[PATCH v2 3/6] powerpc64/bpf: Tailcall handling with trampolines

[bot+bpf-ci at kernel.org]

> diff --git a/arch/powerpc/net/bpf_jit_comp.c b/arch/powerpc/net/bpf_jit_comp.c
> index 069a8822c30d..e3088cf089d1 100644
> --- a/arch/powerpc/net/bpf_jit_comp.c
> +++ b/arch/powerpc/net/bpf_jit_comp.c

[ ... ]

> +static void bpf_trampoline_setup_tail_call_info(u32 *image, struct codegen_context *ctx,
> +					       int func_frame_offset,
> +					       int bpf_dummy_frame_size, int r4_off)
> +{
> +	if (IS_ENABLED(CONFIG_PPC64)) {
> +		/* See bpf_jit_stack_tailcallinfo_offset() */
> +		int tailcallinfo_offset = BPF_PPC_TAILCALL;
> +		/*
> +		 * func_frame_offset =                                   ...(1)
> +		 *     bpf_dummy_frame_size + trampoline_frame_size
> +		 */
> +		EMIT(PPC_RAW_LD(_R4, _R1, func_frame_offset));
> +		EMIT(PPC_RAW_LD(_R3, _R4, -tailcallinfo_offset));
                              ^^^^

Should this LD instruction be an ADDI instead? Looking at the stack frame
setup, after the two STLU instructions in __arch_prepare_bpf_trampoline():

  STLU _R1, _R1, -bpf_dummy_frame_size  ->  stores original _R1 at dummy frame
  STLU _R1, _R1, -bpf_frame_size        ->  stores dummy frame ptr at tramp frame