From patchwork Wed Aug 23 13:13:47 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Alexandru Elisei X-Patchwork-Id: 13362391 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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 1B605EE49A3 for ; Wed, 23 Aug 2023 13:19:33 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235885AbjHWNTd (ORCPT ); Wed, 23 Aug 2023 09:19:33 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51356 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235887AbjHWNSz (ORCPT ); Wed, 23 Aug 2023 09:18:55 -0400 Received: from foss.arm.com (foss.arm.com [217.140.110.172]) by lindbergh.monkeyblade.net (Postfix) with ESMTP id 9E88A1996; Wed, 23 Aug 2023 06:18:23 -0700 (PDT) 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 6AF6E16F8; Wed, 23 Aug 2023 06:18:30 -0700 (PDT) Received: from e121798.cable.virginm.net (unknown [172.31.20.19]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 2CE8A3F740; Wed, 23 Aug 2023 06:17:44 -0700 (PDT) From: Alexandru Elisei To: catalin.marinas@arm.com, will@kernel.org, oliver.upton@linux.dev, maz@kernel.org, james.morse@arm.com, suzuki.poulose@arm.com, yuzenghui@huawei.com, arnd@arndb.de, akpm@linux-foundation.org, 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, bristot@redhat.com, vschneid@redhat.com, mhiramat@kernel.org, rppt@kernel.org, hughd@google.com Cc: pcc@google.com, steven.price@arm.com, anshuman.khandual@arm.com, vincenzo.frascino@arm.com, david@redhat.com, eugenis@google.com, kcc@google.com, hyesoo.yu@samsung.com, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, kvmarm@lists.linux.dev, linux-fsdevel@vger.kernel.org, linux-arch@vger.kernel.org, linux-mm@kvack.org, linux-trace-kernel@vger.kernel.org Subject: [PATCH RFC 34/37] arm64: mte: Handle fatal signal in reserve_metadata_storage() Date: Wed, 23 Aug 2023 14:13:47 +0100 Message-Id: <20230823131350.114942-35-alexandru.elisei@arm.com> X-Mailer: git-send-email 2.34.1 In-Reply-To: <20230823131350.114942-1-alexandru.elisei@arm.com> References: <20230823131350.114942-1-alexandru.elisei@arm.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-trace-kernel@vger.kernel.org As long as a fatal signal is pending, alloc_contig_range() will fail with -EINTR. This makes it impossible for tag storage allocation to succeed, and the page allocator will print an OOM splat. The process is going to be killed, so return 0 (success) from reserve_metadata_storage() to allow the page allocator to make progress. set_pte_at() will map it with PAGE_METADATA_NONE and subsequent accesses from different threads will trap until the signal is delivered. Signed-off-by: Alexandru Elisei --- arch/arm64/kernel/mte_tag_storage.c | 17 +++++++++++++++++ arch/arm64/mm/fault.c | 23 +++++++++++++++++++++++ 2 files changed, 40 insertions(+) diff --git a/arch/arm64/kernel/mte_tag_storage.c b/arch/arm64/kernel/mte_tag_storage.c index ce378f45f866..1ccbcc144979 100644 --- a/arch/arm64/kernel/mte_tag_storage.c +++ b/arch/arm64/kernel/mte_tag_storage.c @@ -556,6 +556,23 @@ int reserve_metadata_storage(struct page *page, int order, gfp_t gfp) break; } + /* + * alloc_contig_range() returns -EINTR from + * __alloc_contig_migrate_range() if a fatal signal is pending. + * As long as the signal hasn't been handled, it is impossible + * to reserve tag storage for any page. Treat it as an error, + * but return 0 so the page allocator can make forward progress, + * instead of printing an OOM splat. + * + * The tagged page with missing tag storage will be mapped with + * PAGE_METADATA_NONE in set_pte_at(), and accesses until the + * signal is delivered will cause a fault. + */ + if (ret == -EINTR) { + ret = 0; + goto out_error; + } + if (ret) goto out_error; diff --git a/arch/arm64/mm/fault.c b/arch/arm64/mm/fault.c index 7e2dcf5e3baf..64c5d77664c8 100644 --- a/arch/arm64/mm/fault.c +++ b/arch/arm64/mm/fault.c @@ -37,7 +37,9 @@ #include #include #include +#include #include +#include #include #include #include @@ -936,10 +938,31 @@ void do_debug_exception(unsigned long addr_if_watchpoint, unsigned long esr, } NOKPROBE_SYMBOL(do_debug_exception); +static void save_zero_page_tags(struct page *page) +{ + void *tags; + + clear_page(page_address(page)); + + tags = kmalloc(MTE_PAGE_TAG_STORAGE_SIZE, GFP_KERNEL | __GFP_ZERO); + if (WARN_ON(!tags)) + return; + + if (WARN_ON(mte_save_page_tags_by_pfn(page, tags))) + mte_free_tags_mem(tags); +} + void tag_clear_highpage(struct page *page) { /* Tag storage pages cannot be tagged. */ WARN_ON_ONCE(is_migrate_metadata_page(page)); + + if (metadata_storage_enabled() && + unlikely(!page_tag_storage_reserved(page))) { + save_zero_page_tags(page); + return; + } + /* Newly allocated page, shouldn't have been tagged yet */ WARN_ON_ONCE(!try_page_mte_tagging(page)); mte_zero_clear_page_tags(page_address(page));