report: determine library search paths dynamically

The library search order from `ld.so` differs from the hard-coded list:

```
$ ld.so --help
[...]
Shared library search path:
  (libraries located via /etc/ld.so.cache)
  /lib/x86_64-linux-gnu (system search path)
  /usr/lib/x86_64-linux-gnu (system search path)
  /lib (system search path)
  /usr/lib (system search path)
```

So determine the library search paths dynamically from `ld.so`.

Signed-off-by: Benjamin Drung <[email protected]>

apport/report.py

@@ -282,6 +282,21 @@ def _get_gdb_path(gdb_sandbox: str | None, same_arch: bool) -> str:
     return gdb_path
 
 
+def _get_ld_search_paths(ld_so: str = "ld.so") -> list[str]:
+    """Query the given ld.so binary for the shared library search paths."""
+    diagnostics = subprocess.run(
+        [ld_so, "--list-diagnostics"], check=True, stdout=subprocess.PIPE, text=True
+    )
+    # Example matching line: path.system_dirs[0x0]="/lib/x86_64-linux-gnu/"
+    matches = re.findall(
+        r'^path\.system_dirs\[(0x[0-9a-f]+)\]="([^"]+)"$',
+        diagnostics.stdout,
+        flags=re.MULTILINE,
+    )
+    ld_search_paths = {int(index, 0): path for (index, path) in matches}
+    return [path for (index, path) in sorted(ld_search_paths.items())]
+
+
 def _run_hook(report, ui, hook):
     if not os.path.exists(hook):
         return False
@@ -1890,6 +1905,8 @@ def gdb_command(
 
         if sandbox:
             native_multiarch = "x86_64-linux-gnu"
+            host_library_paths = _get_ld_search_paths()
+            sandbox_library_paths = [f"{sandbox}{path}" for path in host_library_paths]
             # N.B. set solib-absolute-prefix is an alias for set sysroot
             command += [
                 "--ex",
@@ -1900,16 +1917,13 @@ def gdb_command(
                 "add-auto-load-safe-path " + sandbox,
                 # needed to fix /lib64/ld-linux-x86-64.so.2 broken symlink
                 "--ex",
-                f"set solib-search-path {sandbox}/lib/{native_multiarch}"
-                f":{sandbox}/usr/lib/{native_multiarch}",
+                f"set solib-search-path {':'.join(sandbox_library_paths)}",
             ]
             if gdb_sandbox:
-                ld_lib_path = (
-                    f"{gdb_sandbox}/lib"
-                    f":{gdb_sandbox}/lib/{native_multiarch}"
-                    f":{gdb_sandbox}/usr/lib/{native_multiarch}"
-                    f":{gdb_sandbox}/usr/lib"
-                )
+                gdb_sandbox_library_paths = [
+                    f"{gdb_sandbox}{path}" for path in host_library_paths
+                ]
+                ld_lib_path = ":".join(gdb_sandbox_library_paths)
                 pyhome = f"{gdb_sandbox}/usr"
                 # env settings need to be modified for gdb in a sandbox
                 environ |= {

tests/unit/test_report.py

@@ -1528,3 +1528,53 @@ def test_add_kernel_crash_info_fail(self, run_mock: MagicMock) -> None:
         tmpfile = called_cmd[-1]
         self.assertRegex(tmpfile, r"^/.*/apport_vmcore_\w{8}$")
         self.assertFalse(pathlib.Path(tmpfile).exists())
+
+    @unittest.mock.patch("subprocess.run")
+    def test_get_ld_search_paths(self, run_mock: MagicMock) -> None:
+        run_mock.return_value = subprocess.CompletedProcess(
+            args=MagicMock(),
+            returncode=0,
+            stdout=textwrap.dedent(
+                """\
+                path.prefix="/usr"
+                path.sysconfdir="/etc"
+                path.system_dirs[0x0]="/lib/x86_64-linux-gnu/"
+                path.system_dirs[0x1]="/usr/lib/x86_64-linux-gnu/"
+                path.system_dirs[0x2]="/lib/"
+                path.system_dirs[0x3]="/usr/lib/"
+                """
+            ),
+        )
+        ld_search_paths = apport.report._get_ld_search_paths()
+        self.assertEqual(
+            ld_search_paths,
+            [
+                "/lib/x86_64-linux-gnu/",
+                "/usr/lib/x86_64-linux-gnu/",
+                "/lib/",
+                "/usr/lib/",
+            ],
+        )
+        run_mock.assert_called_once_with(
+            ["ld.so", "--list-diagnostics"],
+            check=True,
+            stdout=subprocess.PIPE,
+            text=True,
+        )
+
+    @unittest.mock.patch("subprocess.run")
+    def test_get_ld_search_paths_sorting(self, run_mock: MagicMock) -> None:
+        run_mock.return_value = subprocess.CompletedProcess(
+            args=MagicMock(),
+            returncode=0,
+            stdout=textwrap.dedent(
+                """\
+                path.system_dirs[0x2]="third"
+                path.system_dirs[0x1]="second"
+                path.system_dirs[0x0]="first"
+                """
+            ),
+        )
+        ld_search_paths = apport.report._get_ld_search_paths("ld.so")
+        self.assertEqual(ld_search_paths, ["first", "second", "third"])
+        run_mock.assert_called_once()