linux.git/tools/testing/selftests/bpf/libarena, branch master

selftests/bpf: Remove duplicate copies of the arena spinlock qnodes

2026-08-17T17:31:12+00:00

bpf_arena_spin_lock.h defines its 64KB qnodes array in the header, so
every translation unit including it emits a copy. __weak makes them all
resolve to one instance, but bpftool gen object merges only the symbols
and concatenates each input's .addr_space.1 bytes, leaving the surplus
copies unreferenced in the linked object.

libarena links ten such units, so nine copies were dead weight (bytes):

  object                             before       after
  -----------------------------------------------------
  .addr_space.1 in libarena.bpf.o    676200       86376
  libarena.skel.h                   2100123      892371
  libarena_asan.skel.h              2641124     1466477

Declare qnodes in the header and let each program define it once:
libarena in src/common.bpf.c, and the arena_spin_lock test beside the
lock it guards.

Tested with test_progs -t arena_spin_lock and -t libarena.

Signed-off-by: Changwoo Min 
Reviewed-by: Emil Tsalapatis 
Link: https://lore.kernel.org/bpf/20260817160249.655916-1-changwoo@igalia.com
Signed-off-by: Kumar Kartikeya Dwivedi

libarena: Use compiler load-acquire/store-release in bpf_atomic.h

2026-07-22T16:21:32+00:00

Teach libarena's BPF atomic primitives to use compiler builtins for
load-acquire and store-release when Clang advertises
__BPF_FEATURE_LOAD_ACQ_STORE_REL. Older compilers continue to use the
existing barrier-based fallback.

Notably, as BPF programs begin running on arm64, it is better to use the
more appropriate variants since we can no longer rely on x86 TSO ordering.

Commit 880442305a39 ("bpf: Introduce load-acquire and store-release instructions")
introduced support, hence kernels from 6.15 onwards are needed when
compiling with compilers supporting these instructions. We have
relatively recent kernel version requirements in libarena anyway, and
have not cut first release, hence declare such a dependency.

Signed-off-by: Puranjay Mohan 
Reviewed-by: Emil Tsalapatis 
Link: https://lore.kernel.org/bpf/20260722141003.2841007-1-puranjay@kernel.org
Signed-off-by: Kumar Kartikeya Dwivedi

selftests/bpf: Silence maybe-uninitialized compiler warning in libarena

2026-07-20T19:00:57+00:00

When compiling BPF selftests with -O2, GCC reports a maybe-uninitialized
warning in libarena code:

    In file included from /bpf-next/tools/testing/selftests/bpf/prog_tests/libarena_asan.c:11:
    In function ‘libarena_asan_init’,
        inlined from ‘run_test’ at /bpf-next/tools/testing/selftests/bpf/prog_tests/libarena_asan.c:59:8,
        inlined from ‘test_libarena_asan’ at /bpf-next/tools/testing/selftests/bpf/prog_tests/libarena_asan.c:91:2:
    /bpf-next/tools/testing/selftests/bpf/libarena/include/libarena/userspace.h:126:14: error: ‘globals_pages’ may be used uninitialized [-Werror=maybe-uninitialized]
      126 |         args = (struct asan_init_args){
          |         ~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~
      127 |                 .arena_all_pages = arena_all_pages,
          |                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      128 |                 .arena_globals_pages = globals_pages,
          |                 ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
      129 |         };
          |         ~
    /bpf-next/tools/testing/selftests/bpf/libarena/include/libarena/userspace.h: In function ‘test_libarena_asan’:
    /bpf-next/tools/testing/selftests/bpf/libarena/include/libarena/userspace.h:118:13: note: ‘globals_pages’ was declared here
      118 |         u64 globals_pages;
          |             ^~~~~~~~~~~~~

Silence the warning by initializing globals_pages to 0.

Fixes: cfc00618b9df ("selftests/bpf: Add ASAN support for libarena selftests")
Signed-off-by: Viktor Malik 
Link: https://lore.kernel.org/bpf/9f77a5c05c3c731ab2655fd66716ab9de4478b15.1784112948.git.vmalik@redhat.com
Signed-off-by: Kumar Kartikeya Dwivedi

selftests/bpf: Rename libarena struct bitmap to struct arena_bitmap

2026-07-08T03:15:34+00:00

When building bpf selftest with latest bpf-next, I got the following failure:

  In file included from /home/yhs/work/bpf-next/tools/testing/selftests/bpf/libarena/selftests/test_parallel_bitmap.bpf.c:8:
  /home/yhs/work/bpf-next/tools/testing/selftests/bpf/libarena/include/libarena/bitmap.h:11:8: error: redefinition of
        'bitmap'
     11 | struct bitmap {
        |        ^
  /home/yhs/work/bpf-next/tools/testing/selftests/bpf/tools/include/vmlinux.h:51320:8: note: previous definition is here
   51320 | struct bitmap {
         |        ^

The vmlinux.h struct bitmap comes from drivers/md/md-bitmap.c:
  struct bitmap {
	struct bitmap_counts { ... }
	...
  }

To fix the issue, I renamed libarena struct bitmap to arena_bitmap to avoid the conflict.

