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

Leizhen (ThunderTown)
2022-12-15T14:40:55Z

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On 2022/12/15 21:58, Leizhen (ThunderTown) wrote:
>
>
> On 2022/12/15 21:24, Geert Uytterhoeven wrote:
>> Hi Zhen,
>>
>> CC Jason
>>
>> 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.

>
>>
>> However, the binary search sequence looks very suspicious.
>> After investigation, it turns out compare_symbol_name() and strcmp()
>> always return positive numbers.
>>
>> Looks like commit 3bc753c06dd02a35 ("kbuild: treat char as always
>> unsigned") is to blame.
>
> Oh, maybe you can "git reset --hard 30f3bb09778de64" and try again.
> 30f3bb09778de64 kallsyms: Add self-test facility
>
> But the latest kernel is OK on x86. So other patches are unlikely to
> affect this function.
>
> Is m68k big-endian?
>
>>
>> Changing:
>>
>> --- a/arch/m68k/include/asm/string.h
>> +++ b/arch/m68k/include/asm/string.h
>> @@ -42,7 +42,7 @@ static inline char *strncpy(char *dest, const
>> char *src, size_t n)
>> #define __HAVE_ARCH_STRCMP
>> static inline int strcmp(const char *cs, const char *ct)
>> {
>> - char res;
>> + signed char res;
>>
>> asm ("\n"
>> "1: move.b (%0)+,%2\n" /* get *cs */
>>
>> fixes strcmp, but the test still fails:
>>
>> tst: kallsyms_lookup_names() is OK, name=kallsyms_test_func, i=0
>
> i=0, i is impossible zero. Maybe kallsyms_lookup_names() always return success now.
>
>> kallsyms_selftest: kallsyms_lookup_name() for
>> kallsyms_test_func_static failed: addr=8e1c, expect 60cd4
>> kallsyms_selftest: kallsyms_lookup_name() for kallsyms_test_func
>> failed: addr=8e1c, expect 60ce4
>> kallsyms_selftest: kallsyms_lookup_name() for
>> kallsyms_test_func_weak failed: addr=8e1c, expect 60ce6
>> kallsyms_selftest: kallsyms_lookup_name() for vmalloc failed:
>> addr=8e1c, expect c2946
>> kallsyms_selftest: kallsyms_lookup_name() for vfree failed:
>> addr=8e1c, expect c235e
>> kallsyms_selftest: kallsyms_on_each_match_symbol() for
>> kallsyms_test_func_static failed: count=25068, addr=1f3d3c, expect
>> 60cd4
>> kallsyms_selftest: kallsyms_on_each_match_symbol() for
>> kallsyms_test_func failed: count=25068, addr=1f3d3c, expect 60ce4
>> kallsyms_selftest: kallsyms_on_each_match_symbol() for
>> kallsyms_test_func_weak failed: count=25068, addr=1f3d3c, expect 60ce6
>> kallsyms_selftest: kallsyms_on_each_match_symbol() for vmalloc
>> failed: count=25068, addr=1f3d3c, expect c2946
>> kallsyms_selftest: kallsyms_on_each_match_symbol() for vfree
>> failed: count=25068, addr=1f3d3c, expect c235e
>> kallsyms_selftest: abort
>>
>> Dropping -funsigned-char doesn't improve upon that...
>>
>> 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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From c065ac86cfd9153e4fb71bbc06d440a41834b878 Mon Sep 17 00:00:00 2001
From: Zhen Lei <thunder.leizhen@huawei.com>
Date: Thu, 15 Dec 2022 20:12:38 +0800
Subject: [PATCH v2] kallsyms: debug m68k

Signed-off-by: Zhen Lei <thunder.leizhen@huawei.com>
---
kernel/kallsyms.c | 57 ++++++++++++++++++++++++++++++++++++++
kernel/kallsyms_selftest.c | 3 ++
2 files changed, 60 insertions(+)

diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
index 83f499182c9aa31..80251da9952b957 100644
--- a/kernel/kallsyms.c
+++ b/kernel/kallsyms.c
@@ -267,6 +267,63 @@ static int kallsyms_lookup_names(const char *name,
return 0;
}

+void tst_kallsyms_lookup_name(const char *name, void *addr)
+{
+ int i;
+ int ret;
+ int low, mid, high;
+ unsigned int seq, off;
+ char namebuf[KSYM_NAME_LEN];
+
+ ret = kallsyms_lookup_names(name, &i, NULL);
+ if (!ret) {
+ pr_warn("tst: kallsyms_lookup_names() is OK, name=%s, i=%d\n", name, i);
+ if (addr == (void *)kallsyms_sym_address(get_symbol_seq(i)))
+ pr_warn("tst: lookup address is OK\n");
+ return;
+ }
+
+
+ for (i = 0; i < kallsyms_num_syms; i++) {
+ seq = get_symbol_seq(i);
+ off = get_symbol_offset(seq);
+ kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
+ ret = compare_symbol_name(name, namebuf);
+ if (!ret) {
+ pr_warn("tst: found %s at index=%d\n", name, i);
+ if (addr == (void *)kallsyms_sym_address(get_symbol_seq(i)))
+ pr_warn("tst: lookup address is OK\n");
+ break;
+ }
+ }
+
+ if (i == kallsyms_num_syms) {
+ pr_warn("tst: found %s failed\n", name);
+ return;
+ }
+
+ low = 0;
+ high = kallsyms_num_syms - 1;
+
+ while (low <= high) {
+ mid = low + (high - low) / 2;
+ seq = get_symbol_seq(mid);
+ off = get_symbol_offset(seq);
+ kallsyms_expand_symbol(off, namebuf, ARRAY_SIZE(namebuf));
+ pr_warn("tst: [%d] = %s, seq=%d, offset=%d\n", mid, namebuf, seq, off);
+ ret = compare_symbol_name(name, namebuf);
+ if (ret > 0)
+ low = mid + 1;
+ else if (ret < 0)
+ high = mid - 1;
+ else
+ break;
+ }
+
+ if (mid == i)
+ pr_warn("tst: binary search is OK\n");
+}
+
/* Lookup the address for this symbol. Returns 0 if not found. */
unsigned long kallsyms_lookup_name(const char *name)
{
diff --git a/kernel/kallsyms_selftest.c b/kernel/kallsyms_selftest.c
index f35d9cc1aab1544..f0f7c9fc72c5d53 100644
--- a/kernel/kallsyms_selftest.c
+++ b/kernel/kallsyms_selftest.c
@@ -293,6 +293,9 @@ static int test_kallsyms_basic_function(void)
unsigned long addr, lookup_addr;
char namebuf[KSYM_NAME_LEN];
struct test_stat *stat, *stat2;
+ extern void tst_kallsyms_lookup_name(const char *name, void *addr);
+
+ tst_kallsyms_lookup_name("kallsyms_test_func", kallsyms_test_func);

stat = kmalloc(sizeof(*stat) * 2, GFP_KERNEL);
if (!stat)
--
2.25.1