Aw: [PATCH] tpm: introduce struct tpm_buf

[Peter Huewe]

Hi,
> Betreff: [PATCH] tpm: introduce struct tpm_buf
> This patch introduces struct tpm_buf that provides a string buffer for
> constructing TPM commands. This allows to construct variable sized TPM
> commands. This feature is needed for TPM 2.0 commands in order to allow
> policy authentication and algorithmic agility.
> 
> The commands in the tpm2-cmd.c have been updated to use struct tpm_buf.
> Lots of awkward length calculations could be dropped because the buffer
> knows its length.
> 
> The code is is along the lines of the string buffer code in
> security/trusted/trusted.h.
> 

> --- a/drivers/char/tpm/tpm.h
> +++ b/drivers/char/tpm/tpm.h
> @@ -382,6 +382,93 @@ struct tpm_cmd_t {
> tpm_cmd_params params;
> } __packed;
> 
> +/* A string buffer type for constructing TPM commands. This is based on the
> + * code in security/keys/trusted.h.
> + */
> +
> +#define TPM_BUF_SIZE 512
Where does 512 come from? What about longer commands? Isn't TPM_BUF_SIZE defined elsewhere as 4096?
> 
> +
> +struct tpm_buf {
> + u8 data[TPM_BUF_SIZE];
> +};
> +

> +static inline void tpm_buf_append(struct tpm_buf *buf,
> + const unsigned char *data,
> + unsigned int len)
> +{
> + struct tpm_input_header *head = (struct tpm_input_header *) buf->data;
> +
> + BUG_ON((len + tpm_buf_length(buf)) > TPM_BUF_SIZE);
> +
> + memcpy(&buf->data[tpm_buf_length(buf)], data, len);
> + head->length = cpu_to_be32(tpm_buf_length(buf) + len);
> +}
> +
> +static inline void tpm_buf_store(struct tpm_buf *buf,
> + unsigned int pos,
> + const unsigned char *data,
> + unsigned int len)
> +{
> + BUG_ON((pos + len) > TPM_BUF_SIZE);
> +
> + memcpy(&buf->data[pos], data, len);
Isn't the updating of the length missing?
> +}

Thanks,
Peter

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