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Message-ID: <20151014195141.GX8645@brightrain.aerifal.cx>
Date: Wed, 14 Oct 2015 15:51:42 -0400
From: Rich Felker <dalias@...c.org>
To: musl@...ts.openwall.com
Subject: Re: [PATCHv3 1/3] fix matching errors for overwritten
registers in x86 CFI generation script
On Wed, Oct 14, 2015 at 09:44:50PM +0200, Alex wrote:
> On Wed, Oct 14, 2015 at 9:27 PM, Rich Felker <dalias@...c.org> wrote:
>
> > On Wed, Oct 14, 2015 at 09:23:59PM +0200, Alex wrote:
> > > On Wed, Oct 14, 2015 at 9:14 PM, Rich Felker <dalias@...c.org> wrote:
> > >
> > > > On Wed, Oct 14, 2015 at 12:21:05PM +0200, Alex wrote:
> > > > > This has been an interesting exercise so far. Is there any other arch
> > > > which
> > > > > you think it would be worthwhile to develop a CFI generation script
> > for?
> > > > It
> > > > > should be something which has enough users to avoid problems with
> > bitrot.
> > > >
> > > > CFI is probably a lot less interesting on archs where you have a
> > > > plenty registers not to need to manipulate stack frames in asm
> > > > functions, since in that case the debugger mostly works fine without
> > > > CFI. I don't know right off which of the other archs have significant
> > > > amounts of asm that adjusts the stack pointer, but you could go
> > > > through and check them. Having ABI info for them all would be helpful;
> > > > I'm pasting my draft ABI reference (which might have errors) below.
> > >
> > > Fair enough. If it's not likely to help anyone, I'll leave the CFI
> > > generation here.
> > >
> > > Another idea: are you interested in an implementation of POSIX AIO which
> > > uses the native AIO syscalls? Bad idea?
> >
> > Those syscalls have nothing at all to do with POSIX AIO. They're
> > completely different. :(
>
> The interface presented by the raw syscalls is not the POSIX AIO interface,
> but I haven't seen any reason yet why io_setup, io_submit, io_getevents,
> etc. couldn't be used to implement the POSIX AIO interface. Is there such a
> reason?
They only work on certain types of devices/files, and only when the
offset and memory source/dest meet some arbitrary alignment
requirements. And those are just the big problems. I don't see any
indication that they match the subtle behavior requirements for POSIX
AIO in any way.
Rich
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