linux-kernel - Re: [PATCH v4 5/5] powerpc/vdso: Wire up getrandom() vDSO implementation on PPC64

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Message-ID: <dac37bce-9616-450c-8c1e-aa24dcbfb882@csgroup.eu>
Date: Mon, 2 Sep 2024 16:27:12 +0200
From: Christophe Leroy <christophe.leroy@...roup.eu>
To: "Jason A. Donenfeld" <Jason@...c4.com>,
 Michael Ellerman <mpe@...erman.id.au>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
 Steven Rostedt <rostedt@...dmis.org>, Masami Hiramatsu
 <mhiramat@...nel.org>, Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Nicholas Piggin <npiggin@...il.com>, Naveen N Rao <naveen@...nel.org>,
 Nathan Chancellor <nathan@...nel.org>,
 Nick Desaulniers <ndesaulniers@...gle.com>, Bill Wendling
 <morbo@...gle.com>, Justin Stitt <justinstitt@...gle.com>,
 Shuah Khan <shuah@...nel.org>, linux-kernel@...r.kernel.org,
 linuxppc-dev@...ts.ozlabs.org, linux-kselftest@...r.kernel.org,
 llvm@...ts.linux.dev, linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
 linux-trace-kernel@...r.kernel.org,
 Adhemerval Zanella <adhemerval.zanella@...aro.org>,
 Xi Ruoyao <xry111@...111.site>
Subject: Re: [PATCH v4 5/5] powerpc/vdso: Wire up getrandom() vDSO
 implementation on PPC64

Hi Jason, hi Michael,

Le 02/09/2024 à 16:19, Jason A. Donenfeld a écrit :
> On Mon, Sep 02, 2024 at 04:16:48PM +0200, Christophe Leroy wrote:
>> Can do that, but there will still be a problem with chacha selftests if
>> I don't opt-out the entire function content when it is ppc64. It will
>> build properly but if someone runs it on a ppc64 it will likely crash
>> because only the low 32 bits of registers will be saved.
> 
> What if you don't wire up the selftests _at all_ until the ppc64 commit?
> Then there'll be no risk.
> 
> (And I think I would prefer to see the 32-bit code all in the 32-bit
> commit; that'd make it more straight forward to review too.)

I'd be fine with that but I'd like feedback from Michael on it: Is there 
a risk to only get PPC32 part merged as a first step or will both PPC32 
and PPC64 go together anyway ?

I would prefer not to delay PPC32 because someone doesn't feel confident 
with PPC64.

Christophe