[llvm-dev] [MTE] Tagging Globals

[Zhaoshi Zheng via llvm-dev]

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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