Hello, Is the branch where the MTE patches currently are being applied for-net/mte? It looks like that's the place, but I want to confirm. On Tue, Sep 8, 2020 at 11:42 AM Catalin Marinas <catalin.marinas@xxxxxxx> wrote: > > On Tue, Sep 08, 2020 at 04:02:06PM +0200, Andrey Konovalov wrote: > > On Thu, Aug 27, 2020 at 2:16 PM Catalin Marinas <catalin.marinas@xxxxxxx> wrote: > > > On Thu, Aug 27, 2020 at 11:56:49AM +0100, Vincenzo Frascino wrote: > > > > On 8/27/20 11:38 AM, Catalin Marinas wrote: > > > > > On Fri, Aug 14, 2020 at 07:27:06PM +0200, Andrey Konovalov wrote: > > > > >> diff --git a/arch/arm64/kernel/mte.c b/arch/arm64/kernel/mte.c > > > > >> index 7717ea9bc2a7..cfac7d02f032 100644 > > > > >> --- a/arch/arm64/kernel/mte.c > > > > >> +++ b/arch/arm64/kernel/mte.c > > > > >> @@ -18,10 +18,14 @@ > > > > >> > > > > >> #include <asm/barrier.h> > > > > >> #include <asm/cpufeature.h> > > > > >> +#include <asm/kasan.h> > > > > >> +#include <asm/kprobes.h> > > > > >> #include <asm/mte.h> > > > > >> #include <asm/ptrace.h> > > > > >> #include <asm/sysreg.h> > > > > >> > > > > >> +u64 gcr_kernel_excl __read_mostly; > > > > > > > > > > Could we make this __ro_after_init? > > > > > > > > Yes, it makes sense, it should be updated only once through mte_init_tags(). > > > > > > > > Something to consider though here is that this might not be the right approach > > > > if in future we want to add stack tagging. In such a case we need to know the > > > > kernel exclude mask before any C code is executed. Initializing the mask via > > > > mte_init_tags() it is too late. > > > > > > It depends on how stack tagging ends up in the kernel, whether it uses > > > ADDG/SUBG or not. If it's only IRG, I think it can cope with changing > > > the GCR_EL1.Excl in the middle of a function. > > > > > > > I was thinking to add a compilation define instead of having gcr_kernel_excl in > > > > place. This might not work if the kernel excl mask is meant to change during the > > > > execution. > > > > > > A macro with the default value works for me. That's what it basically is > > > currently, only that it ends up in a variable. > > > > Some thoughts on the topic: gcr_kernel_excl is currently initialized > > in mte_init_tags() and depends on the max_tag value dynamically > > provided to it, so it's not something that can be expressed with a > > define. In the case of KASAN the max_tag value is static, but if we > > rely on that we make core MTE code depend on KASAN, which doesn't seem > > right from the design perspective. > > The design is debatable. If we want MTE to run on production devices, we > either (1) optimise out some bits of KASAN (configurable) or (2) we > decouple MTE and KASAN completely and add new callbacks in the core code > (slab allocator etc.) specific to MTE. > > My first choice is (1), unless there is a strong technical argument why > it is not possible. > > -- > Catalin > > _______________________________________________ > linux-arm-kernel mailing list > linux-arm-kernel@xxxxxxxxxxxxxxxxxxx > http://lists.infradead.org/mailman/listinfo/linux-arm-kernel -- Derrick McKee Phone: (703) 957-9362 Email: derrick.mckee@xxxxxxxxx
