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Message-ID: <aBJGJwVyp3pvRlqE@kernel.org>
Date: Wed, 30 Apr 2025 18:47:51 +0300
From: Jarkko Sakkinen <jarkko@...nel.org>
To: Stefano Garzarella <sgarzare@...hat.com>
Cc: Christophe Leroy <christophe.leroy@...roup.eu>,
Peter Huewe <peterhuewe@....de>,
Alexandre Belloni <alexandre.belloni@...tlin.com>,
Jens Wiklander <jens.wiklander@...aro.org>,
Claudiu Beznea <claudiu.beznea@...on.dev>,
Naveen N Rao <naveen@...nel.org>,
Nicholas Piggin <npiggin@...il.com>, linuxppc-dev@...ts.ozlabs.org,
Nicolas Ferre <nicolas.ferre@...rochip.com>,
Michael Ellerman <mpe@...erman.id.au>,
Madhavan Srinivasan <maddy@...ux.ibm.com>,
James Bottomley <James.Bottomley@...senpartnership.com>,
linux-integrity@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org,
Sumit Garg <sumit.garg@...nel.org>, linux-kernel@...r.kernel.org,
Jason Gunthorpe <jgg@...pe.ca>
Subject: Re: [PATCH v3 3/4] tpm/tpm_ftpm_tee: support TPM_CHIP_FLAG_SYNC
On Mon, Apr 14, 2025 at 04:56:52PM +0200, Stefano Garzarella wrote:
> From: Stefano Garzarella <sgarzare@...hat.com>
>
> This driver does not support interrupts, and receiving the response is
> synchronous with sending the command.
>
> So we can set TPM_CHIP_FLAG_SYNC to support synchronous send() and
"Enable synchronous send() with TPM_CHIP_FLAG_SYNC, which implies that
->send() already fills the provided buffer with a reponse, and ->recv()
is not implemented."
So, instead of jargon it is better to explicitly state what the heck
is going on.
> return responses in the same buffer used for commands. This way we
> don't need the 4KB internal buffer used to cache the response before
> .send() and .recv(). Also we don't need to implement recv() op.
>
> Signed-off-by: Stefano Garzarella <sgarzare@...hat.com>
> ---
> 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
>
BR, Jarkko
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