kernel/tools/testing/selftests/mm/uffd-unit-tests.c, branch linux-rolling-stable

selftests/mm: fix thread state check in uffd-unit-tests

2025-12-23T19:23:14Z

In the thread_state_get() function, the logic to find the thread's state character was using `sizeof(header) - 1` to calculate the offset from the "State:\t" string. The `header` variable is a `const char *` pointer. `sizeof()` on a pointer returns the size of the pointer itself, not the length of the string literal it points to. This makes the code's behavior dependent on the architecture's pointer size. This bug was identified on a 32-bit ARM build (`gsi_tv_arm`) for Android, running on an ARMv8-based device, compiled with Clang 19.0.1. On this 32-bit architecture, `sizeof(char *)` is 4. The expression `sizeof(header) - 1` resulted in an incorrect offset of 3, causing the test to read the wrong character from `/proc/[tid]/status` and fail. On 64-bit architectures, `sizeof(char *)` is 8, so the expression coincidentally evaluates to 7, which matches the length of "State:\t". This is why the bug likely remained hidden on 64-bit builds. To fix this and make the code portable and correct across all architectures, this patch replaces `sizeof(header) - 1` with `strlen(header)`. The `strlen()` function correctly calculates the string's length, ensuring the correct offset is always used. Link: https://lkml.kernel.org/r/20251210091408.3781445-1-wakel@google.com Fixes: f60b6634cd88 ("mm/selftests: add a test to verify mmap_changing race with -EAGAIN") Signed-off-by: Wake Liu Acked-by: Peter Xu Reviewed-by: Mike Rapoport (Microsoft) Cc: Bill Wendling Cc: Justin Stitt Cc: Liam Howlett Cc: Lorenzo Stoakes Cc: Michal Hocko Cc: Nathan Chancellor Cc: Shuah Khan Cc: Suren Baghdasaryan Cc: Vlastimil Babka Cc: Signed-off-by: Andrew Morton

selftests/mm/uffd: initialize char variable to Null

2025-11-29T18:41:09Z

In "uffd-stress.c" & "uffd-unit-tests.c". address of char variable having garbage value (uninitialized) is passed to 'write' syscall triggers warning. uffd-stress.c:246:39: warning: variable 'c' is uninitialized when passed as a const pointer argument here [-Wuninitialized-const-pointer] uffd-unit-tests.c:581:31: warning: variable 'c' is uninitialized when passed as a const pointer argument here [-Wuninitialized-const-pointer] so the fix is to assign char variable to '\0' to prevent writing of garbage value. Link: https://lkml.kernel.org/r/20251126160830.52124-1-ankitkhushwaha.linux@gmail.com Signed-off-by: Ankit Khushwaha Reviewed-by: Mike Rapoport (Microsoft) Cc: Bill Wendling Cc: Justin Stitt Cc: Liam Howlett Cc: Lorenzo Stoakes Cc: Michal Hocko Cc: Nathan Chancellor Cc: Peter Xu Cc: Shuah Khan Cc: Suren Baghdasaryan Cc: Vlastimil Babka Signed-off-by: Andrew Morton

selftests/mm: fix division-by-zero in uffd-unit-tests

2025-11-24T22:25:17Z

Commit 4dfd4bba8578 ("selftests/mm/uffd: refactor non-composite global vars into struct") moved some of the operations previously implemented in uffd_setup_environment() earlier in the main test loop. The calculation of nr_pages, which involves a division by page_size, now occurs before checking that default_huge_page_size() returns a non-zero This leads to a division-by-zero error on systems with !CONFIG_HUGETLB. Fix this by relocating the non-zero page_size check before the nr_pages calculation, as it was originally implemented. Link: https://lkml.kernel.org/r/20251113034623.3127012-1-cmllamas@google.com Fixes: 4dfd4bba8578 ("selftests/mm/uffd: refactor non-composite global vars into struct") Signed-off-by: Carlos Llamas Acked-by: David Hildenbrand (Red Hat) Reviewed-by: Lorenzo Stoakes Reviewed-by: Mike Rapoport (Microsoft) Reviewed-by: Ujwal Kundur Cc: Brendan Jackman Cc: Liam Howlett Cc: Michal Hocko Cc: Peter Xu Cc: Shuah Khan Cc: Suren Baghdasaryan Cc: Vlastimil Babka Cc: Signed-off-by: Andrew Morton

selftests/mm/uffd: refactor non-composite global vars into struct

2025-09-21T21:21:59Z

Refactor macros and non-composite global variable definitions into a struct that is defined at the start of a test and is passed around instead of relying on global vars. Link: https://lkml.kernel.org/r/20250829155600.2000-1-ujwal.kundur@gmail.com Signed-off-by: Ujwal Kundur Acked-by: Peter Xu Reviewed-by: Brendan Jackman Cc: David Hildenbrand Cc: Liam Howlett Cc: Lorenzo Stoakes Cc: Michal Hocko Cc: Mike Rapoport Cc: Shuah Khan Cc: Suren Baghdasaryan Cc: Vlastimil Babka Signed-off-by: Andrew Morton

