External find now searches all dynamic linker paths (#33800)

Add spack.ld_so_conf.host_dynamic_linker_search_paths

Retrieve the current host runtime search paths for shared libraries;
for GNU and musl Linux we try to retrieve the dynamic linker from the
current Python interpreter and then find the corresponding config file
(e.g. ld.so.conf or ld-musl-<arch>.path). Similar can be done for
BSD and others, but this is not implemented yet. The default paths
are always returned. We don't check if the listed directories exist.

Use this in spack external find for libraries.

Co-authored-by: Harmen Stoppels <harmenstoppels@gmail.com>

3 files changed, 211 insertions, 12 deletions

diff --git a/lib/spack/spack/detection/path.py b/lib/spack/spack/detection/path.py
index b7a7f6702d..bf42fa6144 100644
--- a/lib/spack/spack/detection/path.py
+++ b/lib/spack/spack/detection/path.py
@@ -17,6 +17,7 @@ import llnl.util.tty
 
 import spack.operating_systems.windows_os as winOs
 import spack.util.environment
+import spack.util.ld_so_conf
 
 from .common import (
     DetectedPackage,
@@ -75,9 +76,10 @@ def executables_in_path(path_hints=None):
     return path_to_exe
 
 
-def libraries_in_ld_library_path(path_hints=None):
+def libraries_in_ld_and_system_library_path(path_hints=None):
     """Get the paths of all libraries available from LD_LIBRARY_PATH,
-    LIBRARY_PATH, DYLD_LIBRARY_PATH, and DYLD_FALLBACK_LIBRARY_PATH.
+    LIBRARY_PATH, DYLD_LIBRARY_PATH, DYLD_FALLBACK_LIBRARY_PATH, and
+    standard system library paths.
 
     For convenience, this is constructed as a dictionary where the keys are
     the library paths and the values are the names of the libraries
@@ -90,14 +92,14 @@ def libraries_in_ld_library_path(path_hints=None):
         path_hints (list): list of paths to be searched. If None the list will be
             constructed based on the set of LD_LIBRARY_PATH, LIBRARY_PATH,
             DYLD_LIBRARY_PATH, and DYLD_FALLBACK_LIBRARY_PATH environment
-            variables.
+            variables as well as the standard system library paths.
     """
-    path_hints = path_hints or spack.util.environment.get_path(
-        "LIBRARY_PATH"
-    ) + spack.util.environment.get_path("LD_LIBRARY_PATH") + spack.util.environment.get_path(
-        "DYLD_LIBRARY_PATH"
-    ) + spack.util.environment.get_path(
-        "DYLD_FALLBACK_LIBRARY_PATH"
+    path_hints = (
+        path_hints
+        or spack.util.environment.get_path("LD_LIBRARY_PATH")
+        + spack.util.environment.get_path("DYLD_LIBRARY_PATH")
+        + spack.util.environment.get_path("DYLD_FALLBACK_LIBRARY_PATH")
+        + spack.util.ld_so_conf.host_dynamic_linker_search_paths()
     )
     search_paths = llnl.util.filesystem.search_paths_for_libraries(*path_hints)
 
@@ -129,14 +131,17 @@ def by_library(packages_to_check, path_hints=None):
     # Other libraries could use the strings function to extract it as described
     # in https://unix.stackexchange.com/questions/58846/viewing-linux-library-executable-version-info
     """Return the list of packages that have been detected on the system,
-    searching by LD_LIBRARY_PATH.
+    searching by LD_LIBRARY_PATH, LIBRARY_PATH, DYLD_LIBRARY_PATH,
+    DYLD_FALLBACK_LIBRARY_PATH, and standard system library paths.
 
