Note, the openocd installed by sudo apt-get install openocd is not work on ubuntu 20.04. The error prompted Error: invalid command name "dap". So you shall compile the openocd by yourself. Please refer to the link https://hackaday.io/page/4991-compiling-openocd-from-source-on-ubuntu-1604. (Though it is targetting for ubuntu 16.04, the 20.04 still follow these build steps.)
1. JLink Brief
We should use the three command terminals to launch the Jlink debugger. They are openocd/telnet/gbd-multiarch separately.
40-pin gpio connect
gpio22-27 Alternative Function Assignments all are ALT4.
connect following gpio pin to jlink pin.
PIN NAME
GPIO Function ALT
GPIO22
ARM_TRST
GPIO23
ARM_RTCK
GPIO24
ARM_TDO
GPIO25
ARM_TCK
GPIO26
ARM_TDI
GPIO27
ARM_TMS
3.3v
Vref
GPIO09
GND
On the openocd command line, should type the cmd is:
sudo openocd -f jlink.cfg -f raspi4.cfg
On the telnet command line, should type the cmds are:
On the gdb command line, should ytpe the cmds are:
gdb-multiarch --tui benos.elf
> target remote localhost:3333
> b ldr_start
> c
> n
> layout regs
2. QEMU Brief
The QEMU is more simple and more quicker than the JLink debugger env.
On the QEMU side, just type the qemu-system-aarch64 -machine raspi4 -nographic -kernel benos.bin -S -s to launch the QEMU. For the gdb-multiarch side, gdb-multiarch --tui benos.elf
gdb-multiarch --tui benos.elf, the localhost port is 1234.
gdb-multiarch --tui benos.elf
> target remote localhost:1234
> b ldr_start
> c
> n
> layout regs
For the config files, you can get them by https://gist.github.com/carloscn/538d57d36b828e52bf8f88d6362b1528
gdb-multiarch --tui benos.elf
gdb> file benos.elf
gdb> target remote localhost:1234
gdb> b ldr_test // 设定断点
gdb> c
gdb> n
gdb> next //下一步
gdb> info register // 查看所有寄存器
gdb> info x1 x2 x3 // 查看x1/x2/x3寄存器
gdb> x 0x80000 // 读取内存0x80000值 32位
gdb> x/xg 0x80000 // 读取内存0x80000值64位
gdb> layout src
gdb> layout regs
gdb> layout split
## Base operation
```
gdb-multiarch --tui benos.elf
gdb> file benos.elf
gdb> target remote localhost:1234
gdb> b ldr_test // 设定断点
gdb> c
gdb> n
gdb> next //下一步
gdb> info register // 查看所有寄存器
gdb> info x1 x2 x3 // 查看x1/x2/x3寄存器
gdb> x 0x80000 // 读取内存0x80000值 32位
gdb> x/xg 0x80000 // 读取内存0x80000值64位
gdb> layout src
gdb> layout regs
gdb> layout split
```
## tui window operation
```
gdb> info win
gdb> fs src
```
### Deal with signal
* 改变gdb信号处理的设置
比如,以下设置会告诉gdb在接收到SIGINT时不要停止、打印出来、传递给调试目标程序
```
=====================================
(gdb) handle SIGINT nostop print pass
SIGINT is used by the debugger.
Are you sure you want to change it? (y or n) y
Signal Stop Print Pass to program Description
SIGINT No Yes Yes Interrupt
(gdb)
=====================================
```
* 使用gdb命令直接向调试的应用程序发送信号
首先在你希望发送信号的语句处设置断点，然后运行程序，当停止到断点所在位置后，用gdb的signal命令发送信号给调试目标程序
```
====================================
(gdb) signal SIGINT
Continuing with signal SIGINT.
Breakpoint 1, handler (signal=2) at main.cpp:15
15 printf( "Signal handler.../n ");
====================================
```
