debug kernel in qemu

[Patrick Welche <prlw1%cam.ac.uk@localhost>]

I have an apparently working -current/amd64 in qemu started with

qemu-system-x86_64 \
        -m 512 \
        -drive file=wd.img,if=virtio,format=raw,media=disk,snapshot=on \
        -object rng-random,filename=/dev/random,id=rng0 \
        -device virtio-rng-pci,rng=rng0 \
        -accel nvmm \
        -soundhw hda \
        -no-reboot \
        -nographic -curses \
        -serial mon:stdio

I was under the impression that debugging the kernel might be as simple
as adding -s -S and setting breakpoints, but apparently not:

(gdb) target remote localhost:1234
Remote debugging using localhost:1234
0x000000000000fff0 in ?? ()
(gdb) break radix_tree_init
Breakpoint 1 at 0xffffffff80e0a104: file ../../../../../../lib/libkern/../../...
(gdb) c
Continuing.

and off it goes never hitting the breakpoint. What else needs to be done?


Cheers,

Patrick