Re: [PATCH 05/12] tpm: add buffer function to point to returned parameters

[Jarkko Sakkinen <jarkko@kernel.org>]

On Thu, Feb 16, 2023 at 03:14:03PM -0500, James Bottomley wrote:
> Introducing encryption sessions changes where the return parameters
> are located in the buffer because if a return session is present
> they're 4 bytes beyond the header with those 4 bytes showing the
> parameter length.  If there is no return session, then they're in the
> usual place immediately after the header.  The tpm_buf_parameters()
> encapsulates this calculation and should be used everywhere
> &buf.data[TPM_HEADER_SIZE] is used now
> 
> Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
> ---
>  drivers/char/tpm/tpm-buf.c | 10 ++++++++++
>  include/linux/tpm.h        |  2 ++
>  2 files changed, 12 insertions(+)
> 
> diff --git a/drivers/char/tpm/tpm-buf.c b/drivers/char/tpm/tpm-buf.c
> index b76158f9bcd0..2518b675e866 100644
> --- a/drivers/char/tpm/tpm-buf.c
> +++ b/drivers/char/tpm/tpm-buf.c
> @@ -183,3 +183,13 @@ u32 tpm_get_inc_u32(const u8 **ptr)
>  	return val;
>  }
>  EXPORT_SYMBOL_GPL(tpm_get_inc_u32);
> +
> +u8 *tpm_buf_parameters(struct tpm_buf *buf)

kdoc

> +{
> +	int offset = TPM_HEADER_SIZE;
> +
> +	if (tpm_buf_tag(buf) == TPM2_ST_SESSIONS)
> +		offset += 4;
> +
> +	return &buf->data[offset];
> +}
> diff --git a/include/linux/tpm.h b/include/linux/tpm.h
> index f7cff1d114b0..fa8d1f932c0f 100644
> --- a/include/linux/tpm.h
> +++ b/include/linux/tpm.h
> @@ -339,6 +339,8 @@ u8 tpm_get_inc_u8(const u8 **ptr);
>  u16 tpm_get_inc_u16(const u8 **ptr);
>  u32 tpm_get_inc_u32(const u8 **ptr);
>  
> +u8 *tpm_buf_parameters(struct tpm_buf *buf);
> +
>  /*
>   * Check if TPM device is in the firmware upgrade mode.
>   */
> -- 
> 2.35.3
> 

BR, Jarkko