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Golang内置函数和过程调用汇编代码分析

Posted on 2015-04-24 08:55:17 golang

在Golang汇编快速指南这篇博客中，简单介绍了Golang中汇编的简单语法以及特殊之处。下面介绍Golang中的内置函数和相关操作代码的汇编实现，可以作为上篇博客的补充和实践。

汇编中过程调用的参数是通过栈来传递的，在栈上的布局如下：

参数3
参数2
参数1  <-FP
保存PC <-SP
...
...

内置函数: new, make, append

package main

import (
    "fmt"
)

type new_int int

var (
    gobal_1 = "this is global var"
)

func main() {
    auto_1 := "this is auto_1"

    s0 := new(new_int)

    s1 := make([]int, 10)
    s2 := make([]int, 10)

    append(s2, 9999)
    fmt.Println(s1, s2)
    fmt.Println(s0)
}

下面是汇编代码:

"".main t=1 size=1936 value=0 args=0x0 locals=0x128
    // 定义函数main，栈帧大小为296字节，0字节的参数(无参数)
    0x0000 00000 (builtin.go:13)    TEXT    "".main+0(SB),$296-0
    // 将线程本地存储(thread local storage)传送到CX
    0x0000 00000 (builtin.go:13)    MOVQ    (TLS),CX
    // 下面是检查栈帧的大小是否超过目前分配的小
    0x0009 00009 (builtin.go:13)    LEAQ    -168(SP),AX
    0x0011 00017 (builtin.go:13)    CMPQ    AX,16(CX)
    0x0015 00021 (builtin.go:13)    JHI ,30
    // 如果超过调用runtime.morestack_noctxt
    0x0017 00023 (builtin.go:13)    CALL    ,runtime.morestack_noctxt(SB)
    0x001c 00028 (builtin.go:13)    JMP ,0
    // 扩大栈帧
    0x001e 00030 (builtin.go:13)    SUBQ    $296,SP
    0x0025 00037 (builtin.go:13)    FUNCDATA    $0,gclocals·e14c7473fe07b0ccdc0fdfa1a770087b+0(SB)
    0x0025 00037 (builtin.go:13)    FUNCDATA    $1,gclocals·7a70fcb413ec620f2a7a8c3ba5f394c1+0(SB)

    // 局部变量auto_1
    0x0025 00037 (builtin.go:14)    LEAQ    go.string."this is auto_1"+0(SB),BX
    // string在golang中是由数据本身和其长度组成的
    // 将数据的地址移动到BP
    0x002c 00044 (builtin.go:14)    MOVQ    (BX),BP
    // 移动BP到栈指针152字节的位置
    0x002f 00047 (builtin.go:14)    MOVQ    BP,"".auto_1+152(SP)
    // 将字符串长度移动到BP
    0x0037 00055 (builtin.go:14)    MOVQ    8(BX),BP
    // 移动BP到栈指针160字节的位置
    0x003b 00059 (builtin.go:14)    MOVQ    BP,"".auto_1+160(SP)

    // new_int类型的初始化
    // 将类型本身移动到BX
    0x0043 00067 (builtin.go:17)    MOVQ    $type."".new_int+0(SB),BX
    // 将BX移动到栈顶
    0x004a 00074 (builtin.go:17)    MOVQ    BX,(SP)
    0x004e 00078 (builtin.go:17)    PCDATA  $0,$1
    // 调用runtime.newobject
    0x004e 00078 (builtin.go:17)    CALL    ,runtime.newobject(SB)
    // 将返回的结果移动到BX
    0x0053 00083 (builtin.go:17)    MOVQ    8(SP),BX
    // 移动BP到栈指针80字节的位置
    0x0058 00088 (builtin.go:17)    MOVQ    BX,"".s1+80(SP)
    0x005d 00093 (builtin.go:17)    NOP ,

    // 创建slice s1
    // 将类型移动到BX
    0x005d 00093 (builtin.go:18)    MOVQ    $type.[]int+0(SB),BX
    // 将BX(类型)移动到栈顶
    0x0064 00100 (builtin.go:18)    MOVQ    BX,(SP)
    // 将长度参数len移动到相对于栈顶8字节的位置
    0x0068 00104 (builtin.go:18)    MOVQ    $10,8(SP)
    // 将容量参数cap移动到相对于栈顶16字节的位置
    0x0071 00113 (builtin.go:18)    MOVQ    $10,16(SP)
    0x007a 00122 (builtin.go:18)    PCDATA  $0,$2
    // 调用runtime.makeslice
    0x007a 00122 (builtin.go:18)    CALL    ,runtime.makeslice(SB)
    // 创建出的s1的参数分别保存在相对栈顶24, 32, 40字节的位置
    0x007f 00127 (builtin.go:18)    MOVQ    24(SP),DX
    0x0084 00132 (builtin.go:18)    MOVQ    32(SP),CX
    0x0089 00137 (builtin.go:18)    MOVQ    40(SP),BX

