linux.git/tools/testing/selftests/vm/userfaultfd.c, branch v5.17

kselftest/vm: fix tests build with old libc

2022-03-05T19:08:32+00:00

The error message when I build vm tests on debian10 (GLIBC 2.28):

    userfaultfd.c: In function `userfaultfd_pagemap_test':
    userfaultfd.c:1393:37: error: `MADV_PAGEOUT' undeclared (first use
    in this function); did you mean `MADV_RANDOM'?
      if (madvise(area_dst, test_pgsize, MADV_PAGEOUT))
                                         ^~~~~~~~~~~~
                                         MADV_RANDOM

This patch includes these newer definitions from UAPI linux/mman.h, is
useful to fix tests build on systems without these definitions in glibc
sys/mman.h.

Link: https://lkml.kernel.org/r/20220227055330.43087-2-zhouchengming@bytedance.com
Signed-off-by: Chengming Zhou 
Reviewed-by: Shuah Khan 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

kselftest/vm: revert "tools/testing/selftests/vm/userfaultfd.c: use swap() to make code cleaner"

2022-02-04T17:25:05+00:00

With this change, userfaultfd fails to build with undefined reference
swap() error:

  userfaultfd.c: In function `userfaultfd_stress':
  userfaultfd.c:1530:17: warning: implicit declaration of function `swap'; did you mean `swab'? [-Wimplicit-function-declaration]
   1530 |                 swap(area_src, area_dst);
        |                 ^~~~
        |                 swab
  /usr/bin/ld: /tmp/ccDGOAdV.o: in function `userfaultfd_stress':
  userfaultfd.c:(.text+0x549e): undefined reference to `swap'
  /usr/bin/ld: userfaultfd.c:(.text+0x54bc): undefined reference to `swap'
  collect2: error: ld returned 1 exit status

Revert the commit to fix the problem.

Link: https://lkml.kernel.org/r/20220202003340.87195-1-skhan@linuxfoundation.org
Fixes: 2c769ed7137a ("tools/testing/selftests/vm/userfaultfd.c: use swap() to make code cleaner")
Signed-off-by: Shuah Khan 
Cc: Shuah Khan 
Cc: Minghao Chi 

Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

userfaultfd/selftests: clean up hugetlb allocation code

2022-01-15T14:30:30+00:00

The message for commit f5c73297181c ("userfaultfd/selftests: fix hugetlb
area allocations") says there is no need to create a hugetlb file in the
non-shared testing case.  However, the commit did not actually change
the code to prevent creation of the file.

While it is technically true that there is no need to create and use a
hugetlb file in the case of non-shared-testing, it is useful.  This is
because 'hole punching' of a hugetlb file has the potentially incorrect
side effect of also removing pages from private mappings.  The
userfaultfd test relies on this side effect for removing pages from the
destination buffer during rounds of stress testing.

Remove the incomplete code that was added to deal with no hugetlb file.
Just keep the code that prevents reserves from being created for the
destination area.

Link: https://lkml.kernel.org/r/20220104021729.111006-1-mike.kravetz@oracle.com
Signed-off-by: Mike Kravetz 
Reviewed-by: Axel Rasmussen 
Cc: Peter Xu 
Cc: Andrea Arcangeli 
Cc: Mina Almasry 
Cc: Shuah Khan 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

selftests/uffd: allow EINTR/EAGAIN

2022-01-15T14:30:30+00:00

This allow test to continue with interruptions like gdb.

Link: https://lkml.kernel.org/r/20211115135219.85881-1-peterx@redhat.com
Signed-off-by: Peter Xu 
Reviewed-by: Axel Rasmussen 
Cc: Andrea Arcangeli 
Cc: Nadav Amit 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

tools/testing/selftests/vm/userfaultfd.c: use swap() to make code cleaner

2022-01-15T14:30:27+00:00

Fix the following coccicheck REVIEW:

 tools/testing/selftests/vm/userfaultfd.c:1531:21-22:use swap() to make code cleaner

Link: https://lkml.kernel.org/r/20211124031632.35317-1-chi.minghao@zte.com.cn
Signed-off-by: chiminghao 
Reported-by: Zeal Robot 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

userfaultfd/selftests: fix hugetlb area allocations

2021-12-31T17:20:12+00:00

Currently, userfaultfd selftest for hugetlb as run from run_vmtests.sh
or any environment where there are 'just enough' hugetlb pages will
always fail with:

  testing events (fork, remap, remove):
		ERROR: UFFDIO_COPY error: -12 (errno=12, line=616)

The ENOMEM error code implies there are not enough hugetlb pages.
However, there are free hugetlb pages but they are all reserved.  There
is a basic problem with the way the test allocates hugetlb pages which
has existed since the test was originally written.

