Re: [RFC PATCH 2/3] tpm/tpm_ftpm_tee: use send_recv() op
From: Sumit Garg
Date: Thu Mar 13 2025 - 05:13:07 EST
+ Jens
Hi Stefano,
On Tue, Mar 11, 2025 at 11:01:29AM +0100, Stefano Garzarella wrote:
> This driver does not support interrupts, and receiving the response is
> synchronous with sending the command.
>
> It used an internal buffer to cache the response when .send() is called,
> and then return it when .recv() is called.
>
> Let's simplify the driver by implementing the new send_recv() op, so that
> we can also remove the 4KB internal buffer used to cache the response.
Looks like a nice cleanup to me but it needs to be tested. Jens, can you
give this patch a try?
>
> Signed-off-by: Stefano Garzarella <sgarzare@xxxxxxxxxx>
> ---
> Note: I don't know how to test this driver, so I just build it.
> If someone can test it, or tell me how to do, it will be great!
The fTPM is now maintained as part of OP-TEE project here [1]. The
instructions to test it on Qemu can be found here [2] as part of CI
pipeline.
[1] https://github.com/OP-TEE/optee_ftpm
[2] https://github.com/OP-TEE/optee_ftpm/blob/master/.github/workflows/ci.yml
-Sumit
> ---
> drivers/char/tpm/tpm_ftpm_tee.h | 4 --
> drivers/char/tpm/tpm_ftpm_tee.c | 86 ++++++++-------------------------
> 2 files changed, 21 insertions(+), 69 deletions(-)
>
> diff --git a/drivers/char/tpm/tpm_ftpm_tee.h b/drivers/char/tpm/tpm_ftpm_tee.h
> index f98daa7bf68c..72b2f5c41274 100644
> --- a/drivers/char/tpm/tpm_ftpm_tee.h
> +++ b/drivers/char/tpm/tpm_ftpm_tee.h
> @@ -23,16 +23,12 @@
> * @chip: struct tpm_chip instance registered with tpm framework.
> * @state: internal state
> * @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 139556b21cc6..f0393d843780 100644
> --- a/drivers/char/tpm/tpm_ftpm_tee.c
> +++ b/drivers/char/tpm/tpm_ftpm_tee.c
> @@ -31,45 +31,19 @@ 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_recv() - 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.
> + * @buf_len: the size of the buffer.
> + * @cmd_len: the number of bytes to send.
> *
> * 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_recv(struct tpm_chip *chip, u8 *buf,
> + size_t buf_len, size_t cmd_len)
> {
> struct ftpm_tee_private *pvt_data = dev_get_drvdata(chip->dev.parent);
> size_t resp_len;
> @@ -80,16 +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) {
> @@ -103,7 +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,
> },
> };
> @@ -115,7 +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,
> @@ -156,38 +129,21 @@ 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_len) {
> + dev_err(&chip->dev,
> + "%s: Invalid size in recv: buf_len=%zd, resp_len=%zd\n",
> + __func__, buf_len, resp_len);
> + return -EIO;
> + }
>
> - /* sanity checks look good, cache the response */
> - memcpy(pvt_data->resp_buf, temp_buf, resp_len);
> - pvt_data->resp_len = resp_len;
> -
> - return 0;
> -}
> -
> -static void ftpm_tee_tpm_op_cancel(struct tpm_chip *chip)
> -{
> - /* not supported */
> -}
> -
> -static u8 ftpm_tee_tpm_op_status(struct tpm_chip *chip)
> -{
> - return 0;
> -}
> + memcpy(buf, temp_buf, resp_len);
>
> -static bool ftpm_tee_tpm_req_canceled(struct tpm_chip *chip, u8 status)
> -{
> - return false;
> + 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,
> - .cancel = ftpm_tee_tpm_op_cancel,
> - .status = ftpm_tee_tpm_op_status,
> - .req_complete_mask = 0,
> - .req_complete_val = 0,
> - .req_canceled = ftpm_tee_tpm_req_canceled,
> + .send_recv = ftpm_tee_tpm_op_send_recv,
> };
>
> /*
> --
> 2.48.1
>
>