    // CX中保存的是slice的len参数
    0x008e 00142 (builtin.go:20)    MOVQ    CX,"".s2_len+64(SP)
    0x0093 00147 (builtin.go:20)    NOP ,

    // 将slice的array, len, cap传送给s2
    0x0093 00147 (builtin.go:21)    MOVQ    DX,"".s2+168(SP)
    0x009b 00155 (builtin.go:21)    MOVQ    CX,"".s2+176(SP)
    0x00a3 00163 (builtin.go:21)    MOVQ    BX,"".s2+184(SP)
    0x00ab 00171 (builtin.go:21)    MOVQ    BX,AX
    // 从BX中减去CX的值，结果保存在BX
    0x00ae 00174 (builtin.go:21)    SUBQ    CX,BX
    0x00b1 00177 (builtin.go:21)    CMPQ    BX,$1
    0x00b5 00181 (builtin.go:21)    JGE ,262
    // 将类型传送到栈顶
    0x00b7 00183 (builtin.go:21)    MOVQ    $type.[]int+0(SB),BX
    0x00be 00190 (builtin.go:21)    MOVQ    BX,(SP)
    // 将旧的slice传送到栈的第二个参数
    0x00c2 00194 (builtin.go:21)    MOVQ    DX,"".autotmp_0001+240(SP)
    0x00ca 00202 (builtin.go:21)    MOVQ    DX,8(SP)
    // 将长度传送到栈上第三个参数(s2的长度)
    0x00cf 00207 (builtin.go:21)    MOVQ    CX,"".autotmp_0001+248(SP)
    0x00d7 00215 (builtin.go:21)    MOVQ    CX,16(SP)
    // 将33行的BX的值重新保存到24(SP)，即s2的array
    0x00dc 00220 (builtin.go:21)    MOVQ    AX,"".autotmp_0001+256(SP)
    0x00e4 00228 (builtin.go:21)    MOVQ    AX,24(SP)
    // 将s2的长度置为1
    0x00e9 00233 (builtin.go:21)    MOVQ    $1,32(SP)
    // 调用growslice
    0x00f2 00242 (builtin.go:21)    PCDATA  $0,$2
    0x00f2 00242 (builtin.go:21)    CALL    ,runtime.growslice(SB)
    // 3个返回值(sliceStruct)
    0x00f7 00247 (builtin.go:21)    MOVQ    40(SP),DX
    0x00fc 00252 (builtin.go:21)    MOVQ    48(SP),CX
    0x0101 00257 (builtin.go:21)    MOVQ    56(SP),AX
    // 增加返回的结构中len参数长度，增加1
    0x0106 00262 (builtin.go:21)    MOVQ    CX,SI
    0x0109 00265 (builtin.go:21)    INCQ    ,SI
    // 变址寻址，DX+CX*8
    0x010c 00268 (builtin.go:21)    LEAQ    (DX)(CX*8),BX
    // 将立即数9999传递到(BX)的内存位置
    0x0110 00272 (builtin.go:21)    MOVQ    $9999,(BX)
    0x0117 00279 (builtin.go:21)    NOP ,
    0x0117 00279 (builtin.go:21)    MOVQ    DX,"".autotmp_0001+240(SP)
    0x011f 00287 (builtin.go:21)    MOVQ    SI,"".autotmp_0001+248(SP)
    0x0127 00295 (builtin.go:21)    MOVQ    AX,"".autotmp_0001+256(SP)
    // 将新的slice的参数传递给s2
    0x012f 00303 (builtin.go:21)    MOVQ    DX,"".s2+168(SP)
    0x0137 00311 (builtin.go:21)    MOVQ    SI,"".s2+176(SP)
    0x013f 00319 (builtin.go:21)    MOVQ    AX,"".s2+184(SP)
    0x0147 00327 (builtin.go:21)    NOP ,

内置函数: copy

package main

import (
    "fmt"
)

func main() {
    s1 := make([]int, 10)
    s2 := make([]int, 10)

    copy(s1, s2)
    fmt.Println(s1, s2)
}

下面是汇编代码:

