[RFC,v9,0/7] Implementation of RTLD_SHARED for dlmopen

  This is a revision of a previous patchset that I posted here
regarding https://sourceware.org/bugzilla/show_bug.cgi?id=22745 

Introduction:

=======================================================================
  As discussed in the URL above dlmopen requires a mechanism for
  [optionally] sharing some objects between more than one namespace.

  The following patchset provides an implementation for this: If an
  object is loaded with the new RTLD_SHARED flag we instead ensure
  that a "master" copy exists (and is flagged as no-delete) in the
  main namespace and a thin wrapper or clone is placed in the target
  namespace.

  This patch series should address all the comments received on the
  earlier (v1-v8) series.

  This series (v9) also lifts the requirement for an ld which supports
  -z unique / DT_GNU_FLAGS_1+DF_GNU_1_UNIQUE directly. If lack of
  support is detected the new dynamic flag section is added via linker
  scripts and a dummy dynamic-notes.os object instead.
=======================================================================

In addition this patch series implements the following:

 - dlmopen will implicitly apply RTLD_SHARED to the libc/libpthread group
   (requires a patched binutils/ld so that the libc family DSOs can
   be flagged as requiring this behaviour)

   - binutils patchset accepted upstream;
   - https://sourceware.org/git/?p=binutils-gdb.git
   - commit 8a87b2791181eb7fc1533ffaeb95df8d87d41493

 - LD_AUDIT paths will NOT apply this implict sharing rule:
   audit libraries will continue to be completely isolated.

 - The mechanism for tagging DSOs as implicitly shared has been changed
   from a DT_FLAGS_1 flag to a DT_VALRNGHI/LO range dynamic section tag.
   (Based on feedback on the binutils side of this patch series).

  - DT_GNU_FLAGS_1/DF_GNU_1_UNIQUE

 - A flag RTLD_ISOLATE which is used inernally to suppress RTLD_SHARED
   behaviour when audit libraries are being loaded, and is also made available
   to users who really want a completely separate copy of glibc in their new
   namespace.

 - Tests for the new dlmopen behaviour

 - Adds the unique dso flag to htl/libpthread.so as well as nptl

I have not yet implemented, but plan to address once this series is
accepted/acceptable:

 - Sensible RTLD_GLOBAL semantics for dlmopened DSOs in non-base namespaces

 - dl_iterate_ns_phdr (cf dl_iterate_phdr but taking a namespace argument)

Vivek Das Mohapatra (7):
  Define a new dynamic section tag - DT_GNU_FLAGS_1 (bug 22745)
  Abstract loaded-DSO search code into a helper function
  Use the new DSO finder helper function
  Add DT_GNU_FLAGS_1/DF_GNU_1_UNIQUE to glibc DSOs (bug 22745)
  Implement dlmopen RTLD_SHARED flag (bug 22745)
  Add dlmopen / RTLD_SHARED tests
  Restore separate libc loading for the TLS/namespace storage test

