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)> /Jarkko
