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 60188C44507 for ; Tue, 7 Jul 2026 19:06:18 +0000 (UTC) Received: from boromir.ozlabs.org (localhost [127.0.0.1]) by lists.ozlabs.org (Postfix) with ESMTP id 4gvrKr3MHxz3bsj; Wed, 08 Jul 2026 05:06:08 +1000 (AEST) Authentication-Results: lists.ozlabs.org; arc=none smtp.remote-ip=172.105.4.254 ARC-Seal: i=1; a=rsa-sha256; d=lists.ozlabs.org; s=201707; t=1783451168; cv=none; b=BdZzsqMPj/gcMZdz3wL/An9HGsq7Ly/NR4jzTlfd4HFcj5UQmtudM972R4dIkHJ4q6GpuSma3ExA8SaWbyhFdLUq/G8oRKNesUnZ9C3bOXtsDL4KUTV2wH2Tj+ah0WEVq958IFJrBRW72SxlQOpb4odYzMOnQXK8wRidR1OfwXp6Ha138EZBCjeGH/l9kTb0s153uim1UHolqexs+ba0aqh0YhpBoLidpYMSCRvGpRFjaTJYl9P+zCB7xYgPo6oy5RACRgvUyyXFIE7dEbkEtU4tNi1qufrsa7F6spBliJUBWrVSn6jVThkNfAUfcLGWUBYNK2/nLLafMTR1uSHIbA== ARC-Message-Signature: i=1; a=rsa-sha256; d=lists.ozlabs.org; s=201707; t=1783451168; c=relaxed/relaxed; bh=On6NfRZNP83GQAwWkJi2QY5gy7RW6c7PPEtomv7P1Dc=; h=Date:Message-ID:From:To:Cc:Subject:References:MIME-Version: Content-Type; b=VsDf+RO0F5YqbaApRXXOuB041texjPSnvJVhF8jnbYzb3AwNUAiGg7OcmMZohmysIv1XgrFkDBO4caS/be7bdJUWWh5NiaFhzLRoHtMrXp4Qf6DoaPY/9rFrJZPZbNHuY+L28LyC9qzz19Mf5sH8UOgAIi4gY2jnQYP+avEKBIWXswlNGG+plVJlFNq2yrCZMCspno9LRQMGegQO7Fgwf26H3mOHX2RxZtxk6rVkBcFZH3T+H/GGushZ6lm5AaYft5/r3V3k722rX7OVqKVYGTO5ZCKdI9U8SfJpu3l0KCy2OZ6yP6654otGLXmDWiROCPWRM0SeFIlin2ov5vckVw== ARC-Authentication-Results: i=1; lists.ozlabs.org; dmarc=pass (p=quarantine dis=none) header.from=kernel.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=Kyf4FHpF; dkim-atps=neutral; spf=pass (client-ip=172.105.4.254; helo=tor.source.kernel.org; envelope-from=tglx@kernel.org; receiver=lists.ozlabs.org) smtp.mailfrom=kernel.org Authentication-Results: lists.ozlabs.org; dmarc=pass (p=quarantine dis=none) header.from=kernel.org Authentication-Results: lists.ozlabs.org; dkim=pass (2048-bit key; unprotected) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=Kyf4FHpF; dkim-atps=neutral Authentication-Results: lists.ozlabs.org; spf=pass (sender SPF authorized) smtp.mailfrom=kernel.org (client-ip=172.105.4.254; helo=tor.source.kernel.org; envelope-from=tglx@kernel.org; receiver=lists.ozlabs.org) Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange x25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by lists.ozlabs.org (Postfix) with ESMTPS id 4gvrKq4NN0z2xnp for ; Wed, 08 Jul 2026 05:06:07 +1000 (AEST) 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> 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-Type: text/plain; charset=UTF-8 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