Table of Contents
casm1 - call C function from asm
casm3 - call asm function from C
hello world
hello.asm
section .data
msg db "hello, world!",`\n`
section .text
global _start
_start:
;; write syscall
mov rax, 1
;; file descriptor, standard output
mov rdi, 1
;; message address
mov rsi, msg
;; length of message
mov rdx, 14
;; call write syscall
syscall
;; exit
mov rax, 60
mov rdi, 0
syscall
makefile
all:
nasm -f elf64 -o hello.o hello.asm
ld -o hello hello.o
clean:
rm hello hello.o
float
circle_fpu_87c.c
#include <stdio.h>
extern int printResult(double result);
int printResult(double result) {
printf("Circle radius is - %f\n", result);
return 0;
}
circle_fpu_87.asm
extern printResult
section .data
radius dq 1.7
result dq 0
SYS_EXIT equ 60
EXIT_CODE equ 0
section .text
global _start
_start:
fld qword [radius]
fld qword [radius]
fmul
fldpi
fmul
fstp qword [result]
mov rax, 0
movq xmm0, [result]
call printResult
mov rax, SYS_EXIT
mov rdi, EXIT_CODE
syscall
makefile
build:
gcc -g -c circle_fpu_87c.c -o c.o
nasm -f elf64 circle_fpu_87.asm -o circle_fpu_87.o
ld -dynamic-linker /lib64/ld-linux-x86-64.so.2 -lc circle_fpu_87.o c.o -o testFloat1
clean:
rm -rf *.o
rm -rf testFloat1
stack
stack.asm
section .data
SYS_WRITE equ 1
STD_IN equ 1
SYS_EXIT equ 60
EXIT_CODE equ 0
NEW_LINE db 0xa
WRONG_ARGC db "Must be two command line argument", 0xa
section .text
global _start
_start:
;; rcx - argc
pop rcx
;;
;; Check argc
;;
cmp rcx, 3
jne argcError
;;
;; start to sum arguments
;;
;; skip argv[0] - program name
add rsp, 8
;; get argv[1]
pop rsi
;; convert argv[1] str to int
call str_to_int
;; put first num to r10
mov r10, rax
;; get argv[2]
pop rsi
;; convert argv[2] str to int
call str_to_int
;; put second num to r10
mov r11, rax
;; sum it
add r10, r11
;;
;; Convert to string
;;
mov rax, r10
;; number counter
xor r12, r12
;; convert to string
jmp int_to_str
;;
;; Print argc error
;;
argcError:
;; sys_write syscall
mov rax, 1
;; file descritor, standard output
mov rdi, 1
;; message address
mov rsi, WRONG_ARGC
;; length of message
mov rdx, 34
;; call write syscall
syscall
;; exit from program
jmp exit
;;
;; Convert int to string
;;
int_to_str:
;; reminder from division
mov rdx, 0
;; base
mov rbx, 10
;; rax = rax / 10
div rbx
;; add \0
add rdx, 48
add rdx, 0x0
;; push reminder to stack
push rdx
;; go next
inc r12
;; check factor with 0
cmp rax, 0x0
;; loop again
jne int_to_str
;; print result
jmp print
;;
;; Convert string to int
;;
str_to_int:
;; accumulator
xor rax, rax
;; base for multiplication
mov rcx, 10
next:
;; check that it is end of string
cmp [rsi], byte 0
;; return int
je return_str
;; mov current char to bl
mov bl, [rsi]
;; get number
sub bl, 48
;; rax = rax * 10
mul rcx
;; ax = ax + digit
add rax, rbx
;; get next number
inc rsi
;; again
jmp next
return_str:
ret
;;
;; Print number
;;
print:
;;;; calculate number length
mov rax, 1
mul r12
mov r12, 8
mul r12
mov rdx, rax
;;;;
;;;; print sum
mov rax, SYS_WRITE
mov rdi, STD_IN
mov rsi, rsp
;; call sys_write
syscall
;;
;; newline
jmp printNewline
;;
;; Print number
;;
printNewline:
mov rax, SYS_WRITE
mov rdi, STD_IN
mov rsi, NEW_LINE
mov rdx, 1
syscall
jmp exit
;;
;; Exit from program
;;
exit:
;; syscall number
mov rax, SYS_EXIT
;; exit code
mov rdi, EXIT_CODE
;; call sys_exit
syscall
makefile
all:
nasm -f elf64 -o stack.o stack.asm
ld -o stack stack.o
clean:
rm stack stack.o
string
reverse.asm
;;
;; initialized data
;;
section .data
SYS_WRITE equ 1
STD_OUT equ 1
SYS_EXIT equ 60
EXIT_CODE equ 0
NEW_LINE db 0xa
INPUT db "Hello world!"
