From nobody Mon Feb 9 05:58:47 2026 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by smtp.subspace.kernel.org (Postfix) with ESMTP id AFB682C21FB; Mon, 15 Dec 2025 16:35:45 +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=1765816547; cv=none; b=G72HhgcUEq7uzXMy0kB1R0R+cwWgYLYDUwFMJRVGik8ECXuGBH3HexZ5SfTPxC/WmiwerU4OqRdjL6Wfl+m/1maLeaLZ2yqrPq+6gFiZQKhtl3Gk/AMXijWcLzfE4gDQzVGjRj8JeMqFCjgn/EeLmMXPo/8bG85w7X03xEnnqE4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1765816547; c=relaxed/simple; bh=5YJChROSh+unZNlq0l84LRHUsrQFCSp86rmYxmvAFUo=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=T8W+FaXkHHhsv3KdVjDrESNop+c5UC4e4GkmVWQqVwT022tl/RCk72fF8p+BEZ6xugbTL9+aGgffg1HdhDP1pt4LwNFZU84uEVREkdF+CtNryPueyyeWaTojhPsJcmxe53cZdRDJ2rBiEl7DLJAcm6S8j1Sq/KTrP9QkgypxVEE= 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 F0FE8165C; Mon, 15 Dec 2025 08:35:37 -0800 (PST) Received: from e125769.cambridge.arm.com (e125769.cambridge.arm.com [10.1.196.27]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 992853F694; Mon, 15 Dec 2025 08:35:41 -0800 (PST) From: Ryan Roberts To: 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 , Mark Rutland , "Jason A. Donenfeld" , Ard Biesheuvel , Jeremy Linton Cc: Ryan Roberts , 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: [PATCH v2 2/3] prandom: Convert prandom_u32_state() to __always_inline Date: Mon, 15 Dec 2025 16:35:16 +0000 Message-ID: <20251215163520.1144179-3-ryan.roberts@arm.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20251215163520.1144179-1-ryan.roberts@arm.com> References: <20251215163520.1144179-1-ryan.roberts@arm.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" 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 --- 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; }; =20 -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 =3D TAUSWORTHE(state->s1, 6U, 13U, 4294967294U, 18U); + state->s2 =3D TAUSWORTHE(state->s2, 2U, 27U, 4294967288U, 2U); + state->s3 =3D TAUSWORTHE(state->s3, 13U, 21U, 4294967280U, 7U); + state->s4 =3D 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); =20 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 =20 -/** - * 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 =3D TAUSWORTHE(state->s1, 6U, 13U, 4294967294U, 18U); - state->s2 =3D TAUSWORTHE(state->s2, 2U, 27U, 4294967288U, 2U); - state->s3 =3D TAUSWORTHE(state->s3, 13U, 21U, 4294967280U, 7U); - state->s4 =3D 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 * --=20 2.43.0