     Args:
         packages_to_check (list): list of packages to be detected
         path_hints (list): list of paths to be searched. If None the list will be
-            constructed based on the LD_LIBRARY_PATH environment variable.
+            constructed based on the LD_LIBRARY_PATH, LIBRARY_PATH,
+            DYLD_LIBRARY_PATH, DYLD_FALLBACK_LIBRARY_PATH environment variables
+            and standard system library paths.
     """
-    path_to_lib_name = libraries_in_ld_library_path(path_hints=path_hints)
+    path_to_lib_name = libraries_in_ld_and_system_library_path(path_hints=path_hints)
     lib_pattern_to_pkgs = collections.defaultdict(list)
     for pkg in packages_to_check:
         if hasattr(pkg, "libraries"):
diff --git a/lib/spack/spack/test/util/ld_so_conf.py b/lib/spack/spack/test/util/ld_so_conf.py
new file mode 100644
index 0000000000..ea1c86e896
--- /dev/null
+++ b/lib/spack/spack/test/util/ld_so_conf.py
@@ -0,0 +1,54 @@
+# Copyright 2013-2022 Lawrence Livermore National Security, LLC and other
+# Spack Project Developers. See the top-level COPYRIGHT file for details.
+#
+# SPDX-License-Identifier: (Apache-2.0 OR MIT)
+
+import os
+
+import spack.util.ld_so_conf as ld_so_conf
+
+
+def test_ld_so_conf_parsing(tmpdir):
+    cwd = os.getcwd()
+    tmpdir.ensure("subdir", dir=True)
+
+    # Entrypoint config file
+    with open(str(tmpdir.join("main.conf")), "wb") as f:
+        f.write(b"  \n")
+        f.write(b"include subdir/*.conf\n")
+        f.write(b"include non-existent/file\n")
+        f.write(b"include #nope\n")
+        f.write(b"include     \n")
+        f.write(b"include\t\n")
+        f.write(b"include\n")
+        f.write(b"/main.conf/lib # and a comment\n")
+        f.write(b"relative/path\n\n")
+        f.write(b"#/skip/me\n")
+
+    # Should be parsed: subdir/first.conf
+    with open(str(tmpdir.join("subdir", "first.conf")), "wb") as f:
+        f.write(b"/first.conf/lib")
+
+    # Should be parsed: subdir/second.conf
+    with open(str(tmpdir.join("subdir", "second.conf")), "wb") as f:
+        f.write(b"/second.conf/lib")
+
+    # Not matching subdir/*.conf
+    with open(str(tmpdir.join("subdir", "third")), "wb") as f:
+        f.write(b"/third/lib")
+
+    paths = ld_so_conf.parse_ld_so_conf(str(tmpdir.join("main.conf")))
+
+    assert len(paths) == 3
+    assert "/main.conf/lib" in paths
+    assert "/first.conf/lib" in paths
+    assert "/second.conf/lib" in paths
+
+    # Make sure globbing didn't change the working dir
+    assert os.getcwd() == cwd
+
+
+def test_host_dynamic_linker_search_paths():
+    assert {"/usr/lib", "/usr/lib64", "/lib", "/lib64"}.issubset(
+        ld_so_conf.host_dynamic_linker_search_paths()
+    )
diff --git a/lib/spack/spack/util/ld_so_conf.py b/lib/spack/spack/util/ld_so_conf.py
new file mode 100644
index 0000000000..dd7f0e0ee6
--- /dev/null
+++ b/lib/spack/spack/util/ld_so_conf.py
@@ -0,0 +1,140 @@
+# Copyright 2013-2022 Lawrence Livermore National Security, LLC and other
+# Spack Project Developers. See the top-level COPYRIGHT file for details.
+#
+# SPDX-License-Identifier: (Apache-2.0 OR MIT)
+
+import glob
+import os
+import re
+import sys
+
+from llnl.util.lang import dedupe
+
+import spack.util.elf as elf_utils
+
+
+def parse_ld_so_conf(conf_file="/etc/ld.so.conf"):
+    """Parse glibc style ld.so.conf file, which specifies default search paths for the
+    dynamic linker. This can in principle also be used for musl libc.
+
+    Arguments:
+        conf_file (str or bytes): Path to config file
+
+    Returns:
+        list: List of absolute search paths
+    """
+    # Parse in binary mode since it's faster
+    is_bytes = isinstance(conf_file, bytes)
+    if not is_bytes:
+        conf_file = conf_file.encode("utf-8")
+
+    # For globbing in Python2 we need to chdir.
+    cwd = os.getcwd()
+    try:
+        paths = _process_ld_so_conf_queue([conf_file])
+    finally:
+        os.chdir(cwd)
+
