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From:   Geert Uytterhoeven <geert@linux-m68k.org>
Date:   Thu, 15 Dec 2022 15:51:52 +0100
Message-ID: <CAMuHMdWAAQNJd21fhodDONb40LFMae3V_517iT22FykCqG90Og@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>,
        "Jason A. Donenfeld" <Jason@zx2c4.com>
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Hi Zhen,

On Thu, Dec 15, 2022 at 3:40 PM Leizhen (ThunderTown)
<thunder.leizhen@huawei.com> wrote:
> On 2022/12/15 21:58, Leizhen (ThunderTown) wrote:
> > On 2022/12/15 21:24, Geert Uytterhoeven wrote:
> >> On Thu, Dec 15, 2022 at 1:34 PM Leizhen (ThunderTown)
> >> <thunder.leizhen@huawei.com> wrote:
> >>> On 2022/12/15 17:39, Geert Uytterhoeven wrote:
> >>>> 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.
> >>
> >> Still fails:
> >>
> >>     tst: found kallsyms_test_func at index=12845
> >>     tst: [12533] = kallsyms_test_func, seq=17370, offset=191223
> >>     tst: [18800] = kallsyms_test_func, seq=23193, offset=259263
> >>     tst: [21934] = kallsyms_test_func, seq=2527, offset=22331
> >>     tst: [23501] = kallsyms_test_func, seq=11792, offset=126366
> >>     tst: [24284] = kallsyms_test_func, seq=8427, offset=87395
> >>     tst: [24676] = kallsyms_test_func, seq=21896, offset=243536
> >>     tst: [24872] = kallsyms_test_func, seq=22571, offset=251856
> >>     tst: [24970] = kallsyms_test_func, seq=23264, offset=260074
> >>     tst: [25019] = kallsyms_test_func, seq=9003, offset=93752
> >>     tst: [25043] = kallsyms_test_func, seq=14324, offset=155117
> >>     tst: [25055] = kallsyms_test_func, seq=5942, offset=62266
> >>     tst: [25061] = kallsyms_test_func, seq=14347, offset=155467
> >>     tst: [25064] = kallsyms_test_func, seq=14350, offset=155512
> >>     tst: [25066] = kallsyms_test_func, seq=14346, offset=155457
> >>     tst: [25067] = kallsyms_test_func, seq=14354, offset=155565
> >
> > -               pr_warn("tst: [%d] = %s, seq=%d, offset=%d\n", mid, name, seq, off);
> > +               pr_warn("tst: [%d] = %s, seq=%d, offset=%d\n", mid, namebuf, seq, off);
> >
> > Sorry, a variable in the debugging code is incorrectly written. 'name' should
> > be replaced with 'namebuf', then we can see which function the comparison is wrong.
>
> I attached debug patch v2.

On 30f3bb09778de64 with your debug patch v2:

kallsyms_selftest: start
tst: kallsyms_lookup_names() is OK, name=kallsyms_test_func, i=0
kallsyms_selftest: kallsyms_lookup_name() for
kallsyms_test_func_static failed: addr=8dbc, expect 60498
kallsyms_selftest: kallsyms_lookup_name() for kallsyms_test_func
failed: addr=8dbc, expect 604a8
kallsyms_selftest: kallsyms_lookup_name() for kallsyms_test_func_weak
failed: addr=8dbc, expect 604aa
kallsyms_selftest: kallsyms_lookup_name() for vmalloc failed:
addr=8dbc, expect bde18
kallsyms_selftest: kallsyms_lookup_name() for vfree failed: addr=8dbc,
expect bd86e
kallsyms_selftest: kallsyms_on_each_match_symbol() for
kallsyms_test_func_static failed: count=24891, addr=1eea00, expect
60498
kallsyms_selftest: kallsyms_on_each_match_symbol() for
kallsyms_test_func failed: count=24891, addr=1eea00, expect 604a8
kallsyms_selftest: kallsyms_on_each_match_symbol() for
kallsyms_test_func_weak failed: count=24891, addr=1eea00, expect 604aa
kallsyms_selftest: kallsyms_on_each_match_symbol() for vmalloc failed:
count=24891, addr=1eea00, expect bde18
kallsyms_selftest: kallsyms_on_each_match_symbol() for vfree failed:
count=24891, addr=1eea00, expect bd86e
kallsyms_selftest: abort

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