ch3: 增加Delve调试器内容

.gitignore

@@ -31,3 +31,6 @@ _book
 a.out
 
 .oracle_jre_usage
+
+# Delve
+debug

SUMMARY.md

@@ -30,7 +30,8 @@
    * [3.5. 控制流](ch3-asm/ch3-05-control-flow.md)
    * [3.6. 再论函数](ch3-asm/ch3-06-func-again.md)
    * [3.7. 例子：Goroutine ID](ch3-asm/ch3-07-goroutine-id.md)
-   * [3.8. 补充说明](ch3-asm/ch3-08-faq.md)
+   * [3.8. Delve调试器](ch3-asm/ch3-08-debug.md)
+   * [3.9. 补充说明](ch3-asm/ch3-09-faq.md)
 * [第四章 RPC和Protobuf](ch4-rpc/readme.md)
    * [4.1. RPC入门](ch4-rpc/ch4-01-rpc-intro.md)
    * [4.2. Protobuf](ch4-rpc/ch4-02-pb-intro.md)

ch3-asm/ch3-08-debug.md

@@ -0,0 +1,331 @@
+# 3.8. Delve调试器
+
+目前Go语言支持GDB、LLDB和Delve几种调试器。其中GDB是最早支持的调试工具，LLDB是macOS系统推荐的标准调试工具。但是GDB和LLDB对Go语言的专有特性都缺乏很大支持，而只有Delve是专门为Go语言设计开发的调试工具。而且Delve本身也是采用Go语言开发，对Windows平台也提供了一样的支持。本节我们基于Delve简单解释如何调试Go汇编程序。
+
+## Delve入门
+
+首先根据官方的文档正确安装Delve调试器。我们会先构造一个简单的Go语言代码，用于熟悉下Delve的简单用法。
+
+创建main.go文件，main函数先通过循初始化一个切片，然后输出切片的内容：
+
+```go
+package main
+
+import (
+	"fmt"
+)
+
+func main() {
+	nums := make([]int, 5)
+	for i := 0; i < len(nums); i++ {
+		nums[i] = i * i
+	}
+	fmt.Println(nums)
+}
+```
+
+命令行进入包所在目录，然后输入`dlv debug`命令进入调试：
+
+```
+$ dlv debug
+Type 'help' for list of commands.
+(dlv)
+```
+
+输入help命令可以查看到Delve提供的调试命令列表：
+
+```
+(dlv) help
+The following commands are available:
+    args ------------------------ Print function arguments.
+    break (alias: b) ------------ Sets a breakpoint.
+    breakpoints (alias: bp) ----- Print out info for active breakpoints.
+    clear ----------------------- Deletes breakpoint.
+    clearall -------------------- Deletes multiple breakpoints.
+    condition (alias: cond) ----- Set breakpoint condition.
+    config ---------------------- Changes configuration parameters.
+    continue (alias: c) --------- Run until breakpoint or program termination.
+    disassemble (alias: disass) - Disassembler.
+    down ------------------------ Move the current frame down.
+    exit (alias: quit | q) ------ Exit the debugger.
+    frame ----------------------- Set the current frame, or execute command on a different frame.
+    funcs ----------------------- Print list of functions.
+    goroutine ------------------- Shows or changes current goroutine
+    goroutines ------------------ List program goroutines.
+    help (alias: h) ------------- Prints the help message.
+    list (alias: ls | l) -------- Show source code.
+    locals ---------------------- Print local variables.
+    next (alias: n) ------------- Step over to next source line.
+    on -------------------------- Executes a command when a breakpoint is hit.
+    print (alias: p) ------------ Evaluate an expression.
+    regs ------------------------ Print contents of CPU registers.
+    restart (alias: r) ---------- Restart process.
+    set ------------------------- Changes the value of a variable.
+    source ---------------------- Executes a file containing a list of delve commands
+    sources --------------------- Print list of source files.
+    stack (alias: bt) ----------- Print stack trace.
+    step (alias: s) ------------- Single step through program.
+    step-instruction (alias: si)  Single step a single cpu instruction.
+    stepout --------------------- Step out of the current function.
+    thread (alias: tr) ---------- Switch to the specified thread.
+    threads --------------------- Print out info for every traced thread.
+    trace (alias: t) ------------ Set tracepoint.
+    types ----------------------- Print list of types
+    up -------------------------- Move the current frame up.
+    vars ------------------------ Print package variables.
+    whatis ---------------------- Prints type of an expression.
+Type help followed by a command for full documentation.
+(dlv)
+```
+
+每个Go程序的入口是main.main函数，我们可以用break在此设置一个断点：
+
+```
+(dlv) break main.main
+Breakpoint 1 set at 0x10ae9b8 for main.main() ./main.go:7
+```
+
+然后通过breakpoints查看已经设置的所有断点：
+
+```
+(dlv) breakpoints
+Breakpoint unrecovered-panic at 0x102a380 for runtime.startpanic() /usr/local/go/src/runtime/panic.go:588 (0)
+        print runtime.curg._panic.arg
+Breakpoint 1 at 0x10ae9b8 for main.main() ./main.go:7 (0)
+```
+
+我们发现除了我们自己设置的main.main邯郸断点外，Delve内部已经为panic异常函数设置了一个断点。
+
+然后就可以通过continue命令让程序运行到下一个断点处：
+
+```
+(dlv) continue
+> main.main() ./main.go:7 (hits goroutine(1):1 total:1) (PC: 0x10ae9b8)
+     2:
+     3: import (
+     4:         "fmt"
+     5: )
+     6:
+=>   7: func main() {
+     8:         nums := make([]int, 5)
+     9:         for i := 0; i < len(nums); i++ {
+    10:                 nums[i] = i * i
+    11:         }
+    12:         fmt.Println(nums)
+(dlv)
+```
+
+输入next命令单步执行进入main函数内部：
+
+```
+(dlv) next
+> main.main() ./main.go:8 (PC: 0x10ae9cf)
+     3: import (
+     4:         "fmt"
+     5: )
+     6:
