From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pf1-f198.google.com (mail-pf1-f198.google.com [209.85.210.198]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6AFE63803E8 for ; Thu, 10 Sep 2026 02:34:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.210.198 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789007657; cv=none; b=e0mIz2K2m0743Hsky3dpt44EsptkUDj84JPZQht+R1ETnD2uNt/h43KccBiu/jV55UNZnHrKwvvv0eWKAnSoLgBoi7G0yB3TyDd64Xd8gdh+3Nt5XDtZ7L/aA5cPGeN+Sc5yP/wgOIRNTtEZmLkHg7/Kuo7SMd8GWB9+1xcIxPk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1789007657; c=relaxed/simple; bh=sNUsnOz3881yNGNwfqwE8niZ2cr7QsyszKIYdVRvJ5o=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=UK/lFm33fRk8aZUKHTjbjIUHP/D2708ESslBpG/GPnNCSNBe3lyTmxGypvbJIoUzbCMKss0YVaSvw9wONmGMCppFkcETELGQcfiYBrz8IafxoYQYIZ4lIjW1GnxrPMSndzf6mP4ozJSpUR6v5tgb2Cz2nwQmjM0QCiAJxgc3UYY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--jthoughton.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=a2Ji4Vbm; arc=none smtp.client-ip=209.85.210.198 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--jthoughton.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="a2Ji4Vbm" Received: by mail-pf1-f198.google.com with SMTP id d2e1a72fcca58-848568a6f62so6489779b3a.0 for ; Wed, 09 Sep 2026 19:34:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20251104; t=1789007656; x=1789612456; darn=vger.kernel.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=HN8r1OTKJ5otXSKxSHXxiuMnoDfjm4NiMKL8K3DQtoE=; b=a2Ji4VbmDnPBH+46m78m/HnU4ic4KWA0XBYW0HXyYQ7fmcr9QSpcgbd98pesF0uZJO j8LslOrjcW0fXEmifeyEBk5ldSJM8CTfKF8aOeB6vzKVXHKceFWDGocl8p7bOfAcwYh1 e0Ww6I6EYGTIVViL/9RfCdE+Nvq6ZdR2P2m0IqDcRve9XqPq8RGUjw+K9b0+UPrHuXKp r2g57g1xvTnmu8/UGtUPHqSsaXpqNd13m5wFNxnf01y6jp/L+yeVb1topyJxn7Iw+J5x zJ08yzIfFcj381Dn1AzulG03KDWdKY40N+Mnp/X3A28LNdCyLarJy7byNNd8q3+g8Fjm pxmQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1789007656; x=1789612456; 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=HN8r1OTKJ5otXSKxSHXxiuMnoDfjm4NiMKL8K3DQtoE=; b=IP/d6pc61bsZ5FK4xPsfsx6br4q0OXRiRyCOayB+GzSf/h9TJ0OAEhxAEYFwmA/rOj Q52eVMBgrBd34UmvUQYDMgfyxeHZN1wIHfo5NRzG8FyP58UiOEd11RrxkyOLNkAtIJtA bQPOz7y1sztEtY6S2b2rDm1pzSeab3cQTHw3Eyl6RhDjYXaR9PrYvpwKZUkfCKaQqekl shNYuy9vkrZqVmJ9oWTbes/p1ruPaRkV5TaQuETixVvsEvAhIbA+cLcka+/5pyNFTFWc 2YLekbasyhvS8s3VJOSYxWa5xUUMzV8iGGgj5vwfmZ/CtsIELdbwaS8B4MhJiUnqx3HV Uk0w== X-Forwarded-Encrypted: i=1; AKwUvByMrsxDnuAIAVRpDcVK99J6Mm6HiGzaD2Z4uvdgWsOLiSr74LEUp1xeCy983bu1dLK686X9mOuHc/p4CHE=@vger.kernel.org X-Gm-Message-State: AFuF++l4XU2wHEtuuTd0kR3b+7FK884QErwSisCLvR1AzwHpSEGVi9Nn ZMo4B/YX8YIiJFQsH84MrXQXebOxUZ2SJOd6rwk+UM2oOBvG6zczHQ+nl7JtVDW0READV/Em5Lr YEJ5h+K/ZdR+bkaWTdYthww== X-Received: from pfbfy14.prod.google.com ([2002:a05:6a00:828e:b0:868:6325:1e0f]) (user=jthoughton job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6a00:17a6:b0:857:7384:b5fd with SMTP id d2e1a72fcca58-86948e29d5amr3444561b3a.25.1789007654727; Wed, 09 Sep 2026 19:34:14 -0700 (PDT) Date: Thu, 10 Sep 2026 02:34:11 +0000 In-Reply-To: <20260910023411.514987-1-jthoughton@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20260910023411.514987-1-jthoughton@google.com> X-Mailer: git-send-email 2.55.0.1007.g17ff1f9808-goog Message-ID: <20260910023411.514987-2-jthoughton@google.com> Subject: [PATCH v3 2/2] mm: selftests: Adjust the MADV_COLLAPSE uffd-minor selftests From: James Houghton To: Andrew Morton Cc: David Hildenbrand , Lorenzo Stoakes , Zi Yan , Baolin Wang , liam@infradead.org, Nico Pache , Ryan Roberts , Dev Jain , Barry Song , Lance Yang , Usama Arif , Yang Shi , zokeefe@google.com, hughd@google.com, Kiryl Shutsemau , jthoughton@google.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset="UTF-8" The behavior of MADV_COLLAPSE with uffd-minor VMAs has changed: MADV_COLLAPSE will no longer install PTEs where none existed before. Update the selftest to demonstrate this new behavior. On an unpatched kernel, the test will hit "unexpected memory contents after collapse". If the selftest is left unpatched but the kernel is patched, the selftest will SKIP when it gets EINVAL back from MADV_COLLAPSE. Signed-off-by: James Houghton --- tools/testing/selftests/mm/uffd-unit-tests.c | 75 ++++++++++++++++++-- 1 file changed, 68 insertions(+), 7 deletions(-) diff --git a/tools/testing/selftests/mm/uffd-unit-tests.c