 Makeconfig                           |   3 +
 Makerules                            |  19 +-
 bits/dlfcn.h                         |  10 +
 config.make.in                       |   1 +
 configure                            |  54 +-
 configure.ac                         |  32 +-
 dynamic-notes.c                      |   4 +
 elf/Makefile                         | 104 +++-
 elf/dl-close.c                       |  43 +-
 elf/dl-fini.c                        |   6 +-
 elf/dl-init.c                        |   4 +-
 elf/dl-load.c                        | 221 ++++++-
 elf/dl-object.c                      |  78 +++
 elf/dl-open.c                        | 109 +++-
 elf/dl-sym.c                         |  14 +
 elf/elf.h                            |   7 +-
 elf/get-dynamic-info.h               |  12 +
 elf/rtld.c                           |   2 +-
 elf/tst-dlmopen-auditmod.c           |  23 +
 elf/tst-dlmopen-common.h             |  32 +
 elf/tst-dlmopen-main.h               | 873 +++++++++++++++++++++++++++
 elf/tst-dlmopen-modules.h            |  21 +
 elf/tst-dlmopen-rtld-audit-shared1.c |   8 +
 elf/tst-dlmopen-rtld-audit-shared2.c |   8 +
 elf/tst-dlmopen-rtld-audit-shared3.c |   7 +
 elf/tst-dlmopen-rtld-audit-shared4.c |   8 +
 elf/tst-dlmopen-rtld-audit-shared5.c |   8 +
 elf/tst-dlmopen-rtld-audit-shared6.c |   8 +
 elf/tst-dlmopen-rtld-audit-unique1.c |   7 +
 elf/tst-dlmopen-rtld-audit-unique2.c |   7 +
 elf/tst-dlmopen-rtld-audit-unique3.c |   7 +
 elf/tst-dlmopen-rtld-audit-unique4.c |   7 +
 elf/tst-dlmopen-rtld-audit-unique5.c |   7 +
 elf/tst-dlmopen-rtld-audit-unique6.c |   7 +
 elf/tst-dlmopen-rtld-shared1.c       |   7 +
 elf/tst-dlmopen-rtld-shared1.h       |  64 ++
 elf/tst-dlmopen-rtld-shared2.c       |   7 +
 elf/tst-dlmopen-rtld-shared2.h       |  66 ++
 elf/tst-dlmopen-rtld-shared3.c       |   7 +
 elf/tst-dlmopen-rtld-shared3.h       |  43 ++
 elf/tst-dlmopen-rtld-shared4.c       |   7 +
 elf/tst-dlmopen-rtld-shared4.h       |  14 +
 elf/tst-dlmopen-rtld-shared5.c       |   7 +
 elf/tst-dlmopen-rtld-shared5.h       |  25 +
 elf/tst-dlmopen-rtld-shared6.c       |   7 +
 elf/tst-dlmopen-rtld-shared6.h       |  36 ++
 elf/tst-dlmopen-rtld-unique1.c       |   7 +
 elf/tst-dlmopen-rtld-unique1.h       |  86 +++
 elf/tst-dlmopen-rtld-unique2.c       |   7 +
 elf/tst-dlmopen-rtld-unique2.h       |  25 +
 elf/tst-dlmopen-rtld-unique3.c       |   7 +
 elf/tst-dlmopen-rtld-unique3.h       |  13 +
 elf/tst-dlmopen-rtld-unique4.c       |   7 +
 elf/tst-dlmopen-rtld-unique4.h       |  14 +
 elf/tst-dlmopen-rtld-unique5.c       |   7 +
 elf/tst-dlmopen-rtld-unique5.h       |  58 ++
 elf/tst-dlmopen-rtld-unique6.c       |   7 +
 elf/tst-dlmopen-rtld-unique6.h       |  51 ++
 elf/tst-dlmopen-sharedmod-norm.c     |  11 +
 elf/tst-dlmopen-sharedmod-uniq.c     |  11 +
 elf/tst-dlmopen-std-do-test.c        |  12 +
 elf/tst-tls-ie-dlmopen.c             |   4 +-
 extra-lib.mk                         |   3 +
 htl/Makefile                         |   3 +
 iconvdata/Makefile                   |   3 +
 iconvdata/extra-module.mk            |   4 +
 include/elf.h                        |   2 +
 include/link.h                       |   7 +-
 nptl/Makefile                        |   3 +
 sysdeps/generic/ldsodefs.h           |   9 +
 sysdeps/mips/bits/dlfcn.h            |  10 +
 71 files changed, 2355 insertions(+), 67 deletions(-)
 create mode 100644 dynamic-notes.c
 create mode 100644 elf/tst-dlmopen-auditmod.c
 create mode 100644 elf/tst-dlmopen-common.h
 create mode 100644 elf/tst-dlmopen-main.h
 create mode 100644 elf/tst-dlmopen-modules.h
 create mode 100644 elf/tst-dlmopen-rtld-audit-shared1.c
 create mode 100644 elf/tst-dlmopen-rtld-audit-shared2.c
 create mode 100644 elf/tst-dlmopen-rtld-audit-shared3.c
 create mode 100644 elf/tst-dlmopen-rtld-audit-shared4.c
 create mode 100644 elf/tst-dlmopen-rtld-audit-shared5.c
 create mode 100644 elf/tst-dlmopen-rtld-audit-shared6.c
 create mode 100644 elf/tst-dlmopen-rtld-audit-unique1.c
 create mode 100644 elf/tst-dlmopen-rtld-audit-unique2.c
 create mode 100644 elf/tst-dlmopen-rtld-audit-unique3.c
 create mode 100644 elf/tst-dlmopen-rtld-audit-unique4.c
 create mode 100644 elf/tst-dlmopen-rtld-audit-unique5.c
 create mode 100644 elf/tst-dlmopen-rtld-audit-unique6.c
 create mode 100644 elf/tst-dlmopen-rtld-shared1.c
 create mode 100644 elf/tst-dlmopen-rtld-shared1.h
 create mode 100644 elf/tst-dlmopen-rtld-shared2.c
 create mode 100644 elf/tst-dlmopen-rtld-shared2.h
 create mode 100644 elf/tst-dlmopen-rtld-shared3.c
 create mode 100644 elf/tst-dlmopen-rtld-shared3.h
 create mode 100644 elf/tst-dlmopen-rtld-shared4.c
 create mode 100644 elf/tst-dlmopen-rtld-shared4.h
 create mode 100644 elf/tst-dlmopen-rtld-shared5.c
 create mode 100644 elf/tst-dlmopen-rtld-shared5.h
 create mode 100644 elf/tst-dlmopen-rtld-shared6.c
 create mode 100644 elf/tst-dlmopen-rtld-shared6.h
 create mode 100644 elf/tst-dlmopen-rtld-unique1.c
 create mode 100644 elf/tst-dlmopen-rtld-unique1.h
 create mode 100644 elf/tst-dlmopen-rtld-unique2.c
 create mode 100644 elf/tst-dlmopen-rtld-unique2.h
 create mode 100644 elf/tst-dlmopen-rtld-unique3.c
 create mode 100644 elf/tst-dlmopen-rtld-unique3.h
 create mode 100644 elf/tst-dlmopen-rtld-unique4.c
 create mode 100644 elf/tst-dlmopen-rtld-unique4.h
 create mode 100644 elf/tst-dlmopen-rtld-unique5.c
 create mode 100644 elf/tst-dlmopen-rtld-unique5.h
 create mode 100644 elf/tst-dlmopen-rtld-unique6.c
 create mode 100644 elf/tst-dlmopen-rtld-unique6.h
 create mode 100644 elf/tst-dlmopen-sharedmod-norm.c
 create mode 100644 elf/tst-dlmopen-sharedmod-uniq.c
 create mode 100644 elf/tst-dlmopen-std-do-test.c