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 4EF93CA5FA2 for ; Mon, 28 Sep 2026 17:43:22 +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=7RH6hoqk7EsLMc9nVwpPE+90gab30BNeM/1qTHEr8Y8=; b=D28kuroC4pJHh2qYtcvYpWgcl8 dfTONowMZZbD+qxYJS3Nd16pnMfWIPSCpziWO1JUGuRoG4Qmes7s6Hinrsqpw8yRKdT8phv16CaPv bubd/Ke8EgPaZRX7luh71WHvQkcoVj3YXWYkEsbxU1TOjPCjKqFbF2G2bWljh8lWVmV+30j8PpyG5 Ja/FFbSz33IiyA6RSGhd5+KSTIaHi36QsPc3Yj25kOdaKy1sFUayLsvCxu9PLI06f07tk4Ezu2GSQ gyBVaOfnQe6lv0a1LAdl3MDJTxFrYW+jDOb48aAsWCUR+67CDRA5BunWh0ivr7s98hkJ2E4yoGD1l 0FOqMbKQ==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1xBFNh-00000001DP4-3VNd; Mon, 28 Sep 2026 17:43:13 +0000 Received: from mail-wr1-x445.google.com ([2a00:1450:4864:20::445]) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1xBFMc-00000001Chq-1qAa for linux-arm-kernel@lists.infradead.org; Mon, 28 Sep 2026 17:42:08 +0000 Received: by mail-wr1-x445.google.com with SMTP id ffacd0b85a97d-4870142fd5cso1672792f8f.0 for ; Mon, 28 Sep 2026 10:42:05 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1790617324; x=1791222124; 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=7RH6hoqk7EsLMc9nVwpPE+90gab30BNeM/1qTHEr8Y8=; b=PEKR2uyegVfKaIwWeGpZ9AfmjdhNbWMg96bfwkArgSOxF/f6q9aG26NuBmnaInvjKF IbOySxmje/Ng16ae6fD+uPJXNsm00wo3/YXVTIgpz3PPbvck9tcPpbceZ1ARdf8fT2fC AnEQKm3BZ2CD14mNgjVGcaLCQnDR6iLba7KGgywEfviM8TF/Qo5x36Qcr7FDmkzG4cXh yK59fnVa7VrhdsgRVNp5m0+gq/wSi+8VGuFUTYOj7XDptihOdmijF3v4v16N6RsB3+dG QwOg5yamQfv0fq6ylTfKBnsCUwflsBw2BCnbu8mzfxJH4R6IMrBnAcZJft4SV2WxoCEV RzyQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20260707; t=1790617324; x=1791222124; 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=7RH6hoqk7EsLMc9nVwpPE+90gab30BNeM/1qTHEr8Y8=; b=VLePsStRq9Esrp7/pfN3TUEMQn2qR7nupNrRz65o+9Gsz0wRA5J0SrG6dx4hbYd4G0 TfC8DuejkuILfeLjJ53kHCHiPCEYu0CaImc/eTlqg646JQXIEdT7OPL06yTLTbI/WIrZ 1ffhjrH8o2xWLJymHQtADoc93oWKl0zCNxdOfl5E4q6K381N5JhPJNHXsOKbhNI+zEC7 xPuRlYB+FBsQUY88dbEqWI7stIg7WjLLl8tv1CvfYC0dd2QliLUIvRnCqSXoTJtEkpUv Ebsl9w+3tUEUObtaITvZpeVZ5wpqOqoJh3U13o8ZmkfsdsVkBBUEiV6FlYAltCS6IFhc pNNQ== X-Forwarded-Encrypted: i=1; AKwUvBzkKfWqTssi2NutwldPojwHCpCVjbqUHIopIKAPcHNEMRG12fNPw7n/Kl/iiNl/rACquV6SYoUMXtYDs9YuLliA@lists.infradead.org X-Gm-Message-State: AFuF++kAILEDTlCoC7PKoBtCG7NKfvrf66fy/odCYV8/I/ce+JgVQWBq 6zLaoPv7edc77yCoPN1XfIcDIwiRDxMVUWbjopMQk12TZwNqQE+7bUxpiljP8uB+SkaqjiEq+Td t/yHLlio8a19TTA== X-Received: from wmon22.prod.google.com ([2002:a05:600c:4656:b0:49e:7ce3:41f9]) (user=smostafa job=prod-delivery.src-stubby-dispatcher) by 2002:a05:600c:a15:b0:49f:e444:cc4c with SMTP id 5b1f17b1804b1-49ff06bdb00mr183042675e9.12.1790617324124; Mon, 28 Sep 2026 10:42:04 -0700 (PDT) Date: Mon, 28 Sep 2026 17:41:20 +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: <20260928174122.3380703-14-smostafa@google.com> Subject: [RFC PATCH 13/15] fork: Implement partial VMAP stack allocation 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 , Pasha Tatashin , Linus Walleij , David Stevens Content-Type: text/plain; charset="UTF-8" X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260928_104206_619552_8775B5B3 X-CRM114-Status: GOOD ( 17.98 ) 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 When CONFIG_ARCH_HAS_VARIABLE_STACK_SIZE is enabled, architectures can allocate a VMAP stack that is smaller than the full THREAD_SIZE. This introduces arch abstraction arch_vm_stack_pages() which defaults to THREAD_SIZE / PAGE_SIZE. During stack allocation, the kernel will map only the requested number of pages at the top of the THREAD_SIZE virtual area (as the stack grows down), leaving the bottom unmapped. This saves memory while retaining the same virtual alignment and guard page overflow detection