linux-kernel - Re: [PATCH resend ] tracepoint: Print the function symbol when tracepoint

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Message-ID: <b098cbdf-394b-4f20-9dcd-393ad1b734b7@amperemail.onmicrosoft.com>
Date: Thu, 6 Mar 2025 11:37:38 +0800
From: Shijie Huang <shijie@...eremail.onmicrosoft.com>
To: Mathieu Desnoyers <mathieu.desnoyers@...icios.com>,
 Huang Shijie <shijie@...amperecomputing.com>, rostedt@...dmis.org
Cc: patches@...erecomputing.com, cl@...ux.com, yang@...amperecomputing.com,
 peterz@...radead.org, jpoimboe@...nel.org, linux-kernel@...r.kernel.org,
 linux-trace-kernel@...r.kernel.org
Subject: Re: [PATCH resend ] tracepoint: Print the function symbol when
 tracepoint_debug is set


On 2025/3/5 21:53, Mathieu Desnoyers wrote:
> On 2025-03-04 20:55, Huang Shijie wrote:
>> When tracepoint_debug is set, we may get the output in kernel log:
>>       [  380.013843] Probe 0 : 00000000f0d68cda
>>
>> It is not readable, so change to print the function symbol.
>> After this patch, the output may becomes:
>>       [   54.930567] Probe 0 : perf_trace_sched_wakeup_template
>
> What would it print if the address is corrupted ?
>
> Perhaps we could do like the backtrace code and print e.g.
>
> [<00000000f0d68cda>] perf_trace_sched_wakeup_template+0xNN/0xMM 

If we want this format, we can change code to:

    ---
  kernel/tracepoint.c | 3 ++-
  1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/kernel/tracepoint.c b/kernel/tracepoint.c
index abfd0ac1177f..5a5041f32cc8 100644
--- a/kernel/tracepoint.c
+++ b/kernel/tracepoint.c
@@ -127,7 +127,8 @@ static void debug_print_probes(struct 
tracepoint_func *funcs)
                 return;

         for (i = 0; funcs[i].func; i++)
-               printk(KERN_DEBUG "Probe %d : %p\n", i, funcs[i].func);
+               printk(KERN_DEBUG "Probe %d : [ %p ] %pS\n",
+                               i, funcs[i].func, funcs[i].func);
  }


The output will look like:

[   63.818829] Probe 0 : [ 0000000032848d41 ] 
perf_trace_sched_wakeup_template+0x0/0x20
[   63.819287] Probe 0 : [ 00000000fe8cca4d ] 
perf_trace_sched_switch+0x0/0x20
[   65.325638] Probe 0 : [ 0000000032848d41 ] 
perf_trace_sched_wakeup_template+0x0/0x20
[   65.695631] Probe 0 : [ 00000000fe8cca4d ] 
perf_trace_sched_switch+0x0/0x20

Thanks

Huang Shijie