[all-commits] [llvm/llvm-project] 2abed7: [AIX][PGO] Handle atexit functions when dlclose'in...

[Wael Yehia via All-commits]

  Branch: refs/heads/main
  Home:   https://github.com/llvm/llvm-project
  Commit: 2abed78b4da0f4eb133e971c70734e664d5f87fd
      https://github.com/llvm/llvm-project/commit/2abed78b4da0f4eb133e971c70734e664d5f87fd
  Author: Wael Yehia <44115484+w2yehia at users.noreply.github.com>
  Date:   2024-08-27 (Tue, 27 Aug 2024)

  Changed paths:
    M compiler-rt/lib/profile/GCDAProfiling.c
    M compiler-rt/lib/profile/InstrProfilingFile.c
    M compiler-rt/lib/profile/InstrProfilingUtil.c
    M compiler-rt/lib/profile/InstrProfilingUtil.h
    A compiler-rt/test/profile/AIX/gcov-dlopen-dlclose.test
    A compiler-rt/test/profile/Posix/instrprof-dlopen-norpath.test
    A compiler-rt/test/profile/instrprof-fork.c

  Log Message:
  -----------
  [AIX][PGO] Handle atexit functions when dlclose'ing shared libraries (#102940)

Problem:
On AIX, functions registered by atexit in a shared library are not run
when the library is dlclosed, but instead run (and fail because the
function pointer is no longer valid) during main program exit.

The profile-rt registers some functions with atexit:

 1. writeFileWithoutReturn that writes out the profile file
 2. llvm_delete_reset_function_list that does some cleanup in the gcov 
    instrumentation library (not sure)

And so right now, we get an "Illegal instruction (core dumped)" when an
instrumented shared object is dlopen'ed and dlclosed.

Solution:
  When a shared library is dlclose'd, destructors from the library are
  called. So create a destructor function that iterates over all known
  functions that profile-rt registers with atexit, and unregister the ones
  that have been registered and execute them.

Scenarios tested:
(0) gcov dlopen/dlclose                                       (AIX/gcov-dlopen-dlclose.test)
(1) multiple dlopen/dlclose of the same lib and multiple libs (instrprof-dlopen-dlclose.test)
(2) dlopen but no dlclose                                     (exists: Posix/instrprof-dlopen.test)
(3) a simple fork testcase with dlopen/dlclose                (instrprof-dlopen-dlclose.test)
(4) dlopen/dlclose by multiple threads.                       (instrprof-dlopen-dlclose.test)
(5) regular dynamic-linking of instrumented shared libs       (exists: AIX/shared-bexpall-pgo.c)
(6) a simple fork testcase produces correct profile           (instrprof-fork.c)


---------

Co-authored-by: Hubert Tong <hstong at ca.ibm.com>



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