support syscall in assembler, and compiler

Author: katsyoshi

lib/vaporware/compiler/assembler/elf.rb

@@ -10,7 +10,7 @@ def initialize(type:, input:, output:, debug:)
       @header = Header.new(type:)
       @sections = Sections.new
     end
-        
+
     def build(input: @input, output: @output, debug: false)
       program_size = 0
       read!(input:)
@@ -60,6 +60,7 @@ def build(input: @input, output: @output, debug: false)
 
     private
     def init_assemble! = (note!; symtab!)
+
     def read!(input: @input, text: @sections.text.body)
       read = { main: false }
       File.open(input, "r") do |r|

lib/vaporware/compiler/assembler/elf/section/text.rb

@@ -49,6 +49,8 @@ def opecode(op, *operands)
       sete(op, *operands)
     when "je", "jmp"
       jump(op, *operands)
+    when "syscall"
+      [0x0f, 0x05]
     when "ret"
       [0xc3]
     else

lib/vaporware/compiler/generator.rb

@@ -57,6 +57,9 @@ def already_build_methods? = @defined_methods.sort == @doned.to_a.sort
       def epilogue(output)
         output.puts "  mov rsp, rbp"
         output.puts "  pop rbp"
+        output.puts "  mov rdi, rax"
+        output.puts "  mov rax, 60"
+        output.puts "  syscall"
         output.puts "  ret"
       end