"".main t=1 size=624 value=0 args=0x0 locals=0x108
    0x0000 00000 (builtin.go:7) TEXT    "".main+0(SB),$264-0
    0x0000 00000 (builtin.go:7) MOVQ    (TLS),CX
    0x0009 00009 (builtin.go:7) LEAQ    -136(SP),AX
    0x0011 00017 (builtin.go:7) CMPQ    AX,16(CX)
    0x0015 00021 (builtin.go:7) JHI ,30
    0x0017 00023 (builtin.go:7) CALL    ,runtime.morestack_noctxt(SB)
    0x001c 00028 (builtin.go:7) JMP ,0
    0x001e 00030 (builtin.go:7) SUBQ    $264,SP
    0x0025 00037 (builtin.go:7) FUNCDATA    $0,gclocals·7c13896baab3273e10662a9a37b348ce+0(SB)
    0x0025 00037 (builtin.go:7) FUNCDATA    $1,gclocals·978d33e7717760c8870a69548dc9a2fb+0(SB)

    // 创建切片s1
    0x0025 00037 (builtin.go:8) MOVQ    $type.[]int+0(SB),BX
    0x002c 00044 (builtin.go:8) MOVQ    BX,(SP)
    0x0030 00048 (builtin.go:8) MOVQ    $10,8(SP)
    0x0039 00057 (builtin.go:8) MOVQ    $10,16(SP)
    0x0042 00066 (builtin.go:8) PCDATA  $0,$0
    0x0042 00066 (builtin.go:8) CALL    ,runtime.makeslice(SB)
    0x0047 00071 (builtin.go:8) MOVQ    24(SP),DX
    0x004c 00076 (builtin.go:8) MOVQ    32(SP),CX
    0x0051 00081 (builtin.go:8) MOVQ    40(SP),AX
    0x0056 00086 (builtin.go:8) MOVQ    DX,"".s1+88(SP)
    0x005b 00091 (builtin.go:8) MOVQ    CX,"".s1+96(SP)
    0x0060 00096 (builtin.go:8) MOVQ    AX,"".s1+104(SP)

    // 创建切片s2
    0x0065 00101 (builtin.go:9) MOVQ    $type.[]int+0(SB),BX
    0x006c 00108 (builtin.go:9) MOVQ    BX,(SP)
    0x0070 00112 (builtin.go:9) MOVQ    $10,8(SP)
    0x0079 00121 (builtin.go:9) MOVQ    $10,16(SP)
    0x0082 00130 (builtin.go:9) PCDATA  $0,$1
    0x0082 00130 (builtin.go:9) CALL    ,runtime.makeslice(SB)
    0x0087 00135 (builtin.go:9) MOVQ    24(SP),DX
    0x008c 00140 (builtin.go:9) MOVQ    32(SP),CX
    0x0091 00145 (builtin.go:9) MOVQ    40(SP),AX

    // 将s1的数据保存到SI, BP, BX
    0x0096 00150 (builtin.go:11)    MOVQ    "".s1+88(SP),SI
    0x009b 00155 (builtin.go:11)    MOVQ    "".s1+96(SP),BP
    0x00a0 00160 (builtin.go:11)    MOVQ    "".s1+104(SP),BX

    // 将BX保存到224(SP)
    0x00a5 00165 (builtin.go:11)    MOVQ    BX,"".autotmp_0005+224(SP)

    // 将s2的数据保存到栈上
    0x00ad 00173 (builtin.go:11)    MOVQ    DX,"".s2+64(SP)
    0x00b2 00178 (builtin.go:11)    MOVQ    CX,"".s2+72(SP)
    0x00b7 00183 (builtin.go:11)    MOVQ    AX,"".s2+80(SP)

    // 将AX保存到152(SP)
    0x00bc 00188 (builtin.go:11)    MOVQ    AX,"".autotmp_0006+152(SP)
    // 将BP保存到216(SP)
    0x00c4 00196 (builtin.go:11)    MOVQ    BP,"".autotmp_0000+216(SP)

    // 从204到220是比较s1和s2的长度
    // 哪个比较大就用它作为参数
    // 复制BP到AX, BP保存的是s1的len
    0x00cc 00204 (builtin.go:11)    MOVQ    BP,AX
    // 将CX保存到144(SP)
    0x00cf 00207 (builtin.go:11)    MOVQ    CX,"".autotmp_0006+144(SP)
    // 比较s2的长度(CX)和s1的长度(BP)
    // 如果小于0则跳转到223
    // 否则执行220
    0x00d7 00215 (builtin.go:11)    CMPQ    CX,BP
    0x00da 00218 (builtin.go:11)    JGE ,223