selftests/mm: reduce uffd-unit-test poison test to minimum

2025-07-10T05:42:20Z

The test will still generate quite some unwanted MCE error messages to syslog. There was old proposal ratelimiting the MCE messages from kernel, but that has risk of hiding real useful information on production systems. We can at least reduce the test to minimum to not over-pollute dmesg, however trying to not lose its coverage too much. [peterx@redhat.com: reduce uffd-unit-test poison test to minimum] Link: https://lkml.kernel.org/r/aF2RSsjuEOtzXcUa@x1.local Link: https://lkml.kernel.org/r/20250620150058.1729489-1-peterx@redhat.com Signed-off-by: Peter Xu Cc: Axel Rasmussen Cc: Brendan Jackman Cc: David Hildenbrand Cc: Shuah Khan Signed-off-by: Andrew Morton

mm/selftests: add a test to verify mmap_changing race with -EAGAIN

2025-05-13T06:50:45Z

Add an unit test to verify the recent mmap_changing ABI breakage. Note that I used some tricks here and there to make the test simple, e.g. I abused UFFDIO_MOVE on top of shmem with the fact that I know what I want to test will be even earlier than the vma type check. Rich comments were added to explain trivial details. Before that fix, -EAGAIN would have been written to the copy field most of the time but not always; the test should be able to reliably trigger the outlier case. After the fix, it's written always, the test verifies that making sure corresponding field (e.g. copy.copy for UFFDIO_COPY) is updated. [akpm@linux-foundation.org: coding-style cleanups] Link: https://lkml.kernel.org/r/20250424215729.194656-3-peterx@redhat.com Signed-off-by: Peter Xu Cc: Andrea Arcangeli Cc: Axel Rasmussen Cc: Mike Rapoport Cc: Suren Baghdasaryan Signed-off-by: Andrew Morton

selftests/mm: uffd-unit-tests support for hugepages > 2M

2025-03-22T05:03:15Z

uffd-unit-tests uses a memory area with a fixed 32M size. Then it calculates the number of pages by dividing by page_size, which itself is either the base page size or the PMD huge page size depending on the test config. For the latter, we end up with nr_pages=1 for arm64 16K base pages, and nr_pages=0 for 64K base pages. This doesn't end well. So let's make the 32M size a floor and also ensure that we have at least 2 pages given the PMD size. With this change, the tests pass on arm64 64K base page size configuration. Link: https://lkml.kernel.org/r/20250318174343.243631-2-ryan.roberts@arm.com Signed-off-by: Ryan Roberts Acked-by: Peter Xu Acked-by: Rafael Aquini Cc: Shuah Khan Signed-off-by: Andrew Morton

selftests/mm/uffd: rename nr_cpus -> nr_parallel

2025-03-17T05:06:38Z

A later commit will bound this variable so it no longer necessarily matches the number of CPUs. Rename it appropriately. Link: https://lkml.kernel.org/r/20250311-mm-selftests-v4-4-dec210a658f5@google.com Signed-off-by: Brendan Jackman Reviewed-by: Dev Jain Cc: Lorenzo Stoakes Cc: Mateusz Guzik Cc: Shuah Khan Signed-off-by: Andrew Morton

Revert "selftests/mm: remove local __NR_* definitions"

2025-03-06T05:36:12Z

This reverts commit a5c6bc590094a1a73cf6fa3f505e1945d2bf2461. The general approach described in commit e076eaca5906 ("selftests: break the dependency upon local header files") was taken one step too far here: it should not have been extended to include the syscall numbers. This is because doing so would require per-arch support in tools/include/uapi, and no such support exists. This revert fixes two separate reports of test failures, from Dave Hansen[1], and Li Wang[2]. An excerpt of Dave's report: Before this commit (a5c6bc590094a1a73cf6fa3f505e1945d2bf2461) things are fine. But after, I get: running PKEY tests for unsupported CPU/OS An excerpt of Li's report: I just found that mlock2_() return a wrong value in mlock2-test [1] https://lore.kernel.org/dc585017-6740-4cab-a536-b12b37a7582d@intel.com [2] https://lore.kernel.org/CAEemH2eW=UMu9+turT2jRie7+6ewUazXmA6kL+VBo3cGDGU6RA@mail.gmail.com Link: https://lkml.kernel.org/r/20250214033850.235171-1-jhubbard@nvidia.com Fixes: a5c6bc590094 ("selftests/mm: remove local __NR_* definitions") Signed-off-by: John Hubbard Cc: Dave Hansen Cc: Li Wang Cc: David Hildenbrand Cc: Jeff Xu Cc: Andrei Vagin Cc: Axel Rasmussen Cc: Christian Brauner Cc: Kees Cook Cc: Kent Overstreet Cc: Liam R. Howlett Cc: Muhammad Usama Anjum Cc: Peter Xu Cc: Rich Felker Cc: Shuah Khan Cc: Signed-off-by: Andrew Morton

selftests/mm: fix -Wmaybe-uninitialized warnings

2025-01-14T06:40:53Z

A few -Wmaybe-uninitialized warnings show up when building the mm tests with -O2. None of them looks worrying; silence them by initialising the problematic variables. Link: https://lkml.kernel.org/r/20241209095019.1732120-3-kevin.brodsky@arm.com Signed-off-by: Kevin Brodsky Cc: Aruna Ramakrishna Cc: Catalin Marinas Cc: Dave Hansen Cc: Joey Gouly Cc: Keith Lucas Cc: Ryan Roberts Cc: Shuah Khan Signed-off-by: Andrew Morton