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Message-ID: <CACsECNe0uszx6aU2vY7oCwN6OieaQfhVe716auTC1CZifUkS8g@mail.gmail.com>
Date: Wed, 14 Oct 2015 22:27:17 +0200
From: Alex <alexinbeijing@...il.com>
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 9:51 PM, Rich Felker <dalias@...c.org> wrote:
> 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.
Gotcha, thanks.
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