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AJvYcCWZgVvLYzEqZC83Q7e+wZuelZ1kEcpjTpOtLvdyUhU14x108ksfe062y0+xPwKTnVGhlnaxz9vV9g==@kvack.org X-Gm-Message-State: AOJu0YyaIIoGwxbrMryRCLZW8vfIXZbwhLV39chOKzpWZZajPh0B7vby KrKwXnF6wUuobb4P2R+nAcv6+dpwTLjoUWFd8pqrs+mb/7RII9GLhKAqr5+kZTs= X-Google-Smtp-Source: AGHT+IGaroc9U1gTQH8oIv9XintQoQrlC7c5FvJNC3/Om1CneZ+0NGXExK3IjmCzNnhwYO6jdZ3JsA== X-Received: by 2002:a05:6870:d60e:b0:288:aed8:c43d with SMTP id 586e51a60fabf-2890cf88610mr4183890fac.15.1729268758143; Fri, 18 Oct 2024 09:25:58 -0700 (PDT) Received: from [192.168.1.128] ([38.175.170.29]) by smtp.gmail.com with ESMTPSA id 46e09a7af769-718195da5f0sm377033a34.60.2024.10.18.09.25.56 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 18 Oct 2024 09:25:57 -0700 (PDT) Message-ID: <3a41a1b5-e9a7-43db-b50e-84d6cc275d10@linuxfoundation.org> Date: Fri, 18 Oct 2024 10:25:55 -0600 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 4/4] selftests/mm: add self tests for guard page feature To: Lorenzo Stoakes Cc: Andrew Morton , Suren Baghdasaryan , "Liam R . Howlett" , Matthew Wilcox , Vlastimil Babka , "Paul E . McKenney" , Jann Horn , David Hildenbrand , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Muchun Song , Richard Henderson , Ivan Kokshaysky , Matt Turner , Thomas Bogendoerfer , "James E . J . Bottomley" , Helge Deller , Chris Zankel , Max Filippov , Arnd Bergmann , linux-alpha@vger.kernel.org, linux-mips@vger.kernel.org, linux-parisc@vger.kernel.org, linux-arch@vger.kernel.org, Shuah Khan , Christian Brauner , linux-kselftest@vger.kernel.org, Sidhartha Kumar , Jeff Xu , Christoph Hellwig , Shuah Khan References: <8b1add3c511effb62d68183cae8a954d8339286c.1729196871.git.lorenzo.stoakes@oracle.com> <1d0bbc60-fda7-4c14-bf02-948bdbf8f029@linuxfoundation.org> <22d386cd-e62f-43f9-905e-2d0881781abe@linuxfoundation.org> <7bbfc635-8d42-4c3d-8808-cb060cd9f658@lucifer.local> Content-Language: en-US From: Shuah Khan In-Reply-To: <7bbfc635-8d42-4c3d-8808-cb060cd9f658@lucifer.local> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam03 X-Rspam-User: X-Rspamd-Queue-Id: 05D744001D X-Stat-Signature: efywfaw5keaup1h1we4m9pikypxb1kas X-HE-Tag: 1729268749-857429 X-HE-Meta: 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 Rr1xrtQv jT6QmlT9axy57DzCKeAJdTnhsyld6a9QMiWpd/Z2ikHAUkQlH7xTvIbMxj84kVIZbOrODQYYjhc+BNlD0J9i/1f0bJLBZAtbORD7NoOLohto+Njphb9vjzoUYPxHWJpN2ct7WbeD/rWdRmJzIy0+UUbu/RM9S+JLm97md4cQWIhf3EsvhoDlVfGdH0BAL1fWvmmOY1Xmgh9M15XyGcny+qifMm5weIlAWyquST9BtRlvJW4aT+j5d/cMJtDCANHuCL6UTAAZev71mAnDMJm+xMqN9/VVet4NXDzDAH8XP6b+wD31HeWvFDNUT5DiThnRJUCui3UnqCDitut6F7dXv+SvZjuF5aSKtIeXjjjQT3zir2+OPCrY7PoTSYQ== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 10/18/24 10:07, Lorenzo Stoakes wrote: > On Fri, Oct 18, 2024 at 09:32:17AM -0600, Shuah Khan wrote: >> On 10/18/24 01:12, Lorenzo Stoakes wrote: >>> On Thu, Oct 17, 2024 at 03:24:49PM -0600, Shuah Khan wrote: >>>> On 10/17/24 14:42, Lorenzo Stoakes wrote: >>>>> Utilise the kselftest harmness to implement tests for the guard page >>>> >>>> Splleing NIT - harmness -> harness >>>> >>>>> implementation. >>>>> >>>>> We start by implement basic tests asserting that guard pages