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bin/gems/sass-embedded-1.83.4-x86_64-linux-gnu/lib/sass/elf.rb

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+# frozen_string_literal: true
+
+module Sass
+  # The {ELF} class.
+  #
+  # It parses ELF header to extract interpreter.
+  # @see https://github.com/torvalds/linux/blob/HEAD/include/uapi/linux/elf.h
+  # @see https://github.com/torvalds/linux/blob/HEAD/kernel/kexec_elf.c
+  class ELF
+    module PackInfo
+      PACK_MAP = {
+        Elf32_Ehdr: 'S<2L<5S<6',
+        Elf64_Ehdr: 'S<2L<Q<3L<S<6',
+        Elf32_Phdr: 'L<8',
+        Elf64_Phdr: 'L<2Q<6'
+      }.freeze
+
+      SIZE_MAP = {
+        Elf32_Ehdr: 36,
+        Elf64_Ehdr: 48,
+        Elf32_Phdr: 32,
+        Elf64_Phdr: 56
+      }.freeze
+
+      STRUCT_MAP = {
+        Elf32_Ehdr: %i[
+          e_type
+          e_machine
+          e_version
+          e_entry
+          e_phoff
+          e_shoff
+          e_flags
+          e_ehsize
+          e_phentsize
+          e_phnum
+          e_shentsize
+          e_shnum
+          e_shstrndx
+        ].freeze,
+        Elf64_Ehdr: %i[
+          e_type
+          e_machine
+          e_version
+          e_entry
+          e_phoff
+          e_shoff
+          e_flags
+          e_ehsize
+          e_phentsize
+          e_phnum
+          e_shentsize
+          e_shnum
+          e_shstrndx
+        ].freeze,
+        Elf32_Phdr: %i[
+          p_type
+          p_offset
+          p_vaddr
+          p_paddr
+          p_filesz
+          p_memsz
+          p_flags
+          p_align
+        ].freeze,
+        Elf64_Phdr: %i[
+          p_type
+          p_flags
+          p_offset
+          p_vaddr
+          p_paddr
+          p_filesz
+          p_memsz
+          p_align
+        ].freeze
+      }.freeze
+    end
+
+    private_constant :PackInfo
+
+    # These constants are for the segment types stored in the image headers
+    PT_NULL         = 0
+    PT_LOAD         = 1
+    PT_DYNAMIC      = 2
+    PT_INTERP       = 3
+    PT_NOTE         = 4
+    PT_SHLIB        = 5
+    PT_PHDR         = 6
+    PT_TLS          = 7
+    PT_LOOS         = 0x60000000
+    PT_HIOS         = 0x6fffffff
+    PT_LOPROC       = 0x70000000
+    PT_HIPROC       = 0x7fffffff
+
+    # These constants define the different elf file types
+    ET_NONE   = 0
+    ET_REL    = 1
+    ET_EXEC   = 2
+    ET_DYN    = 3
+    ET_CORE   = 4
+    ET_LOPROC = 0xff00
+    ET_HIPROC = 0xffff
+
+    EI_NIDENT = 16
+
+    # e_ident[] indexes
+    EI_MAG0    = 0
+    EI_MAG1    = 1
+    EI_MAG2    = 2
+    EI_MAG3    = 3
+    EI_CLASS   = 4
+    EI_DATA    = 5
+    EI_VERSION = 6
+    EI_OSABI   = 7
+    EI_PAD     = 8
+
+    # EI_MAG
+    ELFMAG0 = 0x7f
+    ELFMAG1 = 0x45
+    ELFMAG2 = 0x4c
+    ELFMAG3 = 0x46
+    ELFMAG  = [ELFMAG0, ELFMAG1, ELFMAG2, ELFMAG3].pack('C*')
+    SELFMAG = 4
+
+    # e_ident[EI_CLASS]
+    ELFCLASSNONE = 0
+    ELFCLASS32   = 1
+    ELFCLASS64   = 2
+    ELFCLASSNUM  = 3
+
+    # e_ident[EI_DATA]
+    ELFDATANONE = 0
+    ELFDATA2LSB = 1
+    ELFDATA2MSB = 2
+
+    def initialize(buffer)
+      @buffer = buffer
+
+      @ehdr = { e_ident: @buffer.read(EI_NIDENT).unpack('C*') }
+      raise ArgumentError unless @ehdr[:e_ident].slice(EI_MAG0, SELFMAG).pack('C*') == ELFMAG
+
+      case @ehdr[:e_ident][EI_CLASS]
+      when ELFCLASS32
+        elf_ehdr = :Elf32_Ehdr
+        elf_phdr = :Elf32_Phdr
+      when ELFCLASS64
+        elf_ehdr = :Elf64_Ehdr
+        elf_phdr = :Elf64_Phdr
+      else
+        raise EncodingError
+      end
+
+      case @ehdr[:e_ident][EI_DATA]
+      when ELFDATA2LSB
+        little_endian = true
+      when ELFDATA2MSB
+        little_endian = false
+      else
+        raise EncodingError
+      end
+
+      @ehdr.merge!(read(elf_ehdr, little_endian))
+
+      @buffer.seek(@ehdr[:e_phoff], IO::SEEK_SET)
+      @proghdrs = Array.new(@ehdr[:e_phnum]) do
+        read(elf_phdr, little_endian)
+      end
+    end
+
+    def relocatable?
+      @ehdr[:e_type] == ET_REL
+    end
+
+    def executable?
+      @ehdr[:e_type] == ET_EXEC
+    end
+
+    def shared_object?
+      @ehdr[:e_type] == ET_DYN
+    end
+
+    def core?
+      @ehdr[:e_type] == ET_CORE
+    end
+
+    def interpreter
+      phdr = @proghdrs.find { |p| p[:p_type] == PT_INTERP }
+      return if phdr.nil?
+
+      @buffer.seek(phdr[:p_offset], IO::SEEK_SET)
+      interpreter = @buffer.read(phdr[:p_filesz])
+      raise EncodingError unless interpreter.end_with?("\0")
+
+      interpreter.chomp!("\0")
+    end
+
+    private
+
+    def read(type, little_endian)
+      size = PackInfo::SIZE_MAP[type]
+      format = little_endian ? PackInfo::PACK_MAP[type] : PackInfo::PACK_MAP[type].tr('<', '>')
+      [PackInfo::STRUCT_MAP[type], @buffer.read(size).unpack(format)].transpose.to_h
+    end
+
+    INTERPRETER = begin
+      proc_self_exe = '/proc/self/exe'
+      if File.exist?(proc_self_exe)
+        File.open(proc_self_exe, 'rb') do |file|
+          elf = ELF.new(file)
+          interpreter = elf.interpreter
+          if interpreter.nil? && elf.shared_object?
+            File.readlink(proc_self_exe)
+          else
+            interpreter
+          end
+        end
+      end
+    end.freeze
+  end
+
+  private_constant :ELF
+end