From: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
To: Mimi Zohar <zohar@linux.ibm.com>
Cc: Nayna Jain <nayna@linux.ibm.com>,
Roberto Sassu <roberto.sassu@huawei.com>,
linux-integrity@vger.kernel.org,
linux-security-module@vger.kernel.org,
linux-kernel@vger.kernel.org, silviu.vlasceanu@huawei.com,
Ken Goldman <kgold@linux.vnet.ibm.com>,
Kenneth Goldman <kgoldman@us.ibm.com>
Subject: Re: [PATCH v4 1/6] tpm: dynamically allocate active_banks array
Date: Thu, 8 Nov 2018 20:57:29 +0200 [thread overview]
Message-ID: <20181108185729.GB20608@linux.intel.com> (raw)
In-Reply-To: <1541690993.4502.26.camel@linux.ibm.com>
On Thu, Nov 08, 2018 at 10:29:53AM -0500, Mimi Zohar wrote:
> On Thu, 2018-11-08 at 17:21 +0200, Jarkko Sakkinen wrote:
> > On Thu, Nov 08, 2018 at 07:20:51PM +0530, Nayna Jain wrote:
> > > Based on a discussion with Ken, the count in the TPML_PCR_SELECTION returns
> > > the number of possible algorithms supported. In the example below, two
> > > possible algorithms - SHA1 and SHA256 - are returned.
> > >
> > > # /usr/local/bin/tssgetcapability -cap 5
> > > 2 PCR selections
> > > hash TPM_ALG_SHA1
> > > TPMS_PCR_SELECTION length 3
> > > ff ff ff
> > > hash TPM_ALG_SHA256
> > > TPMS_PCR_SELECTION length 3
> > > 00 00 00
> > >
> > > The pcr_select fields - "ff ff ff" and "00 00 00" - are bit masks for the
> > > enabled PCRs. The SHA1 bank is enabled for all PCRs (0-23), while the SHA256
> > > bank is not enabled.
> > >
> > > The current code works, but it unnecessarily extends some banks. Instead of
> > > basing the number of active banks on the number of algorithms returned, it
> > > should be based on the pcr_select field.
> > >
> > > - Mimi & Nayna
> >
> > I would just allocate array of the size of possible banks and grow
> > nr_active_banks for active algorithms to keep the code simple because
> > we are talking about insignificant amount of wasted space (might be
> > even zero bytes given how kernel allocators works)>
>
> That's fine. Remember the memory is just one concern, but the other
> concerns are the performance of calculating the unneeded hash and the
> TPM performance of including it in the PCR extend.
The driver would initialize only as many entries as are active array and
set nr_active_banks accordingly.
/Jarkko
next prev parent reply other threads:[~2018-11-08 18:57 UTC|newest]
Thread overview: 41+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-11-06 15:01 [PATCH v4 0/6] tpm: retrieve digest size of unknown algorithms from TPM Roberto Sassu
2018-11-06 15:01 ` [PATCH v4 1/6] tpm: dynamically allocate active_banks array Roberto Sassu
2018-11-07 6:14 ` Nayna Jain
2018-11-07 9:41 ` Roberto Sassu
2018-11-08 13:50 ` Nayna Jain
2018-11-08 14:40 ` Roberto Sassu
2018-11-08 15:21 ` Jarkko Sakkinen
2018-11-08 15:29 ` Mimi Zohar
2018-11-08 18:57 ` Jarkko Sakkinen [this message]
2018-11-08 15:54 ` Ken Goldman
2018-12-13 20:21 ` Ken Goldman
2018-11-07 11:10 ` Mimi Zohar
2018-11-08 13:46 ` Jarkko Sakkinen
2018-11-08 14:24 ` Roberto Sassu
2018-11-08 15:22 ` Jarkko Sakkinen
2018-11-13 13:34 ` Roberto Sassu
2018-11-13 17:04 ` Jarkko Sakkinen
2018-11-13 13:53 ` Roberto Sassu
2018-11-06 15:01 ` [PATCH v4 2/6] tpm: remove definition of TPM2_ACTIVE_PCR_BANKS Roberto Sassu
2018-11-08 14:02 ` Jarkko Sakkinen
2018-11-08 14:03 ` Jarkko Sakkinen
2018-11-08 14:52 ` Roberto Sassu
2018-11-08 19:05 ` Jarkko Sakkinen
2018-11-06 15:01 ` [PATCH v4 3/6] tpm: rename and export tpm2_digest and tpm2_algorithms Roberto Sassu
2018-11-06 15:01 ` [PATCH v4 4/6] tpm: modify tpm_pcr_read() definition to pass a TPM hash algorithm Roberto Sassu
2018-11-08 14:04 ` Jarkko Sakkinen
2018-11-08 14:16 ` Roberto Sassu
2018-11-08 15:15 ` Jarkko Sakkinen
2018-11-08 15:19 ` Peter Huewe
2018-11-08 19:08 ` Jarkko Sakkinen
2018-11-13 12:34 ` Jarkko Sakkinen
2018-11-13 12:39 ` Roberto Sassu
2018-11-13 16:56 ` Jarkko Sakkinen
2018-11-06 15:01 ` [PATCH v4 5/6] tpm: retrieve digest size of unknown algorithms with PCR read Roberto Sassu
2018-11-06 15:01 ` [PATCH v4 6/6] tpm: ensure that the output of PCR read contains the correct digest size Roberto Sassu
2018-11-08 14:08 ` Jarkko Sakkinen
2018-11-08 14:47 ` Roberto Sassu
2018-11-08 18:52 ` Jarkko Sakkinen
2018-11-13 13:08 ` Roberto Sassu
2018-11-13 16:59 ` Jarkko Sakkinen
2018-11-08 13:51 ` [PATCH v4 0/6] tpm: retrieve digest size of unknown algorithms from TPM Jarkko Sakkinen
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