Messages in this thread | | | Date | Thu, 17 Jul 2008 08:14:32 -0500 | From | Jason Wessel <> | Subject | Re: Usage of kgdb in v2.6.26 |
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Do you have CONFIG_DEBUG_RODATA=y in your kernel config?
There is a presently a known problem where breakpoints will silently fail to plant when this is turned on.
Jason.
ZC Miao wrote: > I tried to use the kgdb from v2.6.26, but met few problems. > I use : > 1. gdb 6.8 (gdb-6.8-11.fc9.i386) > 2. kernel v2.6.26 source code > 3. Qemu 0.9.1 (qemu-0.9.1-5.fc9.i386) > 4. Host is : 2.6.25.10-86.fc9.i686 > 5. Cpu : Intel(R) Core(TM)2 Duo CPU T5450 @ 1.66GHz > > > * Firstly I compile kernel 2.6.26 with kgdb support : > CONFIG_KGDB=y > CONFIG_KGDB_SERIAL_CONSOLE=y > > * Then I use qemu to boot my kernel along with a rootfs that I created, > with a qemu option that makes a local tcp port a listening service as a > serial port for the emulated system. The kernel arguments I gave is : > nfsroot=192.168.200.1:/path/to/rootfs,udp,nolock ip=dhcp root=/dev/nfs > ro single kgdboc=ttyS0,115200 kgdbwait > > * After the kernel loaded and boot for a while, the gdb receives a > signal and hangs the kernel : > kgdb_register_io_module (new_kgdb_io_ops=<value optimized out>) > at /data/home/hellwolf/mydoc/prog/linux/linux-2.6/kernel/kgdb.c:1674 > (gdb) > > Question 1 : > * If I type "b sys_read", and then "c", the kernel continues until I > get : > > --------------------------------------------------------------- > [New Thread 1] > Cannot remove breakpoints because program is no longer writable. > It might be running in another process. > Further execution is probably impossible. > > Breakpoint 1, sys_read (fd=3, buf=0xbfdb31dc "", count=512) > > at /data/home/hellwolf/mydoc/prog/linux/linux-2.6/fs/read_write.c:360 > (gdb) > --------------------------------------------------------------- > > Why "program is no longer writable" happens here? > > Question 2 : > * If I directly type "c" when kgdbwait triggered. And use Sys-Rq+G to > interrupt the kernel, I will get : > --------------------------------------------------------------- > [New Thread -1] > > Program received signal SIGTRAP, Trace/breakpoint trap. > [Switching to Thread -1] > sysrq_handle_gdb (key=103, tty=0xc78f6400) > at /data/home/hellwolf/mydoc/prog/linux/linux-2.6/kernel/kgdb.c:167 > (gdb) > --------------------------------------------------------------- > Here if I type "c sys_read" and "c", it never actually makes any break > points, I will never receive a break from gdb. > > > I don't know if I made anything wrong, or I missed any important thing, > so I post here and would like to get some help from you. > > Thanks. > > -- > ZC Miao (hellwolf.misty@gmail.com) > Blog http://hellwolf.cublog.cn > > gpg --keyserver pgp.mit.edu --recv-key 0x6B174C6F > > Most people deserve each other. > -- Shirley > > > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ >
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