mirror of
https://github.com/chai2010/advanced-go-programming-book.git
synced 2025-05-29 08:12:21 +00:00
ch3-08: 完善
This commit is contained in:
chai2010
parent
fd70b3b73a
commit
c3a20903de
@ -239,7 +239,19 @@ Goroutine 1:
|
||||
|
||||
用Delve调试Go汇编程序的过程比调试Go语言程序更加简单。调试汇编程序时，我们需要时刻关注寄存器的状态，如果涉及函数调用或局部变量或参数还需要重点关注栈寄存器SP的状态。
|
||||
|
||||
为了编译演示，我们用汇编重新实现main函数，简单打印一个字符串：
|
||||
为了编译演示，我们重新实现一个更简单的main函数：
|
||||
|
||||
```go
|
||||
package main
|
||||
|
||||
func main() { asmSayHello() }
|
||||
|
||||
func asmSayHello()
|
||||
```
|
||||
|
||||
在main函数中调用汇编语言实现的asmSayHello函数输出一个字符串。
|
||||
|
||||
asmSayHello函数在main_amd64.s文件中实现：
|
||||
|
||||
```
|
||||
#include "textflag.h"
|
||||
@ -250,8 +262,8 @@ DATA text<>+0(SB)/8,$"Hello Wo"
|
||||
DATA text<>+8(SB)/8,$"rld!\n"
|
||||
GLOBL text<>(SB),NOPTR,$16
|
||||
|
||||
// func main()
|
||||
TEXT ·main(SB), $16-0
|
||||
// func asmSayHello()
|
||||
TEXT ·asmSayHello(SB), $16-0
|
||||
NO_LOCAL_POINTERS
|
||||
MOVQ $text<>+0(SB), AX
|
||||
MOVQ AX, (SP)
|
||||
@ -260,19 +272,50 @@ TEXT ·main(SB), $16-0
|
||||
RET
|
||||
```
|
||||
|
||||
然后依然用break命令在main函数设置断点，并且输入continue命令让调试器执行到断点位置停下：
|
||||
参考前面的调试流程，在执行到main函数断点时，可以disassemble反汇编命令查看main函数对应的汇编代码：
|
||||
|
||||
```
|
||||
(dlv) break main.main
|
||||
Breakpoint 1 set at 0x105018f for main.main() ./main_amd64.s:10
|
||||
Breakpoint 1 set at 0x105011f for main.main() ./main.go:3
|
||||
(dlv) continue
|
||||
> main.main() ./main_amd64.s:10 (hits goroutine(1):1 total:1) (PC: 0x105018f)
|
||||
> main.main() ./main.go:3 (hits goroutine(1):1 total:1) (PC: 0x105011f)
|
||||
1: package main
|
||||
2:
|
||||
=> 3: func main() { asmSayHello() }
|
||||
4:
|
||||
5: func asmSayHello()
|
||||
(dlv) disassemble
|
||||
TEXT main.main(SB) /Users/chai/go/src/github.com/chai2010/advanced-go-programming-book/vendor/gobook.examples/ch3-08-debug/hello-asm/main.go
|
||||
main.go:3 0x1050110 65488b0c25a0080000 mov rcx, qword ptr gs:[0x8a0]
|
||||
main.go:3 0x1050119 483b6110 cmp rsp, qword ptr [rcx+0x10]
|
||||
main.go:3 0x105011d 761a jbe 0x1050139
|
||||
=> main.go:3 0x105011f* 4883ec08 sub rsp, 0x8
|
||||
main.go:3 0x1050123 48892c24 mov qword ptr [rsp], rbp
|
||||
main.go:3 0x1050127 488d2c24 lea rbp, ptr [rsp]
|
||||
main.go:3 0x105012b e880000000 call $main.asmSayHello
|
||||
main.go:3 0x1050130 488b2c24 mov rbp, qword ptr [rsp]
|
||||
main.go:3 0x1050134 4883c408 add rsp, 0x8
|
||||
main.go:3 0x1050138 c3 ret
|
||||
main.go:3 0x1050139 e87288ffff call $runtime.morestack_noctxt
|
||||
main.go:3 0x105013e ebd0 jmp $main.main
|
||||
(dlv)
|
||||
```
|
||||
|
||||
