linux-kernel - Re: [PATCH bpf-next] samples/bpf: fix broken bpf programs due to function inlining

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Date:   Mon, 7 Mar 2022 22:11:36 -0800
From:   Andrii Nakryiko <andrii.nakryiko@...il.com>
To:     Muhammad Falak R Wani <falakreyaz@...il.com>
Cc:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Networking <netdev@...r.kernel.org>, bpf <bpf@...r.kernel.org>,
        open list <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH bpf-next] samples/bpf: fix broken bpf programs due to
 function inlining

On Sun, Mar 6, 2022 at 4:15 AM Muhammad Falak R Wani
<falakreyaz@...il.com> wrote:
>
> commit: "be6bfe36db17 block: inline hot paths of blk_account_io_*()"
> inlines the function `blk_account_io_done`. As a result we can't attach a
> kprobe to the function anymore. Use `__blk_account_io_done` instead.
>
> Signed-off-by: Muhammad Falak R Wani <falakreyaz@...il.com>
> ---
>  samples/bpf/task_fd_query_kern.c | 2 +-
>  samples/bpf/tracex3_kern.c       | 2 +-
>  2 files changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/samples/bpf/task_fd_query_kern.c b/samples/bpf/task_fd_query_kern.c
> index c821294e1774..186ac0a79c0a 100644
> --- a/samples/bpf/task_fd_query_kern.c
> +++ b/samples/bpf/task_fd_query_kern.c

samples/bpf/task_fd_query_user.c also needs adjusting, no? Have you
tried running those samples?


> @@ -10,7 +10,7 @@ int bpf_prog1(struct pt_regs *ctx)
>         return 0;
>  }
>
> -SEC("kretprobe/blk_account_io_done")
> +SEC("kretprobe/__blk_account_io_done")
>  int bpf_prog2(struct pt_regs *ctx)
>  {
>         return 0;
> diff --git a/samples/bpf/tracex3_kern.c b/samples/bpf/tracex3_kern.c
> index 710a4410b2fb..bde6591cb20c 100644
> --- a/samples/bpf/tracex3_kern.c
> +++ b/samples/bpf/tracex3_kern.c
> @@ -49,7 +49,7 @@ struct {
>         __uint(max_entries, SLOTS);
>  } lat_map SEC(".maps");
>
> -SEC("kprobe/blk_account_io_done")
> +SEC("kprobe/__blk_account_io_done")
>  int bpf_prog2(struct pt_regs *ctx)
>  {
>         long rq = PT_REGS_PARM1(ctx);
> --
> 2.35.1
>