+     7: func main() {
+=>   8:         nums := make([]int, 5)
+     9:         for i := 0; i < len(nums); i++ {
+    10:                 nums[i] = i * i
+    11:         }
+    12:         fmt.Println(nums)
+    13: }
+(dlv)
+```
+
+进入函数之后可以通过args和locals命令查看函数的参数和局部变量：
+
+```
+(dlv) args
+(no args)
+(dlv) locals
+nums = []int len: 842350763880, cap: 17491881, nil
+```
+
+因为main函数没有参数，因此args命令没有任何输出。而locals命令则输出了局部变量nums切片的值：此时切片还未完成初始化，切片的底层指针为nil，长度和容量都是一个随机数值。
+
+再次输入next命令单步执行后就可以查看到nums切片初始化之后的结果了：
+
+```
+(dlv) next
+> main.main() ./main.go:9 (PC: 0x10aea12)
+     4:         "fmt"
+     5: )
+     6:
+     7: func main() {
+     8:         nums := make([]int, 5)
+=>   9:         for i := 0; i < len(nums); i++ {
+    10:                 nums[i] = i * i
+    11:         }
+    12:         fmt.Println(nums)
+    13: }
+(dlv) locals
+nums = []int len: 5, cap: 5, [...]
+i = 17601536
+(dlv)
+```
+
+此时因为调试器已经到了for语句行，因此局部变量出现了还未初始化的循环迭代变量i。
+
+下面我们通过组合使用break和condition命令，在循环内部设置一个条件断点，当循环变量i等于3时断点生效：
+
+```
+(dlv) break main.go:10
+Breakpoint 2 set at 0x10aea33 for main.main() ./main.go:10
+(dlv) condition 2 i==3
+(dlv)
+```
+
+然后通过continue执行到刚设置的条件断点，并且输出局部变量：
+
+```
+(dlv) continue
+> main.main() ./main.go:10 (hits goroutine(1):1 total:1) (PC: 0x10aea33)
+     5: )
+     6:
+     7: func main() {
+     8:         nums := make([]int, 5)
+     9:         for i := 0; i < len(nums); i++ {
+=>  10:                 nums[i] = i * i
+    11:         }
+    12:         fmt.Println(nums)
+    13: }
+(dlv) locals
+nums = []int len: 5, cap: 5, [...]
+i = 3
+(dlv) print nums
+[]int len: 5, cap: 5, [0,1,4,0,0]
+(dlv)
+```
+
+我们发现当循环变量i等于3时，nums切片的前3个元素已经正确初始化。
+
+我们还可以通过stack查看当前执行函数的栈帧信息：
+
+```
+(dlv) stack
+0  0x00000000010aea33 in main.main
+   at ./main.go:10
+1  0x000000000102bd60 in runtime.main
+   at /usr/local/go/src/runtime/proc.go:198
+2  0x0000000001053bd1 in runtime.goexit
+   at /usr/local/go/src/runtime/asm_amd64.s:2361
+(dlv)
+```
+
+或者通过goroutine和goroutines命令查看当前Goroutine相关的信息：
+
+```
+(dlv) goroutine
+Thread 101686 at ./main.go:10
+Goroutine 1:
+        Runtime: ./main.go:10 main.main (0x10aea33)
+        User: ./main.go:10 main.main (0x10aea33)
+        Go: /usr/local/go/src/runtime/asm_amd64.s:258 runtime.rt0_go (0x1051643)
+        Start: /usr/local/go/src/runtime/proc.go:109 runtime.main (0x102bb90)
+(dlv) goroutines
+[4 goroutines]
+* Goroutine 1 - User: ./main.go:10 main.main (0x10aea33) (thread 101686)
+  Goroutine 2 - User: /usr/local/go/src/runtime/proc.go:292 runtime.gopark (0x102c189)
+  Goroutine 3 - User: /usr/local/go/src/runtime/proc.go:292 runtime.gopark (0x102c189)
+  Goroutine 4 - User: /usr/local/go/src/runtime/proc.go:292 runtime.gopark (0x102c189)
+(dlv)
+```
+
+最后完成调试工作后输入quit命令退出调试器。至此我们已经掌握了Delve调试器器的简单用法。
+
+## 调试汇编程序
+
+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：
+
+```
+#include "textflag.h"
+#include "funcdata.h"
+
+// "Hello World!\n"
+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
+	NO_LOCAL_POINTERS
+	MOVQ $text<>+0(SB), AX
+	MOVQ AX, (SP)
+	MOVQ $16, 8(SP)
+	CALL runtime·printstring(SB)
+	RET
+```
+
+然后依然用break命令在main函数设置断点，并且输入continue命令让调试器执行到断点位置停下：
+
+```
+(dlv) break main.main
+Breakpoint 1 set at 0x105018f for main.main() ./main_amd64.s:10
+(dlv) continue
+> main.main() ./main_amd64.s:10 (hits goroutine(1):1 total:1) (PC: 0x105018f)
+     5: DATA  text<>+0(SB)/8,$"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
+    11:         NO_LOCAL_POINTERS
+    12:         MOVQ $text<>+0(SB), AX
+    13:         MOVQ AX, (SP)
+    14:         MOVQ $16, 8(SP)
+    15:         CALL runtime·printstring(SB)
+(dlv)
+```
+
+此时我们可以通过regs查看全部的寄存器状态：
+
+```
+(dlv) regs
+       rax = 0x0000000001050180
+       rbx = 0x0000000000000000
+       rcx = 0x000000c420000300
+       rdx = 0x0000000001070bc0
+       rdi = 0x000000c42007c020
+       rsi = 0x0000000000000001
+       rbp = 0x00007fffffe00000
+       rsp = 0x000000c420049f80
+        r8 = 0x7fffffffffffffff
+        r9 = 0xffffffffffffffff
+       r10 = 0x0000000000000100
+       r11 = 0x0000000000000286
+       r12 = 0x000000c41fffff7c
+       r13 = 0x0000000000000000
+       r14 = 0x0000000000000178
+       r15 = 0x0000000000000004
+       rip = 0x000000000105018f
+    rflags = 0x0000000000000202
+...
+(dlv)
+```
+
+因为AMD64的各种寄存器非常多，项目的信息中刻意省略了非通用的寄存器。如果再单步执行到13行时，可以发现AX寄存器值的变化。
+
+```
+(dlv) regs
+       rax = 0x00000000010a4060
+       rbx = 0x0000000000000000
+       rcx = 0x000000c420000300
+...
+(dlv)
+```
+
+因此我们可以推断汇编程序内部定义的`text<>`数据的地址为0x00000000010a4060。我们可以用过print命令来查看该内存内的数据：
+
+```
+(dlv) print *(*[5]byte)(uintptr(0x00000000010a4060))
+[5]uint8 [72,101,108,108,111]
+(dlv)
+```
+
+我们可以发现输出的`[5]uint8 [72,101,108,108,111]`刚好是对应“Hello”字符串。通过类似的方法，我们可以通过查看SP对应的栈指针位置，然后查看栈中局部变量的值。
+
+至此我们就掌握了Go汇编程序的简单调试技术。