虽然main函数内部只有一行函数调用语句，但是却生成了很多汇编指令。在函数的开头通过比较rsp寄存器判断栈空间是否不足，如果不足则跳转到0x1050139地址调用runtime.morestack函数进行栈扩容，然后跳回到main函数开始位置重新进行栈空间测试。而在asmSayHello函数调用之前，先扩展rsp空间用于临时存储rbp寄存器的状态，在函数返回后通过栈恢复rbp的值并回收临时栈空间。通过对比Go语言代码和对应的汇编代码，我们可以加深对Go汇编语言的理解。
|
||||
|
||||
从汇编语言角度深刻Go语言各种特性的工作机制对调试工作也是一个很大的帮助。现在我们依然用break命令在asmSayHello函数设置断点，并且输入continue命令让调试器执行到断点位置停下：
|
||||
|
||||
```
|
||||
(dlv) break main.asmSayHello
|
||||
Breakpoint 2 set at 0x10501bf for main.asmSayHello() ./main_amd64.s:10
|
||||
(dlv) continue
|
||||
> main.asmSayHello() ./main_amd64.s:10 (hits goroutine(1):1 total:1) (PC: 0x10501bf)
|
||||
5: DATA text<>+0(SB)/8,$"Hello Wo"
|
||||
6: DATA text<>+8(SB)/8,$"rld!\n"
|
||||
7: GLOBL text<>(SB),NOPTR,$16
|
||||
8:
|
||||
9: // func main()
|
||||
=> 10: TEXT ·main(SB), $16-0
|
||||
9: // func asmSayHello()
|
||||
=> 10: TEXT ·asmSayHello(SB), $16-0
|
||||
11: NO_LOCAL_POINTERS
|
||||
12: MOVQ $text<>+0(SB), AX
|
||||
13: MOVQ AX, (SP)
|
||||
@ -285,14 +328,14 @@ Breakpoint 1 set at 0x105018f for main.main() ./main_amd64.s:10
|
||||
|
||||
```
|
||||
(dlv) regs
|
||||
rax = 0x0000000001050180
|
||||
rax = 0x0000000001050110
|
||||
rbx = 0x0000000000000000
|
||||
rcx = 0x000000c420000300
|
||||
rdx = 0x0000000001070bc0
|
||||
rdx = 0x0000000001070be0
|
||||
rdi = 0x000000c42007c020
|
||||
rsi = 0x0000000000000001
|
||||
rbp = 0x00007fffffe00000
|
||||
rsp = 0x000000c420049f80
|
||||
rbp = 0x000000c420049f78
|
||||
rsp = 0x000000c420049f70
|
||||
r8 = 0x7fffffffffffffff
|
||||
r9 = 0xffffffffffffffff
|
||||
r10 = 0x0000000000000100
|
||||
@ -301,8 +344,8 @@ Breakpoint 1 set at 0x105018f for main.main() ./main_amd64.s:10
|
||||
r13 = 0x0000000000000000
|
||||
r14 = 0x0000000000000178
|
||||
r15 = 0x0000000000000004
|
||||
rip = 0x000000000105018f
|
||||
rflags = 0x0000000000000202
|
||||
rip = 0x00000000010501bf
|
||||
rflags = 0x0000000000000206
|
||||
...
|
||||
(dlv)
|
||||
```
|
||||
|
||||
@ -1,7 +1,5 @@
|
||||
// Copyright 2018 <chaishushan{AT}gmail.com>. All rights reserved.
|
||||
// Use of this source code is governed by a BSD-style
|
||||
// license that can be found in the LICENSE file.
|
||||
|
||||
package main
|
||||
|
||||
func main()
|
||||
func main() { asmSayHello() }
|
||||
|
||||
func asmSayHello()
|
||||
|
||||
@ -6,8 +6,8 @@ DATA text<>+0(SB)/8,$"Hello Wo"
|
||||
DATA text<>+8(SB)/8,$"rld!\n"
|
||||
GLOBL text<>(SB),NOPTR,$16
|
||||
|
||||
// func main()
|
||||
TEXT ·main(SB), $16-0
|
||||
// func asmSayHello()
|
||||
TEXT ·asmSayHello(SB), $16-0
|
||||
NO_LOCAL_POINTERS
|
||||
MOVQ $text<>+0(SB), AX
|
||||
MOVQ AX, (SP)
|
||||
|
||||
Loading…
x
Reference in New Issue
Block a user