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From: Rich Felker <dalias@aerifal.cx>
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Subject: Re: semtcl for x86_64
Date: Sat, 22 Sep 2012 08:25:29 -0400
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On Sat, Sep 22, 2012 at 02:17:08PM +0200, Jens wrote:
> 
> 
> On Sat, 22 Sep 2012, Rich Felker wrote:
> 
> >On Sat, Sep 22, 2012 at 11:17:14AM +0200, Jens wrote:
> >>
> >>
> >>On Sat, 22 Sep 2012, Jens wrote:
> >>
> >>>
> >>>Hello I have some trouble getting semctl working:
> >>>
> >>>Tried in both musl and uclibc to compare.
> >>
> >>Forgot to mention its musl 0.9.6.
> >>
> >>Cheers,
> >>Jens
> >
> >Should be fixed now... Please let me know if it's still broken.
> 
> Ah. great! And I just finished the analysis.. :-)

Basically, some archs (approximately the 32-bit ones) have ancient
legacy versions of the IPC structures that only support 16-bit
uid/gid, etc. musl does not support using these, and always uses the
modern structures, which requires the IPC_64 flag (0x100) when making
the syscall. I assumed this flag would be a no-op on systems where
it's not needed, but for some reason the kernel rejects it, so we have
to go to the trouble of omitting it..

Rich