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

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Message-ID: <CAMuHMdWM6+pC3yUqy+hHRrAf1BCz2sz1KQv2zxS+Wz-639X-aA@mail.gmail.com>
Date:   Thu, 15 Dec 2022 09:50:45 +0100
From:   Geert Uytterhoeven <geert@...ux-m68k.org>
To:     Zhen Lei <thunder.leizhen@...wei.com>
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

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?

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