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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> Content-Language: en-US From: Shuah Khan In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit 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