From: Peter =?iso-8859-15?q?H=FCwe?= <PeterHuewe@gmx.de>
To: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Subject: Re: [PATCH v2] tpm: introduce struct tpm_buf
Date: Mon, 8 Jun 2015 22:39:32 +0200
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Cc: jgunthorpe@obsidianresearch.com, safford@us.ibm.com,
        Marcel Selhorst <tpmdd@selhorst.net>,
        "moderated list:TPM DEVICE DRIVER" 
	<tpmdd-devel@lists.sourceforge.net>,
        open list <linux-kernel@vger.kernel.org>
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Hi,


Am Mittwoch, 3. Juni 2015, 18:39:14 schrieb Jarkko Sakkinen:
> 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.
> 
> Changes since v1:
> 
> - Fixed potential alignment issues in tpm_buf_tag().
> 
> Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>

> +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);
> +}

Don't you have to update the ->length here?


Thanks,
Peter

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