Re: [PATCH bpf-next v11 03/10] bpf: Introduce global percpu data

[Eduard Zingerman <eddyz87@gmail.com>]

On Fri, 2026-08-07 at 00:31 +0800, Leon Hwang wrote:

...

> diff --git a/kernel/bpf/fixups.c b/kernel/bpf/fixups.c
> index 440e73e1b11b..f2398749103b 100644
> --- a/kernel/bpf/fixups.c
> +++ b/kernel/bpf/fixups.c
> @@ -1817,6 +1817,43 @@ int bpf_do_misc_fixups(struct bpf_verifier_env *env)
>  			goto next_insn;
>  		}
>  
> +		if (bpf_jit_supports_percpu_insn() &&
> +		    insn->code == (BPF_LD | BPF_IMM | BPF_DW) &&
> +		    (insn->src_reg == BPF_PSEUDO_MAP_VALUE ||
> +		     insn->src_reg == BPF_PSEUDO_MAP_IDX_VALUE)) {
> +			struct bpf_map *map;
> +
> +			aux = &env->insn_aux_data[i + delta];
> +			map = env->used_maps[aux->map_index];
> +			if (map->map_type != BPF_MAP_TYPE_PERCPU_ARRAY)
> +				goto next_insn;
> +
> +			prog->jit_required = true;
> +
> +			/*
> +			 * We are *skipping* first half of ld_imm64 insn
> +			 * with 'i++;', patching over second half of it
> +			 * with that same half + mov64_percpu_reg insn.
> +			 * All because bpf_patch_insn_data() can only
> +			 * replace one 8-byte insn, which does not work
> +			 * well for ld_imm64 insn.
> +			 */
> +
> +			insn_buf[0] = insn[1];
> +			insn_buf[1] = BPF_MOV64_PERCPU_REG(insn->dst_reg, insn->dst_reg);
> +			cnt = 2;

Hi Leon,

Sorry for joining the discussion so late, but Andrii asked me to take
a look at the verifier part of the changes. Could you please elaborate
on what exactly does not work with 16-byte instructions and
bpf_patch_insn_data()? Note that e.g. 'if (insn->imm == BPF_FUNC_timer_set_callback) {'
case in the same bpf_do_misc_fixups() applies a patch containing BPF_LD_IMM64().

The rest of the patch lgtm.

> +
> +			i++;
> +			new_prog = bpf_patch_insn_data(env, i + delta, insn_buf, cnt);
> +			if (!new_prog)
> +				return -ENOMEM;
> +
> +			delta    += cnt - 1;
> +			env->prog = prog = new_prog;
> +			insn      = new_prog->insnsi + i + delta;
> +			goto next_insn;
> +		}
> +
>  		if (insn->code != (BPF_JMP | BPF_CALL))
>  			goto next_insn;
>  		if (insn->src_reg == BPF_PSEUDO_CALL)

...