[PATCH v4 3/4] tpm/tpm_ftpm_tee: support TPM_CHIP_FLAG_SYNC

[Stefano Garzarella]

From: Stefano Garzarella <sgarzare at redhat.com>

This driver does not support interrupts, and receiving the response is
synchronous with sending the command.

Enable synchronous send() with TPM_CHIP_FLAG_SYNC, which implies that
->send() already fills the provided buffer with a response, and ->recv()
is not implemented.

Reviewed-by: Sumit Garg <sumit.garg at oss.qualcomm.com>
Signed-off-by: Stefano Garzarella <sgarzare at redhat.com>
---
v4:
- added Sumit's R-b
- reworked commit description [Jarkko]
v2:
- set TPM_CHIP_FLAG_SYNC and support it in the new send()
- removed Jens' T-b
v1:
- added Jens' T-b
---
 drivers/char/tpm/tpm_ftpm_tee.h |  4 ---
 drivers/char/tpm/tpm_ftpm_tee.c | 64 ++++++++++-----------------------
 2 files changed, 19 insertions(+), 49 deletions(-)

diff --git a/drivers/char/tpm/tpm_ftpm_tee.h b/drivers/char/tpm/tpm_ftpm_tee.h
index e39903b7ea07..8d5c3f0d2879 100644
--- a/drivers/char/tpm/tpm_ftpm_tee.h
+++ b/drivers/char/tpm/tpm_ftpm_tee.h
@@ -22,16 +22,12 @@
  * struct ftpm_tee_private - fTPM's private data
  * @chip:     struct tpm_chip instance registered with tpm framework.
  * @session:  fTPM TA session identifier.
- * @resp_len: cached response buffer length.
- * @resp_buf: cached response buffer.
  * @ctx:      TEE context handler.
  * @shm:      Memory pool shared with fTPM TA in TEE.
  */
 struct ftpm_tee_private {
 	struct tpm_chip *chip;
 	u32 session;
-	size_t resp_len;
-	u8 resp_buf[MAX_RESPONSE_SIZE];
 	struct tee_context *ctx;
 	struct tee_shm *shm;
 };
diff --git a/drivers/char/tpm/tpm_ftpm_tee.c b/drivers/char/tpm/tpm_ftpm_tee.c
index 637cc8b6599e..b9adc040ca6d 100644
--- a/drivers/char/tpm/tpm_ftpm_tee.c
+++ b/drivers/char/tpm/tpm_ftpm_tee.c
@@ -31,46 +31,18 @@ static const uuid_t ftpm_ta_uuid =
 		  0x82, 0xCB, 0x34, 0x3F, 0xB7, 0xF3, 0x78, 0x96);
 
 /**
- * ftpm_tee_tpm_op_recv() - retrieve fTPM response.
- * @chip:	the tpm_chip description as specified in driver/char/tpm/tpm.h.
- * @buf:	the buffer to store data.
- * @count:	the number of bytes to read.
- *
- * Return:
- *	In case of success the number of bytes received.
- *	On failure, -errno.
- */
-static int ftpm_tee_tpm_op_recv(struct tpm_chip *chip, u8 *buf, size_t count)
-{
-	struct ftpm_tee_private *pvt_data = dev_get_drvdata(chip->dev.parent);
-	size_t len;
-
-	len = pvt_data->resp_len;
-	if (count < len) {
-		dev_err(&chip->dev,
-			"%s: Invalid size in recv: count=%zd, resp_len=%zd\n",
-			__func__, count, len);
-		return -EIO;
-	}
-
-	memcpy(buf, pvt_data->resp_buf, len);
-	pvt_data->resp_len = 0;
-
-	return len;
-}
-
-/**
- * ftpm_tee_tpm_op_send() - send TPM commands through the TEE shared memory.
+ * ftpm_tee_tpm_op_send() - send TPM commands through the TEE shared memory
+ * and retrieve the response.
  * @chip:	the tpm_chip description as specified in driver/char/tpm/tpm.h
- * @buf:	the buffer to send.
- * @len:	the number of bytes to send.
+ * @buf:	the buffer to send and to store the response.
+ * @cmd_len:	the number of bytes to send.
  * @buf_size:	the size of the buffer.
  *
  * Return:
- *	In case of success, returns 0.
+ *	In case of success, returns the number of bytes received.
  *	On failure, -errno
  */
-static int ftpm_tee_tpm_op_send(struct tpm_chip *chip, u8 *buf, size_t len,
+static int ftpm_tee_tpm_op_send(struct tpm_chip *chip, u8 *buf, size_t cmd_len,
 				size_t buf_size)
 {
 	struct ftpm_tee_private *pvt_data = dev_get_drvdata(chip->dev.parent);
@@ -82,16 +54,15 @@ static int ftpm_tee_tpm_op_send(struct tpm_chip *chip, u8 *buf, size_t len,
 	struct tee_param command_params[4];
 	struct tee_shm *shm = pvt_data->shm;
 
