mm: slub: test: Use the kunit_get_current_test() function

Use the newly-added function kunit_get_current_test() instead of
accessing current->kunit_test directly. This function uses a static key
to return more quickly when KUnit is enabled, but no tests are actively
running. There should therefore be a negligible performance impact to
enabling the slub KUnit tests.

Other than the performance improvement, this should be a no-op.

Cc: Oliver Glitta <glittao@gmail.com>
Cc: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: David Rientjes <rientjes@google.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: David Gow <davidgow@google.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Signed-off-by: Shuah Khan <skhan@linuxfoundation.org>

mm/slub, kunit: Add a test case for kmalloc redzone check

kmalloc redzone check for slub has been merged, and it's better to add
a kunit case for it, which is inspired by a real-world case as described
in commit 120ee599b5bf ("staging: octeon-usb: prevent memory corruption"):

"
octeon-hcd will crash the kernel when SLOB is used. This usually happens
after the 18-byte control transfer when a device descriptor is read.
The DMA engine is always transferring full 32-bit words and if the
transfer is shorter, some random garbage appears after the buffer.
The problem is not visible with SLUB since it rounds up the allocations
to word boundary, and the extra bytes will go undetected.
"

To avoid interrupting the normal functioning of kmalloc caches, a
kmem_cache mimicing kmalloc cache is created with similar flags, and
kmalloc_trace() is used to really test the orig_size and redzone setup.

Suggested-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Feng Tang <feng.tang@intel.com>
Reviewed-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

mm/slub, kunit: add SLAB_SKIP_KFENCE flag for cache creation

When kfence is enabled, the buffer allocated from the test case
could be from a kfence pool, and the operation could be also
caught and reported by kfence first, causing the case to fail.

With default kfence setting, this is very difficult to be triggered.
By changing CONFIG_KFENCE_NUM_OBJECTS from 255 to 16383, and
CONFIG_KFENCE_SAMPLE_INTERVAL from 100 to 5, the allocation from
kfence did hit 7 times in different slub_kunit cases out of 900
times of boot test.

To avoid this, initially we tried is_kfence_address() to check this
and repeated allocation till finding a non-kfence address. Vlastimil
Babka suggested SLAB_SKIP_KFENCE flag could be used to achieve this,
and better add a wrapper function for simplifying cache creation.

Signed-off-by: Feng Tang <feng.tang@intel.com>
Reviewed-by: Marco Elver <elver@google.com>
Reviewed-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>

mm/slub, kunit: Make slub_kunit unaffected by user specified flags

slub_kunit does not expect other debugging flags to be set when running
tests. When SLAB_RED_ZONE flag is set globally, test fails because the
flag affects number of errors reported.

To make slub_kunit unaffected by user specified debugging flags,
introduce SLAB_NO_USER_FLAGS to ignore them. With this flag, only flags
specified in the code are used and others are ignored.

Suggested-by: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: Hyeonggon Yoo <42.hyeyoo@gmail.com>
Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
Link: https://lore.kernel.org/r/Yk0sY9yoJhFEXWOg@hyeyoo

mm/slub, kunit: add a KUnit test for SLUB debugging functionality

SLUB has resiliency_test() function which is hidden behind #ifdef
SLUB_RESILIENCY_TEST that is not part of Kconfig, so nobody runs it.
KUnit should be a proper replacement for it.

Try changing byte in redzone after allocation and changing pointer to next
free node, first byte, 50th byte and redzone byte. Check if validation
finds errors.

There are several differences from the original resiliency test: Tests
create own caches with known state instead of corrupting shared kmalloc
caches.

The corruption of freepointer uses correct offset, the original resiliency
test got broken with freepointer changes.

Scratch changing random byte test, because it does not have meaning in
this form where we need deterministic results.

Add new option CONFIG_SLUB_KUNIT_TEST in Kconfig. Tests next_pointer,
first_word and clobber_50th_byte do not run with KASAN option on. Because
the test deliberately modifies non-allocated objects.

Use kunit_resource to count errors in cache and silence bug reports.
Count error whenever slab_bug() or slab_fix() is called or when the count
of pages is wrong.

[glittao@gmail.com: remove unused function test_exit(), from SLUB KUnit test]
Link: https://lkml.kernel.org/r/20210512140656.12083-1-glittao@gmail.com
[akpm@linux-foundation.org: export kasan_enable/disable_current to modules]

Link: https://lkml.kernel.org/r/20210511150734.3492-2-glittao@gmail.com
Signed-off-by: Oliver Glitta <glittao@gmail.com>
Reviewed-by: Vlastimil Babka <vbabka@suse.cz>
Acked-by: Daniel Latypov <dlatypov@google.com>
Acked-by: Marco Elver <elver@google.com>
Cc: Brendan Higgins <brendanhiggins@google.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Joonsoo Kim <iamjoonsoo.kim@lge.com>
Cc: Pekka Enberg <penberg@kernel.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>