KGDB--Cannot insert breakpoint

内核编译选项CONFIG_DEBUG_RODATA，会对kernel text做write protect。 那么kgdb就不能设置断点了。

解决方法是：

编辑kernel source目录下生成的.config文件， 禁用CONFIG_DEBUG_RODATA=n (read only data)重新编译即可

http://www.mail-archive.com/[email protected]/msg03464.html

Hi Folks,

I’m wondering if anyone has had issues with setting breakpoints. I’m
able to break into the kernel, access data, do a backtrace, etc, but
when I attempt to set a breakpoint, then continue, I get the following error:

Cannot insert breakpoint 1.
Error accessing memory address 0xffffffff81310931: Unknown error 4294967295.

I’m attaching a sample session, I had set remote debug to 1

Thanks!
Pat Thomson

Hi Thomson,

It seems that your problem is the CONFIG_DEBUG_RODATA option was
enabled, It is recommend to turn CONFIG_DEBUG_RODATA off when using kgdb.

From the kgdb document(DocBook/kgdb.tmpl):

If the architecture that you are using supports the kernel option
CONFIG_DEBUG_RODATA, you should consider turning it off.  This
option will prevent the use of software breakpoints because it
marks certain regions of the kernel's memory space as read-only.
If kgdb supports it for the architecture you are using, you can
use hardware breakpoints if you desire to run with the
CONFIG_DEBUG_RODATA option turned on, else you need to turn off
this option.

Thanks, Dongdong