lddtree: use ldso's --argv0 when available

Newer glibc has a --argv0 option in current releases to explicitly
set argv[0].  This is useful for the generated shell wrappers as we
need to rename it (with an .elf suffix) and that can either confuse
the output or break tools that inspect their argv[0] strictly.

Signed-off-by: Mike Frysinger <vapier@gentoo.org>

1 files changed, 20 insertions, 6 deletions

diff --git a/lddtree.py b/lddtree.py
index 7ec04fa..fae39e0 100755
--- a/lddtree.py
+++ b/lddtree.py
@@ -43,6 +43,7 @@ import argparse
 import functools
 import glob
 import errno
+import mmap
 import os
 import shutil
 import sys
@@ -123,6 +124,17 @@ def dedupe(items):
     return [seen.setdefault(x, x) for x in items if x not in seen]
 
 
+@functools.lru_cache(maxsize=None)
+def interp_supports_argv0(interp) -> bool:
+    """See whether |interp| supports the --argv0 option.
+
+    Starting with glibc-2.33, the ldso supports --argv0 to override argv[0].
+    """
+    with open(interp, 'rb') as fp:
+        with mmap.mmap(fp.fileno(), 0, prot=mmap.PROT_READ) as mm:
+            return mm.find(b'--argv0') >= 0
+
+
 def GenerateLdsoWrapper(root, path, interp, libpaths=()):
     """Generate a shell script wrapper which uses local ldso to run the ELF
 
@@ -145,6 +157,7 @@ def GenerateLdsoWrapper(root, path, interp, libpaths=()):
                                interp_name),
         'libpaths': ':'.join(['${basedir}/' + os.path.relpath(p, basedir)
                               for p in libpaths]),
+        'argv0_arg': '--argv0 "$0"' if interp_supports_argv0(interp) else '',
     }
     wrapper = """#!/bin/sh
 if ! base=$(realpath "$0" 2>/dev/null); then
@@ -154,12 +167,13 @@ if ! base=$(realpath "$0" 2>/dev/null); then
   esac
 fi
 basedir=${base%%/*}
-exec \
-  "${basedir}/%(interp)s" \
-  --library-path "%(libpaths)s" \
-  --inhibit-cache \
-  --inhibit-rpath '' \
-  "${base}.elf" \
+exec \\
+  "${basedir}/%(interp)s" \\
+  %(argv0_arg)s \\
+  --library-path "%(libpaths)s" \\
+  --inhibit-cache \\
+  --inhibit-rpath '' \\
+  "${base}.elf" \\
   "$@"
 """
     wrappath = root + path