[PATCH] example of 64-bit debug

[pasha (biblio)]

Add example of 64-bit debugging.

---
 contributing.mdwn | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/contributing.mdwn b/contributing.mdwn
index c4a3787d..90705d93 100644
--- a/contributing.mdwn
+++ b/contributing.mdwn
@@ -199,6 +199,23 @@ After you have a Hurd vm set up and running:
 * Start hacking.
 * For shutting down, use `reboot`, then press `c` in grub and issue halt (to 
avoid filesystem corruption). Adding `--no-reboot` to the qemu line should 
help, too.
 
+## Debug 64-bit gnumach
+
+[[build|microkernel/mach/gnumach/building/]] 64-bit gnumach
+
+run a spare Hurd vm (prepare for data loss in vm):
+
+* `kvm -net user,hostfwd=tcp:127.0.0.1:2222-:22 -net nic,model=e1000 -drive 
file=$(echo debian-hurd*.img),cache=writeback -m 1G`
+* `cd gnumach/build`
+* `scp -P 2222 gnumach.gz user@127.0.0.1:/home/user/`
+* You may copy `gnumach.gz` (also create new grub entry) or replace using `mv 
/home/user/gnumach.gz /boot/gnumach-xxx.gz`
+* Shutdown vm.
+* Append `console=com0` in boot menu and switch to console mode in qemu. (We 
have known issues with vga output for 64-bit.)
+* `kvm -s -S -net user,hostfwd=tcp:127.0.0.1:2222-:22 -net nic,model=e1000 
-drive file=$(echo debian-hurd*.img),cache=writeback -m 1G` (note: `-s -S` 
added.)
+* `gdb ./gnumach`
+* `(gdb) target remote :1234`
+* Press `c` to continue booting.
+
 ---
 <a name="hurd_on_modern_microkernel"></a>
 # Design / Research: GNU Hurd on a Modern Microkernel
-- 
2.30.2