diff options
| -rw-r--r-- | microkernel/mach/gnumach/debugging.mdwn | 48 |
1 files changed, 47 insertions, 1 deletions
diff --git a/microkernel/mach/gnumach/debugging.mdwn b/microkernel/mach/gnumach/debugging.mdwn index 9534c758..a134b618 100644 --- a/microkernel/mach/gnumach/debugging.mdwn +++ b/microkernel/mach/gnumach/debugging.mdwn @@ -77,7 +77,53 @@ and then type continue, to let Mach continue execution. The debugger will be ent When you're [[running_a_system_in_QEMU|hurd/running/qemu]] you can directly [use GDB on the running -kernel](http://www.nongnu.org/qemu/qemu-doc.html#SEC48). +kernel](https://www.qemu.org/docs/master/system/gdb.html). + +When debugggin 32-bit gnumach, you can specify the kernel file in the +command line with the `-kernel` option and the boot modules with +`-initrd`, as described in [[hurd/running/qemu]]. This however does +not work for 64-bit gnumach, due to a [limitation in +qemu](https://gitlab.com/qemu-project/qemu/-/issues/243). To overcome +this, you can either patch qemu to enable multiboot also for 64-bit +ELF, or build a bootable ISO image with `grub-mkrescue`. + +To enable the gdbserver on a running instance, you need to access the +qemu monitor and use the `gdbserver` command. For example, with +libvirt/virt-manager + + $ virsh --connect qemu:///session qemu-monitor-command --domain hurd --hmp --cmd gdbserver + +Otherwise, if you start qemu manually, you can use the `-s` and `-S` +shortcuts, that will open a tcp connection on port 1234 and wait for +gdb to attach before starting the vm. + +If you don't need a graphical interface, e.g. you're working on the +boot process, you could use stdio as an emulated serial port with +`-nographic`, and append `console=com0` to the kernel command line, +either in grub or with the `-append` option. + +Once qemu has started, you can connect to the gdbserver with + + $ gdb gnumach + ... + (gdb) target remote :1234 + (gdb) c + +You can also automate some steps with a `.gdbinit` file in your +working directory. For example: + + set print pretty + target remote :1234 + # let's set some breakpoints + b Panic + b c_boot_entry + b user_bootstrap + b ../i386/intel/pmap.c:1981 + # we can also refer to virtual addresses in userspace + b *0x804901d + # this shows the instruction being executed + display/i $pc + layout asm ## [[open_issues/debugging_gnumach_startup_qemu_gdb]] |