linux-kernel - Re: [PATCHv2 bpf-next 3/9] bpf: Add support for uprobe multi session context

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Message-ID: <CAEf4BzbvA98fVtc9yf5zP2Bf3WbJ1wc7ZeXSR3FSvG-VV3zAKA@mail.gmail.com>
Date: Tue, 2 Jul 2024 14:31:25 -0700
From: Andrii Nakryiko <andrii.nakryiko@...il.com>
To: Jiri Olsa <jolsa@...nel.org>
Cc: Oleg Nesterov <oleg@...hat.com>, Peter Zijlstra <peterz@...radead.org>, 
	Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, 
	Andrii Nakryiko <andrii@...nel.org>, bpf@...r.kernel.org, Martin KaFai Lau <kafai@...com>, 
	Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>, 
	John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...omium.org>, 
	Stanislav Fomichev <sdf@...gle.com>, Hao Luo <haoluo@...gle.com>, Steven Rostedt <rostedt@...dmis.org>, 
	Masami Hiramatsu <mhiramat@...nel.org>, linux-kernel@...r.kernel.org, 
	linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCHv2 bpf-next 3/9] bpf: Add support for uprobe multi session context

On Mon, Jul 1, 2024 at 9:42 AM Jiri Olsa <jolsa@...nel.org> wrote:
>
> Placing bpf_session_run_ctx layer in between bpf_run_ctx and
> bpf_uprobe_multi_run_ctx, so the session data can be retrieved
> from uprobe_multi link.
>
> Plus granting session kfuncs access to uprobe session programs.
>
> Signed-off-by: Jiri Olsa <jolsa@...nel.org>
> ---
>  kernel/trace/bpf_trace.c | 23 +++++++++++++++--------
>  1 file changed, 15 insertions(+), 8 deletions(-)
>

Acked-by: Andrii Nakryiko <andrii@...nel.org>


> diff --git a/kernel/trace/bpf_trace.c b/kernel/trace/bpf_trace.c
> index 1b19c1cdb5e1..d431b880ca11 100644
> --- a/kernel/trace/bpf_trace.c
> +++ b/kernel/trace/bpf_trace.c
> @@ -3184,7 +3184,7 @@ struct bpf_uprobe_multi_link {
>  };
>
>  struct bpf_uprobe_multi_run_ctx {
> -       struct bpf_run_ctx run_ctx;
> +       struct bpf_session_run_ctx session_ctx;
>         unsigned long entry_ip;
>         struct bpf_uprobe *uprobe;
>  };
> @@ -3297,10 +3297,15 @@ static const struct bpf_link_ops bpf_uprobe_multi_link_lops = {
>
>  static int uprobe_prog_run(struct bpf_uprobe *uprobe,
>                            unsigned long entry_ip,
> -                          struct pt_regs *regs)
> +                          struct pt_regs *regs,
> +                          bool is_return, void *data)
>  {
>         struct bpf_uprobe_multi_link *link = uprobe->link;
>         struct bpf_uprobe_multi_run_ctx run_ctx = {
> +               .session_ctx = {
> +                       .is_return = is_return,
> +                       .data = data,
> +               },
>                 .entry_ip = entry_ip,
>                 .uprobe = uprobe,
>         };
> @@ -3319,7 +3324,7 @@ static int uprobe_prog_run(struct bpf_uprobe *uprobe,
>
>         migrate_disable();
>
> -       old_run_ctx = bpf_set_run_ctx(&run_ctx.run_ctx);
> +       old_run_ctx = bpf_set_run_ctx(&run_ctx.session_ctx.run_ctx);
>         err = bpf_prog_run(link->link.prog, regs);
>         bpf_reset_run_ctx(old_run_ctx);
>
> @@ -3349,7 +3354,7 @@ uprobe_multi_link_handler(struct uprobe_consumer *con, struct pt_regs *regs,
>         struct bpf_uprobe *uprobe;
>
>         uprobe = container_of(con, struct bpf_uprobe, consumer);
> -       return uprobe_prog_run(uprobe, instruction_pointer(regs), regs);
> +       return uprobe_prog_run(uprobe, instruction_pointer(regs), regs, false, data);
>  }
>
>  static int
> @@ -3359,14 +3364,15 @@ uprobe_multi_link_ret_handler(struct uprobe_consumer *con, unsigned long func, s
>         struct bpf_uprobe *uprobe;
>
>         uprobe = container_of(con, struct bpf_uprobe, consumer);
> -       return uprobe_prog_run(uprobe, func, regs);
> +       return uprobe_prog_run(uprobe, func, regs, true, data);
>  }
>
>  static u64 bpf_uprobe_multi_entry_ip(struct bpf_run_ctx *ctx)
>  {
>         struct bpf_uprobe_multi_run_ctx *run_ctx;
>
> -       run_ctx = container_of(current->bpf_ctx, struct bpf_uprobe_multi_run_ctx, run_ctx);
> +       run_ctx = container_of(current->bpf_ctx, struct bpf_uprobe_multi_run_ctx,
> +                              session_ctx.run_ctx);
>         return run_ctx->entry_ip;
>  }
>
> @@ -3374,7 +3380,8 @@ static u64 bpf_uprobe_multi_cookie(struct bpf_run_ctx *ctx)
>  {
>         struct bpf_uprobe_multi_run_ctx *run_ctx;
>
> -       run_ctx = container_of(current->bpf_ctx, struct bpf_uprobe_multi_run_ctx, run_ctx);
> +       run_ctx = container_of(current->bpf_ctx, struct bpf_uprobe_multi_run_ctx,
> +                              session_ctx.run_ctx);
>         return run_ctx->uprobe->cookie;
>  }
>
> @@ -3565,7 +3572,7 @@ static int bpf_kprobe_multi_filter(const struct bpf_prog *prog, u32 kfunc_id)
>         if (!btf_id_set8_contains(&kprobe_multi_kfunc_set_ids, kfunc_id))
>                 return 0;
>
> -       if (!is_kprobe_session(prog))
> +       if (!is_kprobe_session(prog) && !is_uprobe_session(prog))
>                 return -EACCES;
>
>         return 0;
> --
> 2.45.2
>
>