Thread (37 messages) 37 messages, 8 authors, 2024-08-09

Re: [PATCH v2 3/3] tracing/kprobes: Use APIs that matches symbols without .XXX suffix

From: Steven Rostedt <rostedt@goodmis.org>
Date: 2024-08-06 20:00:03
Also in: live-patching, lkml

On Tue, 6 Aug 2024 19:35:07 +0000
Song Liu [off-list ref] wrote:
quoted
quoted
+ if (IS_ENABLED(CONFIG_LTO_CLANG) && !addr)
+ addr = kallsyms_lookup_name_without_suffix(trace_kprobe_symbol(tk));
+  
So you do the lookup twice if this is enabled?

Why not just use "kallsyms_lookup_name_without_suffix()" the entire time,
and it should work just the same as "kallsyms_lookup_name()" if it's not
needed?  
We still want to give priority to full match. For example, we have:

[root@~]# grep c_next /proc/kallsyms
ffffffff81419dc0 t c_next.llvm.7567888411731313343
ffffffff81680600 t c_next
ffffffff81854380 t c_next.llvm.14337844803752139461

If the goal is to explicitly trace c_next.llvm.7567888411731313343, the
user can provide the full name. If we always match _without_suffix, all
of the 3 will match to the first one. 

Does this make sense?
Yes. Sorry, I missed the "&& !addr)" after the "IS_ENABLED()", which looked
like you did the command twice.

I blame jetlag ;-)

-- Steve
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