Introduced LoadSegment

Author: david942j

lib/elftools/elf_file.rb

@@ -290,10 +290,7 @@ def segment_at(n)
     #   #=> 4919 # 0x1337
     def offset_from_vma(vma, size = 0)
       segments_by_type(:load) do |seg|
-        if vma >= (seg.header.p_vaddr & -seg.header.p_align) &&
-           vma + size <= seg.header.p_vaddr + seg.header.p_filesz
-          return vma - seg.header.p_vaddr + seg.header.p_offset
-        end
+        return seg.vma_to_offset(vma) if seg.vma_in?(vma, size)
       end
     end
 

lib/elftools/segments/load_segment.rb

@@ -0,0 +1,89 @@
+require 'elftools/segments/segment'
+
+module ELFTools
+  module Segments
+    # For DT_LOAD segment.
+    # Able to query between file offset and virtual memory address.
+    class LoadSegment < Segment
+      # Returns the start of this segment.
+      # @return [Integer]
+      #   The file offset.
+      def file_head
+        header.p_offset.to_i
+      end
+
+      # Returns size in file.
+      # @return [Integer]
+      #   The size.
+      def size
+        header.p_filesz.to_i
+      end
+
+      # Returns the end of this segment.
+      # @return [Integer]
+      #   The file offset.
+      def file_tail
+        file_head + size
+      end
+
+      # Returns the start virtual address of this segment.
+      # @return [Integer]
+      #   The vma.
+      def mem_head
+        header.p_vaddr.to_i
+      end
+
+      # Returns size in memory.
+      # @return [Integer]
+      #   The size.
+      def mem_size
+        header.p_memsz.to_i
+      end
+
+      # Returns the end virtual address of this segment.
+      # @return [Integer]
+      #   The vma.
+      def mem_tail
+        mem_head + mem_size
+      end
+
+      # Query if the given file offset located in this segment.
+      # @param [Integer] offset
+      #   File offset.
+      # @param [Integer] size
+      #   Size.
+      # @return [Boolean]
+      def offset_in?(offset, size = 0)
+        file_head <= offset && offset + size < file_tail
+      end
+
+      # Convert file offset into virtual memory address.
+      # @param [Integer] offset
+      #   File offset.
+      # @return [Integer]
+      def offset_to_vma(offset)
+        # XXX: What if file_head is not aligned with p_vaddr (which is invalid according to ELF spec)?
+        offset - file_head + header.p_vaddr
+      end
+
+      # Query if the given virtual memory address located in this segment.
+      # @param [Integer] vma
+      #   Virtual memory address.
+      # @param [Integer] size
+      #   Size.
+      # @return [Boolean]
+      def vma_in?(vma, size = 0)
+        vma >= (header.p_vaddr & -header.p_align) &&
+          vma + size <= mem_tail
+      end
+
+      # Convert virtual memory address into file offset.
+      # @param [Integer] vma
+      #   Virtual memory address.
+      # @return [Integer]
+      def vma_to_offset(vma)
+        vma - header.p_vaddr + header.p_offset
+      end
+    end
+  end
+end

lib/elftools/segments/segments.rb

@@ -4,6 +4,7 @@
 
 require 'elftools/segments/dynamic_segment'
 require 'elftools/segments/interp_segment'
+require 'elftools/segments/load_segment'
 require 'elftools/segments/note_segment'
 
 module ELFTools
@@ -20,6 +21,7 @@ def create(header, stream, *args)
         klass = case header.p_type
                 when Constants::PT_DYNAMIC then DynamicSegment
                 when Constants::PT_INTERP then InterpSegment
+                when Constants::PT_LOAD then LoadSegment
                 when Constants::PT_NOTE then NoteSegment
                 else Segment
                 end

spec/full_test/i386_spec.rb

@@ -26,5 +26,7 @@
     expect(@elf.segment_by_type(:interp).interp_name).to eq '/lib/ld-linux.so.2'
     expect(@elf.segment_by_type(:note).notes.size).to be 2
     expect(@elf.segment_by_type(:gnu_stack).executable?).to be false
+    expect(@elf.segment_by_type(:load).offset_in?(0x12345678)).to be false
+    expect(@elf.segment_by_type(:load).offset_to_vma(0)).to be 0x8048000
   end
 end

spec/full_test/pie_spec.rb

@@ -24,5 +24,7 @@
     expect(@elf.segment_by_type(:interp).interp_name).to eq '/lib/ld-linux.so.2'
     expect(@elf.segment_by_type(:note).notes.size).to be 2
     expect(@elf.segment_by_type(:gnu_stack).executable?).to be false
+    expect(@elf.segment_by_type(:load).offset_in?(0x12345678)).to be false
+    expect(@elf.segment_by_type(:load).offset_to_vma(0x33)).to be 0x33
   end
 end

spec/full_test/striped_spec.rb

@@ -23,5 +23,7 @@
     expect(@elf.segment_by_type(:interp).interp_name).to eq '/lib64/ld-linux-x86-64.so.2'
     expect(@elf.segment_by_type(:note).notes.size).to be 2
     expect(@elf.segment_by_type(:gnu_stack).executable?).to be false
+    expect(@elf.segment_by_type(:load).offset_in?(0x33)).to be true
+    expect(@elf.segment_by_type(:load).offset_to_vma(0x33)).to be 0x400033
   end
 end

spec/segments_spec.rb

@@ -36,6 +36,12 @@
       expect(dynamic).to be_a ELFTools::Segments::DynamicSegment
       expect(dynamic.respond_to?(:tags)).to be true
     end
+
+    it 'load' do
+      load_seg = ELFTools::Segments::Segment.create(@header_maker.call(type: 1), nil)
+      expect(load_seg).to be_a ELFTools::Segments::LoadSegment
+      expect(load_seg.respond_to?(:vma_to_offset)).to be true
+    end
   end
 
   describe 'common methods' do