Adjust symtab section header

lib/caotral/binary/elf.rb

@@ -24,6 +24,15 @@ def [](idx) = @sections[idx]
       def find_by_name(section_name) = @sections.find { section_name == it.section_name }
       def select_by_name(section_name) = @sections.select { section_name == it.section_name }
       def index(section_name) = @sections.index { section_name == it.section_name }
+      def select_by_names(section_names)
+        @sections.select do |section|
+          next true if section.section_name.nil?
+          section_names.any? do |name|
+            re = Regexp === name
+            re ? section.section_name.match(name) : section.section_name == name
+          end
+        end
+      end
     end
   end
 end

lib/caotral/binary/elf/section_header.rb

@@ -46,6 +46,7 @@ def size = @size.pack("C*").unpack1("Q<")
         def type = SHT_BY_VALUE[@type.pack("C*").unpack1("L<")]
         def info = @info.pack("C*").unpack1("L<")
         def addr = @addr.pack("C*").unpack1("Q<")
+        def link = @link.pack("C*").unpack1("L<")
 
         private def bytes = [@name, @type, @flags, @addr, @offset, @size, @link, @info, @addralign, @entsize]
       end

lib/caotral/linker/writer.rb

@@ -4,7 +4,7 @@ module Caotral
   class Linker
     class Writer
       include Caotral::Binary::ELF::Utils
-      ALLOW_SECTIONS = %w(.text .strtab .shstrtab).freeze
+      ALLOW_SECTIONS = [".text", ".strtab", ".shstrtab", ".symtab", /\.rela\./, /\.rel\./].freeze
       R_X86_64_PC32 = 2
       R_X86_64_PLT32 = 4
       ALLOW_RELOCATION_TYPES = [R_X86_64_PC32, R_X86_64_PLT32].freeze
@@ -15,6 +15,7 @@ def self.write!(elf_obj:, output:, entry: nil, debug: false)
       end
       def initialize(elf_obj:, output:, entry: nil, debug: false)
         @elf_obj, @output, @entry, @debug = elf_obj, output, entry, debug
+        @write_sections = @elf_obj.select_by_names(ALLOW_SECTIONS)
       end
       def write
         f = File.open(@output, "wb")
@@ -70,17 +71,28 @@ def write
         shstrtab_offset = f.pos
         f.write(shstrtab.body.names)
         shstrtab.header.set!(offset: shstrtab_offset, size: shstrtab.body.names.bytesize)
-        write_sections = @elf_obj.sections.select { ALLOW_SECTIONS.include?(it.section_name) || it.section_name.nil? }
         shoffset = f.pos
-        shstrndx = write_sections.index { it.section_name == ".shstrtab" }
-        shnum = write_sections.size
+        shstrndx  = write_section_index(".shstrtab")
+        strtabndx = write_section_index(".strtab")
+        symtabndx = write_section_index(".symtab")
+        shnum = @write_sections.size
         @elf_obj.header.set!(shoffset:, shnum:, shstrndx:)
         names = @elf_obj.find_by_name(".shstrtab").body
 
-        write_sections.each do |section|
+        @write_sections.each do |section|
+          header = section.header
           lookup_name = section.section_name
           name_offset = names.offset_of(lookup_name)
-          section.header.set!(name: name_offset) if name_offset
+          name, info, link, entsize = (name_offset.nil? ? 0 : name_offset), header.info, header.link, 0
+          if header.type == :symtab
+            info = section.body.size
+            link = strtabndx
+            entsize = header.entsize.nonzero? || 24
+          elsif [:rel, :rela].include?(header.type)
+            link = symtabndx
+            info = ref_index(section)
+          end
+          header.set!(name:, info:, link:, entsize:)
           f.write(section.header.build)
         end
 
@@ -90,6 +102,14 @@ def write
       ensure
         f.close if f
       end
+
+      private
+      def write_section_index(section_name) = @write_sections.index { it.section_name == section_name }
+      def ref_index(section)
+        section_name = section.section_name
+        ref = @elf_obj.select_by_names(section_name.split(".").filter { |sn| !sn.empty? && sn != "rel" && sn != "rela" }).first
+        write_section_index(ref.section_name)
+      end
     end
   end
 end

test/caotral/linker/writer_test.rb

@@ -16,7 +16,7 @@ def test_write
     written_output = Caotral::Linker::Writer.write!(elf_obj: @elf_obj, output: "write.o", debug: false)
     read_written_elf = Caotral::Binary::ELF::Reader.read!(input: written_output, debug: false)
     assert_equal @elf_obj.header.shoffset, read_written_elf.header.shoffset
-    assert_equal 4, read_written_elf.sections.size
+    assert_equal 5, read_written_elf.sections.size
     assert_equal 0x401000, read_written_elf.header.entry
   end