Re: [PATCH v2 4/6] powerpc64/bpf: Add arch_bpf_stack_walk() for BPF JIT

Christophe Leroy (CS GROUP)
2026-01-14T12:38:03Z

Le 14/01/2026 à 12:44, adubey@linux.ibm.com a écrit :
> From: Abhishek Dubey <adubey@linux.ibm.com>
>
> This function is used by bpf_throw() to unwind the stack
> until frame of exception-boundary during BPF exception
> handling.
>
> This function is necessary to support BPF exceptions on
> PowerPC.
>
> Signed-off-by: Abhishek Dubey <adubey@linux.ibm.com>
> ---
> arch/powerpc/net/bpf_jit_comp64.c | 28 ++++++++++++++++++++++++++++
> 1 file changed, 28 insertions(+)
>
> diff --git a/arch/powerpc/net/bpf_jit_comp64.c b/arch/powerpc/net/bpf_jit_comp64.c
> index cebf81fbd59f..ec58395f74f7 100644
> --- a/arch/powerpc/net/bpf_jit_comp64.c
> +++ b/arch/powerpc/net/bpf_jit_comp64.c
> @@ -247,6 +247,34 @@ void bpf_jit_build_epilogue(u32 *image, struct codegen_context *ctx)
> bpf_jit_build_fentry_stubs(image, ctx);
> }
>
> +void arch_bpf_stack_walk(bool (*consume_fn)(void *, u64, u64, u64), void *cookie)
> +{
> + // callback processing always in current context
> + unsigned long fp = current_stack_frame();
> +
> + for (;;) {
> + unsigned long *frame = (unsigned long *) fp;
> + unsigned long ip;
> +
> + if (!validate_sp(fp, current))
> + return;
> +
> + ip = frame[STACK_FRAME_LR_SAVE];
> + if (!ip)
> + break;
> +
> + /*
> + * consume_fn common code expects stack pointer(sp) in third
> + * argument. There is no sp in ppc64, rather pass frame
> + * pointer.
> + */
> + if (ip && !consume_fn(cookie, ip, fp, fp))
> + break;
> +
> + fp = frame[0];
> + }
> +}
> +

This fonction looks very close to arch_stack_walk(). Would it be
possible to refactor and have a common part used by both functions, like
ARM64 for instance ?

> int bpf_jit_emit_func_call_rel(u32 *image, u32 *fimage, struct codegen_context *ctx, u64 func)
> {
> unsigned long func_addr = func ? ppc_function_entry((void *)func) : 0;