Re: [PATCH 3/4] fuzz: add mangled object name to linker script

[Darren Kenny <darren.kenny@oracle.com>]

On Monday, 2020-05-11 at 23:01:32 -04, Alexander Bulekov wrote:
> Previously, we relied on "FuzzerTracePC*(.bss*)" to place libfuzzer's
> fuzzer::TPC object into our contiguous shared-memory region. This does
> not work for some libfuzzer builds, so this addition identifies the
> region by its mangled name: *(.bss._ZN6fuzzer3TPCE);
>
> Signed-off-by: Alexander Bulekov <alxndr@bu.edu>

FWIW, since I'm not really familiar with the syntax, but I understand
what the intent is:

Reviewed-by: Darren Kenny <darren.kenny@oracle.com>


> ---
>  tests/qtest/fuzz/fork_fuzz.ld | 5 +++++
>  1 file changed, 5 insertions(+)
>
> This isn't ideal, but I looked at the libfuzzer builds packaged for
> debian, for versions 6, 7, 8, 9, 10 and 11 and this (mangled) object
> name appears consistently in the symbol tables.
>
> diff --git a/tests/qtest/fuzz/fork_fuzz.ld b/tests/qtest/fuzz/fork_fuzz.ld
> index e086bba873..bfb667ed06 100644
> --- a/tests/qtest/fuzz/fork_fuzz.ld
> +++ b/tests/qtest/fuzz/fork_fuzz.ld
> @@ -28,6 +28,11 @@ SECTIONS
>  
>        /* Internal Libfuzzer TracePC object which contains the ValueProfileMap */
>        FuzzerTracePC*(.bss*);
> +      /*
> +       * In case the above line fails, explicitly specify the (mangled) name of
> +       * the object we care about
> +       */
> +       *(.bss._ZN6fuzzer3TPCE);
>    }
>    .data.fuzz_end : ALIGN(4K)
>    {
> -- 
> 2.26.2