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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 98FE3C98321 for ; Thu, 24 Sep 2026 19:25:24 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 9FF756B0098; Thu, 24 Sep 2026 15:25:23 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 98A0A6B009B; Thu, 24 Sep 2026 15:25:23 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 852446B009D; Thu, 24 Sep 2026 15:25:23 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 4979B6B0098 for ; Thu, 24 Sep 2026 15:25:23 -0400 (EDT) Received: from smtpin03.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay03.hostedemail.com (Postfix) with ESMTP id BA435A0451 for ; Thu, 24 Sep 2026 19:25:22 +0000 (UTC) X-FDA: 85249634484.03.B16E614 Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf15.hostedemail.com (Postfix) with ESMTP id DDE58A0006 for ; Thu, 24 Sep 2026 19:25:20 +0000 (UTC) Authentication-Results: imf15.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=E2pUprhT; spf=pass (imf15.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1790277921; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=t2tvt0mN+rfQIn0XcEUNtP28LzckUHtZkO5l64gDOok=; b=qlpW9smmRREwc/BMxoF4Sz6NQ8RJS7d5xynwzukWMpr/gA0aTky0lkZASO+LQ5vNp/CmQz v49wPwnCdEmrA/PBOvwITPJtRoCp8tn92psDDqqiOxjsBY2rlpMllvpPZUMy1QVSrJumKD Ttz/haalBOdvVK3wALGzPwsUhX2AluM= ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1790277921; b=TQ4X4rFo7DhU705ggHHHJSsJ2zS3Pua5JbsUa+huA4grEkndXA0xlKhNamUSZFeTjg2o0U lhCNm8sur7JNtalwphOBv/ZXwwgYzPRVye573DwhHYxnmdXQ0TmKX32RcvRLjfxKpaR1nc k6CoOI2E2apzf9nUhnUplAH87O08WQs= ARC-Authentication-Results: i=1; imf15.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=E2pUprhT; spf=pass (imf15.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 0B63741795; Thu, 24 Sep 2026 19:25:20 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id C02C01F00893; Thu, 24 Sep 2026 19:25:16 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1790277919; bh=t2tvt0mN+rfQIn0XcEUNtP28LzckUHtZkO5l64gDOok=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=E2pUprhT9/xwQ9JjC3QDHZ6WqHqRvyWkQ/fT1SA+mJGJ9Sscsom0u+SS0svWOgisH sV2vxa8TOvmlrSnsAYnQJr8BEE/wmhpasXR4FfFuEhaOMO1XJrREILb1bqKgT0mjio JgC1sT1fMupQp75dEFBL4vjEl0gyZ5cMv8e/VXVkTFnACzYMADFFnYEIUW7Me3vxSc 3e+BYAyaEqTReMGpedv1kTZjQBnMY3mjhTVUynxRiOR3pdmGBY866Mwo17cVmQDFdH e0uKVSmK7/mDX9uwSrAKwea1RIZJeVTFuYc5aKQoH5RJnV4c2B/JfnurcivxoUo5VM 1B0UJ7z0GKODw== Message-ID: <2c1def7b-aceb-45c7-9cf0-8518ef26dff3@kernel.org> Date: Thu, 24 Sep 2026 21:25:07 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] selftests/mm: fix mlock2 errno handling and false PASS on ENOSYS To: Park Tae-sun , Andrew Morton , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Shuah Khan , Brendan Jackman , Muhammad Usama Anjum Cc: linux-mm@kvack.org, linux-kselftest@vger.kernel.org, linux-kernel@vger.kernel.org References: <20260923-selftests-mm-mlock2-fix-v1-1-750b627854c6@dgu.ac.kr> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: <20260923-selftests-mm-mlock2-fix-v1-1-750b627854c6@dgu.ac.kr> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: