Message-ID: <24ebf2ef-7ea6-67a1-65f1-08ce3e5529c4@gmail.com>
Date:   Mon, 27 Dec 2021 19:39:53 +0800
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Subject: Re: [PATCH 2/2] libbpf: Support repeated legacy kprobes on same
 function
Content-Language: en-US
To:     Qiang Wang <wangqiang.wq.frank@bytedance.com>, ast@kernel.org,
        daniel@iogearbox.net, andrii@kernel.org, kafai@fb.com,
        songliubraving@fb.com, yhs@fb.com, john.fastabend@gmail.com,
        kpsingh@kernel.org
Cc:     netdev@vger.kernel.org, bpf@vger.kernel.org,
        linux-kernel@vger.kernel.org, zhouchengming@bytedance.com,
        songmuchun@bytedance.com, duanxiongchun@bytedance.com,
        shekairui@bytedance.com
References: <20211225083242.38498-1-wangqiang.wq.frank@bytedance.com>
 <20211225083242.38498-2-wangqiang.wq.frank@bytedance.com>
From:   Hengqi Chen <hengqi.chen@gmail.com>
In-Reply-To: <20211225083242.38498-2-wangqiang.wq.frank@bytedance.com>
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Precedence: bulk


On 2021/12/25 4:32 PM, Qiang Wang wrote:
> If repeated legacy kprobes on same function in one process,
> libbpf will register using the same probe name and got -EBUSY
> error. So append index to the probe name format to fix this
> problem.
> 
> Co-developed-by: Chengming Zhou <zhouchengming@bytedance.com>
> Signed-off-by: Qiang Wang <wangqiang.wq.frank@bytedance.com>
> Signed-off-by: Chengming Zhou <zhouchengming@bytedance.com>
> ---
>  tools/lib/bpf/libbpf.c | 4 +++-
>  1 file changed, 3 insertions(+), 1 deletion(-)
> 
> diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
> index b7d6c951fa09..0c41a45ffd54 100644
> --- a/tools/lib/bpf/libbpf.c
> +++ b/tools/lib/bpf/libbpf.c
> @@ -9634,7 +9634,9 @@ static int append_to_file(const char *file, const char *fmt, ...)
>  static void gen_kprobe_legacy_event_name(char *buf, size_t buf_sz,
>  					 const char *kfunc_name, size_t offset)
>  {
> -	snprintf(buf, buf_sz, "libbpf_%u_%s_0x%zx", getpid(), kfunc_name, offset);
> +	static int index = 0;

Add empty line after variable declaration.

> +	snprintf(buf, buf_sz, "libbpf_%u_%s_0x%zx_%d", getpid(), kfunc_name, offset

Missing a comma after offset.

> +		 __sync_fetch_and_add(&index, 1));
>  }
>  
>  static int add_kprobe_event_legacy(const char *probe_name, bool retprobe,