GAB

图解汇编基础

后端编译任务流程

OS GNU 汇编器

macos -- 内置

linux -- 内置

Windows -- MinGW or linux vm

汇编语言的要素

指令

伪指令

标签

注释

汇编语言组成

常用指令

指令后缀

汇编指令-操作数

x86-64 架构的寄存器

生成汇编代码

clang -S -O2 hello.c -o hello.s

#或者：

gcc -S -O2 hello.c -o hello.s

将汇编代码编译成可执行文件

# // 用汇编器编译成目标文件

as hello.s -o hello.o

# //链接成可执行文件

gcc hello.o -o hello

# //运行程序

./hello

文档目录

第一章

函数调用

函数调用

/*function-call1.c */

#include

int fun1(int a, int b){

int c = 10;

return a+b+c;

}

int main(int argc, char *argv[]){

printf("fun1: %d\n", fun1(1,2));

return 0;

}

生成的汇编代码，文档里有注释:

# function call

# text segment, pure code

.section __TEXT,__text,regular,pure_instructions

_fun1:

# prelude to the function call, setting the stack pointer

pushq %rbp # save the bottom address of the caller's stack frame

movq %rsp , %rbp # set the top address of the caller's stack frame to the bottom of this stack frame

subq $4 , %rsp # extension stack

movl $10 , -4(%rbp) # The variable c is assigned a value of 10, which can also be written as movl $10, (%rsp)

# do addition

movl %edi , %eax # put the first parameter in %eax

addl %esi , %eax # add the second parameter to %eax, %eax is also the register that stores the return value

addl -4(%rbp), %eax # plus the value of c

addq $4 , %rsp # shrink the stack

# at the end of the function call, restore the stack pointer to its original value

pushq %rbp # save the bottom address of the caller's stack frame

movq %rsp , %rbp # set the top address of the caller's stack frame to the bottom of this stack frame

# set the first and second parameters, 1 and 2 respectively

movl $1, %edi

movl $2, %esi

callq _fun1 # call function

# set parameters for pritf

leaq L_.str(%rip), %rdi # the first parameter is the address of the string

movl %eax, %esi # the second parameter is the return value of the previous parameter

# set the return value. This sentence is also commonly used in commands such as xorl %esi, %esi, which are all set to zero

movl $0 , %eax

# restore the bottom value of the caller's stack frame

popq %rbp # restore the bottom value of the caller's stack frame

retq # return

# text segment, save string literal

.section __TEXT,__cstring,cstring_literals

L_.str: ## @.str

.asciz "Hello World! :%d \n"

IF 语句的汇编

.text

.globl _fun1

_fun1:

LFB0:

pushq%rbp

LCFI0:

movq%rsp, %rbp

LCFI1:

movl%edi, -4(%rbp)

jmpL2

L3:

addl$1, -4(%rbp)

L2:

cmpl$9, -4(%rbp)

jleL3

nop

nop

popq%rbp

LCFI2:

ret

LFE0:

.section __TEXT,__eh_frame,coalesced,no_toc+strip_static_syms+live_support

EH_frame1:

.set L$set$0,LECIE1-LSCIE1

.long L$set$0

LSCIE1:

.long0

.byte0x1

.ascii "zR\0"

.byte0x1

.byte0x78

.byte0x10

.byte0x1

.byte0x10

.byte0xc

.byte0x7

.byte0x8

.byte0x90

.byte0x1

.align 3

LECIE1:

LSFDE1:

.set L$set$1,LEFDE1-LASFDE1

.long L$set$1

LASFDE1:

.longLASFDE1-EH_frame1

.quadLFB0-.

