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

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

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.