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

[Steven Rostedt]

On Tue, 6 Aug 2024 19:35:07 +0000
Song Liu <songliubraving@xxxxxxxx> wrote:

> >> + 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