此文档的目标系统为freescale MPC8349E-mITX,对其他采用powerPC,MIPS，ARM的芯片的系统亦具有参考意义。 此文档中内核调试为了简化，采用目标系统中的UBOOT初始化目标板，并通过UBOOT或者BDI2000加载内核到目标板的RAM中。
1. BDI2000配置：
下面是MPC8349E-mITX的BDI2000配置文件，
; BDI-2000 CONfiguraTIon file for the MPC8349E-mITX
; Tip: If after a reset, the BDI-2000 fails to halt at 0x100,
; you may need to power-down the bOArd for a few seconds.
[INIT]
; we use UBOOT to initialize the board
[TARGET]
CPUTYPE 8349
JTAGCLOCK 1
;STARTUP RESET
STARTUP RUN
BREAKMODE HARD
STEPMODE HWBP
BOOTADDR 0x00000100
;If you're getting "Writing to worksPACe faiLED" errors during flash operations,
;then try uncommenting this line instead. This moves the FLASH window to
;high memory, leaving low memory available for DDR.
RCW 0xb060a000 0x04040000 ;Set the HRCW to boot the image at 0xFE000000
MMU XLAT ;0xc0000000
PTBASE 0xf0 ;
[HOST]
IP 192.168.7.90
FILE $u-boot.bin
LOAD MANUAL
PROMPT 8349E-mITX-GP>
DUMP itx-dump.bin
[Flash]
ChipTYPE AM29BX16
CHIPSIZE 0x800000
BUSWIDTH 16
;WORKSPACE 0x1000
FORMAT BIN 0xfe000000
;flash_image.bin is an image file of an entire 8MB flash region.
;Flash this file at 0xfe0000000 to restore all of flash.
;ERASE 0xFE000000 0x10000 127 ; 127 sectors @ 64KB each
;ERASE 0xFE7F0000 0x2000 8 ; 8 sectors @ 8KB each
;FILE $flash_image.bin
;Use these lines if you just want to flash U-Boot
ERASE 0xfe000000 0x10000? 4; Erase 384KB, each sector is 64KB
FILE? mpc8349e/u-boot131-mitx-gp.bin
[REGS]
FILE $reg8349e.def
以上配置文件的【HOST】段的IP要改为主机IP，关键的字段MMU XLAT 和PTBASE 是POWERPC和MIPS经常需要设置的，关于PTBASE的具体设置，超出本文范围，详细情况请参考BDI2000的手册
2.内核修改和配置
为了能够调试内核，需要在内核中的Makefile中增加如下调试选项：
CFLAGS 增加C代码调试选项-g –ggdb
AFLAGS 增加汇编代码调试选项：-Wa,-L -gdwarf-2
去掉CFLAGS编译选项中-fomit-frAME-pointer
GCC的-fomit-frame-pointer选项是优化函数栈回溯(stack backtrace)的，我们调试的时候需要提供函数回溯能力，所以我们要去掉这个选项，当然，有的系统系统不受它的影响，或者说它不起作用，为了统一，我们统一去掉它。
相对个案来说，我是做如下改动的：
--- Makefile 2008-07-08 03:07:38.000000000 +0800
+++ Makefile.debug 2008-07-08 03:06:04.000000000 +0800
…
-CPPFLAGS := -D__KERNEL__ $(LINUXINCLUDE)
+ifdef CONFIG_DEBUG_INFO
+
+ CPPFLAGS := -D__KERNEL__ $(LINUXINCLUDE) -g -ggdb
-CFLAGS := -Wall -Wundef -WstrICt-prototypes -Wno-trigraphs
+ CFLAGS := $(CPPFLAGS) -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs
-fno-strict-aliasing -fno-common
-AFLAGS := -D__ASSEMBLY__
+ AFLAGS := -D__ASSEMBLY__ -Wa,-L -gdwarf-2
+else
+ CPPFLAGS := -D__KERNEL__ $(LINUXINCLUDE)
+ CFLAGS := -Wall -Wundef -Wstrict-prototypes -Wno-trigraphs
+ -fno-strict-aliasing -fno-common
+ AFLAGS := -D__ASSEMBLY__
+
+endif
…
@@ -491,27 +500,33 @@
# Defaults vmlinux but it is usually overridden in the arch makefile
all: vmlinux
-ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE
-CFLAGS += -Os
-else
-CFLAGS += -O2
-endif
include $(SRCtree)/arch/$(ARCH)/Makefile
-ifdef CONFIG_FRAME_POINTER
-CFLAGS += -fno-omit-frame-pointer $(call cc-option,-fno-optimize-sibling-calls,)
-else
-CFLAGS += -fomit-frame-pointer
-endif
ifdef CONFIG_UNWIND_INFO
CFLAGS += -fasynchronous-unwind-tables
endif
-ifdef CONFIG_DEBUG_INFO
-CFLAGS += -g
-endif
+#ifdef CONFIG_DEBUG_INFO
+CFLAGS += -fno-omit-frame-pointer $(call cc-option,-fno-optimize-sibling-calls,)
+CFLAGS += -g -ggdb
+CFLAGS += -O
+#else
+
+# ifdef CONFIG_FRAME_POINTER
+ CFLAGS += -fno-omit-frame-pointer $(call cc-option,-fno-optimize-sibling-calls,)
+# else
+ CFLAGS += -fomit-frame-pointer
+# endif
+
+# ifdef CONFIG_CC_OPTIMIZE_FOR_SIZE
+ CFLAGS += -Os
+# else
+ CFLAGS += -O2
+# endif
+
+#endif
通过以上修改后，系统的的调试信息简单的通过CONFIG_DEBUG_INFO宏来控制了，那么CONFIG_DEBUG_INFO宏又是从哪里来的呢?它其实是从内核的配置文件.config里面来的。
一般内核通过make menuconfig做配置的时候，都有
Kernel hacking --->
[*] Kernel debugging
[*] Compile the kernel with debug info
[*] Force gcc to inline functions marked 'inline' (2.6比较新的内核有这一项)
[*] Include BDI-2000 user context switcher (有的系统直接提供了这个选项，它和BDI2000的PTBASE设置配合)
通过保存后，以上选项会生成如下配置选项：
CONFIG_DEBUG_KERNEL=y
CONFIG_DEBUG_INFO=y
CONFIG_FORCED_INLINING=y
CONFIG_BDI_SWITCH=y
值得关注的是PowerPC内核中CONFIG_BDI_SWITCH,它到底在内核中怎样起作用的?
我们看arch/powerpc/kernel/head_32.S的关键代码：
…
/* Load up the kernel Context */
2: bl load_up_mmu
#ifdef CONFIG_BDI_SWITCH
/* Add helper information for the Abatron bdiGDB debugger.
* We do this here because we know the mmu is dISAbLED, and
* will be enabled for real in just a few instructions.
*/
lis r5, abatron_pteptrs@h
ori r5, r5, abatron_pteptrs@l
stw r5, 0xf0(r0)??? /* This much match your Abatron config */
lis r6, swapper_pg_dir@h
ori r6, r6, swapper_pg_dir@l
tophys(r5, r5)
stw r6, 0(r5)
#endif /* CONFIG_BDI_SWITCH */
/* Now turn on the MMU for real! */
…
它在MMU真正时能之前先增加了BDI2000帮助信息。在arch/powerpc/kernel/head_32.S的最后通过abatron_pteptrs保留了8个自己的空间给BDI2000用于保存2个页表指针，如下:
本文关键字：暂无联系方式嵌入式系统-技术，单片机-工控设备 - 嵌入式系统-技术
