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 7398BCA5FA6 for ; Mon, 28 Sep 2026 17:43:20 +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:Cc:To:From: Subject:Message-ID:References:Mime-Version:In-Reply-To:Date:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=GvWsjS4kJdvoXcVGD6geTFWpf+d6azd0mBr60JzC1QM=; b=L5zKf/ee+nQfFd13q2I/qNtAke jozKXyHroqkIxZ1HyxEXDavUA/lXZ1kYm91wyT+MwsYiST6DE55EVYp3mikYJQXUjo88GpvT89KBe qVQEx1MjDgEO9FMwFeQlHAPeFrJWCiH7otzjLcc2h65eNNUon0/uCtaxacjF8zQWKOYzNDPJlmtTP 5tTdUT+KyVio2DXsKfYuYMSbv+lZiMNTaEL6fbSTtQidAuTsed3bTYx/SXwY8d+Zm6itvjkFXTk/r 4v5XreuG4/wXP819RrMjubHN3lkcjfkF5TEpzzug7bneRhEonCHCDkg7vQuiBogkcRjJlIhJiLzKN BdbrgNlw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1xBFNh-00000001DNu-1mEo; Mon, 28 Sep 2026 17:43:13 +0000 Received: from mail-wm1-x345.google.com ([2a00:1450:4864:20::345]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1xBFMf-00000001Cnm-2LkG for linux-arm-kernel@lists.infradead.org; Mon, 28 Sep 2026 17:42:11 +0000 Received: by mail-wm1-x345.google.com with SMTP id 5b1f17b1804b1-49e6b5c5f44so50955945e9.2 for ; Mon, 28 Sep 2026 10:42:08 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1790617327; x=1791222127; darn=lists.infradead.org; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:from:to:cc:subject:date:message-id:reply-to :content-type; bh=GvWsjS4kJdvoXcVGD6geTFWpf+d6azd0mBr60JzC1QM=; b=UEvK1gb8CFguAsIcrH+Dl6UR8TzzVfNBvol2qvyMgH97eCSZ+TcFyTv85RFG7BzHKA KLz6GtsQYWU3UmUG03qas01HQsr0140KsI6L+aiamuu1QMS5h1ksq2H2FT3tDxcrqq0X 3KTFDrpBWez0e4z9DLvqJB0KlCYdvG2XeYv2ZkNG7pAouw6a+5SwRNHALxZkvhiwL150 llL46sYSz9veAQM5j6GSwoRRJLXUoTy1AFSW15por5ju5CBp7JYtj/C05sCA/agV85MT tAo3uUzIdS2FnniHukORoEpfMK8H3HI964LtmuTqfz68LtGmbyFpBeHDXosgzPrombAc g3xQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1790617327; x=1791222127; h=content-type:cc:to:from:subject:message-id:references:mime-version :in-reply-to:date:x-gm-message-state:from:to:cc:subject:date :message-id:reply-to:content-type; bh=GvWsjS4kJdvoXcVGD6geTFWpf+d6azd0mBr60JzC1QM=; b=rVaz+1PZlf6mVNWNo8b0UPXYcU5B6YzA8hm+drUTwyQVk0Au+dACw3SkZqAQfKJGSJ 3ju9kWyqjuJg2Vjvj/6n8mmUlpuqWSsTn1I58YE6SukpgPVf9XpSEJlac89yPvPevq/K AvT5pksnv9laia5e7nSuE2595Abb02yvuBYkPH9iqOBt9YY/C5qkz1c9rRwCw6aos2wO rwfKwHfQJ/GuOrZ1F1ONptMXgZpLMUPzy6oP6faQAXYS50iIIMLKqFqAUJBYWnmD5uNZ LaWb2gg9/mEKDP8mcjRDAKWYhWXFn9TZMUEZYzjR5fxElya2iRsnEtUlSFdDLMkwgQbp CpFQ== X-Forwarded-Encrypted: i=1; AKwUvBzghgYcEui7fSiMTguGqlOZn7Svwro+3qPTDGxyZGldkYOTFruj5pxFNTnJqFLh/Aj5hZHI8qguvJUmX25nDhaL@lists.infradead.org X-Gm-Message-State: AFuF++nxGAB17TBWayn7ZG+6LTSeEG9yccjnxQmZQyoW+hnzp2QjsvJu GT0Z+jvznsXB3LwoY+7KELyd4oC9uNJooXIoKAVeIzrRWTDWQ4vUO98Lk6VTjwNGhaFYnwKiUmG DwRuzFn5KudYSqg== X-Received: from wmpr40.prod.google.com ([2002:a05:600c:3228:b0:49f:fde6:649f]) (user=smostafa job=prod-delivery.src-stubby-dispatcher) by 2002:a05:600c:6287:b0:49d:827:e5b6 