    0x00dc 00220 (builtin.go:11)    MOVQ    CX,AX
    
    // 将s1的array作为第一个参数
    0x00df 00223 (builtin.go:11)    MOVQ    SI,"".autotmp_0000+208(SP)
    0x00e7 00231 (builtin.go:11)    MOVQ    SI,(SP)
    // 将s2的array作为第二个参数
    0x00eb 00235 (builtin.go:11)    MOVQ    DX,"".autotmp_0006+136(SP)
    0x00f3 00243 (builtin.go:11)    MOVQ    DX,8(SP)

    // AX中保存的是s2的长度
    0x00f8 00248 (builtin.go:11)    MOVQ    AX,BX
    // shl 左移位操作, 左移3位
    0x00fb 00251 (builtin.go:11)    SHLQ    $3,BX
    // 将BX作为第三个参数
    0x00ff 00255 (builtin.go:11)    MOVQ    BX,16(SP)
    0x0104 00260 (builtin.go:11)    PCDATA  $0,$2
    0x0104 00260 (builtin.go:11)    CALL    ,runtime.memmove(SB)

函数调用

package main

import (
    "fmt"
)

func f1(a int) int {
    fmt.Println(a)
    return a + 123
}

func main() {
    b := f1(123)
    fmt.Println(b)
}

下面是汇编代码:

"".f1 t=1 size=240 value=0 args=0x10 locals=0x70
    0x0000 00000 (builtin.3.go:7)   TEXT    "".f1+0(SB),$112-16
    0x0000 00000 (builtin.3.go:7)   MOVQ    (TLS),CX
    0x0009 00009 (builtin.3.go:7)   CMPQ    SP,16(CX)
    0x000d 00013 (builtin.3.go:7)   JHI ,22
    0x000f 00015 (builtin.3.go:7)   CALL    ,runtime.morestack_noctxt(SB)
    0x0014 00020 (builtin.3.go:7)   JMP ,0
    0x0016 00022 (builtin.3.go:7)   SUBQ    $112,SP
    0x001a 00026 (builtin.3.go:7)   FUNCDATA    $0,gclocals·480b8f52e76ecc554a5236babfd9a6e5+0(SB)
    0x001a 00026 (builtin.3.go:7)   FUNCDATA    $1,gclocals·403a8d79fd24b295e8557f6970497aa3+0(SB)

    // 因为栈帧的大小是112字节
    // 所以在120(FP)处保存的是第一个参数
    0x001a 00026 (builtin.3.go:8)   MOVQ    "".a+120(FP),BX

