From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from lists.ozlabs.org (lists.ozlabs.org [112.213.38.117]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 2890FD29C24 for ; Mon, 19 Jan 2026 13:02:21 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [127.0.0.1]) by lists.ozlabs.org (Postfix) with ESMTP id 4dvrFx695gz3c8h; Tue, 20 Jan 2026 00:02:13 +1100 (AEDT) Authentication-Results: lists.ozlabs.org; arc=none smtp.remote-ip=217.140.110.172 ARC-Seal: i=1; a=rsa-sha256; d=lists.ozlabs.org; s=201707; t=1768827733; cv=none; b=cXpCo888L+Jfvp9nJPWHYjphn1ykIXGxWre+876JWQUV1j/H0WSSs2ERq8rZdm4Tq8iYjUkzmmznwtbBAt6ih/nc0U5rTMbHwXsfBZbBNyOJoOvlIxDxjhWDnsk/p4A2/9DL1fz/roCQdD70v6NxKZXnH/XbevXkAXSnsep1LWufr2kOmq0fecH354ioMg4KOThkxP7iG87Ji6Uxnjw9RveeTQZ5wjkL9hEGkbCWw5ybr3zNkJWKF49TleEq4i1Xe7KMpyvFOaAbYCOyCJe6tDguTehyrs0TBfVuEZRgm2dwWpj8oDsIRZUtRn4gFgJoFawD+xElnIvEpQrBgKUtRw== ARC-Message-Signature: i=1; a=rsa-sha256; d=lists.ozlabs.org; s=201707; t=1768827733; c=relaxed/relaxed; bh=R7ig3Va+cgJWyxLk2AjzSNcEnc0SV+kvjb8+9+gGOlY=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=dkpVam29mgbXD7uHk3zpwQy2DW/yqj8GkOAhkXs+VZV6fRNL1hy0+fdQtEnlDCgrdQclveBY1zbBITY49xGBxDblDFSnxR9nZJLpFUzEXnIllPExhrV9I/4R85lRVwktoy772E6UQbwlugDIq/mY/r45ZX2CS6Rs2PHRIk53op+QkyN7OzSy2WjrSCbvUV3MhhuiIXbLdRXztlioWvz1Jk1y6CqNFRNo8wKMwjAf4q8li8L1Yju42JQ/xR+h53CKunwcIIkBRTHWlMy5dyfzoPg38v+cVARyt441S23idjdyPk4ojjBuyA2Sg7eWv/YtBJuqVkReOPsSjMXGiM8+UA== ARC-Authentication-Results: i=1; lists.ozlabs.org; dmarc=pass (p=none dis=none) header.from=arm.com; spf=pass (client-ip=217.140.110.172; helo=foss.arm.com; envelope-from=ryan.roberts@arm.com; receiver=lists.ozlabs.org) smtp.mailfrom=arm.com Authentication-Results: lists.ozlabs.org; dmarc=pass (p=none dis=none) header.from=arm.com Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=arm.com (client-ip=217.140.110.172; helo=foss.arm.com; envelope-from=ryan.roberts@arm.com; receiver=lists.ozlabs.org) Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lists.ozlabs.org (Postfix) with ESMTP id 4dvrFx0p9Yz3bfG for ; Tue, 20 Jan 2026 00:02:13 +1100 (AEDT) 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 431E11517; Mon, 19 Jan 2026 05:01:35 -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 74ECD3F740; Mon, 19 Jan 2026 05:01:38 -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 , David Laight 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 v4 2/3] prandom: Add __always_inline version of prandom_u32_state() Date: Mon, 19 Jan 2026 13:01:09 +0000 Message-ID: <20260119130122.1283821-3-ryan.roberts@arm.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20260119130122.1283821-1-ryan.roberts@arm.com> References: <20260119130122.1283821-1-ryan.roberts@arm.com> X-Mailing-List: linuxppc-dev@lists.ozlabs.org List-Id: List-Help: List-Owner: List-Post: List-Archive: , List-Subscribe: , , List-Unsubscribe: Precedence: list MIME-Version: 1.0 Content-Transfer-Encoding: 8bit We will shortly use prandom_u32_state() to implement kstack offset randomization and some arches need to call it from non-instrumentable context. So let's implement prandom_u32_state() as an out-of-line wrapper around a new __always_inline prandom_u32_state_inline(). kstack offset randomization will use this new version. Acked-by: Mark Rutland Signed-off-by: Ryan Roberts --- include/linux/prandom.h | 20 ++++++++++++++++++++ lib/random32.c | 8 +------- 2 files changed, 21 insertions(+), 7 deletions(-) diff --git a/include/linux/prandom.h b/include/linux/prandom.h index ff7dcc3fa105..801188680a29 100644 --- a/include/linux/prandom.h +++ b/include/linux/prandom.h @@ -17,6 +17,26 @@ struct rnd_state { __u32 s1, s2, s3, s4; }; +/** + * prandom_u32_state_inline - 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(). + * For use only where the out-of-line version, prandom_u32_state(), cannot be + * used (e.g. noinstr code). + */ +static __always_inline u32 prandom_u32_state_inline(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); +} + u32 prandom_u32_state(struct rnd_state *state); 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..2a02d82e91bc 100644 --- a/lib/random32.c +++ b/lib/random32.c @@ -51,13 +51,7 @@ */ 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); + return prandom_u32_state_inline(state); } EXPORT_SYMBOL(prandom_u32_state); -- 2.43.0