[Bug dynamic-link/17645] RFE: Improve performance of dynamic loader for deeply nested DSO dependencies.

["cvs-commit at gcc dot gnu.org" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=17645

--- Comment #22 from cvs-commit at gcc dot gnu.org <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Adhemerval Zanella
<azanella@sourceware.org>:

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=e6fd79f3795d46dfb583e124be49fc063bc3d58b

commit e6fd79f3795d46dfb583e124be49fc063bc3d58b
Author: Chung-Lin Tang <cltang@codesourcery.com>
Date:   Thu Oct 21 21:41:21 2021 +0800

    elf: Testing infrastructure for ld.so DSO sorting (BZ #17645)

    This is the first of a 2-part patch set that fixes slow DSO sorting
behavior in
    the dynamic loader, as reported in BZ #17645. In order to facilitate such a
    large modification to the dynamic loader, this first patch implements a
testing
    framework for validating shared object sorting behavior, to enable
comparison
    between old/new sorting algorithms, and any later enhancements.

    This testing infrastructure consists of a Python script
    scripts/dso-ordering-test.py' which takes in a description language,
consisting
    of strings that describe a set of link dependency relations between DSOs,
and
    generates testcase programs and Makefile fragments to automatically test
the
    described situation, 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.)

    Two files containing several new tests, elf/dso-sort-tests-[12].def are
added,
    including test scenarios for BZ #15311 and Redhat issue #1162810 [1].

    Due to the nature of dynamic loader tests, where the sorting behavior and
test
    output occurs before/after main(), generating testcases to use
    support/test-driver.c does not suffice to control meaningful timeout for
ld.so.
    Therefore a new utility program 'support/test-run-command', based on
    test-driver.c/support_test_main.c has been added. This does the same
testcase
    control, but for a program specified through a command-line rather than at
the
    source code level. This utility is used to run the dynamic loader testcases
    generated by dso-ordering-test.py.

    [1] https://bugzilla.redhat.com/show_bug.cgi?id=1162810

    Signed-off-by: Chung-Lin Tang  <cltang@codesourcery.com>
    Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

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