DynamoRIO / DynamoRIO/dynamorio
[drmemtrace] Races in AARCH64 drx_insert_counter_update()
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Component-DrMemtrace
Component-Extension
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OpSys-AArch64
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Description
If the no-trace threshold is small enough, the tracer directly adds instructions that subtract from `instr_count` (the global no-trace instruction counter) through `drx_insert_counter_update()`: https://github.com/DynamoRIO/dynamorio/blob/master/clients/drcachesim/tracer/instr_counter.cpp#L371.
The load-counter->add/sub->store-counter instructions we use in the AARCH64 case are not thread safe and can cause races when updating the counter: https://github.com/DynamoRIO/dynamorio/blob/master/ext/drx/drx.c#L558.
We should use atomic instructions when available instead.
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