DDE58A0006 X-Stat-Signature: rgqzwwngpj3qzdr7cg6ye8ch1sfbw4j6 X-HE-Tag: 1790277920-172332 X-HE-Meta: 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 CKdoMK5B XZmUyPMb+xDveL3a7aOdbToOB9VbydOo7qkNdL7apwpar1+aWBZ7TwgwnQDDoYICZe+eds3UAIksM4nTVeGUe5R5fe5J6yrFTRlYqwci415VV3M5kY+uYZRB+FW8QhitIsoMXMU6BuLJg7+LZUWBNZ5LtQ6OVNSI3wDIaIClVKpNCP2pWoZpxZaYzwjpcvHUyzQU1hvPuhXmxbSkeTYfGaQjYLUTmF2Rii4SYtsKEBLMolOC22EOd8P8HfuWegBhjjz0C6OUSxxIQnCZSJSF2xedt7ORnHOIRsy6G Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 9/23/26 11:26, Park Tae-sun wrote: > While inspecting selftests/mm syscall wrappers, I noticed that mlock2_() > in mlock2.h handles the syscall return value differently from other > wrappers: > > int ret = syscall(__NR_mlock2, start, len, flags); > if (ret) { > errno = ret; > return -1; > } > > Commit 1ddae9d67ee1 ("selftests/mm/mlock: print error on failure") > introduced this intending to make mlock2_() behave like libc by setting > errno and returning -1. However, glibc syscall(2) already returns -1 on > failure and sets positive errno. Assigning "errno = ret;" overwrites > errno with -1. > > To verify this, mlock2 was disabled in the kernel (via sys_ni_syscall) to > return -ENOSYS. Testing revealed two interrelated defects: > > 1. In the unmodified test, mlock2_() clobbered errno to -1. The check > "if (ret && errno == ENOSYS)" in main() was bypassed, resulting in an > immediate crash in the first test: > > ~ # ./mlock2-tests > TAP version 13 > 1..15 > Bail out! mlock2(0): Unknown error -1 > # Planned tests != run tests (15 != 0) > # Totals: pass:0 fail:0 xfail:0 xpass:0 skip:0 error:0 > (exit code: 1 - FAIL) > > 2. After restoring mlock2_() to directly return syscall(), errno correctly > retained ENOSYS (38), entering the ENOSYS check in main(). However, it > then called ksft_finished(): > > ~ # ./mlock2-tests > TAP version 13 > # Totals: pass:0 fail:0 xfail:0 xpass:0 skip:0 error:0 > ~ # echo $? > 0 > > Because ksft_set_plan() had not been called yet (ksft_plan == 0) and > zero tests ran (ksft_pass == 0), ksft_finished() evaluated 0 == 0 as > success and exited with KSFT_PASS (code 0) without any TAP skip header. > > Fix both issues by: > 1. Returning the syscall() result directly in mlock2_() so that errno is > preserved. > 2. Calling ksft_exit_skip() on ENOSYS so unsupported kernels report a TAP > skip ("1..0 # SKIP ...") and exit with KSFT_SKIP (code 4). > > Verification on the mlock2-disabled kernel: > > ~ # ./mlock2-tests > TAP version 13 > 1..0 # SKIP mlock2() syscall is not supported > ~ # echo $? > 4 > > Re-enabling mlock2 in the kernel confirmed all 15 tests pass cleanly: > > ~ # ./mlock2-tests > TAP version 13 > 1..15 > ok 1 test_mlock_lock: Locked > ... > ok 15 test_mlockall_future_droppable: droppable memory not locked > # Totals: pass:15 fail:0 xfail:0 xpass:0 skip:0 error:0 > ~ # echo $? > 0 > > Fixes: 1ddae9d67ee1 ("selftests/mm/mlock: print error on failure") > Fixes: 65c89684896d ("selftests/mm: mlock2-tests: conform test to TAP format output") > Signed-off-by: Park Tae-sun > --- Acked-by: David Hildenbrand (Arm) -- Cheers, David