Lab20: GNU Toolchain

QEMU_STM32 + QEMU 操作

• 假設 Lab-19</embedded/Lab19>_ 所使用 QEMU 的目錄已放在 workspace 目錄

.. code-block:: prettyprint

cd workspace file qemu_stm32

• 取得 GDB Automation

.. code-block:: prettyprint

git clone git://github.com/embedded2013/gdb-automation.git cd gdb-automation

• 開啟一個終端機，作以下輸入

.. code-block:: prettyprint

make qemudbg

• 開啟另一個終端機，準備透過 gdb 來追蹤程式。下列 (gdb) 開頭的指令表示在 GDB 內部操作
• 使用 Ubuntu 64-bit 版本時，需要另外安裝 lib32ncurses5
  • sudo apt-get install lib32ncurses5

.. code-block:: prettyprint

cd gdb-automation
arm-none-eabi-gdb
(gdb) file main.elf 
Reading symbols from gdb-automation/main.elf...done.
(gdb) b main
Breakpoint 1 at 0x2206: file main.c, line 8.
(gdb) target remote :3333
Remote debugging using :3333
Reset_Handler ()
    at libraries/CMSIS/CM3/DeviceSupport/ST/STM32F10x/startup/gcc_ride7/startup_stm32f10x_md.s:67
67	  movs	r1, #0
(gdb) c
Continuing.

Breakpoint 1, main () at main.c:8
8		RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO, ENABLE);
(gdb) list
3	
4	int main(void)
5	{
6		int last_button_state, new_button_state;
7	
8		RCC_APB2PeriphClockCmd(RCC_APB2Periph_AFIO, ENABLE);
9		RCC_APB2PeriphClockCmd(RCC_APB2Periph_GPIOC | RCC_APB2Periph_GPIOA, ENABLE);
10						
11		/* Configure PC.12 as output push-pull (LED) */
12		GPIO_WriteBit(GPIOC,GPIO_Pin_12,Bit_SET);
(gdb) b 23
Breakpoint 2 at 0x2264: file main.c, line 23.
(gdb) c
Continuing.

Breakpoint 2, main () at main.c:23
23			new_button_state = GPIOA->IDR & 0x00000001;
(gdb) n
24			if(new_button_state ^ last_button_state) {
(gdb) p new_button_state
$1 = 0
(gdb) info breakpoints 
Num     Type           Disp Enb Address    What
1       breakpoint     keep y   0x00002206 in main at main.c:8
breakpoint already hit 1 time
2       breakpoint     keep y   0x00002264 in main at main.c:23
breakpoint already hit 1 time
(gdb) del 2
(gdb) watch GPIOC->ODR
Hardware watchpoint 3: GPIOC->ODR
(gdb) c
Continuing.

• 在 QEMU monitor 內作以下輸入，試圖模擬按鈕的動作

.. code-block:: prettyprint

sendkey b

• 隨後可發現 GDB 畫面出現變化：

.. code-block:: prettyprint

Hardware watchpoint 3: GPIOC->ODR

Old value = 4096
New value = 0
main () at main.c:29
29			last_button_state = new_button_state;

• 事實上 GPIOC 是個 macro，可透過 GDB 驗證

.. code-block:: prettyprint

(gdb) info macro GPIOC
Defined at libraries/CMSIS/CM3/DeviceSupport/ST/STM32F10x/stm32f10x.h:1410
  included at Lab-2/demo/main.c:2
#define GPIOC ((GPIO_TypeDef *) GPIOC_BASE)

GDB Automation

• 撰寫特別的 GDB script，使得 QEMU 能自動在 UART 畫面印出 “Hello!” 字樣。main.c 檔案的行數應該越少越好，處理動作最好全權交給 GDB
• 在 Makefile 新增 ‘gdbauto’ 的 target，自動進行 QEMU + GDB + UART 輸出
  • 也就是預期執行 make gdbauto 之後，能呼叫 QEMU