add strcmp

Author: h908714124

action.sh

@@ -1,6 +1,17 @@
 #!/bin/bash
-#see .github/workflows/make.yml
+#
+# see .github/workflows/make.yml
 
-cd cat
-make
-make check
+die() {
+  echo "ERROR: $@"
+  exit 1
+}
+
+cd print_int
+
+make print_int || die "make print_int"
+make write || die "make write"
+make strcmp || die "make strcmp"
+make check || die "make check"
+make check_write || die "make check_write"
+make check_strcmp || die "make check_strcmp"

print_int/.gdbinit

@@ -3,4 +3,4 @@ lay asm
 define hook-quit
 	set confirm off
 end
-break print_int
+break string_compare

print_int/.gitignore

@@ -1,2 +1,3 @@
 /print_int
 /write
+/strcmp

print_int/Makefile

@@ -1,17 +1,23 @@
-build:
+print_int:
 	$(CC) main.s -c -o print_int.o
 	$(LD) -e main -o print_int print_int.o
 
-check: build
+check: print_int
 	./print_int | md5sum | grep -q ^3cca2fa && printf "\033[1;32m[OK]\033[0m\n"
 
-build_write:
+write:
 	$(CC) write.s -c -o write.o
 	$(LD) -e main -o write write.o
 
-check_write: build_write
+check_write: write
 	./write | grep -q '^ABC$$' && printf "\033[1;32m[OK]\033[0m\n"
 
+strcmp:
+	$(CC) strcmp.s -c -o strcmp.o
+	$(LD) -e main -o strcmp strcmp.o
+
+check_strcmp: strcmp
+	./strcmp | md5sum | grep -q ^00350de && printf "\033[1;32m[OK]\033[0m\n"
 
 clean:
-	rm -f *.o write print_int
+	rm -f *.o write print_int strcmp

print_int/print_int.s

@@ -37,6 +37,14 @@
 	add	$24, %rsp
 	.endm
 
+	.macro strcmp s1 s2 count
+	push	\s1
+	push	\s2
+	push	\count
+	call	string_compare
+	add	$24, %rsp
+	.endm
+
 	.macro write address size
 	push	\address
 	push	\size
@@ -191,9 +199,9 @@ copymem:
 	enter
 	push_all
 	push	%rax
-	mov	32(%rbp), %rsi			# param: source
-	mov	24(%rbp), %rdi			# param: destination
-	mov	16(%rbp), %rdx			# param: count
+	mov	32(%rbp), %rsi			# char *source
+	mov	24(%rbp), %rdi			# char *destination
+	mov	16(%rbp), %rdx			# int count
 	mov	$0, %rcx
 	test	%rdx, %rdx
 	jz	copymem_done
@@ -207,3 +215,30 @@ copymem_done:
 	pop	%rax
 	pop_all
 	return
+
+string_compare:
+	enter
+	push_all
+	mov	32(%rbp), %rsi			# char *s1
+	mov	24(%rbp), %rdi			# char *s2
+	mov	16(%rbp), %rdx			# int count
+	mov	$0, %rcx
+	test	%rdx, %rdx
+	jz	string_compare_ret0
+string_compare_loop:
+	mov	(%rsi, %rcx), %rax
+	mov	(%rdi, %rcx), %rbx
+	cmp	%al, %bl
+	jne	string_compare_ret1
+	inc	%rcx
+	cmp	%rcx, %rdx
+	je	string_compare_ret0
+	jmp	string_compare_loop
+string_compare_ret1:
+	mov	$1, %rax
+	jmp	string_compare_done
+string_compare_ret0:
+	mov	$0, %rax
+string_compare_done:
+	pop_all
+	return

print_int/strcmp.s

@@ -0,0 +1,41 @@
+	.data
+foo:
+	.ascii "abc"
+	.text
+	.globl main
+
+.include "print_int.s"
+
+main:
+	enter
+	sub	$48, %rsp
+	movb	$0x41, -24(%rbp)
+	movb	$0x42, -23(%rbp)
+	movb	$0x43, -22(%rbp)
+	movb	$0x44, -21(%rbp)
+	movb	$0x41, -48(%rbp)
+	movb	$0x42, -47(%rbp)
+	movb	$0x43, -46(%rbp)
+	movb	$0x12, -45(%rbp)
+	mov	$2, %rax
+	mov	%rbp, %rsi
+	mov	%rbp, %rdi
+	sub	$24, %rsi
+	sub	$48, %rdi
+	strcmp	%rsi, %rdi, $3
+	log 	%rax
+	mov	$2, %rax
+	strcmp	%rdi, %rsi, $3
+	log 	%rax
+	mov	$2, %rax
+	strcmp	%rdi, %rsi, $4
+	log 	%rax
+	mov	$2, %rax
+	strcmp	%rdi, %rsi, $3
+	log 	%rax
+	call	exit
+
+exit:
+	movq	$EXIT, %rax
+	movq	$0, %rdi
+	syscall