From: "Leizhen (ThunderTown)" <thunder.leizhen@huawei.com>
To: Jiri Olsa <olsajiri@gmail.com>
Cc: Josh Poimboeuf <jpoimboe@kernel.org>,
Jiri Kosina <jikos@kernel.org>, Miroslav Benes <mbenes@suse.cz>,
Petr Mladek <pmladek@suse.com>,
Joe Lawrence <joe.lawrence@redhat.com>,
<live-patching@vger.kernel.org>, <linux-kernel@vger.kernel.org>,
Masahiro Yamada <masahiroy@kernel.org>,
Alexei Starovoitov <ast@kernel.org>,
Kees Cook <keescook@chromium.org>,
Andrew Morton <akpm@linux-foundation.org>,
Luis Chamberlain <mcgrof@kernel.org>,
<linux-modules@vger.kernel.org>,
Steven Rostedt <rostedt@goodmis.org>,
Ingo Molnar <mingo@redhat.com>,
David Laight <David.Laight@aculab.com>,
Stephen Rothwell <sfr@canb.auug.org.au>
Subject: Re: [PATCH v8 7/9] livepatch: Improve the search performance of module_kallsyms_on_each_symbol()
Date: Mon, 14 Nov 2022 19:30:16 +0800 [thread overview]
Message-ID: <955eebae-0b36-d13f-0199-2f1b32af7da6@huawei.com> (raw)
In-Reply-To: <Y3IY6gzDtk1ze3u7@krava>
On 2022/11/14 18:31, Jiri Olsa wrote:
> On Mon, Nov 14, 2022 at 06:00:38PM +0800, Leizhen (ThunderTown) wrote:
>>
>>
>> On 2022/11/14 17:27, Jiri Olsa wrote:
>>> On Mon, Nov 14, 2022 at 04:50:25PM +0800, Leizhen (ThunderTown) wrote:
>>>>
>>>> On 2022/11/14 15:47, Jiri Olsa wrote:
>>>>> On Wed, Nov 02, 2022 at 04:49:19PM +0800, 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.
>>>>> hi,
>>>>> sorry for delayed answer, I did not notice this until Stephen's email
>>>>> about merge issue with recent bpf change [1]
>>>>>
>>>>>> Let's add a new parameter 'const char *modname' to function
>>>>>> module_kallsyms_on_each_symbol(), then we can compare the module names
>>>>> we have use case for iterating all modules and their symbols when we
>>>>> want to resolve passed addresses for tracing
>>>>>
>>>>> we don't have 'modname' that we could pass, we need to iterate all modules
>>>>>
>>>>> so perhaps this could be made optional like with passing NULL for modname?
>>>> The deletion of modname was suggested by Petr Mladek. The reason is that
>>>> everyone passes modname as NULL, there was no actual demand at the time.
>>>> https://lkml.org/lkml/2022/9/20/682
>>>>
>>>>>> directly in this function and call hook 'fn' after matching. And the
>>>>>> parameter 'struct module *' in the hook 'fn' can also be deleted.
>>>>> we need 'struct module *' argument in the callback as well because we are
>>>>> taking the module reference if we trace function in it, so it wont get
>>>>> unloaded
>>>>>
>>>>> please let me know if I should do the change or can help in any way
>>>> It seems that we should take the module reference before invoking callback
>>>> and put it after it is called, without passing modname.
>>> we take the module ref only if we (callback) find the traced address in
>>> the module, we don't have the module object before
>>>
>>> jirka
>>>
>>
>> Do it in function module_kallsyms_on_each_symbol()?
>>
>> But I just saw that mutex_lock(&module_mutex) protection is already
>> provided in this function. So reference counting protection may not
>> be required.
>
> we take the module ref so it won't unload even outside of the
> module_kallsyms_on_each_symbol function
There's another way to do it, but it's more time consuming.
struct module *__module_text_address(unsigned long addr);
struct module *__module_address(unsigned long addr);
Which way do you think is more appropriate?
>
> jirka
> .
>
--
Regards,
Zhen Lei
next prev parent reply other threads:[~2022-11-14 11:30 UTC|newest]
Thread overview: 35+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-11-02 8:49 [PATCH v8 0/9] kallsyms: Optimizes the performance of lookup symbols Zhen Lei
2022-11-02 8:49 ` [PATCH v8 1/9] scripts/kallsyms: rename build_initial_tok_table() Zhen Lei
2022-11-02 8:49 ` [PATCH v8 2/9] kallsyms: Improve the performance of kallsyms_lookup_name() Zhen Lei
2022-11-02 8:49 ` [PATCH v8 3/9] kallsyms: Correctly sequence symbols when CONFIG_LTO_CLANG=y Zhen Lei
2022-11-02 8:49 ` [PATCH v8 4/9] kallsyms: Reduce the memory occupied by kallsyms_seqs_of_names[] Zhen Lei
2022-11-02 12:00 ` David Laight
2022-11-07 8:01 ` Leizhen (ThunderTown)
2022-11-02 8:49 ` [PATCH v8 5/9] kallsyms: Add helper kallsyms_on_each_match_symbol() Zhen Lei
2022-11-02 8:49 ` [PATCH v8 6/9] livepatch: Use kallsyms_on_each_match_symbol() to improve performance Zhen Lei
2022-11-23 13:28 ` Petr Mladek
2022-11-24 2:36 ` Leizhen (ThunderTown)
2022-11-24 8:29 ` Petr Mladek
2022-12-06 22:08 ` Luis Chamberlain
2022-12-07 1:30 ` Leizhen (ThunderTown)
2022-11-02 8:49 ` [PATCH v8 7/9] livepatch: Improve the search performance of module_kallsyms_on_each_symbol() Zhen Lei
2022-11-14 7:47 ` Jiri Olsa
2022-11-14 8:50 ` Leizhen (ThunderTown)
2022-11-14 9:27 ` Jiri Olsa
2022-11-14 10:00 ` Leizhen (ThunderTown)
2022-11-14 10:31 ` Jiri Olsa
2022-11-14 11:30 ` Leizhen (ThunderTown) [this message]
2022-11-14 13:26 ` Jiri Olsa
2022-11-14 15:46 ` Luis Chamberlain
2022-11-15 2:10 ` Leizhen (ThunderTown)
2022-11-15 7:30 ` Jiri Olsa
2022-11-15 7:54 ` Luis Chamberlain
2022-11-15 8:14 ` Leizhen (ThunderTown)
2022-11-15 20:11 ` Stephen Rothwell
2022-11-23 13:57 ` Petr Mladek
2022-11-24 2:41 ` Leizhen (ThunderTown)
2022-11-02 8:49 ` [PATCH v8 8/9] kallsyms: Delete an unused parameter related to kallsyms_on_each_symbol() Zhen Lei
2022-11-02 8:49 ` [PATCH v8 9/9] kallsyms: Add self-test facility Zhen Lei
2022-11-13 2:44 ` [PATCH v8 0/9] kallsyms: Optimizes the performance of lookup symbols Luis Chamberlain
2022-11-13 2:55 ` Luis Chamberlain
2022-11-14 1:25 ` Leizhen (ThunderTown)
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