Re: [PATCH v5 15/22] elf: Run constructors if executable has a soname of a dependency

[Adhemerval Zanella <adhemerval.zanella@linaro.org>]

On 11/11/2021 09:30, Florian Weimer wrote:
> * Adhemerval Zanella:
> 
>> The DSO constructor should not be ignored if the main executable
>> has the SONAME set to a dependency.  It fixes the case where
>> (using the scripts/dso-ordering-test.py definition):
>>
>>   {}->a->b->c;soname({})=c
>>
>> Where the constructors should return
>>
>>   c>b>a>{}<a<b<c
>>
>> Checked on x86_64-linux-gnu.
>> ---
>>  elf/dl-load.c            | 9 +++++++--
>>  elf/dso-sort-tests-1.def | 5 ++++-
>>  2 files changed, 11 insertions(+), 3 deletions(-)
>>
>> diff --git a/elf/dl-load.c b/elf/dl-load.c
>> index 4a0ff9d010..d585e1795d 100644
>> --- a/elf/dl-load.c
>> +++ b/elf/dl-load.c
>> @@ -1998,13 +1998,18 @@ _dl_map_object (struct link_map *loader, const char *name,
>>    assert (nsid >= 0);
>>    assert (nsid < GL(dl_nns));
>>  
>> +  /* Special case: trying to map itself.  */
>> +  if (name[0] == '\0')
>> +    return GL(dl_ns)[nsid]._ns_loaded;
> 
> Can you expand the comment a bit?  As far as I can see, "" corresponds
> to a NULL argument for dlopen, and we interpret that as returning the
> head object of the namespace.  The head link map must exist because the
> dlopen call with NULL/"" has to come from some.

I have changed to:

  /* Special case: trying to map itself.  An empty name correspond to
     a NULL or "" argument for dlopen(), and it returns the head object                                        
     of the namespace.  */

> 
> Do you know if we have explict tests for this behavior?

Yes, dlfcn/tststatic4 (I have to add this special case for this).

> 
> The change itself looks okay.  The reference count is updated by the
> caller in elf/dl-open.c.
> 
> Thanks,
> Florian
>