Due to the way 'cleanup' was done between different phases of the test,
this issue was masked until recently.  The issue was uncovered by commit
8ba6e8640844 ("userfaultfd/selftests: reinitialize test context in each
test").

For the hugetlb test, src and dst areas are allocated as PRIVATE
mappings of a hugetlb file.  This means that at mmap time, pages are
reserved for the src and dst areas.  At the start of event testing (and
other tests) the src area is populated which results in allocation of
huge pages to fill the area and consumption of reserves associated with
the area.  Then, a child is forked to fault in the dst area.  Note that
the dst area was allocated in the parent and hence the parent owns the
reserves associated with the mapping.  The child has normal access to
the dst area, but can not use the reserves created/owned by the parent.
Thus, if there are no other huge pages available allocation of a page
for the dst by the child will fail.

Fix by not creating reserves for the dst area.  In this way the child
can use free (non-reserved) pages.

Also, MAP_PRIVATE of a file only makes sense if you are interested in
the contents of the file before making a COW copy.  The test does not do
this.  So, just use MAP_ANONYMOUS | MAP_HUGETLB to create an anonymous
hugetlb mapping.  There is no need to create a hugetlb file in the
non-shared case.

Link: https://lkml.kernel.org/r/20211217172919.7861-1-mike.kravetz@oracle.com
Signed-off-by: Mike Kravetz 
Cc: Axel Rasmussen 
Cc: Peter Xu 
Cc: Andrea Arcangeli 
Cc: Mina Almasry 
Cc: Shuah Khan 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

userfaultfd/selftests: fix calculation of expected ioctls

2021-11-06T20:30:39+00:00

Today, we assert that the ioctls the kernel reports as supported for a
registration match a precomputed list.  We decide which ioctls are
supported by examining the memory type.  Then, in several locations we
"fix up" this list by adding or removing things this initial decision
got wrong.

What ioctls the kernel reports is actually a function of several things:
- The memory type
- Kernel feature support (e.g., no writeprotect on aarch64)
- The registration type (e.g., CONTINUE only supported for MINOR mode)

So, we can't fully compute this at the start, in set_test_type.  It
varies per test, depending on what registration mode(s) those tests use.

Instead, introduce a new function which computes the correct list.  This
centralizes the add/remove of ioctls depending on these function inputs
in one place, so we don't have to repeat ourselves in various tests.

Not only is the resulting code a bit shorter, but it fixes a real bug in
the existing code: previously, we would incorrectly require the
writeprotect ioctl to be present on aarch64, where it isn't actually
supported.

Link: https://lkml.kernel.org/r/20210930212309.4001967-4-axelrasmussen@google.com
Signed-off-by: Axel Rasmussen 
Reviewed-by: Peter Xu 
Cc: Shuah Khan 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

userfaultfd/selftests: fix feature support detection

2021-11-06T20:30:39+00:00

Before any tests are run, in set_test_type, we decide what feature(s) we
are going to be testing, based upon our command line arguments.
However, the supported features are not just a function of the memory
type being used, so this is broken.

For instance, consider writeprotect support.  It is "normally" supported
for anonymous memory, but furthermore it requires that the kernel has
CONFIG_HAVE_ARCH_USERFAULTFD_WP.  So, it is *not* supported at all on
aarch64, for example.

So, this fixes this by querying the kernel for the set of features it
supports in set_test_type, by opening a userfaultfd and issuing a
UFFDIO_API ioctl.  Based upon the reported features, we toggle what
tests are enabled.