b/tools/testing/selftests/mm/uffd-unit-tests.c index ef9b3956bdcf..6f2360f9b75d 100644 --- a/tools/testing/selftests/mm/uffd-unit-tests.c +++ b/tools/testing/selftests/mm/uffd-unit-tests.c @@ -518,19 +518,34 @@ static void uffd_wp_fork_pin_with_event_test(uffd_global_test_opts_t *gopts, uff uffd_wp_fork_pin_test_common(gopts, args, true); } -static void check_memory_contents(uffd_global_test_opts_t *gopts, char *p) +static int __check_memory_contents(unsigned long offset, + unsigned long nr_pages, + uffd_global_test_opts_t *gopts, + char *p) { unsigned long i, j; uint8_t expected_byte; - for (i = 0; i < gopts->nr_pages; ++i) { + if (nr_pages + offset < nr_pages) + err("overflow in memory check"); + if (nr_pages + offset > gopts->nr_pages) + err("out of bounds memory check"); + + for (i = offset; i < offset + nr_pages; ++i) { expected_byte = ~((uint8_t)(i % ((uint8_t)-1))); for (j = 0; j < gopts->page_size; j++) { uint8_t v = *(uint8_t *)(p + (i * gopts->page_size) + j); if (v != expected_byte) - err("unexpected page contents"); + return 1; } } + + return 0; +} + +static int check_memory_contents(uffd_global_test_opts_t *gopts, char *p) +{ + return __check_memory_contents(0, gopts->nr_pages, gopts, p); } static void uffd_minor_test_common(uffd_global_test_opts_t *gopts, bool test_collapse, bool test_wp) @@ -539,6 +554,8 @@ static void uffd_minor_test_common(uffd_global_test_opts_t *gopts, bool test_col pthread_t uffd_mon; char c = '\0'; struct uffd_args args = { 0 }; + unsigned long checked = 0; + bool bad_contents; args.gopts = gopts; /* @@ -564,24 +581,65 @@ static void uffd_minor_test_common(uffd_global_test_opts_t *gopts, bool test_col if (pthread_create(&uffd_mon, NULL, uffd_poll_thread, &args)) err("uffd_poll_thread create"); + if (test_collapse) { + /* + * Read just a single page and try collapsing. The collapse + * should either be rejected or be a no-op. + */ + if (__check_memory_contents(0, 1, gopts, gopts->area_dst_alias)) + err("unexpected memory contents before collapse"); + + /* MADV_COLLAPSE might return EINVAL for uffd-minor VMAs. */ + madvise(gopts->area_dst_alias, gopts->nr_pages * gopts->page_size, + MADV_COLLAPSE); + /* + * If the above collapse mapped pages that were not explicitly + * CONTINUE'd, the below __check_memory_contents() will not + * fault on some pages, resulting in incorrect contents. The + * PTE for the first page may get retracted, so avoid checking + * that page, as we might take a second fault, flipping the + * contents a second time. + */ + checked = 1; + } + /* * Read each of the pages back using the UFFD-registered mapping. We * expect that the first time we touch a page, it will result in a minor * fault. uffd_poll_thread will resolve the fault by bit-flipping the * page's contents, and then issuing a CONTINUE ioctl. */ - check_memory_contents(gopts, gopts->area_dst_alias); + bad_contents = !!__check_memory_contents(checked, gopts->nr_pages - checked, + gopts, gopts->area_dst_alias); if (write(gopts->pipefd[1], &c, sizeof(c)) != sizeof(c)) err("pipe write"); if (pthread_join(uffd_mon, NULL)) err("join() failed"); + if (bad_contents && test_collapse) { + uffd_test_fail("unexpected memory contents after collapse"); + return; + } + + if (bad_contents) { + uffd_test_fail("unexpected memory contents"); + return; + } + if (test_collapse) { + /* + * MADV_COLLAPSE will fail unless userfaultfd-minor is + * unregistered. + */ + if (uffd_unregister(gopts->uffd, gopts->area_dst_alias, + gopts->nr_pages * gopts->page_size)) + err("uffd_unregister before MADV_COLLAPSE failed"); + + /* MADV_COLLAPSE should succeed with userfaultfd unregistered. */ if (madvise(gopts->area_dst_alias, gopts->nr_pages * gopts->page_size, MADV_COLLAPSE)) { - /* It's fine to fail for this one... */ - uffd_test_skip("MADV_COLLAPSE failed"); + uffd_test_fail("MADV_COLLAPSE failed"); return; } @@ -593,7 +651,10 @@ static void uffd_minor_test_common(uffd_global_test_opts_t *gopts, bool test_col * This won't cause uffd-fault - it purely just makes sure there * was no corruption. */ - check_memory_contents(gopts, gopts->area_dst_alias); + if (check_memory_contents(gopts, gopts->area_dst_alias)) { + uffd_test_fail("unexpected memory contents"); + return; + } } if (args.missing_faults != 0 || args.minor_faults != gopts->nr_pages) -- 2.55.0.1007.g17ff1f9808-goog