linux-kernel - Re: [PATCH v8 7/9] livepatch: Improve the search performance of module_kallsyms_on_each

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Date:   Wed, 23 Nov 2022 14:57:00 +0100
From:   Petr Mladek <pmladek@...e.com>
To:     Zhen Lei <thunder.leizhen@...wei.com>
Cc:     Josh Poimboeuf <jpoimboe@...nel.org>,
        Jiri Kosina <jikos@...nel.org>,
        Miroslav Benes <mbenes@...e.cz>,
        Joe Lawrence <joe.lawrence@...hat.com>,
        live-patching@...r.kernel.org, linux-kernel@...r.kernel.org,
        Masahiro Yamada <masahiroy@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Jiri Olsa <jolsa@...nel.org>,
        Kees Cook <keescook@...omium.org>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Luis Chamberlain <mcgrof@...nel.org>,
        linux-modules@...r.kernel.org,
        Steven Rostedt <rostedt@...dmis.org>,
        Ingo Molnar <mingo@...hat.com>,
        David Laight <David.Laight@...lab.com>
Subject: Re: [PATCH v8 7/9] livepatch: Improve the search performance of
 module_kallsyms_on_each_symbol()

On Wed 2022-11-02 16:49:19, Zhen Lei wrote:
> Currently we traverse all symbols of all modules to find the specified
> function for the specified module. But in reality, we just need to find
> the given module and then traverse all the symbols in it.
> 
> Let's add a new parameter 'const char *modname' to function
> module_kallsyms_on_each_symbol(), then we can compare the module names
> directly in this function and call hook 'fn' after matching. And the
> parameter 'struct module *' in the hook 'fn' can also be deleted.
> 
> Phase1: mod1-->mod2..(subsequent modules do not need to be compared)
>                 |
> Phase2:          -->f1-->f2-->f3

Just for record. The patch looks good from the livepatching code POV.

But I guess that it will need to get updated to support the new
callers in the ftrace and bpf code.

Best Regards,
Petr