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Message-ID: <20220308215956.GQ7074@brightrain.aerifal.cx>
Date: Tue, 8 Mar 2022 16:59:56 -0500
From: Rich Felker <dalias@...c.org>
To: Florian Weimer <fweimer@...hat.com>
Cc: musl@...ts.openwall.com
Subject: Re: __WORDSIZE on x32
OK, following up on this rather late...
On Tue, Nov 23, 2021 at 09:22:24PM +0100, Florian Weimer wrote:
> * Rich Felker:
>
> > On Tue, Nov 23, 2021 at 08:51:36PM +0100, Florian Weimer wrote:
> >> This looks a bid suspicious:
> >
> > Come on, you missed a chance to say "sus". :-)
>
> Sorry? I typo'ed “bit”, but that's not it?
In the past year or two, "sus" has entered the vernacular for
gaming-related reasons. ;-)
> >> arch/x32/bits/reg.h:#undef __WORDSIZE
> >> arch/x32/bits/reg.h:#define __WORDSIZE 32
> >> arch/x32/bits/user.h:#undef __WORDSIZE
> >> arch/x32/bits/user.h:#define __WORDSIZE 64
> >>
> >> I don't know if it causes any actual problems. I discovered it while
> >> checking whether musl defines/uses __WORDSIZE.
> >
> > Thanks for the find. Now... which is it supposed to be?
> >
> > commit 664cd341921007cea52c8891f27ce35927dca378 introduced x32 as a
> > patch against a copy of x86_64 and changed one instance from 64 to 32,
> > so presumably the intent was to change both. Is this in agreement with
> > what it means on glibc or elsewhere?
>
> glibc uses __WORDSIZE == 64 to differentiate x86-64 from x86-64-32, so
> it should be 32 for x32.
Fixing this now.
> However, arch/x32/bits/user.h looks written as if define __WORDSIZE to
> 64 changes the width of long to 64. I think struct user_regs_struct
> needs to have unsigned long long members on x32. (It's what glibc uses
> for both x86-64 and x86-64-32.) Likewise a most of the members of
> struct user.
For user_regs_struct, it's pretty clear they need to be 64-bit. I'm
not sure about the long fields in struct user -- these may be 32-bit
on ELF32? Let's keep this part open until someone looks into it more.
Rich
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