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From: Nikos Dragazis <ndragazis@arrikto.com>
Subject: Force global-dynamic TLS model
Message-ID: <889e96a3-f7d0-4703-c3d7-66a4d5913d72@arrikto.com>
Date: Tue, 23 Jun 2020 23:37:24 +0300
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Hi all,

Apologies if this has already been answered before.

I am experimenting with thread-local variables. I was wondering if it is
possible to make gcc force a specific TLS access model for some TLS
variables.

For example, let's say we have an ELF executable that defines and
accesses a TLS variable. From gcc's man page, I read that, in this case,
gcc will use the initial-exec TLS model by default. My question is if we
can change that and, say, use the global-dynamic model. To this end, I
have tried the `-ftls-model=global-dynamic` option and the `tls_model`
gcc variable attribute. None of these worked.

So, my question is: In this particular example, can we force gcc to use
the global-dynamic instead of the initial-exec TLS model?  And, in
general, can we force gcc to use global-dynamic for all accesses to
thread-local variables?

Thanks,
Nikos