with SMTP id 5b1f17b1804b1-49fe7babaadmr223084505e9.20.1790617327143; Mon, 28 Sep 2026 10:42:07 -0700 (PDT) Date: Mon, 28 Sep 2026 17:41:22 +0000 In-Reply-To: <20260928174122.3380703-1-smostafa@google.com> Mime-Version: 1.0 References: <20260928174122.3380703-1-smostafa@google.com> X-Mailer: git-send-email 2.56.0.rc1.315.gc6ed9934b7-goog Message-ID: <20260928174122.3380703-16-smostafa@google.com> Subject: [RFC PATCH 15/15] arm64: mm: Set stack size from the kernel command line From: Mostafa Saleh To: linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, linux-mm@kvack.org, linux-hardening@vger.kernel.org, linux-rt-devel@lists.linux.dev Cc: corbet@lwn.net, skhan@linuxfoundation.org, rdunlap@infradead.org, catalin.marinas@arm.com, will@kernel.org, mark.rutland@arm.com, akpm@linux-foundation.org, urezki@gmail.com, mingo@redhat.com, peterz@infradead.org, juri.lelli@redhat.com, vincent.guittot@linaro.org, dietmar.eggemann@arm.com, rostedt@goodmis.org, bsegall@google.com, mgorman@suse.de, vschneid@redhat.com, kprateek.nayak@amd.com, kees@kernel.org, david@kernel.org, ljs@kernel.org, liam@infradead.org, vbabka@kernel.org, rppt@kernel.org, surenb@google.com, mhocko@suse.com, gustavoars@kernel.org, bigeasy@linutronix.de, clrkwllms@kernel.org, Mostafa Saleh Content-Type: text/plain; charset="UTF-8" X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260928_104209_638153_39B22ADB X-CRM114-Status: GOOD ( 18.67 ) X-BeenThere: linux-arm-kernel@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-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Select CONFIG_ARCH_HAS_VARIABLE_STACK_SIZE for arm64 and override arch_vm_stack_pages() to a value set from the command line, this value have the following properties: - Aligned to page size (doesn't need to be a power of 2), so it can be 12kB for example - Min value is chosen to be 8kB - Max value will be the default stack size on arm64 which is used to allocate the VA range for the kernel stack. Signed-off-by: Mostafa Saleh --- .../admin-guide/kernel-parameters.txt | 7 ++++++ arch/arm64/Kconfig | 1 + arch/arm64/include/asm/memory.h | 12 ++++++++++ arch/arm64/kernel/entry.S | 10 +++++--- arch/arm64/kernel/setup.c | 24 +++++++++++++++++++ 5 files changed, 51 insertions(+), 3 deletions(-) diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index 33cd30996e47..e6ef22f01e01 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -2920,6 +2920,13 @@ Kernel parameters keepinitrd [HW,ARM] See retain_initrd. + kernel_stack_pages= + [ARM64,EARLY] + Format: + Number of pages mapped for each task kernel stack. + The virtual area stays THREAD_SIZE and only its top + pages are mapped. + kernelcore= [KNL,X86,PPC,EARLY] Format: nn[KMGTPE] | nn% | "mirror" This parameter specifies the amount of memory usable by diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig