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Date: Wed, 17 Oct 2012 03:49:33 +0200
From: boris brezillon <b.brezillon.musl@...il.com>
To: musl@...ts.openwall.com
Subject: Re: TLS (thread-local storage) support

2012/10/17 Rich Felker <dalias@...ifal.cx>:
> On Wed, Oct 17, 2012 at 02:08:11AM +0200, boris brezillon wrote:
>> >> I agree. This should be made optional. But if we don't compile libc
>> >> with fsplit-stack (-fnosplit-stack).
>> >> Each call to a libc func from an external func compiled with split
>> >> stack may lead to a 64K stack chunk alloc.
>> >
>> > Where does this allocation take place from? There should simply be a
>> > way to inhibit it.
>> In the linker (gold linker).
>
> Well gold isn't running at runtime. I assume you mean it _arranges_
> for this allocation to take place somehow, and that's what I'm
> wondering about whether there's a way to avoid.

The easiest way to avoid big stack chunk allocation is to compile musl
with -fno-split-stack option.
This will not add any overhead to functions (no split stack prolog)
And this will add a note to the shared object which tells the linker
to avoid __morestack to __morestack_non_split replacement.

>
> Rich

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