问题
I'm having problems with debugging my modified Linux-3.11.0 kernel. For debugging the code, I use:
- GDB 7.6
- QEMU 1.6.5
- Linux kernel 3.11.0
My system has Intel(R) Core(TM) i7-2760QM CPU @ 2.40GHz running Ubuntu 12.10
I compiled the modified kernel with a configuration file that I created using 'make menuconfig'. (with modifications in the "kernel hacking" category)
Some of the .config file lines (that I find relevant) are quoted here:
CONFIG_DEBUG_INFO=y
CONFIG_DEBUG_KERNEL=y
CONFIG_MAGIC_SYSRQ=y
CONFIG_DEBUG_FS=y
CONFIG_HAVE_HW_BREAKPOINT=y
CONFIG_HAVE_MIXED_BREAKPOINTS_REGS=y
I use qemu with the "-S" option to boot my kernel, and using gdb I connect to qemu and resume it's execution:
(gdb) target remote :1234
(gdb) continue
When setting breakpoints, for an example:
break schedule I get a confirmation message such as:
Breakpoint 1 at 0xffffffff81736400: file kernel/sched/core.c, line 2509.
So till here everything seems fine!
The problem is that gdb and qemu does not stop at the breakpoints! They both simply continue running...
I tried to set hardware breakpoints as suggested in some places, but I get the message:
No hardware breakpoint support in the target.
which is weird because I have the CONFIG_HAVE_HW_BREAKPOINT set.
I also unset CONFIG_DEBUG_RODATA as suggested in other places,but still no results...
I tried to mess around with the .config file as suggested here: gdbserver inside qemu does not stop on breakpoints but I couldn't figure out the relevant differences between the working .config file and my .config file... (There are too much differences!)
Can anyone please help me?
Thank You!!
回答1:
OK, I found the problem so I'm posting here for other people: Apparently this is a very delicate procedure... My config file was fine. All I needed to do is to define the breakpoints only after I connect to qemu, and not after loading the vmlinux. These breakpoints have to be HARDWARE breakpoints... otherwise they don't break!
来源：https://stackoverflow.com/questions/18931727/remote-gdb-debugging-does-not-stop-at-breakpoints