ch3-asm/ch3-09-faq.md

@@ -1,3 +1,3 @@
-# 3.8. 补充说明
+# 3.9. 补充说明
 
 得益于Go语言的设计，Go汇编语言的优势也非常明显：跨操作系统、不同CPU之间的用法也非常相似、支持C语言预处理器、支持模块。同时Go汇编语言也存在很多不足：它不是一个独立的语言，底层需要依赖Go语言甚至操作系统；很多高级特性很难通过手工汇编完成。虽然Go语言官方尽量保持Go汇编语言简单，但是汇编语言是一个比较大的话题，大到足以写一本Go汇编语言的教程。本章的目的是让大家对Go汇编语言简单入门，在看到底层汇编代码的时候不会一头雾水，在某些遇到性能受限制的场合能够通过Go汇编突破限制。这只是一个开始，后续版本会继续完善。

vendor/gobook.examples/ch3-08-debug/hello-asm/main.go

@@ -0,0 +1,7 @@
+// 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()

vendor/gobook.examples/ch3-08-debug/hello-asm/main_amd64.s

@@ -0,0 +1,16 @@
+#include "textflag.h"
+#include "funcdata.h"
+
+// "Hello World!\n"
+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
+	NO_LOCAL_POINTERS
+	MOVQ $text<>+0(SB), AX
+	MOVQ AX, (SP)
+	MOVQ $16, 8(SP)
+	CALL runtime·printstring(SB)
+	RET

vendor/gobook.examples/ch3-08-debug/hello/main.go

@@ -0,0 +1,13 @@
+package main
+
+import (
+	"fmt"
+)
+
+func main() {
+	nums := make([]int, 5)
+	for i := 0; i < len(nums); i++ {
+		nums[i] = i * i
+	}
+	fmt.Println(nums)
+}