[Bug 901944] Re: gdbserver inside qemu does not stop on breakpoints
As mentioned by Horst, hbreak is needed. If you are getting "Remote 'g' packet reply is too long", see: https://sourceware.org/bugzilla/show_bug.cgi?id=13984 ** Bug watch added: Sourceware.org Bugzilla #13984 http://sourceware.org/bugzilla/show_bug.cgi?id=13984 -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/901944 Title: gdbserver inside qemu does not stop on breakpoints To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/qemu-kvm/+bug/901944/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 901944] Re: gdbserver inside qemu does not stop on breakpoints
More details: - It works if I use hbreak (GDB hardware-assisted breakpoints) instead of break for the very first breakpoint. - After this first breakpoint, normal "break" breakpoints work fine, too. - Accoording to http://chemnitzer.linux-tage.de/2012/vortraege/folien/1061-VirtualDebugging.pdf slide 18 this might be due to GDB not properly dealing with protocol changes. In this case, this is a GDB bug/issue, not a qemu-kvm one. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/901944 Title: gdbserver inside qemu does not stop on breakpoints To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/qemu-kvm/+bug/901944/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
Re: [Bug 901944] Re: gdbserver inside qemu does not stop on breakpoints
status confirmed ** Changed in: qemu-kvm (Ubuntu) Status: Expired => Confirmed -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/901944 Title: gdbserver inside qemu does not stop on breakpoints To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/qemu-kvm/+bug/901944/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 901944] Re: gdbserver inside qemu does not stop on breakpoints
I'm seeing the very same problem, please reopen. Ubuntu 12.10 amd64 (Linux 3.5.0-25-generic x86_64), qemu-kvm 1.2.0+noroms-0ubuntu2.12.10.3. Guest is an i386 eCos test kernel (I can attach it if necessary; I guess you can use anything bootable here), started either via qemu-system-i386 -kernel ecos.elf -s -S or via an ISO image with grub2: qemu-system-i386 -cdrom ecos.iso -s -S I'm attaching GDB with: gdb ecos.elf (gdb) target remote localhost:1234 (gdb) b main (gdb) c The breakpoint never hits, although this perfectly works on my 32-bit Debian Squeeze box. If I start qemu-system-i386 with "-machine accel=tcg", the breakpoint matches very quickly, kvm halts, and the GDB prompt allows me to inspect the state. If I start qemu-system-i386 with "-machine accel=kvm" (the default), I observe the aforementioned behaviour. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/901944 Title: gdbserver inside qemu does not stop on breakpoints To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/qemu-kvm/+bug/901944/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 901944] Re: gdbserver inside qemu does not stop on breakpoints
[Expired for qemu-kvm (Ubuntu) because there has been no activity for 60 days.] ** Changed in: qemu-kvm (Ubuntu) Status: Incomplete => Expired -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/901944 Title: gdbserver inside qemu does not stop on breakpoints To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/qemu-kvm/+bug/901944/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 901944] Re: gdbserver inside qemu does not stop on breakpoints
This config lets me debug the kernel. However, I can not start debugging with qemu's -S option. With -S, qemu waits for a gdb connection to start the VM but gdb can't connect to the default port (:1234). Connection times out. If I start with -s, then everything is good. ** Attachment added: "kernel 2.6.38-10-server config that works for kvm+gdb debugging" https://bugs.launchpad.net/ubuntu/+source/qemu-kvm/+bug/901944/+attachment/2724426/+files/config-for-qemu-gdb -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/901944 Title: gdbserver inside qemu does not stop on breakpoints To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/qemu-kvm/+bug/901944/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 901944] Re: gdbserver inside qemu does not stop on breakpoints
Do you mind posting the new, working, config? There may (likely will) be too much noise in the diff, but it's worth looking for clues. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/901944 Title: gdbserver inside qemu does not stop on breakpoints To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/qemu-kvm/+bug/901944/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 901944] Re: gdbserver inside qemu does not stop on breakpoints
I reconfigured the kernel from the default configuration with the debugging symbols and it now seems to be working okay. There is something in the config I previously posted that makes things weird. The question is how can we track it down? -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/901944 Title: gdbserver inside qemu does not stop on breakpoints To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/qemu-kvm/+bug/901944/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 901944] Re: gdbserver inside qemu does not stop on breakpoints
** Attachment added: "kernel config file for 2.6.38-10-server" https://bugs.launchpad.net/ubuntu/+source/qemu-kvm/+bug/901944/+attachment/2625885/+files/.config -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/901944 Title: gdbserver inside qemu does not stop on breakpoints To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/qemu-kvm/+bug/901944/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 901944] Re: gdbserver inside qemu does not stop on breakpoints
Thanks - please do attach your .config, and I'll try to reproduce. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/901944 Title: gdbserver inside qemu does not stop on breakpoints To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/qemu-kvm/+bug/901944/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 901944] Re: gdbserver inside qemu does not stop on breakpoints
Guest is a 2.6.38-10-server x86_64 kernel with ubuntu patches applied
(configured to have some set of modules built-in + debugging symbols +
non-preemptive + HZ=100). I can provide the config file if necessary.
