linux-kernel - Re: [PATCH] alpha/elf: Fix misc/setarch test of util-linux by removing 32bit support

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Message-ID: <875xmjth15.fsf@email.froward.int.ebiederm.org>
Date: Sun, 12 Jan 2025 23:32:54 -0600
From: "Eric W. Biederman" <ebiederm@...ssion.com>
To: Ivan Kokshaysky <ink@...een.parts>
Cc: John Paul Adrian Glaubitz <glaubitz@...sik.fu-berlin.de>,  Arnd Bergmann
 <arnd@...db.de>,  Richard Henderson <richard.henderson@...aro.org>,  Matt
 Turner <mattst88@...il.com>,  Kees Cook <kees@...nel.org>,  "Paul E.
 McKenney" <paulmck@...nel.org>,  linux-alpha@...r.kernel.org,
  linux-mm@...ck.org,  linux-kernel@...r.kernel.org,  Michael Cree
 <mcree@...on.net.nz>,  Sam James <sam@...too.org>,  "Maciej W. Rozycki"
 <macro@...am.me.uk>,  Geert Uytterhoeven <geert@...ux-m68k.org>,  Michael
 Karcher <kernel@...rcher.dialup.fu-berlin.de>,  Chris Hofstaedtler
 <zeha@...ian.org>,  util-linux@...r.kernel.org,
  linux-mips@...r.kernel.org,  loongarch@...ts.linux.dev
Subject: Re: [PATCH] alpha/elf: Fix misc/setarch test of util-linux by
 removing 32bit support

Ivan Kokshaysky <ink@...een.parts> writes:

> On Fri, Jan 10, 2025 at 06:16:28PM -0600, Eric W. Biederman wrote:
>> 
>> Richard Henderson <richard.henderson@...aro.org> writes[1]:
>> 
>> > There was a Spec benchmark (I forget which) which was memory bound and ran
>> > twice as fast with 32-bit pointers.
>> >
>> > I copied the idea from DEC to the ELF abi, but never did all the other work
>> > to allow the toolchain to take advantage.
>> >
>> > Amusingly, a later Spec changed the benchmark data sets to not fit into a
>> > 32-bit address space, specifically because of this.
>> >
>> > I expect one could delete the ELF bit and personality and no one would
>> > notice. Not even the 10 remaining Alpha users.
>> 
>> In [2] it was pointed out that parts of setarch weren't working
>> properly on alpha because it has it's own SET_PERSONALITY
>> implementation.  In the discussion that followed Richard Henderson
>> pointed out that the 32bit pointer support for alpha was never
>> completed.
>> 
>> Fix this by removing alpha's 32bit pointer support.
>> 
>> As a bit of paranoia refuse to execute any alpha binaries that hafe
>> the EF_ALPHA_32BIT flag set.  Just to fail explicitly in case someone
>> somewhere has binaries that trying to use alpha's 32bit pointer
>> support.
>
> In general I agree, but then someone ought to remove the "--taso" option
> from GNU ld, which produces such binaries.

Please feel free to write such a patch.  I don't know the GNU ld process
well enough to write that patch.

It would be good to remove dead code and confusing code from GNU ld,
as well as from the linux kernel.

Eric