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

From: Leizhen (ThunderTown)
Date: Thu Dec 15 2022 - 07:34:25 EST



On 2022/12/15 17:39, Geert Uytterhoeven wrote:
> Hi Zhen,
>
> On Thu, Dec 15, 2022 at 10:16 AM Leizhen (ThunderTown)
> <thunder.leizhen@xxxxxxxxxx> wrote:
>> On 2022/12/15 16:50, Geert Uytterhoeven wrote:
>>> On Tue, Nov 15, 2022 at 9:41 AM Zhen Lei <thunder.leizhen@xxxxxxxxxx> 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@xxxxxxxxxx>
>>>
>>> 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.

>
> Gr{oetje,eeting}s,
>
> Geert
>
> --
> Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- geert@xxxxxxxxxxxxxx
>
> 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
From 8dfaa3f7a837737ed4205d4a0f0f859d485bb97b Mon Sep 17 00:00:00 2001
From: Zhen Lei <thunder.leizhen@xxxxxxxxxx>
Date: Thu, 15 Dec 2022 20:12:38 +0800
Subject: [PATCH] kallsyms: debug m68k

Signed-off-by: Zhen Lei <thunder.leizhen@xxxxxxxxxx>
---
kernel/kallsyms.c | 53 ++++++++++++++++++++++++++++++++++++++
kernel/kallsyms_selftest.c | 3 +++
2 files changed, 56 insertions(+)

diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
index 83f499182c9aa31..3396725d39842a3 100644
--- a/kernel/kallsyms.c
+++ b/kernel/kallsyms.c
@@ -267,6 +267,59 @@ static int kallsyms_lookup_names(const char *name,
return 0;
}

+void tst_kallsyms_lookup_name(const char *name)
+{
+ 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);
+ 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);
+ 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, name, 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..73a25a5fbe3e9ef 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);
+
+ tst_kallsyms_lookup_name("kallsyms_test_func");

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