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

Geert Uytterhoeven
2022-12-15T08:51:03Z

Hi Zhen,

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?

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