linux-kernel - Re: [PATCH bpf-next v2 2/5] bpf, x86: allow function arguments up to 14 for TRACING

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Message-ID: <CADxym3ZnmD_DhvS_KaJo4yt6PteaUDvifj4dp4gBBRuvoks=-g@mail.gmail.com>
Date:   Fri, 2 Jun 2023 15:40:43 +0800
From:   Menglong Dong <menglong8.dong@...il.com>
To:     olsajiri@...il.com
Cc:     davem@...emloft.net, dsahern@...nel.org, ast@...nel.org,
        daniel@...earbox.net, andrii@...nel.org, martin.lau@...ux.dev,
        song@...nel.org, yhs@...com, john.fastabend@...il.com,
        kpsingh@...nel.org, sdf@...gle.com, haoluo@...gle.com,
        jolsa@...nel.org, tglx@...utronix.de, mingo@...hat.com,
        bp@...en8.de, dave.hansen@...ux.intel.com, x86@...nel.org,
        hpa@...or.com, edumazet@...gle.com, kuba@...nel.org,
        pabeni@...hat.com, mykolal@...com, shuah@...nel.org,
        benbjiang@...cent.com, iii@...ux.ibm.com, imagedong@...cent.com,
        xukuohai@...wei.com, chantr4@...il.com, zwisler@...gle.com,
        eddyz87@...il.com, netdev@...r.kernel.org, bpf@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org
Subject: Re: [PATCH bpf-next v2 2/5] bpf, x86: allow function arguments up to
 14 for TRACING

On Fri, Jun 2, 2023 at 3:01 PM <menglong8.dong@...il.com> wrote:
>
> From: Menglong Dong <imagedong@...cent.com>
> @@ -2262,6 +2327,7 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i
>
>         if (flags & BPF_TRAMP_F_CALL_ORIG) {
>                 restore_regs(m, &prog, nr_regs, regs_off);
> +               prepare_origin_stack(m, &prog, nr_regs, arg_stack_off);
>
>                 if (flags & BPF_TRAMP_F_ORIG_STACK) {
>                         emit_ldx(&prog, BPF_DW, BPF_REG_0, BPF_REG_FP, 8);
> @@ -2321,14 +2387,14 @@ int arch_prepare_bpf_trampoline(struct bpf_tramp_image *im, void *image, void *i
>         if (save_ret)
>                 emit_ldx(&prog, BPF_DW, BPF_REG_0, BPF_REG_FP, -8);
>
> -       EMIT1(0x5B); /* pop rbx */
> +       emit_ldx(&prog, BPF_DW, BPF_REG_6, BPF_REG_FP, -rbx_off);
>         EMIT1(0xC9); /* leave */
>         if (flags & BPF_TRAMP_F_SKIP_FRAME)
>                 /* skip our return address and return to parent */
>                 EMIT4(0x48, 0x83, 0xC4, 8); /* add rsp, 8 */
>         emit_return(&prog, prog);
>         /* Make sure the trampoline generation logic doesn't overflow */
> -       if (WARN_ON_ONCE(prog > (u8 *)image_end - BPF_INSN_SAFETY)) {
> +       if (prog > (u8 *)image_end - BPF_INSN_SAFETY) {

Oops, this line is a mistake, and I should keep it still.

>                 ret = -EFAULT;
>                 goto cleanup;
>         }
> --
> 2.40.1
>