Hi Andrey, On Tue, Jun 26, 2018 at 02:47:50PM +0200, Andrey Konovalov wrote: > On Wed, Jun 20, 2018 at 5:24 PM, Andrey Konovalov <andreyknvl@xxxxxxxxxx> wrote: > > arm64 has a feature called Top Byte Ignore, which allows to embed pointer > > tags into the top byte of each pointer. Userspace programs (such as > > HWASan, a memory debugging tool [1]) might use this feature and pass > > tagged user pointers to the kernel through syscalls or other interfaces. > > > > This patch makes a few of the kernel interfaces accept tagged user > > pointers. The kernel is already able to handle user faults with tagged > > pointers and has the untagged_addr macro, which this patchset reuses. > > > > We're not trying to cover all possible ways the kernel accepts user > > pointers in one patchset, so this one should be considered as a start. > > > > Thanks! > > > > [1] http://clang.llvm.org/docs/HardwareAssistedAddressSanitizerDesign.html > > Is there anything I should do to move forward with this? > > I've received zero replies to this patch set (v3 and v4) over the last > month. The patches in this series look fine but my concern is that they are not sufficient and we don't have (yet?) a way to identify where such annotations are required. You even say in patch 6 that this is "some initial work for supporting non-zero address tags passed to the kernel". Unfortunately, merging (or relaxing) an ABI without a clear picture is not really feasible. While I support this work, as a maintainer I'd like to understand whether we'd be in a continuous chase of ABI breaks with every kernel release or we have a better way to identify potential issues. Is there any way to statically analyse conversions from __user ptr to long for example? Or, could we get the compiler to do this for us? Thanks. -- Catalin
