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Fix aarch64 read_time_counter()#849

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tokatoka merged 3 commits intomainfrom
revert_aarch64
Oct 21, 2022
Merged

Fix aarch64 read_time_counter()#849
tokatoka merged 3 commits intomainfrom
revert_aarch64

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@tokatoka tokatoka commented Oct 21, 2022

introspection does not work on aarch64

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tokatoka commented Oct 21, 2022

Hi @devnexen
We've noticed that your change on #790 does not work well.
You can reproduce this issue by adding "introspection" feature to libfuzzer_libpng and run the fuzzer on a m1mac computer (or any aarch64)
like:

[dependencies]
libafl = { path = "../../libafl/", features = ["default", "introspection"] }

The introspection output does not give meaningful results after #790

[Testcase    #1]  (GLOBAL) run time: 0h-0m-15s, clients: 2, corpus: 299, objectives: 0, executions: 1540160, exec/sec: 97484
                  (CLIENT) corpus: 299, objectives: 0, executions: 1540160, exec/sec: 97484, edges: 802/11460 (6%)
Client 001:
     NaN: Scheduler
     NaN: Manager
  Stage 0:
       NaN: GetInputFromCorpus
       NaN: Mutate
       NaN: MutatePostExec
       NaN: TargetExecution
       NaN: PreExec
       NaN: PostExec
       NaN: PreExecObservers
       NaN: PostExecObservers
       NaN: GetFeedbackInterestingAll
       NaN: GetObjectivesInterestingAll
  Feedbacks:
       NaN: TimeoutFeedback
       NaN: CrashFeedback
       NaN: time
       NaN: mapfeedback_metadata_edges
     NaN: Not Measured

Do you have any suggestion on how to fix this? (We could just fall back to current_nanos() but we want to use your code bc it should be faster)

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tokatoka commented Oct 21, 2022 •
edited
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FYI: this value is print-ed here is always 0

#[cfg(target_arch = "aarch64")]
#[must_use]
pub fn read_time_counter() -> u64 {
    let v: u64 = 0;
    unsafe {
        // TODO pushing a change in core::arch::aarch64 ?
        asm!("mrs {v}, cntvct_el0", v = out(reg) _);
    }
    println!("{}", v);
    v
}

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tokatoka commented Oct 21, 2022

5c6aa2c should be the fix

@tokatoka tokatoka changed the title Revert #790 Changes Fix aarch64 read_time_counter() Oct 21, 2022
@tokatoka tokatoka merged commit 64ec5c3 into main Oct 21, 2022
@tokatoka tokatoka deleted the revert_aarch64 branch October 21, 2022 07:23
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devnexen commented Oct 22, 2022

sorry for late reply, pretty busy at the moment, thx for the change ;).

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@tokatoka @devnexen