From: Szabolcs Nagy <nsz@port70.net>
To: musl@lists.openwall.com
Subject: Re: incompatibility between libtheora/mmx and musl ?
Date: Wed, 14 Sep 2016 16:41:45 +0200 [thread overview]
Message-ID: <20160914144145.GT1280@port70.net> (raw)
In-Reply-To: <20160914142842.GZ15995@brightrain.aerifal.cx>
* Rich Felker <dalias@libc.org> [2016-09-14 10:28:42 -0400]:
> On Wed, Sep 14, 2016 at 04:04:50PM +0200, u-uy74@aetey.se wrote:
> > On Wed, Sep 14, 2016 at 01:24:00PM +0200, Szabolcs Nagy wrote:
> > > there can be some call abi issue (register clobbering,
> > > stack alignment,..) because of the asm, but that's hard
> > > to check.
> >
> > Is musl in any way special compared to glibc/uclibc in its register usage?
>
> Not in principle; this is mandated by the ABI. But it's possible that
> their violation of ABI contracts is visible with some implementations
> but not others. For example if they're calling malloc from code that's
> using asm it's possible that they assume the floating point registers
> (or mmx state) are call-saved rather than call-clobbered. This is an
> invalid assumption that might happen to actively break on musl but not
> glibc. IIRC you need some special instructions to switch between x87
> and (original) mmx usage; perhaps they're missing this somewhere.
>
this might be an issue:
musl uses float instructions in malloc,
if mmx needs different fpu state and
they don't change it back for a malloc
call that can corrupt the heap.
to test this, try to use the 'non-float bin index'
code in musl from here:
http://port70.net/~nsz/musl/malloc.c
next prev parent reply other threads:[~2016-09-14 14:41 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-09-13 18:06 u-uy74
2016-09-13 19:20 ` Markus Wichmann
2016-09-13 20:41 ` Rich Felker
2016-09-13 20:43 ` Rich Felker
2016-09-14 10:32 ` u-uy74
2016-09-14 11:24 ` Szabolcs Nagy
2016-09-14 14:04 ` u-uy74
2016-09-14 14:28 ` Rich Felker
2016-09-14 14:31 ` Timo Teras
2016-09-14 14:39 ` Rich Felker
2016-09-14 14:40 ` Rich Felker
2016-09-14 14:41 ` Szabolcs Nagy [this message]
2016-09-14 15:11 ` u-uy74
2016-10-02 10:59 ` "non-float" malloc (was: incompatibility between libtheora/mmx and musl) u-uy74
2016-10-02 11:17 ` u-uy74
2016-10-02 12:08 ` Szabolcs Nagy
2016-10-02 12:24 ` u-uy74
2016-10-02 13:24 ` u-uy74
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