index 020fcaf36b1b..5e09ae904e34 100644 --- a/arch/arm64/Kconfig +++ b/arch/arm64/Kconfig @@ -58,6 +58,7 @@ config ARM64 select ARCH_HAS_SYSCALL_WRAPPER select ARCH_HAS_TICK_BROADCAST if GENERIC_CLOCKEVENTS_BROADCAST select ARCH_HAS_ZONE_DMA_SET if EXPERT + select ARCH_HAS_VARIABLE_STACK_SIZE select ARCH_HAVE_ELF_PROT select ARCH_HAVE_NMI_SAFE_CMPXCHG select ARCH_HAVE_TRACE_MMIO_ACCESS diff --git a/arch/arm64/include/asm/memory.h b/arch/arm64/include/asm/memory.h index 4545d9b39bd5..1d300b16032d 100644 --- a/arch/arm64/include/asm/memory.h +++ b/arch/arm64/include/asm/memory.h @@ -113,6 +113,13 @@ #define DIRECT_MAP_PHYSMEM_END __pa(PAGE_END - 1) #define MIN_THREAD_SHIFT (14 + KASAN_THREAD_SHIFT) +#define MIN_KERNEL_STACK_SHIFT (13 + KASAN_THREAD_SHIFT) + +#if (MIN_KERNEL_STACK_SHIFT < PAGE_SHIFT) +#define MIN_KERNEL_STACK_SIZE PAGE_SIZE +#else +#define MIN_KERNEL_STACK_SIZE (UL(1) << MIN_KERNEL_STACK_SHIFT) +#endif /* * VMAP'd stacks are allocated at page granularity, so we must ensure that such @@ -130,6 +137,11 @@ #define THREAD_SIZE (UL(1) << THREAD_SHIFT) +#ifndef __ASSEMBLY__ +extern unsigned long kernel_stack_pages; +#define arch_vm_stack_pages() (kernel_stack_pages) +#endif + #define THREAD_ALIGN THREAD_SIZE #define IRQ_STACK_SIZE THREAD_SIZE diff --git a/arch/arm64/kernel/entry.S b/arch/arm64/kernel/entry.S index ea733b673970..39e68aace0a6 100644 --- a/arch/arm64/kernel/entry.S +++ b/arch/arm64/kernel/entry.S @@ -76,9 +76,13 @@ msr spsel, #0 mov x1, sp msr spsel, #1 - sub x1, x1, x0 - cmp x1, #THREAD_SIZE - b.lo .Lstack_ok\@ + + add x0, x0, #THREAD_SIZE + sub x1, x0, x1 + adr_l x0, kernel_stack_pages + ldr x0, [x0] + cmp x1, x0, lsl #PAGE_SHIFT + b.ls .Lstack_ok\@ /* Check whether we are on the IRQ, SDEI or EFI stacks. */ stp x2, x30, [sp, #-16]! diff --git a/arch/arm64/kernel/setup.c b/arch/arm64/kernel/setup.c index 29c6100f0c50..34559048dcca 100644 --- a/arch/arm64/kernel/setup.c +++ b/arch/arm64/kernel/setup.c @@ -278,6 +278,30 @@ u64 cpu_logical_map(unsigned int cpu) return __cpu_logical_map[cpu]; } +unsigned long kernel_stack_pages __ro_after_init = THREAD_SIZE / PAGE_SIZE; + +static int __init setup_kernel_stack_pages(char *str) +{ + unsigned long min = MIN_KERNEL_STACK_SIZE / PAGE_SIZE; + unsigned long max = THREAD_SIZE / PAGE_SIZE; + unsigned long val; + + if (!str) + return -EINVAL; + + if (kstrtoul(str, 10, &val) || val < min || val > max) { + pr_err("Invalid kernel_stack_pages=%s, should be between %lu and %lu\n", + str, min, max); + return 0; + } + + kernel_stack_pages = val; + pr_info("Kernel stack size set to %lu KiB\n", (val * PAGE_SIZE) / SZ_1K); + + return 0; +} +early_param("kernel_stack_pages", setup_kernel_stack_pages); + void __init __no_sanitize_address setup_arch(char **cmdline_p) { setup_initial_init_mm(_text, _etext, _edata, _end); -- 2.56.0.rc1.315.gc6ed9934b7-goog