+    return list(paths) if is_bytes else [p.decode("utf-8") for p in paths]
+
+
+def _process_ld_so_conf_queue(queue):
+    include_regex = re.compile(b"include\\s")
+    paths = []
+    while queue:
+        p = queue.pop(0)
+
+        try:
+            with open(p, "rb") as f:
+                lines = f.readlines()
+        except (IOError, OSError):
+            continue
+
+        for line in lines:
+            # Strip comments
+            comment = line.find(b"#")
+            if comment != -1:
+                line = line[:comment]
+
+            # Skip empty lines
+            line = line.strip()
+            if not line:
+                continue
+
+            is_include = include_regex.match(line) is not None
+
+            # If not an include, it's a literal path (no globbing here).
+            if not is_include:
+                # We only allow absolute search paths.
+                if os.path.isabs(line):
+                    paths.append(line)
+                continue
+
+            # Finally handle includes.
+            include_path = line[8:].strip()
+            if not include_path:
+                continue
+
+            cwd = os.path.dirname(p)
+            os.chdir(cwd)
+            queue.extend(os.path.join(cwd, p) for p in glob.glob(include_path))
+
+    return dedupe(paths)
+
+
+def get_conf_file_from_dynamic_linker(dynamic_linker_name):
+    # We basically assume everything is glibc, except musl.
+    if "ld-musl-" not in dynamic_linker_name:
+        return "ld.so.conf"
+
+    # Musl has a dynamic loader of the form ld-musl-<arch>.so.1
+    # and a corresponding config file ld-musl-<arch>.path
+    idx = dynamic_linker_name.find(".")
+    if idx != -1:
+        return dynamic_linker_name[:idx] + ".path"
+
+
+def host_dynamic_linker_search_paths():
+    """Retrieve the current host runtime search paths for shared libraries;
+    for GNU and musl Linux we try to retrieve the dynamic linker from the
+    current Python interpreter and then find the corresponding config file
+    (e.g. ld.so.conf or ld-musl-<arch>.path). Similar can be done for
+    BSD and others, but this is not implemented yet. The default paths
+    are always returned. We don't check if the listed directories exist."""
+    default_paths = ["/usr/lib", "/usr/lib64", "/lib", "/lib64"]
+
+    # Currently only for Linux (gnu/musl)
+    if not sys.platform.startswith("linux"):
+        return default_paths
+
+    # If everything fails, try this standard glibc path.
+    conf_file = "/etc/ld.so.conf"
+
+    # Try to improve on the default conf path by retrieving the location of the
+    # dynamic linker from our current Python interpreter, and figure out the
+    # config file location from there.
+    try:
+        with open(sys.executable, "rb") as f:
+            elf = elf_utils.parse_elf(f, dynamic_section=False, interpreter=True)
+
+        # If we have a dynamic linker, try to retrieve the config file relative
+        # to its prefix.
+        if elf.has_pt_interp:
+            dynamic_linker = elf.pt_interp_str.decode("utf-8")
+            dynamic_linker_name = os.path.basename(dynamic_linker)
+            conf_name = get_conf_file_from_dynamic_linker(dynamic_linker_name)
+
+            # Typically it is /lib/ld.so, but on Gentoo Prefix it is something
+            # like <long glibc prefix>/lib/ld.so. And on Debian /lib64 is actually
+            # a symlink to /usr/lib64. So, best effort attempt is to just strip
+            # two path components and join with etc/ld.so.conf.
+            possible_prefix = os.path.dirname(os.path.dirname(dynamic_linker))
+            possible_conf = os.path.join(possible_prefix, "etc", conf_name)
+
+            if os.path.exists(possible_conf):
+                conf_file = possible_conf
+    except (IOError, OSError, elf_utils.ElfParsingError):
+        pass
+
+    # Note: ld_so_conf doesn't error if the file does not exist.
+    return list(dedupe(parse_ld_so_conf(conf_file) + default_paths))