Re: [PATCH] kallsyms: let kallsyms_on_each_match_symbol match symbols exactly

[Song Liu <songliubraving@meta.com>]

> On Jun 16, 2023, at 2:31 AM, Leizhen (ThunderTown) <thunder.leizhen@huawei.com> wrote:
> 
> 
> 
> On 2023/6/16 1:00, Song Liu wrote:
>> With CONFIG_LTO_CLANG, kallsyms.c:cleanup_symbol_name() removes symbols
>> suffixes during comparison. This is problematic for livepatch, as
>> kallsyms_on_each_match_symbol may find multiple matches for the same
>> symbol, and fail with:
>> 
>>  livepatch: unresolvable ambiguity for symbol 'xxx' in object 'yyy'
>> 
>> Make kallsyms_on_each_match_symbol() to match symbols exactly. Since
>> livepatch is the only user of kallsyms_on_each_match_symbol(), this
>> change is safe.
>> 
>> Signed-off-by: Song Liu <song@kernel.org>
>> ---
>> kernel/kallsyms.c | 17 +++++++++--------
>> 1 file changed, 9 insertions(+), 8 deletions(-)
>> 
>> diff --git a/kernel/kallsyms.c b/kernel/kallsyms.c
>> index 77747391f49b..2ab459b43084 100644
>> --- a/kernel/kallsyms.c
>> +++ b/kernel/kallsyms.c
>> @@ -187,7 +187,7 @@ static bool cleanup_symbol_name(char *s)
>> return false;
>> }
>> 
>> -static int compare_symbol_name(const char *name, char *namebuf)
>> +static int compare_symbol_name(const char *name, char *namebuf, bool match_exactly)
>> {
>> int ret;
>> 
>> @@ -195,7 +195,7 @@ static int compare_symbol_name(const char *name, char *namebuf)
>> if (!ret)
>> return ret;
>> 
>> - if (cleanup_symbol_name(namebuf) && !strcmp(name, namebuf))
>> + if (!match_exactly && cleanup_symbol_name(namebuf) && !strcmp(name, namebuf))
> 
> This may affect the lookup of static functions.

I am not following why would this be a problem. Could you give an 
example of it?

Thanks,
Song