1. 26 Feb, 2020 9 commits
  2. 25 Feb, 2020 27 commits
  3. 24 Feb, 2020 1 commit
    • Petre-Ionut Tudor's avatar
      Read-only xlat tables for BL31 memory · 60e8f3cf
      Petre-Ionut Tudor authored
      
      
      This patch introduces a build flag which allows the xlat tables
      to be mapped in a read-only region within BL31 memory. It makes it
      much harder for someone who has acquired the ability to write to
      arbitrary secure memory addresses to gain control of the
      translation tables.
      
      The memory attributes of the descriptors describing the tables
      themselves are changed to read-only secure data. This change
      happens at the end of BL31 runtime setup. Until this point, the
      tables have read-write permissions. This gives a window of
      opportunity for changes to be made to the tables with the MMU on
      (e.g. reclaiming init code). No changes can be made to the tables
      with the MMU turned on from this point onwards. This change is also
      enabled for sp_min and tspd.
      
      To make all this possible, the base table was moved to .rodata. The
      penalty we pay is that now .rodata must be aligned to the size of
      the base table (512B alignment). Still, this is better than putting
      the base table with the higher level tables in the xlat_table
      section, as that would cost us a full 4KB page.
      
      Changing the tables from read-write to read-only cannot be done with
      the MMU on, as the break-before-make sequence would invalidate the
      descriptor which resolves the level 3 page table where that very
      descriptor is located. This would make the translation required for
      writing the changes impossible, generating an MMU fault.
      
      The caches are also flushed.
      Signed-off-by: default avatarPetre-Ionut Tudor <petre-ionut.tudor@arm.com>
      Change-Id: Ibe5de307e6dc94c67d6186139ac3973516430466
      60e8f3cf
  4. 21 Feb, 2020 3 commits