From:   Qiang Wang <wangqiang.wq.frank@bytedance.com>
To:     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, hengqi.chen@gmail.com
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,
        Qiang Wang <wangqiang.wq.frank@bytedance.com>
Subject: [PATCH v2 2/2] libbpf: Support repeated legacy kprobes on same function
Date:   Mon, 27 Dec 2021 21:07:13 +0800
Message-Id: <20211227130713.66933-2-wangqiang.wq.frank@bytedance.com>
In-Reply-To: <20211227130713.66933-1-wangqiang.wq.frank@bytedance.com>
References: <20211227130713.66933-1-wangqiang.wq.frank@bytedance.com>
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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 | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/tools/lib/bpf/libbpf.c b/tools/lib/bpf/libbpf.c
index b7d6c951fa09..698e8864da02 100644
--- a/tools/lib/bpf/libbpf.c
+++ b/tools/lib/bpf/libbpf.c
@@ -9634,7 +9634,10 @@ 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;
+
+	snprintf(buf, buf_sz, "libbpf_%u_%s_0x%zx_%d", getpid(), kfunc_name, offset,
+		 __sync_fetch_and_add(&index, 1));
 }
 
 static int add_kprobe_event_legacy(const char *probe_name, bool retprobe,
-- 
2.20.1