Re: [PATCH bpf-next 5/7] selftests/bpf: Add arm64 JIT-sequence tests for __arena kfunc arguments

On 8/11/2026 3:09 AM, Puranjay Mohan wrote:
> Pin the arm64 counterparts of the x86-64 rebase sequences: the single
> extended-register add for an unconditional argument, the nullable
> truncate-test-and-skip variant, and all five argument registers in one
> call. The nullable cases use a local label so the branch is pinned to
> the instruction right after the add, and the label line does not spell
> out the call because arm64 emits either a direct bl or a materialize-
> and-blr pair depending on the distance to the kfunc.
> 
> Note that on arm64 an unconditional argument is one instruction with
> nothing to anchor it against, so arena_arg_jit_rebase alone cannot tell
> the two forms apart; it only requires that nothing is emitted between
> the rebase and the call. The args5 test is what pins the distinction,
> since its four consecutive adds leave no room for a nullable
> truncate-and-branch pair between them.
> 
> Signed-off-by: Puranjay Mohan <[email protected]>
> ---
>   .../selftests/bpf/progs/arena_kfunc_jit.c     | 20 +++++++++++++++++++
>   1 file changed, 20 insertions(+)
> 
> diff --git a/tools/testing/selftests/bpf/progs/arena_kfunc_jit.c b/tools/testing/selftests/bpf/progs/arena_kfunc_jit.c
> index c9b9186626162..b5a01cbc33a73 100644
> --- a/tools/testing/selftests/bpf/progs/arena_kfunc_jit.c
> +++ b/tools/testing/selftests/bpf/progs/arena_kfunc_jit.c
> @@ -32,6 +32,10 @@ __jited("	movl	%edi, %edi")
>   __jited("	addq	%r12, %rdi")
>   __jited("...")
>   __jited("	callq	{{.*}}")
> +__arch_arm64
> +__jited("...")
> +__jited("	add	x0, x28, w0, uxtw")
> +__jited("	{{(bl|mov)	.*}}")
>   __success
>   int arena_arg_jit_rebase(void *ctx)
>   {
> @@ -48,6 +52,12 @@ __jited("	testl	%edi, %edi")
>   __jited("	je	L0")
>   __jited("	addq	%r12, %rdi")
>   __jited("L0:	callq	{{.*}}")
> +__arch_arm64
> +__jited("...")
> +__jited("	mov	w0, w0")
> +__jited("	cbz	w0, L0")
> +__jited("	add	x0, x28, w0, uxtw")
> +__jited("L0:	{{.*}}")
>   __success
>   int arena_arg_jit_nullable(void *ctx)
>   {
> @@ -72,6 +82,16 @@ __jited("	testl	%r8d, %r8d")
>   __jited("	je	L0")
>   __jited("	addq	%r12, %r8")
>   __jited("L0:	callq	{{.*}}")
> +__arch_arm64
> +__jited("...")
> +__jited("	add	x0, x28, w0, uxtw")
> +__jited("	add	x1, x28, w1, uxtw")
> +__jited("	add	x2, x28, w2, uxtw")
> +__jited("	add	x3, x28, w3, uxtw")
> +__jited("	mov	w4, w4")
> +__jited("	cbz	w4, L0")
> +__jited("	add	x4, x28, w4, uxtw")
> +__jited("L0:	{{.*}}")
>   __success
>   int arena_arg_jit_args5(void *ctx)
>   {

Acked-by: Xu Kuohai <[email protected]>