;;
;; non initialized data
;;
section .bss
OUTPUT resb 1
;;
;; code
;;
section .text
global _start
;;
;; main routine
;;
_start:
;; get addres of INPUT
mov rsi, INPUT
;; zeroize rcx for counter
xor rcx, rcx
; df = 0 si++
cld
; remember place after function call
mov rdi, $ + 15
;; get string lengt
call calculateStrLength
;; write zeros to rax
xor rax, rax
;; additional counter for reverseStr
xor rdi, rdi
;; reverse string
jmp reverseStr
;;
;; calculate length of string
;;
calculateStrLength:
;; check is it end of string
cmp byte [rsi], 0
;; if yes exit from function
je exitFromRoutine
;; load byte from rsi to al and inc rsi
lodsb
;; push symbol to stack
push rax
;; increase counter
inc rcx
;; loop again
jmp calculateStrLength
;;
;; back to _start
;;
exitFromRoutine:
;; push return addres to stack again
push rdi
;; return to _start
ret
;;
;; reverse string
;;
;; 31 in stack
reverseStr:
;; check is it end of string
cmp rcx, 0
;; if yes print result string
je printResult
;; get symbol from stack
pop rax
;; write it to output buffer
mov [OUTPUT + rdi], rax
;; decrease length counter
dec rcx
;; increase additional length counter (for write syscall)
inc rdi
;; loop again
jmp reverseStr
;;
;; Print result string
;;
printResult:
mov rdx, rdi
mov rax, 1
mov rdi, 1
mov rsi, OUTPUT
syscall
jmp printNewLine
;;
;; Print new line
;;
printNewLine:
mov rax, SYS_WRITE
mov rdi, STD_OUT
mov rsi, NEW_LINE
mov rdx, 1
syscall
jmp exit
;;
;; Exit from program
;;
exit:
;; syscall number
mov rax, SYS_EXIT
;; exit code
mov rdi, EXIT_CODE
;; call sys_exit
syscall
makefile
all:
nasm -g -f elf64 -o reverse.o reverse.asm
ld -o reverse reverse.o
clean:
rm reverse reverse.o
sum
sum.asm
;initialised data section
section .data
; Define constants
num1: equ 100
num2: equ 50
; http://geekswithblogs.net/MarkPearl/archive/2011/04/13/more-nasm.aspx
msg: db "Sum is correct", 10
;;
;; program code
;;
section .text
global _start
;; entry point
_start:
; get sum of num1 and num2
mov rax, num1
mov rbx, num2
add rax, rbx
; compare rax with correct sum - 150
cmp rax, 150
; if rax is not 150 go to exit
jne .exit
; if rax is 150 print msg
jmp .rightSum
; Print message that sum is correct
.rightSum:
;; write syscall
mov rax, 1
;; file descritor, standard output
mov rdi, 1
;; message address
mov rsi, msg
;; length of message
mov rdx, 15
;; call write syscall
syscall
; exit from program
jmp .exit
; exit procedure
.exit:
mov rax, 60
mov rdi, 0
syscall
makefile
all:
nasm -f elf64 -o sum.o sum.asm
ld -o sum sum.o
clean:
rm sum sum.o
C语言与汇编之间调用
casm1 - call C function from asm
casm.c
#include <stdio.h>
extern int print();
int print() {
printf("Hello World\n");
return 0;
}
casm.asm
global _start
extern print
section .text
_start:
call print
mov rax, 60
mov rdi, 0
syscall
makefile
buildAsmc:
gcc -c casm.c -o c.o
nasm -f elf64 casm.asm -o casm.o
ld -dynamic-linker /lib64/ld-linux-x86-64.so.2 -lc casm.o c.o -o casm
clean:
rm -rf *.o
rm -rf casm
casm2 - gcc inline assembly
casm.c
#include <string.h>
int main() {
char* str = "Hello World\n";
long len = strlen(str);
int ret = 0;
__asm__("movq $1, %%rax \n\t"
"movq $1, %%rdi \n\t"
"movq %1, %%rsi \n\t"
"movl %2, %%edx \n\t"
"syscall"
: "=g"(ret)
: "g"(str), "g" (len));
return 0;
}
makefile
build:
gcc casm.c -o casm
casm3 - call asm function from C
casm.c
#include <string.h>
extern void printHelloWorld(char *str, int len);
int main() {
char* str = "Hello World\n";
int len = strlen(str);
printHelloWorld(str, len);
return 0;
}
casm.asm
global printHelloWorld
section .text
printHelloWorld:
;; 1 arg
mov r10, rdi
;; 2 arg
mov r11, rsi
;; call write syscall
mov rax, 1
mov rdi, 1
mov rsi, r10
mov rdx, r11
syscall
ret
makefile
build:
nasm -f elf64 -o casm.o casm.asm
gcc casm.o casm.c -o casm
GitHub：https://github.com/0xAX/asm