.set L$set$2,LFE0-LFB0

.quad L$set$2

.byte0

.byte0x4

.set L$set$3,LCFI0-LFB0

.long L$set$3

.byte0xe

.byte0x10

.byte0x86

.byte0x2

.byte0x4

.set L$set$4,LCFI1-LCFI0

.long L$set$4

.byte0xd

.byte0x6

.byte0x4

.set L$set$5,LCFI2-LCFI1

.long L$set$5

.byte0xc

.byte0x7

.byte0x8

.align 3

LEFDE1:

.ident"GCC: (Homebrew GCC 9.3.0_1) 9.3.0"

.subsections_via_symbols

另一种写法：

.text

.globl _fun1

_fun1:

LFB0:

pushq%rbp

LCFI0:

movq%rsp, %rbp

LCFI1:

movl%edi, -4(%rbp)

cmpl$10, -4(%rbp)

jleL2

movl$4, %eax

jmpL3

L2:

movl$8, %eax

L3:

popq%rbp

LCFI2:

ret

LFE0:

.section __TEXT,__eh_frame,coalesced,no_toc+strip_static_syms+live_support

EH_frame1:

.set L$set$0,LECIE1-LSCIE1

.long L$set$0

LSCIE1:

.long0

.byte0x1

.ascii "zR\0"

.byte0x1

.byte0x78

.byte0x10

.byte0x1

.byte0x10

.byte0xc

.byte0x7

.byte0x8

.byte0x90

.byte0x1

.align 3

LECIE1:

LSFDE1:

.set L$set$1,LEFDE1-LASFDE1

.long L$set$1

LASFDE1:

.longLASFDE1-EH_frame1

.quadLFB0-.

.set L$set$2,LFE0-LFB0

.quad L$set$2

.byte0

.byte0x4

.set L$set$3,LCFI0-LFB0

.long L$set$3

.byte0xe

.byte0x10

.byte0x86

.byte0x2

.byte0x4

.set L$set$4,LCFI1-LCFI0

.long L$set$4

.byte0xd

.byte0x6

.byte0x4

.set L$set$5,LCFI2-LCFI1

.long L$set$5

.byte0xc

.byte0x7

.byte0x8

.align 3

LEFDE1:

.ident"GCC: (Homebrew GCC 9.3.0_1) 9.3.0"

.subsections_via_symbols

表达浮点型汇编的写法

.text

.p2align 4

.globl _fun1

_fun1:

LFB0:

addss%xmm1, %xmm0 #浮点数传参用XMM寄存器，加法用addss指令

addsslC0(%rip), %xmm0 #把常量2.0加到xmm0上，xmm0保存返回值

ret

LFE0:

.literal4

.align 2

lC0:

.long1073741824

.section __TEXT,__eh_frame,coalesced,no_toc+strip_static_syms+live_support

EH_frame1:

.set L$set$0,LECIE1-LSCIE1

.long L$set$0

LSCIE1:

.long0

.byte0x1

.ascii "zR\0"

.byte0x1

.byte0x78

.byte0x10

.byte0x1

.byte0x10

.byte0xc

.byte0x7

.byte0x8

.byte0x90

.byte0x1

.align 3

LECIE1:

LSFDE1:

.set L$set$1,LEFDE1-LASFDE1

.long L$set$1

LASFDE1:

.longLASFDE1-EH_frame1

.quadLFB0-.

.set L$set$2,LFE0-LFB0

.quad L$set$2

.byte0

.align 3

LEFDE1:

.ident"GCC: (Homebrew GCC 9.3.0_1) 9.3.0"

.subsections_via_symbols

将C代码 生成 汇编代码， 并将汇编代码生成目标文件

C 函数传多个参数的代码：

#include

extern int fun1(int x1, int x2, int x3, int x4, int x5, int x6, int x7, int x8);

int main(int argc, char *argv[])

{

printf("fun1: %d \n", fun1(1,2,3,4,5,6,7,8));

return 0;

}

将生成的汇编代码编译为目标文件，并结合链接器，生成可执行文件或库

# 生成链接文件

as convention-fun1.s -o convention-fun1.o

# 生成可执行文件或库

gcc conv.c convention-fun1.o -o convention