gdb init steps

1. set arch riscv:rv32 set to 32bit for e21
2. target remote :3333 连到openocd端口3333
3. monitor reset halt reset
4. flushregs reset registers
5. file elf_file_full_path 指定elf
6. thread apply all load load elf

gdb commands

1. x /[Length][Format] [Address expression] 显示地址中的数据

int main()
{
    char testArray[] = "0123456789ABCDEF";
    return 0;
}

x/5i $pc 显示从当前位置开始的5条指令
x testArray 显示1个字符和对应的ascii码 0x33323130
x/c testArray 显示1个字符和对应的ascii码 48 '0'
x/3c testArray 显示3个字符和对应的ascii码 48 '0' 49 '1' 50 '2'x/s testArray显示字符串0123456789ABCDEFx/wx testArray显示32bit0x33323130x/gx testArray显示giant-word，64bit0x3736353433323130x/2hx testArray显示half-word,16bit0x3130 0x3332`

2. info b 显示breakpoints
3. info registers 显示的寄存器
4. info all-registers 显示所有的寄存器，包括msr
5. info registers a5 显示a5值
6. backtrace 显示调用stack