Build GDB debugging go program

• preface
• GDB installation
• • Update the brew
  • Check whether GDB mirroring exists
  • Install the GDB
• Go build to compile
• GDB executive
• GDB commands
• GDB debugging
• Problems to sort out
• reference

preface

Learn to use GDB for golang debugging, through a simple go program for simple access to the source code call sequence view.

GDB installation

Update the brew

brew update
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Check whether GDB mirroring exists

brew search gdb
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Install the GDB

brew install gdb
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Go build to compile

GDB executive

Run the GDB main command to enter the GDB environment. Then you can debug and use the GDB environment

$ gdb program
Reading symbols from program...
Loading Go Runtime support.
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GDB commands

GDB debugging

Next, GDB debugging is performed based on a simple Golang program, in order to understand the initialization process of the Golang program.

Execute the list to see the source code for the current file. Here you see the original GO program file we wrote

(gdb) list
1       package main
2       
3       import "fmt"
4       
5       func main() {
6               fmt.Println("hello world"7})Copy the code

Execute info files to view the values of local variables inside the function, as shown below

(gdb) info files
Symbols from "/Users/guanjian/workspace/go/program/program".
Local exec file:
        `/Users/guanjian/workspace/go/program/program', file type mach-o-x86-64. Entry point: 0x10701e0: 0x0000000001001000 - 0x00000000010cbc53 is .text 0x00000000010cbc60 - 0x00000000010cbd62 is __TEXT.__symbol_stub1 0x00000000010cbd80 - 0x0000000001100b19 is __TEXT.__rodata 0x0000000001100b20 - 0x00000000011012bc is __TEXT.__typelink 0x00000000011012c0 - 0x0000000001101328 is __TEXT.__itablink 0x0000000001101328 - 0x0000000001101328 is __TEXT.__gosymtab 0x0000000001101340 - 0x000000000115dae8 is __TEXT.__gopclntab 0x000000000115e000 - 0x000000000115e020 is __DATA.__go_buildinfo 0x000000000115e020 - 0x000000000115e178 is __DATA.__nl_symbol_ptr 0x000000000115e180 - 0x000000000116c4a4 is __DATA.__noptrdata 0x000000000116c4c0 - 0x00000000011738f0 is .data 0x0000000001173900 - 0x00000000011a1170 is .bss 0x00000000011a1180 - 0x00000000011a62f0 is __DATA.__noptrbss (gdb)Copy the code

The top Entry point is Entry Point: 0x10701e0:, where we set the breakpoint to debug the program. Break *0x10701e0:

(gdb) break *0x10701e0
Breakpoint 1 at 0x10701e0: file /usr/local/go/src/runtime/rt0_darwin_amd64.s, line 8.
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Can see already add the breakpoint is successful, then saw the current compilation go program entry in the/usr/local/go/SRC/runtime/rt0_darwin_amd64 s file, we enter into that directory for files starting all rt0 is full. The s at the end of the assembly language implementation, as follows:

$ ls /usr/local/go/src/runtime/rt0_ rt0_aix_ppc64.s rt0_ios_arm64.s rt0_netbsd_arm.s rt0_android_386.s rt0_js_wasm.s rt0_netbsd_arm64.s  rt0_android_amd64.s rt0_linux_386.s rt0_openbsd_386.s rt0_android_arm.s rt0_linux_amd64.s rt0_openbsd_amd64.s rt0_android_arm64.s rt0_linux_arm.s rt0_openbsd_arm.s rt0_darwin_amd64.s rt0_linux_arm64.s rt0_openbsd_arm64.s rt0_darwin_arm64.s rt0_linux_mips64x.s rt0_openbsd_mips64.s rt0_dragonfly_amd64.s rt0_linux_mipsx.s rt0_plan9_386.s rt0_freebsd_386.s rt0_linux_ppc64.s rt0_plan9_amd64.s rt0_freebsd_amd64.s rt0_linux_ppc64le.s rt0_plan9_arm.s rt0_freebsd_arm.s rt0_linux_riscv64.s rt0_solaris_amd64.s rt0_freebsd_arm64.s rt0_linux_s390x.s rt0_windows_386.s rt0_illumos_amd64.s rt0_netbsd_386.s rt0_windows_amd64.s rt0_ios_amd64.s rt0_netbsd_amd64.s rt0_windows_arm.sCopy the code

Let’s look at the rt0_darwin_amd64.s file as follows:

% cat -n rt0_darwin_amd64.s
     1	// Copyright 2009 The Go Authors. All rights reserved.
     2	// Use of this source code is governed by a BSD-style
     3	// license that can be found in the LICENSE file.
     4
     5	#include "textflag.h"7 TEXT _rt0_amd64_darwin(SB),NOSPLIT,$-8 8 JMP _rt0_amd64(SB) // When linking with-shared, this symbol is called when the shared library 11 // is loaded. 12 TEXT _rt0_amd64_darwin_lib(SB),NOSPLIT,$0
    13		JMP	_rt0_amd64_lib(SB)
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Line 8 _rt0_amd64(SB) here is the call entry, i.e

Breakpoint 1 at 0x10701e0: file /usr/local/go/src/runtime/rt0_darwin_amd64.s, line 8.
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Now we need to find_rt0_amd64The location of this assembly method, the search method can be viewed according to their own way, I here in order to facilitate the view, download golang SDK, and then import IDE global search, locate the fileruntime/asm_amd64.sThat is as follows:



And then, let’s look it upThe runtime, rt0_go (SB)The method is as follows



The runtime, rt0_go (SB)Method contains a number of initialization methods. Here is an example of picking rain marks in the article:

The TEXT, the runtime rt0_go (SB), NOSPLIT,$0. // ===== calls the initialization function ===== CALL Runtime ·args(SB) CALL Runtime ·osinit(SB) CALL Runtime ·schedinit(SB) // ===== creates main Goroutine is used to execute runtime.main ===== MOVQ$runtime·mainPC(SB), AX
PUSHQ AX
PUSHQ $0CALL Runtime ·newproc(SB) POPQ AX POPQ AX // ===== Let the current thread start main goroutine ===== CALL Runtime ·mstart(SB) RET DATA The runtime mainPC + 0/8 (SB),$runtime, the main (SB) GLOBL runtime · mainPC (SB), RODATA.$8
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$runtime·main(SB) $runtime·main(SB) $runtime·main(SB) We look at the call through the GDB breakpoint as follows:

(gdb) b runtime.main
Breakpoint 1 at 0x103b4c0: file /usr/local/go/src/runtime/proc.go, line 115.
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So far, we’ve set up a DEBUGGING environment for GDB and some practices for viewing the golang function code.

Problems to sort out

(gdb) run
Starting program: /xxx/main 
Unable to find Mach task port for process-id 35564: (os/kern) failure (0x5).
(please check gdb is codesigned - see taskgated(8))
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(gdb) list
No symbol table is loaded.  Use the "file" command.
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reference

Debugging Go Code with GDB Debugging Go Code with GDB Debugging Go Code with GDB Debugging Go Code with GDB Debugging Go Code with GDB Debugging Go Code with GDB Debugging Go Code with GDB Starting program: [New Thread 0x1103 of Process 843]