Ping x2 Re: [PATCH 1/2][RFC] #17645, fix slow DSO sorting behavior in dynamic loader

[Chung-Lin Tang <chunglin_tang@mentor.com>]

Ping again.

On 2019/9/17 5:55 PM, Chung-Lin Tang wrote:
> Ping?
> 
> On 2019/7/21 1:50 AM, Chung-Lin Tang wrote:
>> Hi, this patch is our attempt at resolving the slow shared object sorting
>> situation in #17645, #15310, and some effort at #15311.  I realize this is
>> pretty unsuitable timing to be submitting a patch of such nature now (probably
>> way too late to be included into 2.30), but still sending now anyways as this
>> will probably need quite some discussion before being approved.
>>
>> Prior attempts at solving this slow sorting behavior appeared to have failed
>> due to inadequate proposed testing, therefore cannot convince reviewers to
>> touch what seems to be perceived as a sensitive and easy to break part of ld.so.
>>
>> Therefore the first part of this patch is not a change to the dynamic loader
>> code proper, but a testing framework for constructing DSO sorting tests.
>> It consists of a new Python script 'dso-ordering-test.py' that serves to
>> generate both testcase source files and the needed Makefile fragments from
>> a short description string, for example:
>>
>>      a->b->c->d          // four objects linked one after another
>>
>>      a->[bc]->d;b->c     // a depends on b and c, which both depend on d,
>>                          // b depends on c (b,c linked to object a in fixed order)
>>
>>      a->b->c;{+a;%a;-a}  // a, b, c serially dependent, main program uses
>>                          // dlopen/dlsym/dlclose on object a
>>
>>      a->b->c;{}!->[abc]  // a, b, c serially dependent; multiple tests generated
>>                          // to test all permutations of a, b, c ordering linked
>>                          // to main program
>>
>>     (Above is just a short description of what the script can do, more
>>      documentation is in the script comments.)
>>
>> and, a patch to glibc/elf/Makefile which uses this script to add a few
>> DSO sorting testcases.  The description string notation and output form of the
>> generated testcases is short enough that both the test descriptions
>> and expected outcomes can all directly be specified in the Makefile.
>>
>> In terms of the tests I added using this script, I am not completely sure they are
>> (together with existing tests) adequate to prove algorithmic integrity in face
>> of any ld.so code changes, but the script should provide a solid tool to further
>> improve on coverage.  Also welcome suggestions if the current features are still
>> lacking in expressing some case of shared object relations, or if the documentation
>> still feels unclear.
>>
>> Thanks,
>> Chung-Lin
>>
>> 2019-07-20  Chung-Lin Tang  <cltang@codesourcery.com>
>>
>>          [BZ #17645]
>>          [BZ #15311]
>>          [BZ #15310]
>>          * elf/Makefile (test_dso_ordering): New make function.
>>          (tst-dso-ordering[123456789]): Define new DSO sorting tests.
>>          (tst-bz15311): Testcase from #15311.
>>          * scripts/dso-ordering-test.py: New script.