Signed-off-by: Yonghong Song 
Reviewed-by: Emil Tsalapatis 
Link: https://lore.kernel.org/bpf/20260707220136.910374-1-yonghong.song@linux.dev
Signed-off-by: Kumar Kartikeya Dwivedi

selftests/bpf: libarena: Add parallel bitmap selftest

2026-07-07T16:09:12+00:00

Add a selftest for testing the atomic bitmap set/clear/
test_and_set/test_and_clear operations. The selftest
checks atomicity by spawning two threads, each of which
either only works on even bits or with odd bits. The
test checks that threads do not affect each other's
bits.

Signed-off-by: Emil Tsalapatis 
Link: https://lore.kernel.org/bpf/20260706181730.21731-7-emil@etsalapatis.com
Signed-off-by: Kumar Kartikeya Dwivedi

selftests/bpf: libarena: Add bitmap selftests

2026-07-07T16:09:09+00:00

Add testing for the new arena bitmap data structure.

Signed-off-by: Emil Tsalapatis 
Acked-by: Ihor Solodrai 
Link: https://lore.kernel.org/bpf/20260706181730.21731-6-emil@etsalapatis.com
Signed-off-by: Kumar Kartikeya Dwivedi

selftests/bpf: Add arena-based bitmap data structure

2026-07-07T16:09:06+00:00

Add an arena-based word-aligned bitmap data struture. The
structure is useful as a building block, e.g., sched-ext
uses it to represent cpumask structures.

Signed-off-by: Emil Tsalapatis 
Link: https://lore.kernel.org/bpf/20260706181730.21731-5-emil@etsalapatis.com
Signed-off-by: Kumar Kartikeya Dwivedi

selftests/bpf: libarena: Clean up allocation state before buddy tests

2026-07-07T16:09:01+00:00

Summary: The buddy allocator requires the global BPF buddy allocator
to not be already initialized. However, the test currently merely resets
the allocator before the buddy tests instead of destroying it, and the
test worked because the buddy test happened to run first. Properly
destroy the allocator instead of resetting it.

Fixes: b1487dc1b181 ("selftests/bpf: Add selftests for libarena buddy allocator")
Signed-off-by: Emil Tsalapatis 
Acked-by: Ihor Solodrai 
Link: https://lore.kernel.org/bpf/20260706181730.21731-4-emil@etsalapatis.com
Signed-off-by: Kumar Kartikeya Dwivedi

selftests/bpf: libarena: Fix can-loop zero variable definition

2026-07-07T16:08:47+00:00

BPF can_loop based loops require the index variable to stay imprecise.
This means we must initialize them from a currently imprecise variable
instead of directly assigning 0 to them, like so:

static volatile u32 zero = 0;

for (i = zero; i < NUM_LOOPS; i++) {
	/* loop body */
}

The libarena implementation of this technique is currently faulty. For
the technique to work, the variable must not be in a map. This includes
the .rodata DATASEC map used for const variables. However, libarena
still defines the zero variable as constant.

Modify the zero variable definition into a volatile variable. This
change adds a complication caused by the compiler optimizing array
derefences from

for (i = zero; i < NUM_LOOPS; i++) {
	val = *(ptr + i);
}

into

for (i = zero; i < NUM_LOOPS; i++) {
	val = *ptr++;
}

and causing verification failures. Use the barrier_var() clobber macro
to prevent this optimization from taking place. Using barrier_var() is
the only way to break the optimization, as annotating the index as
volatile does not suffice.

After that, remove the bpf_for() invocations introduced in libarena for
parallel spmc testing.

Reported-by: Eduard Zingerman 
Signed-off-by: Emil Tsalapatis 
Acked-by: Eduard Zingerman 
Link: https://lore.kernel.org/bpf/20260706181730.21731-3-emil@etsalapatis.com
Signed-off-by: Kumar Kartikeya Dwivedi

selftests/bpf: libarena: Replace leftover st_ prefix with test_

2026-07-07T16:08:43+00:00

The st_ (selftests_) prefix is confusing and has been replaced
with the more descriptive test_. However, last patch did not
properly move all files to the new prefix. Rename the existing
files to complete the move.

Acked-by: Ihor Solodrai 
Signed-off-by: Emil Tsalapatis 
Link: https://lore.kernel.org/bpf/20260706181730.21731-2-emil@etsalapatis.com
Signed-off-by: Kumar Kartikeya Dwivedi