可加载内核模块的调试信息

Question

如何为可加载的Linux内核模块（比如vmlinux- uname -r .debug中的内核模块）构建调试信息？是否在我们构建模块时生成它，如果是这样的话它将位于何处？

Answer 1

Assuming you have built the kernel with CONFIG_DEBUG_INFO the debug symbols should already be in the .ko file for the module in question. However as the module can be dynamically loaded at any address you need to give gdb a bit more information.

cd /sys/module/${MODNAME}/sections
cat .text .data .bss

You can then use this information when telling GDB about the modules:

(gdb) add-symbol-file ${MODPATH} ${TEXT} -s .data ${DATA} -s .bss ${BSS}

There is a tutorial that walks you through this on the Linux Foundation website. Kernel and Module Debugging with GDB

Answer 2

#Modify your Makefile like this then build it
#cat /sys/module/mydriver/sections/.text -> find the address
#Then run like add-symbol-file drivers/mydrivers/mydriver.o address from above #line
obj-m += module_name.o
MY_CFLAGS += -g -DDEBUG
ccflags-y += ${MY_CFLAGS}
CC += ${MY_CFLAGS}


all:
        make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules

debug:
        make -C /lib/modules/$(shell uname -r)/build M=$(PWD) modules 
        EXTRA_CFLAGS="$(MY_CFLAGS)"
clean: make -C /lib/modules/$(shell uname -r)/build M=$(PWD) clean