[Bug 1253638] [NEW] dynamic linker does not use DT_RUNPATH for transitive dependencies

[Moritz Hassert]

Public bug reported:

$ lsb_release -rd
Description:	Ubuntu 13.10
Release:	13.10

$ uname -a
Linux mhassert 3.11.0-13-generic #20-Ubuntu SMP Wed Oct 23 07:38:26 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux

$gcc -dumpversion
4.8

$ ld -v
GNU ld (GNU Binutils for Ubuntu) 2.23.52.20130913

$ LC_ALL=C apt-cache policy libc-bin
libc-bin:
  Installed: 2.17-93ubuntu4

* What you expected to happen
Binaries with DT_RPATH or DT_RUNPATH behaving identical in the absence of LD_LIBRARY_PATH

* What happened instead
DT_RUNPATH not searched for transitive dependencies.


When running a binary that depends on custom libraries which in turn depend on custom libraries, hard-coded search paths in DT_RUNPATH behave differently from those in DT_RPATH.
Paths in DT_RPATH are being considered for everything that is dynamically loaded, even dependencies of dependencies. Paths in DT_RUNPATH seem being considered only for direct dependencies of the binary.

Searching the web I think that the one and only difference between
DT_RPATH and DT_RUNPATH should be that DT_RPATH is considered _before_
LD_LIBRARY_PATH and DT_RUNPATH _afterwards_. In the absence of
LD_LIBRARY_PATH there should be no difference at all.

I stumbled upon this problem when switching from "ld" to "gold" for the
linker. The default for ld on Ubuntu 13.10 is "--disable-new-dtags"
while the default for gold is "--enable-new-dtags". Therefore ld
produces binaries with DT_RPATH and gold ones with DT_RUNPATH.

In the attached minimal example
- the binaries rpath and runpath both depend on libb but not directly on liba.
- libb depends on liba.
- liba and libb are linked without any hard-coded library paths.
- rpath and runpath are linked with  hard-coded library paths for both liba and libb
- rpath is linked with --disable-new-dtags (producing DT_RPATH)
- rpath is linked with --enable-new-dtags (producing DT_RUNPATH)

To test, please run make all and observe how "rpath" works while
"runpath" fails to find liba at runtime.

** Affects: eglibc (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: dynamic hardcoded library linker paths rpath runpath

** Attachment added: "minimal example"
   https://bugs.launchpad.net/bugs/1253638/+attachment/3914081/+files/linker_bug.tar.gz

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https://bugs.launchpad.net/bugs/1253638

Title:
  dynamic linker does not use DT_RUNPATH for transitive dependencies

Status in “eglibc” package in Ubuntu:
  New

Bug description:
  $ lsb_release -rd
  Description:	Ubuntu 13.10
  Release:	13.10

  $ uname -a
  Linux mhassert 3.11.0-13-generic #20-Ubuntu SMP Wed Oct 23 07:38:26 UTC 2013 x86_64 x86_64 x86_64 GNU/Linux

  $gcc -dumpversion
  4.8

  $ ld -v
  GNU ld (GNU Binutils for Ubuntu) 2.23.52.20130913

  $ LC_ALL=C apt-cache policy libc-bin
  libc-bin:
    Installed: 2.17-93ubuntu4

  * What you expected to happen
  Binaries with DT_RPATH or DT_RUNPATH behaving identical in the absence of LD_LIBRARY_PATH

  * What happened instead
  DT_RUNPATH not searched for transitive dependencies.

  
  When running a binary that depends on custom libraries which in turn depend on custom libraries, hard-coded search paths in DT_RUNPATH behave differently from those in DT_RPATH.
  Paths in DT_RPATH are being considered for everything that is dynamically loaded, even dependencies of dependencies. Paths in DT_RUNPATH seem being considered only for direct dependencies of the binary.

  Searching the web I think that the one and only difference between
  DT_RPATH and DT_RUNPATH should be that DT_RPATH is considered _before_
  LD_LIBRARY_PATH and DT_RUNPATH _afterwards_. In the absence of
  LD_LIBRARY_PATH there should be no difference at all.

  I stumbled upon this problem when switching from "ld" to "gold" for
  the linker. The default for ld on Ubuntu 13.10 is "--disable-new-
  dtags" while the default for gold is "--enable-new-dtags". Therefore
  ld produces binaries with DT_RPATH and gold ones with DT_RUNPATH.

  In the attached minimal example
  - the binaries rpath and runpath both depend on libb but not directly on liba.
  - libb depends on liba.
  - liba and libb are linked without any hard-coded library paths.
  - rpath and runpath are linked with  hard-coded library paths for both liba and libb
  - rpath is linked with --disable-new-dtags (producing DT_RPATH)
  - rpath is linked with --enable-new-dtags (producing DT_RUNPATH)

  To test, please run make all and observe how "rpath" works while
  "runpath" fails to find liba at runtime.

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