On Tue, Jun 26, 2018 at 7:29 PM, Catalin Marinas <catalin.marinas@xxxxxxx> wrote: > 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? OK, got it, I'll try to figure out a way to find these conversions. Thanks!