can be >>>> >>>> implmenting? By the way checkpatch will catch spelling stuuf. >>>> Please see comments about warnings below. >>> >>> Thanks. The majority of the checkpatch warnings are invalid so I missed >>> this. Will fix on respin. >>> >>>> >>>>> established (poisoned), cleared (remedied) and that touching poisoned pages >>>>> result in SIGSEGV. We also assert that, in remedying a range, non-poison >>>>> pages remain intact. >>>>> >>>>> We then examine different operations on regions containing poison markers >>>>> behave to ensure correct behaviour: >>>>> >>>>> * Operations over multiple VMAs operate as expected. >>>>> * Invoking MADV_GUARD_POISION / MADV_GUARD_REMEDY via process_madvise() in >>>>> batches works correctly. >>>>> * Ensuring that munmap() correctly tears down poison markers. >>>>> * Using mprotect() to adjust protection bits does not in any way override >>>>> or cause issues with poison markers. >>>>> * Ensuring that splitting and merging VMAs around poison markers causes no >>>>> issue - i.e. that a marker which 'belongs' to one VMA can function just >>>>> as well 'belonging' to another. >>>>> * Ensuring that madvise(..., MADV_DONTNEED) does not remove poison markers. >>>>> * Ensuring that mlock()'ing a range containing poison markers does not >>>>> cause issues. >>>>> * Ensuring that mremap() can move a poisoned range and retain poison >>>>> markers. >>>>> * Ensuring that mremap() can expand a poisoned range and retain poison >>>>> markers (perhaps moving the range). >>>>> * Ensuring that mremap() can shrink a poisoned range and retain poison >>>>> markers. >>>>> * Ensuring that forking a process correctly retains poison markers. >>>>> * Ensuring that forking a VMA with VM_WIPEONFORK set behaves sanely. >>>>> * Ensuring that lazyfree simply clears poison markers. >>>>> * Ensuring that userfaultfd can co-exist with guard pages. >>>>> * Ensuring that madvise(..., MADV_POPULATE_READ) and >>>>> madvise(..., MADV_POPULATE_WRITE) error out when encountering >>>>> poison markers. >>>>> * Ensuring that madvise(..., MADV_COLD) and madvise(..., MADV_PAGEOUT) do >>>>> not remove poison markers. >>>> >>>> Good summary of test. Does the test require root access? >>>> If so does it check and skip appropriately? >>> >>> Thanks and some do, in those cases we skip. >>> >>>> >>>>> >>>>> Signed-off-by: Lorenzo Stoakes >>>>> --- >>>>> tools/testing/selftests/mm/.gitignore | 1 + >>>>> tools/testing/selftests/mm/Makefile | 1 + >>>>> tools/testing/selftests/mm/guard-pages.c | 1168 ++++++++++++++++++++++ >>>>> 3 files changed, 1170 insertions(+) >>>>> create mode 100644 tools/testing/selftests/mm/guard-pages.c >>>>> >>>>> diff --git a/tools/testing/selftests/mm/.gitignore b/tools/testing/selftests/mm/.gitignore >>>>> index 689bbd520296..8f01f4da1c0d 100644 >>>>> --- a/tools/testing/selftests/mm/.gitignore >>>>> +++ b/tools/testing/selftests/mm/.gitignore >>>>> @@ -54,3 +54,4 @@ droppable >>>>> hugetlb_dio >>>>> pkey_sighandler_tests_32 >>>>> pkey_sighandler_tests_64 >>>>> +guard-pages >>>>> diff --git a/tools/testing/selftests/mm/Makefile b/tools/testing/selftests/mm/Makefile >>>>> index 02e1204971b0..15c734d6cfec 100644 >>>>> --- a/tools/testing/selftests/mm/Makefile >>>>> +++ b/tools/testing/selftests/mm/Makefile >>>>> @@ -79,6 +79,7 @@ TEST_GEN_FILES += hugetlb_fault_after_madv >>>>> TEST_GEN_FILES += hugetlb_madv_vs_map >>>>> TEST_GEN_FILES += hugetlb_dio >>>>> TEST_GEN_FILES += droppable >>>>> +TEST_GEN_FILES += guard-pages >>>>> ifneq ($(ARCH),arm64) >>>>> TEST_GEN_FILES += soft-dirty >>>>> diff --git a/tools/testing/selftests/mm/guard-pages.c b/tools/testing/selftests/mm/guard-pages.c >>>>> new file mode 100644 >>>>> index 000000000000..2ab0ff3ba5a0 >>>>> --- /dev/null >>>>> +++ b/tools/testing/selftests/mm/guard-pages.c >>>>> @@ -0,0 +1,1168 @@ >>>>> +// SPDX-License-Identifier: GPL-2.0-or-later >>>>> + >>>>> +#define _GNU_SOURCE >>>>> +#include "../kselftest_harness.h" >>>>> +#include >>>>> +#include >>>>> +#include >>>>> +#include >>>>> +#include >>>>> +#include >>>>> +#include >>>>> +#include >>>>> +#include >>>>> +#include >>>>> +#include >>>>> +#include >>>>> +#include >>>>> +#include >>>>> +#include >>>>> + >>>>> +/* These may not yet be available in the uAPI so define if not. */ >>>>> + >>>>> +#ifndef MADV_GUARD_POISON >>>>> +#define MADV_GUARD_POISON 102 >>>>> +#endif >>>>> + >>>>> +#ifndef MADV_GUARD_UNPOISON >>>>> +#define MADV_GUARD_UNPOISON 103 >>>>> +#endif >>>>> + >>>>> +volatile bool signal_jump_set; >>>> >>>> Can you add a comment about why volatile is needed. >>> >>> I'm not sure it's really necessary, it's completely standard to do this >>> with signal handling and is one of the exceptions to the 'volatile >>> considered harmful' rule. >>> >>>> By the way did you happen to run checkpatck on this. There are >>>> several instances where single statement blocks with braces {} >>>> >>>> I noticed a few and ran checkpatch on your patch. There are >>>> 45 warnings regarding codeing style. >>>> >>>> Please run checkpatch and clean them up so we can avoid followup >>>> checkpatch cleanup patches. >>> >>> No sorry I won't, checkpatch isn't infallible and series trying to 'clean >>> up' things that aren't issues will be a waste of everybody's time. >>> >> >> Sorry - this violates the coding styles and makes it hard to read. >> >> See process/coding-style.rst: >> >> Do not unnecessarily use braces where a single statement will do. >> >> .. code-block:: c >> >> if (condition) >> action(); >> >> and >> >> .. code-block:: c >> >> if (condition) >> do_this(); >> else >> do_that(); >> >> This does not apply if only one branch of a conditional statement is a single >> statement; in the latter case use braces in both branches: >> >> .. code-block:: c >> >> if (condition) { >> do_this(); >> do_that(); >> } else { >> otherwise(); >> } >> >> Also, use braces when a loop contains more than a single simple statement: >> >> .. code-block:: c >> >> while (condition) { >> if (test) >> do_something(); >> } >> >> thanks, >> -- Shuah > > Shuah, quoting coding standards to an experienced kernel developer > (maintainer now) is maybe not the best way to engage here + it may have > been more productive for you to first engage on why it is I'm deviating > here. > This is not the only comment I gave you in this patch and your other patches. thanks, -- Shuah