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

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Message-ID: <ZtXJfiA1lU55JLMM@zx2c4.com>
Date: Mon, 2 Sep 2024 16:19:42 +0200
From: "Jason A. Donenfeld" <Jason@...c4.com>
To: Christophe Leroy <christophe.leroy@...roup.eu>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
	Steven Rostedt <rostedt@...dmis.org>,
	Masami Hiramatsu <mhiramat@...nel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
	Michael Ellerman <mpe@...erman.id.au>,
	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

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.)