-	if (len > MAX_COMMAND_SIZE) {
+	if (cmd_len > MAX_COMMAND_SIZE) {
 		dev_err(&chip->dev,
 			"%s: len=%zd exceeds MAX_COMMAND_SIZE supported by fTPM TA\n",
-			__func__, len);
+			__func__, cmd_len);
 		return -EIO;
 	}
 
 	memset(&transceive_args, 0, sizeof(transceive_args));
 	memset(command_params, 0, sizeof(command_params));
-	pvt_data->resp_len = 0;
 
 	/* Invoke FTPM_OPTEE_TA_SUBMIT_COMMAND function of fTPM TA */
 	transceive_args = (struct tee_ioctl_invoke_arg) {
@@ -105,7 +76,7 @@ static int ftpm_tee_tpm_op_send(struct tpm_chip *chip, u8 *buf, size_t len,
 		.attr = TEE_IOCTL_PARAM_ATTR_TYPE_MEMREF_INPUT,
 		.u.memref = {
 			.shm = shm,
-			.size = len,
+			.size = cmd_len,
 			.shm_offs = 0,
 		},
 	};
@@ -117,7 +88,7 @@ static int ftpm_tee_tpm_op_send(struct tpm_chip *chip, u8 *buf, size_t len,
 		return PTR_ERR(temp_buf);
 	}
 	memset(temp_buf, 0, (MAX_COMMAND_SIZE + MAX_RESPONSE_SIZE));
-	memcpy(temp_buf, buf, len);
+	memcpy(temp_buf, buf, cmd_len);
 
 	command_params[1] = (struct tee_param) {
 		.attr = TEE_IOCTL_PARAM_ATTR_TYPE_MEMREF_INOUT,
@@ -158,17 +129,20 @@ static int ftpm_tee_tpm_op_send(struct tpm_chip *chip, u8 *buf, size_t len,
 			__func__, resp_len);
 		return -EIO;
 	}
+	if (resp_len > buf_size) {
+		dev_err(&chip->dev,
+			"%s: resp_len=%zd exceeds buf_size=%zd\n",
+			__func__, resp_len, buf_size);
+		return -EIO;
+	}
 
-	/* sanity checks look good, cache the response */
-	memcpy(pvt_data->resp_buf, temp_buf, resp_len);
-	pvt_data->resp_len = resp_len;
+	memcpy(buf, temp_buf, resp_len);
 
-	return 0;
+	return resp_len;
 }
 
 static const struct tpm_class_ops ftpm_tee_tpm_ops = {
 	.flags = TPM_OPS_AUTO_STARTUP,
-	.recv = ftpm_tee_tpm_op_recv,
 	.send = ftpm_tee_tpm_op_send,
 };
 
@@ -253,7 +227,7 @@ static int ftpm_tee_probe(struct device *dev)
 	}
 
 	pvt_data->chip = chip;
-	pvt_data->chip->flags |= TPM_CHIP_FLAG_TPM2;
+	pvt_data->chip->flags |= TPM_CHIP_FLAG_TPM2 | TPM_CHIP_FLAG_SYNC;
 
 	/* Create a character device for the fTPM */
 	rc = tpm_chip_register(pvt_data->chip);
-- 
2.49.0