selftests/bpf: libarena: Directly return arena pointers from functions

Now that the __arena annotation includes a BTF type tag, and the
verifier can identify arena pointers at BTF loading time, retu

selftests/bpf: libarena: Directly return arena pointers from functions

Now that the __arena annotation includes a BTF type tag, and the
verifier can identify arena pointers at BTF loading time, return
arena pointers as their true type instead of casting to u64. Remove the
preprocessor typecast wrappers used to hide this from the caller.

Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Emil Tsalapatis <emil@etsalapatis.com>
Link: https://lore.kernel.org/r/20260602004120.17087-6-emil@etsalapatis.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

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selftests/bpf: Remove __arg_arena from the codebase

Now that BPF __arg_arena has been subsumed by __arena, remove
__arg_arena from the codebase. This way the user has one fewer
annotation to worry a

selftests/bpf: Remove __arg_arena from the codebase

Now that BPF __arg_arena has been subsumed by __arena, remove
__arg_arena from the codebase. This way the user has one fewer
annotation to worry about.

To remove __arg_arena we remove the typedefs we were previously
using to minimize __arena annotations. This is because __arena
now also includes a BTF type tag, which is ignored for non-pointer
types. As a result, we cannot capture the whole __arena annotation
inside a typedef and need to directly annotate the pointer type when
declaring the variable.

The extra verbosity is worth it because the use of the __arena tag
is intuitive to the programmer and removes the __arg_arena tag that
has been a consistent source of confusion for users. The typedefs
can be reintroduced later (without __arg_arena) once compilers start
supporting BTF type tags for non-pointer types.

Acked-by: Eduard Zingerman <eddyz87@gmail.com>
Signed-off-by: Emil Tsalapatis <emil@etsalapatis.com>
Link: https://lore.kernel.org/r/20260602004120.17087-5-emil@etsalapatis.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

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selftests/bpf: Add buddy allocator for libarena

Add a byte-oriented buddy allocator for libarena. The buddy
allocator provides an alloc/free interface for small arena allocations
ranging from 16 byt

selftests/bpf: Add buddy allocator for libarena

Add a byte-oriented buddy allocator for libarena. The buddy
allocator provides an alloc/free interface for small arena allocations
ranging from 16 bytes to 512 KiB. Lower allocations values are rounded
up to 16 bytes. The buddy allocator does not handle larger allocations
that can instead use the existing bpf_arena_{alloc, free}_pages() kfunc.

Signed-off-by: Emil Tsalapatis <emil@etsalapatis.com>
Link: https://lore.kernel.org/r/20260426190338.4615-7-emil@etsalapatis.com
Signed-off-by: Alexei Starovoitov <ast@kernel.org>

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