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Message-ID: <20180615020154.GN1392@brightrain.aerifal.cx>
Date: Thu, 14 Jun 2018 22:01:54 -0400
From: Rich Felker <dalias@...c.org>
To: musl@...ts.openwall.com
Subject: Re: broken __kernel_mode_t affecting some big endian archs
On Thu, Jun 14, 2018 at 10:00:23PM -0400, Rich Felker wrote:
> On Wed, Jun 13, 2018 at 08:54:42PM -0400, Rich Felker wrote:
> > It's been semi-known for a long time (I say semi-, because nobody's
> > had the setup to test most of them well, or at least nobody I'm
> > communicating with regularly) that some archs are failing libc-test
> > sysvipc tests. I think I've tracked down the root cause.
> >
> > Linux defined __kernel_mode_t as short on some old archs, and used it
> > in place of mode_t in the ipc_perm structure. The field is padded out
> > to 32 bits, so on little endian archs it's no problem for us to just
> > (as we do) ignore the incorrect type and declare the structure with
> > mode_t, as POSIX requires. However on big-endian archs, the padding is
> > on the wrong side and this trick doesn't work.
> >
> > On MIPS we fixed a similar issue in struct stat, where dev_t was
> > incorrectly padded, with a fixup in syscall_arch.h. However this time
> > a large number of archs are affected, and patching them all up
> > individually seems nasty.
> >
> > My leaning is to have syscall_arch.h expose a macro indicating the
> > bug, and have msgctl, semctl, and shmctl each do the fixup if it's
> > set.
> >
> > FWIW the affected archs seem to be (only in big endian variants):
> > - ARM
> > - M68k (in-progress port)
> > - Microblaze
> > - SH
> > - Sparc (future port)
> >
> > Thoughts?
>
> Here's a draft of the fix, just for shmctl and not including the
> SHM_STAT or SHM_STAT_ALL operations.
And again with a fix so it doesn't break build on non-broken archs...
Rich
View attachment "shmfix.diff" of type "text/plain" (779 bytes)
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