Root fs contains a minimal 10.04 server.
Here is how I launch the VM:
$ qemu-system-x86_64 -s -m 512 -drive file="root1.qcow2" -kernel
../../linux-2.6.38/arch/x86/boot/bzImage -append " console=tty1 root=/dev/sda1
ro "
VM launches fine and drops to a login shell. Then I start gdb and connect to
the server:
$ gdb ../../linux-2.6.38/vmlinux
{Init messages...}
Reading symbols from ../../linux-2.6.38/vmlinux...done.
(gdb) target remote :1234
Remote debugging using :1234
0x81076a0b in pvclock_clocksource_read (src=0x82201fd8) at
arch/x86/kernel/pvclock.c:106
106 if ((valid_flags & PVCLOCK_TSC_STABLE_BIT) &&
(gdb)
At this point the VM is unresponsive. Then I set a breakpoint at
schedule() (which should be called 100 times per second) and let the VM
go.
(gdb) b schedule
Breakpoint 1 at 0x81b2b3f0: file kernel/sched.c, line 3946.
(gdb) c
Continuing.
I would expect the debugger to hit the breakpoint but it never does. VM
is fully functional at this point. Then I pause the VM again with ctrl+c
and print the stack trace:
^C
Program received signal SIGINT, Interrupt.
0x81076a0b in pvclock_clocksource_read (src=0x82201fd8) at
arch/x86/kernel/pvclock.c:106
106 if ((valid_flags & PVCLOCK_TSC_STABLE_BIT) &&
(gdb) where
#0 0x81076a0b in pvclock_clocksource_read (src=0x82201fd8) at
arch/x86/kernel/pvclock.c:106
#1 0x81053255 in arch_safe_halt () at
/DOCS/nmc/linux-2.6.38/arch/x86/include/asm/paravirt.h:110
#2 default_idle () at arch/x86/kernel/process.c:391
#3 0x8104921b in cpu_idle () at arch/x86/kernel/process_64.c:139
#4 0x81ad9cce in device_irq_init (pdata=0x824cdfa0,
chip=0x824c99c0) at drivers/mfd/88pm860x-core.c:508
#5 device_8607_init (chip=0x824c99c0, i2c=,
pdata=0x824cdfa0) at drivers/mfd/88pm860x-core.c:682
#6 0x8247bc6f in start_kernel () at init/main.c:734
#7 0x8247b347 in x86_64_start_reservations (real_mode_data=) at arch/x86/kernel/head64.c:124
#8 0x8247b44d in x86_64_start_kernel
(real_mode_data=0x88001fffb880 " console=tty1") at
arch/x86/kernel/head64.c:94
#9 0x in ?? ()
(gdb)
I see the same stack trace every single time I stop the VM; while sitting idle
on the console, while running a busy-loop application, while doing net/disk IO.
I also set other breakpoints at frequently executed kernel functions like
do_timer() but the VM never stops at these breakpoints.
Please let me know if more information is necessary.
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Title:
gdbserver inside qemu does not stop on breakpoints
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[Bug 901944] Re: gdbserver inside qemu does not stop on breakpoints
Thanks for reporting this bug. Could you show us exactly how to reproduce your failure and what to look for? I see you are on oneiric. We have somewhat recently, successfully, used gdb remotely on oneiric, but it was with very early boot which may affect this. Could you tell us which release+kernel were running in the guest? ** Changed in: qemu (Ubuntu) Status: New => Incomplete ** Package changed: qemu (Ubuntu) => qemu-kvm (Ubuntu) ** Changed in: qemu-kvm (Ubuntu) Importance: Undecided => Low -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/901944 Title: gdbserver inside qemu does not stop on breakpoints To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/qemu-kvm/+bug/901944/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
[Bug 901944] Re: gdbserver inside qemu does not stop on breakpoints
-- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/901944 Title: gdbserver inside qemu does not stop on breakpoints To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/qemu/+bug/901944/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
