linux-kernel - Re: [PATCH v9] kallsyms: Add self-test facility

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Date:   Thu, 15 Dec 2022 17:16:09 +0800
From:   "Leizhen (ThunderTown)" <thunder.leizhen@...wei.com>
To:     Geert Uytterhoeven <geert@...ux-m68k.org>
CC:     Josh Poimboeuf <jpoimboe@...nel.org>,
        Jiri Kosina <jikos@...nel.org>,
        Miroslav Benes <mbenes@...e.cz>,
        Petr Mladek <pmladek@...e.com>,
        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>,
        linux-m68k <linux-m68k@...ts.linux-m68k.org>
Subject: Re: [PATCH v9] kallsyms: Add self-test facility



On 2022/12/15 16:50, Geert Uytterhoeven wrote:
> Hi Zhen,
> 
> On Tue, Nov 15, 2022 at 9:41 AM Zhen Lei <thunder.leizhen@...wei.com> wrote:
>> Added test cases for basic functions and performance of functions
>> kallsyms_lookup_name(), kallsyms_on_each_symbol() and
>> kallsyms_on_each_match_symbol(). It also calculates the compression rate
>> of the kallsyms compression algorithm for the current symbol set.
>>
>> The basic functions test begins by testing a set of symbols whose address
>> values are known. Then, traverse all symbol addresses and find the
>> corresponding symbol name based on the address. It's impossible to
>> determine whether these addresses are correct, but we can use the above
>> three functions along with the addresses to test each other. Due to the
>> traversal operation of kallsyms_on_each_symbol() is too slow, only 60
>> symbols can be tested in one second, so let it test on average once
>> every 128 symbols. The other two functions validate all symbols.
>>
>> If the basic functions test is passed, print only performance test
>> results. If the test fails, print error information, but do not perform
>> subsequent performance tests.
>>
>> Start self-test automatically after system startup if
>> CONFIG_KALLSYMS_SELFTEST=y.
>>
>> Example of output content: (prefix 'kallsyms_selftest:' is omitted
>>  start
>>   ---------------------------------------------------------
>>  | nr_symbols | compressed size | original size | ratio(%) |
>>  |---------------------------------------------------------|
>>  |     107543 |       1357912   |      2407433  |  56.40   |
>>   ---------------------------------------------------------
>>  kallsyms_lookup_name() looked up 107543 symbols
>>  The time spent on each symbol is (ns): min=630, max=35295, avg=7353
>>  kallsyms_on_each_symbol() traverse all: 11782628 ns
>>  kallsyms_on_each_match_symbol() traverse all: 9261 ns
>>  finish
>>
>> Signed-off-by: Zhen Lei <thunder.leizhen@...wei.com>
> 
> Thanks for your patch, which is now commit 30f3bb09778de64e ("kallsyms:
> Add self-test facility") in linus/master.
> 
> I gave this a try on m68k (atari_defconfig + CONFIG_KALLSYMS_SELFTEST=y),
> but it failed:
> 
>     start
>     kallsyms_lookup_name() for kallsyms_test_func_static failed:
> addr=0, expect 60ab0
>     kallsyms_lookup_name() for kallsyms_test_func failed: addr=0, expect 60ac0
>     kallsyms_lookup_name() for kallsyms_test_func_weak failed: addr=0,
> expect 60ac2
>     kallsyms_lookup_name() for vmalloc failed: addr=0, expect c272a
>     kallsyms_lookup_name() for vfree failed: addr=0, expect c2142
>     kallsyms_on_each_match_symbol() for kallsyms_test_func_static
> failed: count=0, addr=0, expect 60ab0
>     kallsyms_on_each_match_symbol() for kallsyms_test_func failed:
> count=0, addr=0, expect 60ac0
>     kallsyms_on_each_match_symbol() for kallsyms_test_func_weak
> failed: count=0, addr=0, expect 60ac2
>     kallsyms_on_each_match_symbol() for vmalloc failed: count=0,
> addr=0, expect c272a
>     kallsyms_on_each_match_symbol() for vfree failed: count=0, addr=0,
> expect c2142
>     abort
> 
> Given all addresses are zero, it looks like some required functionality
> or config option is missing.
> 
> $ grep SYM .config
> CONFIG_KALLSYMS=y
> CONFIG_KALLSYMS_SELFTEST=y
> CONFIG_KALLSYMS_BASE_RELATIVE=y
> # CONFIG_ASYMMETRIC_KEY_TYPE is not set
> CONFIG_SYMBOLIC_ERRNAME=y
> # CONFIG_STRIP_ASM_SYMS is not set
> CONFIG_KALLSYMS_SELFTEST
> 
> Do you have a clue?

cat /proc/kallsyms | grep kallsyms_test_func
Let's see if the compiler-generated symbols have some special suffixes.


> 
> Gr{oetje,eeting}s,
> 
>                         Geert
> 
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@...ux-m68k.org
> 
> In personal conversations with technical people, I call myself a hacker. But
> when I'm talking to journalists I just say "programmer" or something like that.
>                                 -- Linus Torvalds
> 
> .
> 

-- 
Regards,
  Zhen Lei