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Subject: Re: [PATCH v9] kallsyms: Add self-test facility
To:     Geert Uytterhoeven <geert@linux-m68k.org>
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>,
        Jiri Olsa <jolsa@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>,
        linux-m68k <linux-m68k@lists.linux-m68k.org>
References: <20221115083349.1662-1-thunder.leizhen@huawei.com>
 <CAMuHMdWM6+pC3yUqy+hHRrAf1BCz2sz1KQv2zxS+Wz-639X-aA@mail.gmail.com>
 <ad09966d-9357-1c32-e491-a402af8dac6e@huawei.com>
 <CAMuHMdW=KXfYc3Rqz6LizJcDxRX3BzUFTPpdTpDB68sw+QPJ=A@mail.gmail.com>
From:   "Leizhen (ThunderTown)" <thunder.leizhen@huawei.com>
Message-ID: <b00bcc04-0633-bac9-76ab-572f9470901c@huawei.com>
Date:   Thu, 15 Dec 2022 20:33:53 +0800
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On 2022/12/15 17:39, Geert Uytterhoeven wrote:
> Hi Zhen,
> 
> On Thu, Dec 15, 2022 at 10:16 AM Leizhen (ThunderTown)
> <thunder.leizhen@huawei.com> wrote:
>> On 2022/12/15 16:50, Geert Uytterhoeven wrote:
>>> On Tue, Nov 15, 2022 at 9:41 AM Zhen Lei <thunder.leizhen@huawei.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@huawei.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.
> 
> Thanks, looks normal to me:
> 
>     atari:~# cat /proc/kallsyms | grep kallsyms_test_func
>     00060ab0 t kallsyms_test_func_static
>     00060ac0 T kallsyms_test_func
>     00060ac2 W kallsyms_test_func_weak
>     atari:~#

It's incredible. I don't have a m68k environment and I'm trying to build a qemu
environment. If you're in a hurry and willing, you can apply the debugging patch
in the attachment. I'd like to see what's wrong. Use "dmesg | grep tst" to collect
the output information.

> 
> Gr{oetje,eeting}s,
> 
>                         Geert
> 
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@linux-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

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