environment (TEE) interface
+ *
+ * Author: Rijo Thomas <Rijo-john.Thomas@amd.com>
+ *
+ * Copyright 2019 Advanced Micro Devices, Inc.
+ *
+ */
+
+#ifndef __PSP_TEE_H_
+#define __PSP_TEE_H_
+
+#include <linux/types.h>
+#include <linux/errno.h>
+
+/* This file defines the Trusted Execution Environment (TEE) interface commands
+ * and the API exported by AMD Secure Processor driver to communicate with
+ * AMD-TEE Trusted OS.
+ */
+
+/**
+ * enum tee_cmd_id - TEE Interface Command IDs
+ * @TEE_CMD_ID_LOAD_TA: Load Trusted Application (TA) binary into
+ * TEE environment
+ * @TEE_CMD_ID_UNLOAD_TA: Unload TA binary from TEE environment
+ * @TEE_CMD_ID_OPEN_SESSION: Open session with loaded TA
+ * @TEE_CMD_ID_CLOSE_SESSION: Close session with loaded TA
+ * @TEE_CMD_ID_INVOKE_CMD: Invoke a command with loaded TA
+ * @TEE_CMD_ID_MAP_SHARED_MEM: Map shared memory
+ * @TEE_CMD_ID_UNMAP_SHARED_MEM: Unmap shared memory
+ */
+enum tee_cmd_id {
+ TEE_CMD_ID_LOAD_TA = 1,
+ TEE_CMD_ID_UNLOAD_TA,
+ TEE_CMD_ID_OPEN_SESSION,
+ TEE_CMD_ID_CLOSE_SESSION,
+ TEE_CMD_ID_INVOKE_CMD,
+ TEE_CMD_ID_MAP_SHARED_MEM,
+ TEE_CMD_ID_UNMAP_SHARED_MEM,
+};
+
+#ifdef CONFIG_CRYPTO_DEV_SP_PSP
+/**
+ * psp_tee_process_cmd() - Process command in Trusted Execution Environment
+ * @cmd_id: TEE command ID (&enum tee_cmd_id)
+ * @buf: Command buffer for TEE processing. On success, is updated
+ * with the response
+ * @len: Length of command buffer in bytes
+ * @status: On success, holds the TEE command execution status
+ *
+ * This function submits a command to the Trusted OS for processing in the
+ * TEE environment and waits for a response or until the command times out.
+ *
+ * Returns:
+ * 0 if TEE successfully processed the command
+ * -%ENODEV if PSP device not available
+ * -%EINVAL if invalid input
+ * -%ETIMEDOUT if TEE command timed out
+ * -%EBUSY if PSP device is not responsive
+ */
+int psp_tee_process_cmd(enum tee_cmd_id cmd_id, void *buf, size_t len,
+ u32 *status);
+
+#else /* !CONFIG_CRYPTO_DEV_SP_PSP */
+
+static inline int psp_tee_process_cmd(enum tee_cmd_id cmd_id, void *buf,
+ size_t len, u32 *status)
+{
+ return -ENODEV;
+}
+#endif /* CONFIG_CRYPTO_DEV_SP_PSP */
+#endif /* __PSP_TEE_H_ */
--
1.9.1
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