With modern ssh clients and daemons it is required to use AcceptEnv and
SendEnv configuration options to correctly support testing the DSO sort
ordering tests.  This requirement is present because
scripts/dso-ordering-test.py injects GLIBC_TUNABLES to the left of the
${test_wrapper_env} and so it must both be sent by the ssh client and
accepted by the ssh daemon.  This requirement is removed in this change
and the injected GLIBC_TUNABLES is placed after ${run_program_env} and
so still correctly provides the override that the test requires.
This is similar to existing tests like elf/tst-pathopt.sh,
elf/tst-rtld-load-self.sh, and locale/tst-locale-locpath.sh.

Tested that it fixes two failures when cross-testing on aarch64 with
scripts/cross-test-ssh.sh and an ssh client and daemon that do not pass
GLIBC_TUNABLES. Without this fix such a configuration will report the
following failures (since the GLIBC_TUNABLES not preserved):
FAIL: elf/tst-bz15311
FAIL: elf/tst-bz28937

Tested without regression on native x86_64 and aarch64 builds.

Reviewed-by: Florian Weimer <fweimer@redhat.com>

The main program needs to depend on all shared objects, even objects
that have link-time dependencies among shared objects.  Filtering
out shared objects that already have an link-time dependencies is not
necessary here; make will do this automatically.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

The elf/dso-sort-tests-src subdirectory is not changed by this commit,
so it seems that the cut-and-paste error was not material.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

I used these shell commands:

../glibc/scripts/update-copyrights $PWD/../gnulib/build-aux/update-copyright
(cd ../glibc && git commit -am"[this commit message]")

and then ignored the output, which consisted lines saying "FOO: warning:
copyright statement not found" for each of 7061 files FOO.

I then removed trailing white space from math/tgmath.h,
support/tst-support-open-dev-null-range.c, and
sysdeps/x86_64/multiarch/strlen-vec.S, to work around the following
obscure pre-commit check failure diagnostics from Savannah.  I don't
know why I run into these diagnostics whereas others evidently do not.

remote: *** 912-#endif
remote: *** 913:
remote: *** 914-
remote: *** error: lines with trailing whitespace found
...
remote: *** error: sysdeps/unix/sysv/linux/statx_cp.c: trailing lines

Put all sources for DSO sorting tests in the dso-sort-tests-src directory
and compile test relocatable objects with

$(objpfx)tst-dso-ordering1-dir/tst-dso-ordering1-a.os: $(objpfx)dso-sort-tests-src/tst-dso-ordering1-a.c
	$(compile.c) $(OUTPUT_OPTION)

to avoid random $< values from $(before-compile) when compiling test
relocatable objects with

$(objpfx)%$o: $(objpfx)%.c $(before-compile); $$(compile-command.c)
compile-command.c = $(compile.c) $(OUTPUT_OPTION) $(compile-mkdep-flags)
compile.c = $(CC) $< -c $(CFLAGS) $(CPPFLAGS)

for 3 "make -j 28" parallel builds on a machine with 112 cores at the
same time.

This partially fixes BZ #28550.

Reviewed-by: Adhemerval Zanella  <adhemerval.zanella@linaro.org>

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>