On 27/06/2018 16:05, Andrey Konovalov wrote: > 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. This sounds like the kind of thing we should be able to get sparse to do already, no ? It's been many years since I last looked at it but I thought sparse was the tool of choice in the kernel to do this kind of checking. regards Ramana > > Thanks! >
