From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id 70E4B33A6EE; Mon, 19 Jan 2026 10:26:32 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=217.140.110.172 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768818395; cv=none; b=WL2b0QSdQ/Km+jCJC3JrgHDXUpdF3sxcnwBvN1PgO7lLZXRjNTKfRRmHcxSv5YmEKwflnNTT15DEP6SsA7WlPsRQEwdCMERC8CBoT+iXAWsQnJEXSwkytAjPAzKAqRwEccfohvpj5KVVDknHurx2SU4nCMg8EG0wjD1KitVw99E= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1768818395; c=relaxed/simple; bh=truMUfGz88HrWYYlDtyC2qzPqEnF0rZdBWptVaZLC98=; h=Date:From:To:Cc:Subject:Message-ID:References:MIME-Version: Content-Type:Content-Disposition:In-Reply-To; b=sIJuYpr+w6PXIcPNfNBqqnOxVHxh+YjZQPebbUk2gYofGqzoHi6169ykvD1tQ1hUboxUIgWQhe23MnuM9Btp+ReH1TbHnqDg/L9lq+o/TRxqPIn1H1PmdLvV9dRPt0ZMWyx48VNOPnSg4AjtMNacELndwL6Dkcu0sAKlIH6sm5Y= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass smtp.mailfrom=arm.com; arc=none smtp.client-ip=217.140.110.172 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 1246C153B; Mon, 19 Jan 2026 02:26:25 -0800 (PST) Received: from J2N7QTR9R3 (usa-sjc-imap-foss1.foss.arm.com [10.121.207.14]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id B17E53F632; Mon, 19 Jan 2026 02:26:26 -0800 (PST) Date: Mon, 19 Jan 2026 10:26:24 +0000 From: Mark Rutland To: Ryan Roberts Cc: Catalin Marinas , Will Deacon , Huacai Chen , Madhavan Srinivasan , Michael Ellerman , Paul Walmsley , Palmer Dabbelt , Albert Ou , Heiko Carstens , Vasily Gorbik , Alexander Gordeev , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Dave Hansen , Kees Cook , "Gustavo A. R. Silva" , Arnd Bergmann , "Jason A. Donenfeld" , Ard Biesheuvel , Jeremy Linton , linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, loongarch@lists.linux.dev, linuxppc-dev@lists.ozlabs.org, linux-riscv@lists.infradead.org, linux-s390@vger.kernel.org, linux-hardening@vger.kernel.org Subject: Re: [PATCH v3 2/3] prandom: Convert prandom_u32_state() to __always_inline Message-ID: References: <20260102131156.3265118-1-ryan.roberts@arm.com> <20260102131156.3265118-3-ryan.roberts@arm.com> Precedence: bulk X-Mailing-List: linux-s390@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20260102131156.3265118-3-ryan.roberts@arm.com> On Fri, Jan 02, 2026 at 01:11:53PM +0000, Ryan Roberts wrote: > We will shortly use prandom_u32_state() to implement kstack offset > randomization and some arches need to call it from non-instrumentable > context. Given the function is just a handful of operations and doesn't > call out to any other functions, let's take the easy path and make it > __always_inline. > > Signed-off-by: Ryan Roberts I see there were some comments about keeping an out-of-line wrapper. With or without that, this looks good to me, and either way: Acked-by: Mark Rutland Mark. > --- > include/linux/prandom.h | 19 ++++++++++++++++++- > lib/random32.c | 19 ------------------- > 2 files changed, 18 insertions(+), 20 deletions(-) > > diff --git a/include/linux/prandom.h b/include/linux/prandom.h > index ff7dcc3fa105..e797b3709f5c 100644 > --- a/include/linux/prandom.h > +++ b/include/linux/prandom.h > @@ -17,7 +17,24 @@ struct rnd_state { > __u32 s1, s2, s3, s4; > }; > > -u32 prandom_u32_state(struct rnd_state *state); > +/** > + * prandom_u32_state - seeded pseudo-random number generator. > + * @state: pointer to state structure holding seeded state. > + * > + * This is used for pseudo-randomness with no outside seeding. > + * For more random results, use get_random_u32(). > + */ > +static __always_inline u32 prandom_u32_state(struct rnd_state *state) > +{ > +#define TAUSWORTHE(s, a, b, c, d) ((s & c) << d) ^ (((s << a) ^ s) >> b) > + state->s1 = TAUSWORTHE(state->s1, 6U, 13U, 4294967294U, 18U); > + state->s2 = TAUSWORTHE(state->s2, 2U, 27U, 4294967288U, 2U); > + state->s3 = TAUSWORTHE(state->s3, 13U, 21U, 4294967280U, 7U); > + state->s4 = TAUSWORTHE(state->s4, 3U, 12U, 4294967168U, 13U); > + > + return (state->s1 ^ state->s2 ^ state->s3 ^ state->s4); > +} > + > void prandom_bytes_state(struct rnd_state *state, void *buf, size_t nbytes); > void prandom_seed_full_state(struct rnd_state __percpu *pcpu_state); > > diff --git a/lib/random32.c b/lib/random32.c > index 24e7acd9343f..d57baf489d4a 100644 > --- a/lib/random32.c > +++ b/lib/random32.c > @@ -42,25 +42,6 @@ > #include > #include > > -/** > - * prandom_u32_state - seeded pseudo-random number generator. > - * @state: pointer to state structure holding seeded state. > - * > - * This is used for pseudo-randomness with no outside seeding. > - * For more random results, use get_random_u32(). > - */ > -u32 prandom_u32_state(struct rnd_state *state) > -{ > -#define TAUSWORTHE(s, a, b, c, d) ((s & c) << d) ^ (((s << a) ^ s) >> b) > - state->s1 = TAUSWORTHE(state->s1, 6U, 13U, 4294967294U, 18U); > - state->s2 = TAUSWORTHE(state->s2, 2U, 27U, 4294967288U, 2U); > - state->s3 = TAUSWORTHE(state->s3, 13U, 21U, 4294967280U, 7U); > - state->s4 = TAUSWORTHE(state->s4, 3U, 12U, 4294967168U, 13U); > - > - return (state->s1 ^ state->s2 ^ state->s3 ^ state->s4); > -} > -EXPORT_SYMBOL(prandom_u32_state); > - > /** > * prandom_bytes_state - get the requested number of pseudo-random bytes > * > -- > 2.43.0 >