[DTrace-devel] [PATCH 4/4] test: Do not depend on ext4

[Eugene Loh]

E.g.,
     $ uname -r
     5.15.0-205.149.5.1.el9uek.aarch64
     $ sudo grep ext4_dir_operations /proc/kallmodsyms
      ffffc45a59d9ee88 100 D ext4_dir_operations
      $ sudo awk '/ext4/ { print NF }' /proc/kallmodsyms | uniq -c
        2342 4
     $ sudo grep -w ext4 /proc/kallmodsyms

So, lots of ext4 symbols (including ext4_dir_operations) but none of 
them are [ext4].  Bug in... kallmodsyms?

On 10/25/24 17:16, Kris Van Hees wrote:
> I am not too sure about this patch...  We are not using kallmodsyms anymore
> for newer kernels, and on older kernels that symbol certainly be listed as
> [ext4].  So, if ext4_dir_operations *is* in the ext4 module code (compiled in
> or loadable), then the proper ref to it would be ext4`ext4_dir_operations.
> So the test should be able to use that - if not, that seems like a bug rather
> than something to change in the test?
>
> On Fri, Oct 04, 2024 at 12:43:55AM -0400, eugene.loh at oracle.com wrote:
>> From: Eugene Loh <eugene.loh at oracle.com>
>>
>> It is possible that there is no ext4 module, whether built-in or otherwise,
>> even if its symbols are present.  E.g.,
>>      # grep ext4_dir_operations /proc/kallmodsyms
>>      ffffc45a59d9ee88 100 D ext4_dir_operations
>>      # grep -w ext4 /proc/kallmodsyms
>>      #
>>
>> Meanwhile, in
>>      ab883bae "tests, io, scalars: use kallsyms instead of kallmodsyms where possible"
>> we read:
>>      scalars/tst.misc.x needs adjusting to check for the presence of the actual
>>      symbols we are looking up, since the modules might well be built-in, and
>>      thus not show up in /proc/kallsyms.
>>
>> With that patch, in test/unittest/scalars/tst.misc.x, we check:
>>     -if ! $(grep -qw ext4 /proc/kallmodsyms); then
>>     +if ! grep -qw ext4_dir_operations /proc/kallsyms; then
>>          exit 1
>>      fi
>>
>> So it is possible for us to find
>>          `ext4_dir_operations
>> but not
>>      ext4`ext4_dir_operations
>>
>> Change the .d script to look simply for `ext4_dir_operations.
>>
>> Signed-off-by: Eugene Loh <eugene.loh at oracle.com>
>> ---
>>   test/unittest/scalars/tst.misc.d | 2 +-
>>   1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/test/unittest/scalars/tst.misc.d b/test/unittest/scalars/tst.misc.d
>> index 60edab45e..6a5f4ae2e 100644
>> --- a/test/unittest/scalars/tst.misc.d
>> +++ b/test/unittest/scalars/tst.misc.d
>> @@ -20,7 +20,7 @@
>>   BEGIN
>>   {
>>   	printf("\nr_cpu_ids = 0x%x\n", `nr_cpu_ids);
>> -	printf("ext4`ext4_dir_operations = %p\n", &ext4`ext4_dir_operations);
>> +	printf("ext4`ext4_dir_operations = %p\n", &`ext4_dir_operations);
>>   	printf("isofs`isofs_dir_operations = %p\n", &isofs`isofs_dir_operations);
>>   	printf("vmlinux`major_names = %p\n", &vmlinux`major_names);
>>   	x = 123;
>> -- 
>> 2.43.5
>>