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Date: Mon, 25 May 2015 23:01:47 -0400
From: Rich Felker <dalias@...c.org>
To: Solar Designer <solar@...nwall.com>
Cc: writeonce@...ipix.org, john-dev@...ts.openwall.com
Subject: Re: update: JtR for Windows using musl libc

On Tue, May 26, 2015 at 05:53:21AM +0300, Solar Designer wrote:
> Hi,
> 
> On Mon, May 25, 2015 at 04:00:51PM -0700, writeonce@...ipix.org wrote:
> > The midipix runtime layer is now being tested in preparation for its
> > pre-alpha release, and JtR (john-1.8.0) has been very useful for testing
> > times(2), setitimer(2), and signal delivery. To get an idea of where
> > things currently stand, attached is the output of ./john --test along
> > with the corresponding strace report.
> 
> Thanks!  I'm glad you've reached this milestone.
> 
> While are the reported speeds so low?  I guess you're running this under
> a VM, but even then the speeds are surprisingly low.  Are timings
> possibly way off?
> 
> > The profile used for building was linux-x86-64, which means that
> > x86-64.S was compiled without any knowledge of the actual target or its
> > ABI. I suspect this has something to do with the two failed tests, but
> > haven't had time to identify the exact spot.
> 
> This is quite possible.  Maybe a difference in what registers are
> supposed to be callee-saved?

The argument registers for integer arguments are completely different
(rcx,rdx,r8,r9 vs rdi,rsi,rdx,rcx,r8,r9) so I would expect the
behavior to be nonsense. Floating point/vector registers have less
mismatch though so if these functions are operating on vectors,
perhaps it doesn't matter.

Note that there's a GCC attribute, __sysv_abi__, that could be used to
call the standard ABI asm code from a caller that's using the MS ABI.
That would be a way to reuse the asm unmodified rather than having to
wrap it or write a special version for Windows. The attribute just
needs to be put on the declarations of the asm functions in the
translation units they're called from.

Rich

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