On 03/25/20 16:29, Ard Biesheuvel wrote: > The new ArmMmuLib code is easier to reason about, so that is what I did: > currently, when we create mappings that cover existing table entries, we > may end up overwriting those with block entries without taking the mapping > attributes of the original table entries into account. So let's fix this. > > I honestly don't know whether the original code was better at dealing with > this: I do remember some changes from Heyi that may have been related, but > the old code is not easy to follow. In any case, I didn't manage to hit this > case in practice, given that we typically start out with large mappings, and > break them down later (to set permissions), rather than the other way around. > > Patch #1 adds some helpers to hide the insane way the type bits change > meaning when you change to level 3. > > Patch #2 ensures that we only replace (and free) table entries with block > entries if it is guaranteed that doing so will not lose any attribute > information. > > Changes since v2: > - add patch to limit recursion to levels < 3 in FreePageTablesRecursive() > > Changes since v1: > - zero newly allocated pages before splitting a block entry into a table > entry, to avoid garbage in that page being misidentified as entry type > attributes - this should fix the crash observed by Laszlo > > Cc: Laszlo Ersek <ler...@redhat.com> > Cc: Leif Lindholm <l...@nuviainc.com> > Cc: Ashish Singhal <ashishsin...@nvidia.com> > > Ard Biesheuvel (3): > ArmPkg/ArmMmuLib AARCH64: limit recursion when freeing page tables > ArmPkg/ArmMmuLib AARCH64: use helpers to determine table entry types > ArmPkg/ArmMmuLib AARCH64: preserve attributes when replacing a table > entry > > .../Library/ArmMmuLib/AArch64/ArmMmuLibCore.c | 83 +++++++++++++++---- > 1 file changed, 68 insertions(+), 15 deletions(-) >
Tested-by: Laszlo Ersek <ler...@redhat.com> Thanks! Laszlo -=-=-=-=-=-=-=-=-=-=-=- Groups.io Links: You receive all messages sent to this group. View/Reply Online (#56340): https://edk2.groups.io/g/devel/message/56340 Mute This Topic: https://groups.io/mt/72543071/21656 Group Owner: devel+ow...@edk2.groups.io Unsubscribe: https://edk2.groups.io/g/devel/unsub [arch...@mail-archive.com] -=-=-=-=-=-=-=-=-=-=-=-