lwn.git/tools/testing/selftests/bpf/prog_tests/task_local_data.h, branch master

selftests/bpf: Fix tld_get_data() returning garbage data

2026-04-15T19:10:20+00:00

BPF side tld_get_data() currently may return garbage when tld_data_u is not aligned to page_size. This can happen when small amount of memory is allocated for tld_data_u. The misalignment is supposed to be allowed and the BPF side will use tld_data_u->start to reference the tld_data_u in a page. However, since "start" is within tld_data_u, there is no way to know the correct "start" in the first place. As a result, BPF programs will see garbage data. The selftest did not catch this since it tries to allocate the maximum amount of data possible (i.e., a page) such that tld_data_u->start is always correct. Fix it by moving tld_data_u->start to tld_data_map->start. The original field is now renamed as unused instead of removing it because BPF side tld_get_data() views off = 0 returned from tld_fetch_key() as uninitialized. Signed-off-by: Amery Hung Link: https://lore.kernel.org/r/20260413190259.358442-3-ameryhung@gmail.com Signed-off-by: Alexei Starovoitov

selftests/bpf: Prevent allocating data larger than a page

2026-04-15T19:10:20+00:00

Fix a bug in the task local data library that may allocate more than a a page for tld_data_u. This may happen when users set a too large TLD_DYN_DATA_SIZE, so check it when creating dynamic TLD fields and fix the corresponding selftest. Signed-off-by: Amery Hung Link: https://lore.kernel.org/r/20260413190259.358442-2-ameryhung@gmail.com Signed-off-by: Alexei Starovoitov

selftests/bpf: Improve task local data documentation and fix potential memory leak

2026-04-02T22:11:08+00:00

If TLD_FREE_DATA_ON_THREAD_EXIT is not enabled in a translation unit that calls __tld_create_key() first, another translation unit that enables it will not get the auto cleanup feature as pthread key is only created once when allocation metadata. Fix it by always try to create the pthread key when __tld_create_key() is called. Also improve the documentation: - Discourage user from using different options in different translation units - Specify calling tld_free() before thread exit as undefined behavior Signed-off-by: Amery Hung Link: https://lore.kernel.org/r/20260331213555.1993883-6-ameryhung@gmail.com Signed-off-by: Alexei Starovoitov

selftests/bpf: Remove TLD_READ_ONCE() in the user space header

2026-04-02T22:11:08+00:00

TLD_READ_ONCE() is redundant as the only reference passed to it is defined as _Atomic. The load is guaranteed to be atomic in C11 standard (6.2.6.1). Drop the macro. Signed-off-by: Amery Hung Acked-by: Sun Jian Link: https://lore.kernel.org/r/20260331213555.1993883-5-ameryhung@gmail.com Signed-off-by: Alexei Starovoitov

selftests/bpf: Make sure TLD_DEFINE_KEY runs first

2026-04-02T22:11:08+00:00

Without specifying constructor priority of the hidden constructor function defined by TLD_DEFINE_KEY, __tld_create_key(..., dyn_data = false) may run after tld_get_data() called from other constructors. Threads calling tld_get_data() before __tld_create_key(..., dyn_data = false) will not allocate enough memory for all TLDs and later result in OOB access. Therefore, set it to the lowest value available to users. Note that lower means higher priority and 0-100 is reserved to the compiler. Acked-by: Mykyta Yatsenko Signed-off-by: Amery Hung Acked-by: Sun Jian Link: https://lore.kernel.org/r/20260331213555.1993883-4-ameryhung@gmail.com Signed-off-by: Alexei Starovoitov

selftests/bpf: Simplify task_local_data memory allocation

2026-04-02T22:11:08+00:00

Simplify data allocation by always using aligned_alloc() and passing size_pot, size rounded up to the closest power of two to alignment. Currently, aligned_alloc(page_size, size) is only intended to be used with memory allocators that can fulfill the request without rounding size up to page_size to conserve memory. This is enabled by defining TLD_DATA_USE_ALIGNED_ALLOC. The reason to align to page_size is due to the limitation of UPTR where only a page can be pinned to the kernel. Otherwise, malloc(size * 2) is used to allocate memory for data. However, we don't need to call aligned_alloc(page_size, size) to get a contiguous memory of size bytes within a page. aligned_alloc(size_pot, ...) will also do the trick. Therefore, just use aligned_alloc(size_pot, ...) universally. As for the size argument, create a new option, TLD_DONT_ROUND_UP_DATA_SIZE, to specify not rounding up the size. This preserves the current TLD_DATA_USE_ALIGNED_ALLOC behavior, allowing memory allocators with low overhead aligned_alloc() to not waste memory. To enable this, users need to make sure it is not an undefined behavior for the memory allocator to have size not being an integral multiple of alignment. Compared to the current implementation, !TLD_DATA_USE_ALIGNED_ALLOC used to always waste size-byte of memory due to malloc(size * 2). Now the worst case becomes size - 1 and the best case is 0 when the size is already a power of two. Signed-off-by: Amery Hung Link: https://lore.kernel.org/r/20260331213555.1993883-3-ameryhung@gmail.com Signed-off-by: Alexei Starovoitov

selftests/bpf: Fix task_local_data data allocation size

2026-04-02T22:11:08+00:00

Currently, when allocating memory for data, size of tld_data_u->start is not taken into account. This may cause OOB access. Fixed it by adding the non-flexible array part of tld_data_u. Besides, explicitly align tld_data_u->data to 8 bytes in case some fields are added before data in the future. It could break the assumption that every data field is 8 byte aligned and sizeof(tld_data_u) will no longer be equal to offsetof(struct tld_data_u, data), which we use interchangeably. Signed-off-by: Amery Hung Acked-by: Sun Jian Link: https://lore.kernel.org/r/20260331213555.1993883-2-ameryhung@gmail.com Signed-off-by: Alexei Starovoitov

selftests/bpf: Fix compiler warnings in task_local_data.h

2026-03-24T15:46:54+00:00

Fix compiler warnings about unused parameter, narrowing non-constant into a smaller type and comparison between integers of different size. Signed-off-by: Amery Hung Acked-by: Kumar Kartikeya Dwivedi Link: https://lore.kernel.org/r/20260323231133.859941-1-ameryhung@gmail.com Signed-off-by: Alexei Starovoitov

Merge git://git.kernel.org/pub/scm/linux/kernel/git/bpf/bpf before 7.0-rc2

2026-03-01T17:04:00+00:00

Cross-merge BPF and other fixes after downstream PR. No conflicts. Signed-off-by: Alexei Starovoitov

selftests/bpf: Replace strncpy() with strscpy()

2026-02-24T16:19:33+00:00

strncpy() does not guarantee NULL-termination and is considered deprecated [1]. Replace strncpy() calls with strscpy(). [1] https://docs.kernel.org/process/deprecated.html#strncpy-on-nul-terminated-strings Signed-off-by: Ihor Solodrai Link: https://lore.kernel.org/r/20260223190736.649171-4-ihor.solodrai@linux.dev Signed-off-by: Alexei Starovoitov