add factorial assembler program

gnu-asm/factorial1/factorial1.s

@@ -0,0 +1,85 @@
+.intel_syntax noprefix
+
+.section .data
+INum:   .quad 12
+DNum:   .quad 0
+DBy:    .quad 1
+Erg:    .quad 0
+One:    .quad 1
+Zero:   .quad 0
+
+.section .bss
+.lcomm output_buffer, 32
+
+.section .text
+.global _start
+
+_start:
+        mov rax, [rip + One]       # LDA One
+        call print_number          # OUT
+
+NEX:
+        mov rax, [rip + INum]      # LDA INum
+        mov [rip + DNum], rax      # STA DNum
+
+        mov rax, [rip + DBy]       # LDA DBy
+        add rax, [rip + One]       # ADD One
+        mov [rip + DBy], rax       # STA DBy
+
+        mov rax, [rip + INum]      # LDA INum
+        sub rax, [rip + DBy]       # SUB DBy
+
+        jns mod_loop               # BRP mod_loop
+        jmp halt                   # HLT
+
+mod_loop:
+        mov rax, [rip + DNum]      # LDA DNum
+        sub rax, [rip + DBy]       # SUB DBy
+        mov [rip + DNum], rax      # STA DNum
+
+        jz PRT                     # BRZ PRT
+        jns mod_loop               # BRP mod_loop
+        jmp NEX                    # BRA NEX
+
+PRT:
+        mov rax, [rip + DBy]       # LDA DBy
+        call print_number          # OUT
+        jmp NEX                    # BRA NEX
+
+halt:
+        mov rax, 60                # Linux exit syscall
+        xor rdi, rdi               # Exit status 0
+        syscall
+
+
+# ------------------------------------------------------------
+# print_number
+#
+# Input:
+#   RAX = unsigned integer to print
+#
+# Output:
+#   Number followed by a newline
+# ------------------------------------------------------------
+print_number:
+        lea rsi, [rip + output_buffer + 31]
+        mov byte ptr [rsi], 10     # Newline
+        mov rcx, 1                 # Output length
+        mov rbx, 10
+
+.convert:
+        xor rdx, rdx
+        div rbx                    # RAX / 10; remainder in RDX
+        add dl, '0'
+        dec rsi
+        mov [rsi], dl
+        inc rcx
+
+        test rax, rax
+        jne .convert
+
+        mov rax, 1                 # Linux write syscall
+        mov rdi, 1                 # stdout
+        mov rdx, rcx               # Number of bytes
+        syscall
+        ret

gnu-asm/factorial1/run.sh

@@ -0,0 +1,7 @@
+#!/usr/bin/env bash
+as --64 -o factorial1.o factorial1.s
+ld -o factorial1 factorial1.o
+cp factorial1 factorial1.stripped
+strip --strip-all factorial1.stripped
+./factorial1.stripped
+