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Re: [PATCH 1/3] meson: specify fuzz linker script as a project arg


From: Alexander Bulekov
Subject: Re: [PATCH 1/3] meson: specify fuzz linker script as a project arg
Date: Wed, 2 Sep 2020 12:17:06 -0400

On 200902 1745, Paolo Bonzini wrote:
> On 02/09/20 16:37, Alexander Bulekov wrote:
> > With this change, the fuzzer-linker script should be specified outside
> > any --start-group/--end-group pairs. We need this on oss-fuzz, where
> > partially applying the linker-script results in a linker failure
> 
> Is this okay also for targets that don't link to the fuzzing static library?
> 
> Paolo
> 

To be honest, I still do not completely understand why there is a
different behavior when we specify the script within a group. The man
page for ld.bfd doesn't talk about linker arguments between
--start-group and --end-group that are not archives. If I understand the
purpose of these linker groups, the linker script should still apply to
everything (regardless where it is specified). I would expect there to
be no change in behavior, or a complaint about passing linker arguments
that are not archive paths.

I was also worried about what would happen to all the __wrap_qtest
arguments, since those are still in the group, and they can fail silently.
Disassembling the binary confirmed that all the calls to
qtest_{in*,out*} are still wrapped.

Anyways.. I tested this series with and without LIB_FUZZING_ENGINE, and
used nm to confirm that the layout of the symbols/data is correct in
both cases (at least on my machine and the oss-fuzz docker) ..

-Alex



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