Re: [PATCH 04/12] tpm: add cursor based buffer functions for response parsing

[Jarkko Sakkinen <jarkko@kernel.org>]

On Thu, Feb 16, 2023 at 03:14:02PM -0500, James Bottomley wrote:
> Once we have encryption and authentication, marshalling and
> unmarshalling sessions becomes hugely complex.  Add cursor based
> functions which update the current pointer to make response parsing
> easier.

You need to properly introduce the concept of cursor based function,
and how that maps into implementation.

I understand absolutely nothing of the change just by reading the
commit message, it is pretty much useless peace of text.

> 
> Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
> ---
>  drivers/char/tpm/tpm-buf.c | 29 +++++++++++++++++++++++++++++
>  include/linux/tpm.h        |  3 +++
>  2 files changed, 32 insertions(+)
> 
> diff --git a/drivers/char/tpm/tpm-buf.c b/drivers/char/tpm/tpm-buf.c
> index 292c6f14f72c..b76158f9bcd0 100644
> --- a/drivers/char/tpm/tpm-buf.c
> +++ b/drivers/char/tpm/tpm-buf.c
> @@ -7,6 +7,8 @@
>  #include <linux/module.h>
>  #include <linux/tpm.h>
>  
> +#include <asm/unaligned.h>
> +
>  static int __tpm_buf_init(struct tpm_buf *buf)
>  {
>  	buf->data = (u8 *)__get_free_page(GFP_KERNEL);
> @@ -154,3 +156,30 @@ void tpm_buf_append_2b(struct tpm_buf *buf, struct tpm_buf *tpm2b)
>  	tpm_buf_reset_int(tpm2b);
>  }
>  EXPORT_SYMBOL_GPL(tpm_buf_append_2b);
> +
> +/* functions for unmarshalling data and moving the cursor */
> +u8 tpm_get_inc_u8(const u8 **ptr)
> +{
> +	return *((*ptr)++);
> +}
> +EXPORT_SYMBOL_GPL(tpm_get_inc_u8);
> +
> +u16 tpm_get_inc_u16(const u8 **ptr)
> +{
> +	u16 val;
> +
> +	val = get_unaligned_be16(*ptr);
> +	*ptr += sizeof(val);
> +	return val;
> +}
> +EXPORT_SYMBOL_GPL(tpm_get_inc_u16);
> +
> +u32 tpm_get_inc_u32(const u8 **ptr)
> +{
> +	u32 val;
> +
> +	val = get_unaligned_be32(*ptr);
> +	*ptr += sizeof(val);
> +	return val;
> +}
> +EXPORT_SYMBOL_GPL(tpm_get_inc_u32);
> diff --git a/include/linux/tpm.h b/include/linux/tpm.h
> index f2d4dab6d832..f7cff1d114b0 100644
> --- a/include/linux/tpm.h
> +++ b/include/linux/tpm.h
> @@ -335,6 +335,9 @@ void tpm_buf_append_u8(struct tpm_buf *buf, const u8 value);
>  void tpm_buf_append_u16(struct tpm_buf *buf, const u16 value);
>  void tpm_buf_append_u32(struct tpm_buf *buf, const u32 value);
>  void tpm_buf_append_2b(struct tpm_buf *buf, struct tpm_buf *tpm2b);
> +u8 tpm_get_inc_u8(const u8 **ptr);
> +u16 tpm_get_inc_u16(const u8 **ptr);
> +u32 tpm_get_inc_u32(const u8 **ptr);
>  
>  /*
>   * Check if TPM device is in the firmware upgrade mode.
> -- 
> 2.35.3
> 

BR, Jarkko