add print_int

Author: h908714124

cat/cat.s

@@ -137,7 +137,3 @@ _start:
 	call	_close
 	call	_munmap
 	call	_exit
-
-	call	_print_ouch
-
-	leave

hello/hello.s

@@ -6,19 +6,22 @@
 
 .text
 
+# void print_chars(int {rsi}, int {rdx});
+print_chars:
+	movq	$1, %rax
+	movq	$1, %rdi
+	syscall
+	ret
+
 _start:
 	#https://stackoverflow.com/questions/29790175/assembly-x86-leave-instruction
 	pushq	%rbp
 	movq	%rsp, %rbp
 
-	movq	$1, %rax
-	movq	$1, %rdi
 	leaq	.hello.str, %rsi
 	movq	$10, %rdx
-	syscall
+	call	print_chars
 
 	movq	$60, %rax
 	movq	$0, %rdi
 	syscall
-
-	leave

print_int/.gdbinit

@@ -0,0 +1,5 @@
+set debuginfod enabled off
+lay asm
+define hook-quit
+	set confirm off
+end

print_int/.gitignore

@@ -0,0 +1 @@
+hello

print_int/Makefile

@@ -0,0 +1,6 @@
+build:
+	$(CC) print_int.s -c -g
+	$(LD) -o print_int print_int.o
+
+run: build
+	./print_int

print_int/print_int

@@ -0,0 +1,93 @@
+#https://www.youtube.com/watch?v=_hbZN4khAyU
+#https://github.com/xmdi/SCHIZONE
+	.equ	READ, 0
+	.equ	STDOUT, 1
+	.equ	CLOSE, 3
+	.equ	WRITE, 1
+	.equ	OPEN, 2
+	.equ	FSTAT, 5
+	.equ	EXIT, 60
+	.equ	MMAP, 9
+	.equ	MUNMAP, 11
+	.equ	OFFSET_SIZE, 48
+	.equ	CHAR_O, 0x4f
+	.equ	CHAR_U, 0x55
+	.equ	CHAR_C, 0x43
+	.equ	CHAR_H, 0x48
+	.equ	BANG, 0x21
+	.equ	NEWLINE, 0xa
+
+
+	.data
+
+my_number:
+	.quad 0x41
+
+	.text
+	.globl _start
+
+# void print_chars(char *rsi, int rdx);
+print_chars:
+	movq	$WRITE, %rax
+	movq	$STDOUT, %rdi
+	syscall
+	ret
+
+# void print_int_h(int {rsi});
+# 	Prints hexadecimal value in {rsi} to stdout.
+_print_int_h:
+	push	%rax
+	push	%rbp
+	push	%rsi
+	push	%rdx
+
+	mov	%rsp, %rbp 	# save base stack pointer
+
+	# value is kept in {rsi} and low bits are shifted off, four by four
+	# do all arithmetic in {rax}
+
+	# move trailing '\n' onto stack
+	push	$0xa
+
+_loop:
+
+	mov	%sil, %al	#
+	and	$15, %al	# %al contains low nibble of %rsi
+	add	$48, %al	# %al now correctly contains ascii "0"-"9"
+	cmp	$57, %al	#
+	jle	_insert_byte
+	add	$39, %al	# adjust %al for ascii "a"-"f"
+_insert_byte:
+	dec	%rsp
+	mov	%al, (%rsp)	# move this ascii value into next slot on stack
+	shr	$4, %rsi	# go on to next lowest bit
+	test	 %rsi, %rsi	# loop until nothing nonzero left
+	jnz	_loop
+
+	# move leading '0x' onto stack
+	push	$0x78		#x
+	push	$0x30		#0
+
+	# get ready to print
+	mov	%rbp, %rdx	##
+	sub	%rsp, %rdx	## %rdx will be length of number in bytes
+	mov	%rsp, %rsi	## address of top of stack
+	call	print_chars	## print out bytes
+	mov	%rbp, %rsp 	## restore stack pointer
+
+	pop	%rdx
+	pop	%rsi
+	pop	%rbp
+	pop	%rax
+
+	ret
+
+_start:
+	mov	my_number, %rsi
+	call	_print_int_h
+	jmp	_exit
+
+_exit:
+	movq	$EXIT, %rax
+	movq	$0, %rdi
+	syscall