characteristics. Signed-off-by: Pasha Tatashin [Rebased, used vm_area->nr_pages directly in one instance] [Depends on !PREEMPT_RT] Signed-off-by: Linus Walleij [Fix races around accounting] [Use GFP_ATOMIC when executing in the scheduler] [Depend on INIT_STACK_ALL_* config] [Fix bugs in some error paths and edge cases] [Don't cache partially faulted stacks] [Added out-var to tell if address is on target stack] Signed-off-by: David Stevens [Remove dynamic stack related code, and update commit message] [Fix memory leak in error path of alloc_vmap_stack()] and use VM_UNINITIALIZED before installing the pages] Signed-off-by: Mostafa Saleh --- include/linux/thread_info.h | 8 +++++ kernel/fork.c | 68 +++++++++++++++++++++++++++++++++++++ 2 files changed, 76 insertions(+) diff --git a/include/linux/thread_info.h b/include/linux/thread_info.h index 307b8390fc67..8f052ec82402 100644 --- a/include/linux/thread_info.h +++ b/include/linux/thread_info.h @@ -92,6 +92,14 @@ static inline long set_restart_fn(struct restart_block *restart, #define THREAD_ALIGN THREAD_SIZE #endif +/* + * Arch selecting CONFIG_ARCH_HAS_VARIABLE_STACK_SIZE should override this + * with kernel stack size. + */ +#ifndef arch_vm_stack_pages +#define arch_vm_stack_pages() (THREAD_SIZE / PAGE_SIZE) +#endif + #define THREADINFO_GFP (GFP_KERNEL_ACCOUNT | __GFP_ZERO | __GFP_SKIP_KASAN) /* diff --git a/kernel/fork.c b/kernel/fork.c index ca8e68882316..66fbad3d4cbd 100644 --- a/kernel/fork.c +++ b/kernel/fork.c @@ -119,6 +119,8 @@ /* For dup_mmap(). */ #include "../mm/internal.h" +/* For clear_vm_uninitialized_flag(). */ +#include "../mm/vmalloc.h" #include @@ -272,6 +274,71 @@ static bool try_release_thread_stack_to_cache(struct vm_struct *vm_area) return false; } +#ifdef CONFIG_ARCH_HAS_VARIABLE_STACK_SIZE +static struct vm_struct *alloc_vmap_stack(int node) +{ + gfp_t gfp = GFP_VMAP_STACK; + unsigned long addr, end; + struct vm_struct *vm_area; + int err, i; + + vm_area = get_vm_area_node(THREAD_SIZE, THREAD_ALIGN, + VM_MAP | VM_UNINITIALIZED, node, gfp, + __builtin_return_address(0)); + if (!vm_area) + return NULL; + + vm_area->pages = kmalloc_node(sizeof(void *) * (THREAD_SIZE >> PAGE_SHIFT), + gfp, node); + if (!vm_area->pages) + goto cleanup_err; + + for (i = 0; i < arch_vm_stack_pages(); i++) { + vm_area->pages[i] = alloc_pages_node(node, gfp, 0); + if (!vm_area->pages[i]) + goto cleanup_err; + vm_area->nr_pages++; + mod_lruvec_page_state(vm_area->pages[i], NR_VMALLOC, 1); + } + + end = (unsigned long)kasan_reset_tag(vm_area->addr) + THREAD_SIZE; + addr = end - (arch_vm_stack_pages() * PAGE_SIZE); + + err = vmap_pages_range(addr, end, PAGE_KERNEL, vm_area->pages, PAGE_SHIFT); + if (err) + goto cleanup_err; + + clear_vm_uninitialized_flag(vm_area); + return vm_area; + +cleanup_err: + remove_vm_area(vm_area->addr); + if (vm_area->pages) { + for (i = 0; i < vm_area->nr_pages; i++) { + mod_lruvec_page_state(vm_area->pages[i], NR_VMALLOC, -1); + __free_page(vm_area->pages[i]); + } + kfree(vm_area->pages); + } + kfree(vm_area); + return NULL; +} + +static void free_vmap_stack(struct vm_struct *vm_area) +{ + int i; + + remove_vm_area(vm_area->addr); + + for (i = 0; i < vm_area->nr_pages; i++) { + mod_lruvec_page_state(vm_area->pages[i], NR_VMALLOC, -1); + __free_page(vm_area->pages[i]); + } + + kfree(vm_area->pages); + kfree(vm_area); +} +#else static inline struct vm_struct *alloc_vmap_stack(int node) { void *stack; @@ -286,6 +353,7 @@ static inline void free_vmap_stack(struct vm_struct *vm_area) { vfree(vm_area->addr); } +#endif /* CONFIG_ARCH_HAS_VARIABLE_STACK_SIZE */ static void thread_stack_free_work(struct work_struct *work) { -- 2.56.0.rc1.315.gc6ed9934b7-goog