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From:   Geert Uytterhoeven <geert@linux-m68k.org>
Date:   Thu, 15 Dec 2022 10:39:39 +0100
Message-ID: <CAMuHMdW=KXfYc3Rqz6LizJcDxRX3BzUFTPpdTpDB68sw+QPJ=A@mail.gmail.com>
Subject: Re: [PATCH v9] kallsyms: Add self-test facility
To:     "Leizhen (ThunderTown)" <thunder.leizhen@huawei.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>,
        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>
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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:~#

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