lddtree: resolve command line symlinks against the selected root

When we're given a path to look up in the root on the command line,
but it's a symlink itself, we end up implicitly resovling it to the
/ dir.  Add some logic so we resolve it relative to root instead.

BUG=chromium:393018
TEST=`lddtree /usr/bin/as --root /build/stumpy_moblab/` now works
TEST=`cbuildbot arm-generic-full` passes

Change-Id: Ie593686e462a0fe5eb8af2d91ee8160e2fa448d0
Reviewed-on: https://chromium-review.googlesource.com/210354
Reviewed-by: Luis Lozano <llozano@chromium.org>
Commit-Queue: Mike Frysinger <vapier@chromium.org>
Tested-by: Mike Frysinger <vapier@chromium.org>

1 files changed, 21 insertions, 7 deletions

diff --git a/third_party/lddtree.py b/third_party/lddtree.py
index 69cb70475..27924799f 100644
--- a/third_party/lddtree.py
+++ b/third_party/lddtree.py
@@ -4,9 +4,7 @@
 # Copyright 2012-2014 The Chromium OS Authors
 # Use of this source code is governed by a BSD-style license (BSD-3)
 # pylint: disable=C0301
-# $Header: /var/cvsroot/gentoo-projects/pax-utils/lddtree.py,v 1.49 2014/07/30 04:34:09 vapier Exp $
-
-# TODO: Handle symlinks.
+# $Header: /var/cvsroot/gentoo-projects/pax-utils/lddtree.py,v 1.53 2014/08/01 02:20:20 vapier Exp $
 
 """Read the ELF dependency tree and show it
 
@@ -443,7 +441,7 @@ def _NormalizePath(option, _opt, value, parser):
 
 
 def _ShowVersion(_option, _opt, _value, _parser):
-  d = '$Id: lddtree.py,v 1.49 2014/07/30 04:34:09 vapier Exp $'.split()
+  d = '$Id: lddtree.py,v 1.53 2014/08/01 02:20:20 vapier Exp $'.split()
   print('%s-%s %s %s' % (d[1].split('.')[0], d[2], d[3], d[4]))
   sys.exit(0)
 
@@ -696,10 +694,26 @@ they need will be placed into /foo/lib/ only.""")
 
     matched = False
     for p in glob.iglob(path):
+      # Once we've processed the globs, resolve the symlink.  This way you can
+      # operate on a path that is an absolute symlink itself.  e.g.:
+      #   $ ln -sf /bin/bash $PWD/root/bin/sh
+      #   $ lddtree --root $PWD/root /bin/sh
+      # First we'd turn /bin/sh into $PWD/root/bin/sh, then we want to resolve
+      # the symlink to $PWD/root/bin/bash rather than a plain /bin/bash.
+      dbg(options.debug, '  globbed     =', p)
+      if not path.startswith('/'):
+        realpath = os.path.realpath(path)
+      elif options.auto_root:
+        realpath = readlink(p, options.root, prefixed=True)
+      else:
+        realpath = path
+      if path != realpath:
+        dbg(options.debug, '  resolved    =', realpath)
+
       matched = True
       try:
-        elf = ParseELF(p, options.root, options.prefix, ldpaths,
-                       debug=options.debug)
+        elf = ParseELF(realpath, options.root, options.prefix, ldpaths,
+                       display=p, debug=options.debug)
       except exceptions.ELFError as e:
         if options.skip_non_elfs:
           continue
@@ -712,7 +726,7 @@ they need will be placed into /foo/lib/ only.""")
               'runpath': [],
               'rpath': [],
               'path': p,
-              'realpath': p,
+              'realpath': realpath,
             }
             _ActionCopy(options, elf)
             continue