    // 下面的代码将a转换为接口类型
    // 因为fmt.Println需要的是空接口类型的参数
    0x001f 00031 (builtin.3.go:8)   MOVQ    BX,"".autotmp_0001+48(SP)
    0x0024 00036 (builtin.3.go:8)   LEAQ    "".autotmp_0000+72(SP),BX
    0x0029 00041 (builtin.3.go:8)   MOVQ    $0,(BX)
    0x0030 00048 (builtin.3.go:8)   MOVQ    $0,8(BX)
    0x0038 00056 (builtin.3.go:8)   LEAQ    "".autotmp_0000+72(SP),BX
    0x003d 00061 (builtin.3.go:8)   CMPQ    BX,$0
    0x0041 00065 (builtin.3.go:8)   JEQ $1,226
    0x0047 00071 (builtin.3.go:8)   MOVQ    $1,DX
    0x004e 00078 (builtin.3.go:8)   MOVQ    $1,CX
    0x0055 00085 (builtin.3.go:8)   MOVQ    BX,"".autotmp_0002+88(SP)
    0x005a 00090 (builtin.3.go:8)   MOVQ    DX,"".autotmp_0002+96(SP)
    0x005f 00095 (builtin.3.go:8)   MOVQ    CX,"".autotmp_0002+104(SP)
    0x0064 00100 (builtin.3.go:8)   MOVQ    $type.int+0(SB),BX
    0x006b 00107 (builtin.3.go:8)   MOVQ    BX,(SP)
    0x006f 00111 (builtin.3.go:8)   LEAQ    "".autotmp_0001+48(SP),BX
    0x0074 00116 (builtin.3.go:8)   MOVQ    BX,8(SP)
    0x0079 00121 (builtin.3.go:8)   PCDATA  $0,$1
    0x0079 00121 (builtin.3.go:8)   CALL    ,runtime.convT2E(SB)
    0x007e 00126 (builtin.3.go:8)   MOVQ    16(SP),CX
    0x0083 00131 (builtin.3.go:8)   MOVQ    24(SP),AX
    0x0088 00136 (builtin.3.go:8)   MOVQ    "".autotmp_0002+88(SP),BX
    0x008d 00141 (builtin.3.go:8)   MOVQ    BX,(SP)
    0x0091 00145 (builtin.3.go:8)   MOVQ    CX,"".autotmp_0004+56(SP)
    0x0096 00150 (builtin.3.go:8)   MOVQ    CX,8(SP)
    0x009b 00155 (builtin.3.go:8)   MOVQ    AX,"".autotmp_0004+64(SP)
    0x00a0 00160 (builtin.3.go:8)   MOVQ    AX,16(SP)
    0x00a5 00165 (builtin.3.go:8)   PCDATA  $0,$1
    0x00a5 00165 (builtin.3.go:8)   CALL    ,runtime.writebarrieriface(SB)
    // 传递参数给fmt.Println，并调用
    0x00aa 00170 (builtin.3.go:8)   MOVQ    "".autotmp_0002+88(SP),BX
    0x00af 00175 (builtin.3.go:8)   MOVQ    BX,(SP)
    0x00b3 00179 (builtin.3.go:8)   MOVQ    "".autotmp_0002+96(SP),BX
    0x00b8 00184 (builtin.3.go:8)   MOVQ    BX,8(SP)
    0x00bd 00189 (builtin.3.go:8)   MOVQ    "".autotmp_0002+104(SP),BX
    0x00c2 00194 (builtin.3.go:8)   MOVQ    BX,16(SP)
    0x00c7 00199 (builtin.3.go:8)   PCDATA  $0,$2
    0x00c7 00199 (builtin.3.go:8)   CALL    ,fmt.Println(SB)

    // 将a加上123，并返回
    0x00cc 00204 (builtin.3.go:9)   MOVQ    "".a+120(FP),BX
    0x00d1 00209 (builtin.3.go:9)   ADDQ    $123,BX
    0x00d5 00213 (builtin.3.go:9)   MOVQ    BX,"".~r1+128(FP)
    0x00dd 00221 (builtin.3.go:9)   ADDQ    $112,SP
    0x00e1 00225 (builtin.3.go:9)   RET ,
    0x00e2 00226 (builtin.3.go:8)   MOVL    AX,(BX)
    0x00e4 00228 (builtin.3.go:8)   JMP ,71
    
    
    "".main t=1 size=240 value=0 args=0x0 locals=0x70
    0x0000 00000 (builtin.3.go:12)  TEXT    "".main+0(SB),$112-0
    0x0000 00000 (builtin.3.go:12)  MOVQ    (TLS),CX
    0x0009 00009 (builtin.3.go:12)  CMPQ    SP,16(CX)
    0x000d 00013 (builtin.3.go:12)  JHI ,22
    0x000f 00015 (builtin.3.go:12)  CALL    ,runtime.morestack_noctxt(SB)
    0x0014 00020 (builtin.3.go:12)  JMP ,0
    // 将SP减去112(栈的大小)，栈向下增长
    0x0016 00022 (builtin.3.go:12)  SUBQ    $112,SP
    0x001a 00026 (builtin.3.go:12)  FUNCDATA    $0,gclocals·73423680ca5f2d7df4fe760a82d507fb+0(SB)
    0x001a 00026 (builtin.3.go:12)  FUNCDATA    $1,gclocals·403a8d79fd24b295e8557f6970497aa3+0(SB)
    // 将123放在栈顶
    0x001a 00026 (builtin.3.go:13)  MOVQ    $123,(SP)
    0x0022 00034 (builtin.3.go:13)  PCDATA  $0,$0
    // 调用f1
    0x0022 00034 (builtin.3.go:13)  CALL    ,"".f1(SB)
    // 将结果8(SP)存入BX
    0x0027 00039 (builtin.3.go:13)  MOVQ    8(SP),BX
    0x002c 00044 (builtin.3.go:13)  NOP ,

    // 将BX存放到48(SP), 是一个临时变量，BX中保存的是f1的调用结果
    0x002c 00044 (builtin.3.go:14)  MOVQ    BX,"".autotmp_0010+48(SP)

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