Link: https://lkml.kernel.org/r/20210930212309.4001967-3-axelrasmussen@google.com
Signed-off-by: Axel Rasmussen 
Reviewed-by: Peter Xu 
Cc: Shuah Khan 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

userfaultfd/selftests: don't rely on GNU extensions for random numbers

2021-11-06T20:30:39+00:00

Patch series "Small userfaultfd selftest fixups", v2.

This patch (of 3):

Two arguments for doing this:

First, and maybe most importantly, the resulting code is significantly
shorter / simpler.

Then, we avoid using GNU libc extensions.  Why does this matter? It
makes testing userfaultfd with the selftest easier e.g.  on distros
which use something other than glibc (e.g., Alpine, which uses musl);
basically, it makes the test more portable.

Link: https://lkml.kernel.org/r/20210930212309.4001967-2-axelrasmussen@google.com
Signed-off-by: Axel Rasmussen 
Reviewed-by: Peter Xu 
Cc: Shuah Khan 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds

mm/userfaultfd: selftests: fix memory corruption with thp enabled

2021-10-19T06:22:02+00:00

In RHEL's gating selftests we've encountered memory corruption in the
uffd event test even with upstream kernel:

        # ./userfaultfd anon 128 4
        nr_pages: 32768, nr_pages_per_cpu: 32768
        bounces: 3, mode: rnd racing read, userfaults: 6240 missing (6240) 14729 wp (14729)
        bounces: 2, mode: racing read, userfaults: 1444 missing (1444) 28877 wp (28877)
        bounces: 1, mode: rnd read, userfaults: 6055 missing (6055) 14699 wp (14699)
        bounces: 0, mode: read, userfaults: 82 missing (82) 25196 wp (25196)
        testing uffd-wp with pagemap (pgsize=4096): done
        testing uffd-wp with pagemap (pgsize=2097152): done
        testing events (fork, remap, remove): ERROR: nr 32427 memory corruption 0 1 (errno=0, line=963)
        ERROR: faulting process failed (errno=0, line=1117)

It can be easily reproduced when global thp enabled, which is the
default for RHEL.

It's also known as a side effect of commit 0db282ba2c12 ("selftest: use
mmap instead of posix_memalign to allocate memory", 2021-07-23), which
is imho right itself on using mmap() to make sure the addresses will be
untagged even on arm.

The problem is, for each test we allocate buffers using two
allocate_area() calls.  We assumed these two buffers won't affect each
other, however they could, because mmap() could have found that the two
buffers are near each other and having the same VMA flags, so they got
merged into one VMA.

It won't be a big problem if thp is not enabled, but when thp is
agressively enabled it means when initializing the src buffer it could
accidentally setup part of the dest buffer too when there's a shared THP
that overlaps the two regions.  Then some of the dest buffer won't be
able to be trapped by userfaultfd missing mode, then it'll cause memory
corruption as described.

To fix it, do release_pages() after initializing the src buffer.

Since the previous two release_pages() calls are after
uffd_test_ctx_clear() which will unmap all the buffers anyway (which is
stronger than release pages; as unmap() also tear town pgtables), drop
them as they shouldn't really be anything useful.

We can mark the Fixes tag upon 0db282ba2c12 as it's reported to only
happen there, however the real "Fixes" IMHO should be 8ba6e8640844, as
before that commit we'll always do explicit release_pages() before
registration of uffd, and 8ba6e8640844 changed that logic by adding
extra unmap/map and we didn't release the pages at the right place.
Meanwhile I don't have a solid glue anyway on whether posix_memalign()
could always avoid triggering this bug, hence it's safer to attach this
fix to commit 8ba6e8640844.

Link: https://lkml.kernel.org/r/20210923232512.210092-1-peterx@redhat.com
Fixes: 8ba6e8640844 ("userfaultfd/selftests: reinitialize test context in each test")
Bugzilla: https://bugzilla.redhat.com/show_bug.cgi?id=1994931
Signed-off-by: Peter Xu 
Reported-by: Li Wang 
Tested-by: Li Wang 
Reviewed-by: Axel Rasmussen 
Cc: Andrea Arcangeli 
Cc: Nadav Amit 
Cc: 
Signed-off-by: Andrew Morton 
Signed-off-by: Linus Torvalds