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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (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 C8375C43602 for ; Tue, 7 Jul 2026 19:06:13 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:Content-Type:MIME-Version: References:Subject:Cc:To:From:Message-ID:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:In-Reply-To: List-Owner; bh=On6NfRZNP83GQAwWkJi2QY5gy7RW6c7PPEtomv7P1Dc=; b=TbFVSNKisHkcHz c4naTX2U1UzSV39+UexGLsXPorUpNsg9ay5cxnYH6o2rXncM1QUW/0puhm9vxtu5NTH0jhzyfgNj3 M1giOAVa4PNrvcHb9mkNVLlL591Y3YGxBuR7eqCoNclhONl/HXImjs/t+GTqgXXVKaMbAWVzp7M7X 2o+xEelSNCVuYHY814MFKSqGeDInODxRiBpi3aqevK+KSsgAUJ8L8cJXamGQGL3LvsNPWCO95M/JN g4291KOUf8F7W4suztPO4SbA4L6bJ4Ogwu9KHW6+GfW2nP4M9mUh4eN0PCTI4hav9pm1I1tQBOioE /fqJM7wX+IEKziNFMvHQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1whB7V-0000000FgnT-22EW; Tue, 07 Jul 2026 19:06:13 +0000 Received: from tor.source.kernel.org ([2600:3c04:e001:324:0:1991:8:25]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1whB7O-0000000Fghv-1jSF; Tue, 07 Jul 2026 19:06:06 +0000 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by tor.source.kernel.org (Postfix) with ESMTP id A2DD86138A; Tue, 7 Jul 2026 19:06:05 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 836131F00A3A; Tue, 7 Jul 2026 19:06:04 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1783451165; bh=On6NfRZNP83GQAwWkJi2QY5gy7RW6c7PPEtomv7P1Dc=; h=Date:From:To:Cc:Subject:References; b=Kyf4FHpFsIS+Ydmvpd4dDjaw6LA3z5qA3tk9jQCRiEW5qX1inNO9gy7FOgieh3baY hYOJJlHaPUBmLHJ7GT1+snJJu9GDe/I9LBY8DO5JtbHEjuAUTNBhEUGadk4Jt3mT6M jfM460+qa8cBdINqLxhonst5REsB87hmc78d5eqMEOoD5gBYWK0lJNv1XzAl9UsuvK VcyLhfQ5RZnjt+w12lkO4zxWbhBNKXx+std7IviKWtj5txrPrCsYKXUlRXGm9L5b6C x3lWCb9/6igNz1lMUWNia6Ofl2ESSU4en1Tc99OlWes1QnxVBl0HIc9O5ffHHzCd75 Lv0AL/D7KjB7Q== Date: Tue, 07 Jul 2026 21:06:02 +0200 Message-ID: <20260707190253.768842729@kernel.org> User-Agent: quilt/0.69 From: Thomas Gleixner To: LKML Cc: Peter Zijlstra , Kees Cook , Michael Ellerman , Shrikanth Hegde , linuxppc-dev@lists.ozlabs.org, Huacai Chen , loongarch@lists.linux.dev, Paul Walmsley , Palmer Dabbelt , linux-riscv@lists.infradead.org, Sven Schnelle , linux-s390@vger.kernel.org, x86@kernel.org, Mark Rutland , Jinjie Ruan , Andy Lutomirski , Oleg Nesterov , Richard Henderson , Russell King , Catalin Marinas , Guo Ren , Geert Uytterhoeven , Thomas Bogendoerfer , Helge Deller , Yoshinori Sato , Richard Weinberger , Chris Zankel , linux-arm-kernel@lists.infradead.org, linux-alpha@vger.kernel.org, linux-csky@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linux-sh@vger.kernel.org, linux-um@lists.infradead.org, Arnd Bergmann , Vineet Gupta , Will Deacon , Brian Cain , Michal Simek , Dinh Nguyen , "David S. Miller" , Andreas Larsson , linux-snps-arc@lists.infradead.org, linux-hexagon@vger.kernel.org, linux-openrisc@vger.kernel.org, sparclinux@vger.kernel.org, linux-arch@vger.kernel.org, =?UTF-8?q?Michal=20Such=C3=A1nek?= , Jonathan Corbet , linux-doc@vger.kernel.org Subject: [patch 02/18] randomize_kstack: Provide add_random_kstack_offset_irqsoff() References: <20260707181957.433213175@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 X-BeenThere: linux-um@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-um" Errors-To: linux-um-bounces+linux-um=archiver.kernel.org@lists.infradead.org add_random_kstack_offset() uses get/put_cpu_var() which is pointless overhead when it is invoked from low level entry code with interrupts disabled. Provide a irqsoff() variant, which avoids that. Signed-off-by: Thomas Gleixner Cc: Kees Cook --- include/linux/randomize_kstack.h | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) --- a/include/linux/randomize_kstack.h +++ b/include/linux/randomize_kstack.h @@ -77,8 +77,27 @@ static __always_inline u32 get_kstack_of } \ } while (0) +/** + * add_random_kstack_offset_irqsoff - Increase stack utilization by a random offset. + * + * This should be used in the syscall entry path after user registers have been + * stored to the stack. Interrupts must be still disabled. + */ +#define add_random_kstack_offset_irqsoff() \ +do { \ + lockdep_assert_irqs_disabled(); \ + if (static_branch_maybe(CONFIG_RANDOMIZE_KSTACK_OFFSET_DEFAULT, \ + &randomize_kstack_offset)) { \ + u32 offset = prandom_u32_state(raw_cpu_ptr(&kstack_rnd_state)); \ + u8 *ptr = __kstack_alloca(KSTACK_OFFSET_MAX(offset)); \ + /* Keep allocation even after "ptr" loses scope. */ \ + asm volatile("" :: "r"(ptr) : "memory"); \ + } \ +} while (0) + #else /* CONFIG_RANDOMIZE_KSTACK_OFFSET */ #define add_random_kstack_offset() do { } while (0) +#define add_random_kstack_offset_irqsoff() do { } while (0) #endif /* CONFIG_RANDOMIZE_KSTACK_OFFSET */ #endif