Merge pull request #30 from katsyoshi/assembler-writer-align

set assembler section header fields

Author: katsyoshi

lib/caotral/assembler/writer.rb

@@ -3,6 +3,14 @@
 module Caotral
   class Assembler
     class Writer
+      SECTION_TYPE_BY_NAME = {
+        nil => :null,
+        ".symtab" => :symtab,
+        ".shstrtab" => :strtab,
+        ".strtab" => :strtab,
+        ".text" => :progbits,
+     }.freeze
+
       def self.write!(elf_obj:, output:, debug: false) = new(elf_obj:, output:, debug:).write
       def initialize(elf_obj:, output:, debug: false)
         @elf_obj = elf_obj
@@ -56,14 +64,10 @@ def write(output: @output)
                      body.build.size
                    end
             offset = section.section_name.nil? ? 0 : offsets[section_name]
-            type = decide_type(section)
-            if ".symtab" == section.section_name
-              link = @elf_obj.index(".strtab")
-              info = 1
-              header.set!(name:, offset:, size:, type:, info:, link:)
-            else
-              header.set!(name:, offset:, size:, type:)
-            end
+            link = 0
+            type, flags, addralign, info, entsize = [*decide(section)]
+            link = @elf_obj.index(".strtab") if ".symtab" == section.section_name
+            header.set!(name:, flags:, offset:, size:, type:, info:, link:, entsize:, addralign:)
             f.write(header.build)
           end
           @elf_obj.header.set!(shoffset:, shnum:, shstrndx:)
@@ -72,15 +76,62 @@ def write(output: @output)
         end
         output
       end
+      private_constant :SECTION_TYPE_BY_NAME
+
+      private
+      def decide(section)
+        type = SECTION_TYPE_BY_NAME[section.section_name]
+        [
+          _type(type),
+          _flag(type),
+          _addralign(type, section.section_name),
+          _info(type),
+          _entsize(type),
+        ]
+      end 
+        
+      def _type(type_name) = Caotral::Binary::ELF::SectionHeader::SHT[type_name]
+
+      def _flag(section_type)
+        case section_type
+        when :progbits
+          6
+        when :symtab, :strtab, :null
+          0
+        else
+          0
+        end
+      end
 
-      private def decide_type(section)
-        case section.section_name
-        when ".text"
+      def _addralign(type, section_name)
+        case
+        when (type == :progbits && section_name == ".text") || type == :strtab
           1
-        when ".symtab"
-          2
-        when ".shstrtab", ".strtab"
-          3
+        when type == :symtab
+          8
+        when type == :null
+          0
+        else
+          0
+        end
+      end
+
+      def _info(section_type)
+        case section_type
+        when :symtab
+          1
+        when :progbits, :strtab, :null
+          0
+        else
+          0
+        end
+      end
+      def _entsize(section_type)
+        case section_type
+        when :symtab
+          24
+        when :progbits, :strtab, :null
+          0
         else
           0
         end

lib/caotral/binary/elf/reader.rb

@@ -40,7 +40,6 @@ def read
             info = sh_entry[44, 4].unpack("L<").first
             addralign = sh_entry[48, 8].unpack("Q<").first
             entsize = sh_entry[56, 8].unpack("Q<").first
-            type_sym = type(type_val)
             section_header = Caotral::Binary::ELF::SectionHeader.new
             section_header.set!(name:, type: type_val, flags:, addr:, offset:, size:, link:, info:, addralign:, entsize:)
             section_name = i == shstrndx ? ".shstrtab" : nil

lib/caotral/compiler.rb

@@ -3,7 +3,7 @@
 require_relative "compiler/generator"
 
 class Caotral::Compiler
-  attr_reader *%i(generator assembler linker)
+  attr_reader :generator, :assembler, :linker
 
   def self.compile!(input:, output: "tmp.s", debug: false, compiler_options: ["-O0"], shared: false)
     compiler = new(input:, output:, debug:, shared:,)

lib/caotral/linker/writer.rb

@@ -34,7 +34,6 @@ def write
         vaddr = base_addr + text_offset
         paddr = base_addr + text_offset
         start_len = start_bytes.length
-        start_addr = base_addr + text_offset
         main_offset = main_sym.value + start_len
         start_bytes[1, 4] = num2bytes((main_offset - 5), 4)
         start_bytestring = start_bytes.pack("C*")

test/caotral/assembler/writer_test.rb

@@ -8,7 +8,7 @@ def test_write
     output = "amd64.o"
     instructions = Caotral::Assembler::Reader.new(input:).read
     elf_obj = Caotral::Assembler::Builder.new(instructions:).build
-    writer = Caotral::Assembler::Writer.new(elf_obj:, output:).write
+    Caotral::Assembler::Writer.new(elf_obj:, output:).write
     results = Caotral::Binary::ELF::Reader.new(input: output).read
     shstrtab = results.find_by_name(".shstrtab")
     text = results.find_by_name(".text")

test/caotral/compiler_test.rb

@@ -19,7 +19,7 @@ def test_sample_plus
 
   def test_sample_variable
     @file = "sample/variable.rb"
-    @caotral = Caotral.compile!(input: @file, assembler: "self")
+    @caotral = Caotral.compile!(input: @file, assembler: "self", linker: "self")
     File.chmod(755, "tmp")
     IO.popen("./tmp").close
     exit_code, handle_code = check_process($?.to_i)

test/caotral/linker/writer_test.rb

@@ -21,7 +21,7 @@ def test_write
   end
 
   def test_execute_written
-    written_output = Caotral::Linker::Writer.write!(elf_obj: @elf_obj, output: "write", debug: false)
+    Caotral::Linker::Writer.write!(elf_obj: @elf_obj, output: "write", debug: false)
     File.chmod(0755, "./write")
     IO.popen("./write").close
     exit_code, handle_code = check_process($?.to_i)