[llvm-dev] [MTE] Tagging Globals

[Mitch Phillips via llvm-dev]

Hi Zhaoshi,

Currently there's no global tagging instrumentation for MTE. We have a good
idea about the implementation's design - but no patches are ready to be
shared at this stage.

If you'd like - I'd be more than happy to CC yourself and Stephen on any
Phabricator reviews :).

On Tue, Jul 14, 2020 at 5:04 PM Zhaoshi Zheng via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> Hello,
>
>
>
> We’re evaluating memory tagging (MTE) on some internal workloads.
>
>
>
> We noticed that stack variables are tagged by an instrumentation pass and
> heap objects are handled by the allocator (Scudo).
>
>
>
> How about global variables? We tried a simple case using
> -march=armv8a+memtag -fsanitize=memtag, but found no tagging:
>
>
>
> Are we missing anything or tagging globals is still in progress?
>
>
>
> *int global_array[16];*
>
>
>
> *int main(int argc, char **argv) {*
>
> *  global_array[1] = 0;*
>
> *  return global_array[argc + 16];  // BOOM*
>
> *}*
>
>
>
> clang++ -O1 --target=aarch64-linux -march=armv8.5a+memtag
> -fsanitize=memtag test.cpp -S -o test.s
>
>
>
> *main:                                   // @main*
>
> *.Lmain$local:*
>
> *// %bb.0:                               // %entry*
>
> *        adrp    x8, global_array*
>
> *        add     x8, x8, :lo12:global_array*
>
> *        str     wzr, [x8, #4]*
>
> *        add     x8, x8, w0, sxtw #2*
>
> *        ldr     w0, [x8, #64]*
>
> *        ret*
>
> *.Lfunc_end0:*
>
> *        .size   main, .Lfunc_end0-main*
>
>
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