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