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Date: Wed, 16 Jul 2014 11:59:58 -0400
From: Rich Felker <dalias@...c.org>
To: Peter Maydell <peter.maydell@...aro.org>
Cc: QEMU Developers <qemu-devel@...gnu.org>, musl@...ts.openwall.com,
	microblaze-linux@...ts.itee.uq.edu.au,
	Stefan Kristiansson <stefan.kristiansson@...nalahti.fi>,
	"Edgar E. Iglesias" <edgar.iglesias@...alogix.com>
Subject: Re: Re: [Qemu-devel] Bogus struct stat64 for qemu-microblaze
 (user emulation)?

On Wed, Jul 16, 2014 at 09:36:23AM +0100, Peter Maydell wrote:
> On 16 July 2014 05:02, Rich Felker <dalias@...c.org> wrote:
> > The qemu-microblaze definition of struct stat64 seems to mismatch the
> > kernel definition, which is using asm-generic/stat.h. See:
> >
> > http://git.qemu.org/?p=qemu.git;a=blob;f=linux-user/syscall_defs.h;h=c9e6323905486452f518102bf40ba73143c9d601;hb=HEAD#l1469
> > http://git.qemu.org/?p=qemu.git;a=blob;f=linux-user/syscall.c;h=a50229d0d72fc68966515fcf2bc308b833a3c032;hb=HEAD#l4949
> >
> > This seems to be causing a truncated-to-32-bit inode number to be
> > stored in the location where st_ino should reside, and a spurious copy
> > of the inode number to be written in a unused slot at the end of the
> > structure.
> 
> Sounds quite plausible -- we've had issues with other archs
> not having correct stat struct definitions in QEMU. I don't
> suppose anybody's done much testing of the microblaze
> linux-user code.

The bug seems to have been introduced here.

http://git.qemu.org/?p=qemu.git;a=commitdiff;h=a523eb06ec3fb2f4f4f4d362bb23704811d11379

I'm CC'ing the author/committer in case he has any input on why he did
this.

> > Is my analysis correct? Stefan Kristiansson and I found this while
> > working on the or1k port of musl libc, where it seems our structure
> > for the existing microblaze port is wrongly aligned with the qemu
> > definition rather than the definition the real kernel is using. Before
> > I try correcting this on our side, I want to make sure we're working
> > with the right version.
> 
> I would definitely trust the kernel definition, not QEMU's!

Yes.

Rich

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