os/linux/elf: avoid using ldd for listing dynamic dependencies

Library/Homebrew/extend/pathname.rb

@@ -490,6 +490,12 @@ def zipinfo
  .encode(Encoding::UTF_8, invalid: :replace)
  .split("\n")
  end
+
+ sig { params(parent: Pathname).returns(T::Boolean) }
+ def child_of?(parent)
+ ascend { |p| return true if p == parent }
+ false
+ end
 end
 
 require "extend/os/pathname"

Library/Homebrew/os/linux/elf.rb

@@ -1,6 +1,8 @@
 # typed: true
 # frozen_string_literal: true
 
+require "os/linux/ld"
+
 # {Pathname} extension for dealing with ELF files.
 # @see https://en.wikipedia.org/wiki/Executable_and_Linkable_Format#File_header
 #
@@ -130,19 +132,7 @@ def initialize(path)
  @dylib_id, needed = needed_libraries path
  return if needed.empty?
 
- ldd = DevelopmentTools.locate "ldd"
- ldd_output = Utils.popen_read(ldd, path.expand_path.to_s).split("\n")
- return unless $CHILD_STATUS.success?
-
- ldd_paths = ldd_output.filter_map do |line|
- match = line.match(/\t.+ => (.+) \(.+\)|\t(.+) => not found/)
- next unless match
-
- match.captures.compact.first
- end
- @dylibs = ldd_paths.select do |ldd_path|
- needed.include? File.basename(ldd_path)
- end
+ @dylibs = needed.map { |lib| find_full_lib_path(lib).to_s }
  end
 
  private
@@ -157,6 +147,63 @@ def needed_libraries_using_patchelf_rb(path)
  patcher = path.patchelf_patcher
  [patcher.soname, patcher.needed]
  end
+
+ def dt_flags_1(path)
+ readelf = DevelopmentTools.locate "readelf"
+ readelf_output = Utils.popen_read(readelf, "--dynamic", path.expand_path.to_s)
+ return [] unless $CHILD_STATUS.success?
+
+ match = readelf_output.match(/^\s*0x0*6ffffffb\s+\(FLAGS_1\)\s+Flags:\s*(.*)$/)
+ return [] unless match
+
+ match.captures.compact.first.split(/\s+/)
+ end
+
+ def find_full_lib_path(basename)
+ local_paths = (path.patchelf_patcher.runpath || path.patchelf_patcher.rpath)&.split(":")
+
+ # Search for dependencies in the runpath/rpath first
+ local_paths&.each do |local_path|
+ candidate = Pathname(local_path)/basename
+ return candidate if candidate.exist? && candidate.elf?
+ end
+
+ # Check if DF_1_NODEFLIB is set
+ nodeflib_flag = dt_flags_1(path).include?("NODEFLIB")
+
+ linker_library_paths = OS::Linux::Ld.library_paths
+ linker_system_dirs = OS::Linux::Ld.system_dirs
+
+ # If DF_1_NODEFLIB is set, exclude any library paths that are subdirectories
+ # of the system dirs
+ if nodeflib_flag
+ linker_library_paths = linker_library_paths.reject do |linker_library_path|
+ child = Pathname(linker_library_path).realdirpath
+
+ linker_system_dirs.any? do |linker_system_dir|
+ parent = Pathname(linker_system_dir).realdirpath
+ child.child_of? parent
+ end
+ end
+ end
+
+ # If not found, search recursively in the paths listed in ld.so.conf (skipping
+ # paths that are subdirectories of the system dirs if DF_1_NODEFLIB is set)
+ linker_library_paths.each do |linker_library_path|
+ candidate = Pathname(linker_library_path)/basename
+ return candidate if candidate.exist? && candidate.elf?
+ end
+
+ # If not found, search in the system dirs, unless DF_1_NODEFLIB is set
+ unless nodeflib_flag
+ linker_system_dirs.each do |linker_system_dir|
+ candidate = Pathname(linker_system_dir)/basename
+ return candidate if candidate.exist? && candidate.elf?
+ end
+ end
+
+ basename
+ end
  end
  private_constant :Metadata
 

Library/Homebrew/os/linux/ld.rb

@@ -0,0 +1,77 @@
+# typed: true
+# frozen_string_literal: true
+
+module OS
+ module Linux
+ # Helper functions for querying `ld` information.
+ #
+ # @api private
+ module Ld
+ module_function
+
+ sig { returns(String) }
+ def sysconfdir
+ fallback_sysconfdir = "/etc"
+
+ brewed_ld_so = HOMEBREW_PREFIX/"lib/ld.so"
+ return fallback_sysconfdir unless brewed_ld_so.exist?
+
+ ld_so_output = Utils.popen_read(brewed_ld_so, "--list-diagnostics")
+ return fallback_sysconfdir unless $CHILD_STATUS.success?
+
+ match = ld_so_output.match(/path.sysconfdir="(.+)"/)
+ return fallback_sysconfdir unless match
+
+ match.captures.compact.first
+ end
+
+ sig { returns(T::Array[String]) }
+ def system_dirs
+ system_dirs = []
+
+ brewed_ld_so = HOMEBREW_PREFIX/"lib/ld.so"
+ return system_dirs unless brewed_ld_so.exist?
+
+ ld_so_output = Utils.popen_read(brewed_ld_so, "--list-diagnostics").split("\n")
+ return system_dirs unless $CHILD_STATUS.success?
+
+ ld_so_output.each do |line|
+ match = line.match(/path.system_dirs\[0x.*\]="(.*)"/)
+ next unless match
+
+ system_dirs << match.captures.compact.first
+ end
+
+ system_dirs
+ end
+
+ sig { params(conf_path: T.any(String, Pathname)).returns(T::Array[String]) }
+ def library_paths(conf_path = Pathname(sysconfdir)/"ld.so.conf")
+ conf_file = Pathname(conf_path)
+ paths = Set.new
+ directory = conf_file.realpath.dirname
+
+ conf_file.readlines.each do |line|
+ # Remove comments and leading/trailing whitespace
+ line.strip!
+ line.sub!(/\s*#.*$/, "")
+
+ if line.start_with?(/\s*include\s+/)
+ include_path = Pathname(line.sub(/^\s*include\s+/, "")).expand_path
+ wildcard = include_path.absolute? ? include_path : directory/include_path
+
+ Dir.glob(wildcard.to_s).each do |include_file|
+ paths += library_paths(include_file)
+ end
+ elsif line.empty?
+ next
+ else
+ paths << line
+ end
+ end
+
+ paths.to_a
+ end
+ end
+ end
+end

Library/Homebrew/os/linux/ld.rbi

@@ -0,0 +1,9 @@
+# typed: strict
+
+module OS
+ module Linux
+ module Ld
+ requires_ancestor { Pathname }
+ end
+ end
+end