Re: Debug grub scripts without rebooting into grub shell.

[Hongyi Zhao]

On Sun, Jul 9, 2023 at 4:26 PM Andrei Borzenkov <arvidjaar@gmail.com> wrote:
>
> On 09.07.2023 10:00, Hongyi Zhao wrote:
> > On Sun, Jul 9, 2023 at 2:49 PM Andrei Borzenkov <arvidjaar@gmail.com> wrote:
> >>
> >> On 09.07.2023 09:33, Hongyi Zhao wrote:
> >>> On Sun, Jul 9, 2023 at 1:13 PM Andrei Borzenkov <arvidjaar@gmail.com> 
> >>> wrote:
> >>>>
> >>>> On 09.07.2023 03:21, Hongyi Zhao wrote:
> >>>>> On Sat, Jul 8, 2023 at 9:53 PM Andrei Borzenkov <arvidjaar@gmail.com> 
> >>>>> wrote:
> >>>>>>
> >>>>>> On 08.07.2023 14:58, Hongyi Zhao wrote:
> >>>>>>> Hi here,
> >>>>>>>
> >>>>>>> Are there some convenient methods to debug grub scripts without
> >>>>>>> rebooting into grub shell?
> >>>>>>>
> >>>>>>
> >>>>>> You may try grub-emu which emulates grub.
> >>>>>
> >>>>> I tried, but it seems that grub-emu doesn't meet my requirement as
> >>>>> described below.
> >>>>>
> >>>>> I want to debug the grubx64.efi created by the following command:
> >>>>>
> >>>>
> >>>> If you want to debug grubx64.efi, then you of course need to load it
> >>>> either on real hardware or in VM. But you can debug scripts used by
> >>>> grubx64.efi using grub-emu by setting up suitable simulated environment.
> >>>> There are clear limitations (scripts cannot load and start any kernel).
> >>>
> >>> Then, how to access the real hard disk devices and partitions? I can
> >>> only see the following devices via grub-emu:
> >>>
> >>
> >> You create device.map and give names hd0, hd1, ... to your devices.
> >
> > See below:
> >
> > werner@X10DAi:~$ sudo grub-mkdevicemap -n
> > werner@X10DAi:~$ cat /boot/grub/device.map
> > (hd0)    /dev/disk/by-id/nvme-SAMSUNG_MZVL22T0HBLB-00B00_S677NF0R503706
> > (hd1)    /dev/disk/by-id/ata-WDC_WDS100T2B0A-00SM50_191533467906
> >
> > Now, I see the following devices in grub-emu:
> >
> > grub> ls
> > (proc) (hd0) (hd1) (host)
> >
> > But how to access the corresponding partitions on these devices?
> >
>
> Did you try to load partition driver?

I tried as follows, but still failed to see the partitions:

grub> insmod lvm fat ntfs part_msdos part_gpt ext2 btrfs
grub> ls
(proc) (hd0) (hd1) (host)

Any more hints?

Regards,
Zhao

> >>> grub> ls
> >>> (proc) (host)
> >>>
> >>> Best,
> >>> Zhao
> >>>
> >>>>> $ grub-mkstandalone -O x86_64-efi -o grubx64.efi --modules='lvm fat
> >>>>> ntfs part_msdos part_gpt ext2 btrfs probe regexp search configfile'
> >>>>> boot/grub/grub.cfg=./grub.cfg
> >>>>>
> >>>>> The content of the ./grub.cfg is as follows:
> >>>>>
> >>>>> $ egrep -v '^[ ]*(#|$)' grub.cfg
> >>>>> regexp -s __cmdpath_efi '^\(([^,]+)' "$cmdpath"
> >>>>> export __cmdpath_efi
> >>>>> for file in ($__cmdpath_efi,*)/multibootusb.git/grub.cfg; do
> >>>>>      if regexp -s __root '^(\([^*]+\))' "$file"; then
> >>>>>        set __prefix=$__root/multibootusb.git
> >>>>>        export __root
> >>>>>        export __prefix
> >>>>>        configfile $__prefix/grub.cfg
> >>>>>        break
> >>>>>      fi
> >>>>> done
> >>>>>
> >>>>> The files' layout is as follows:
> >>>>>
> >>>>> $ tree .
> >>>>> .
> >>>>> ├── grub.cfg
> >>>>> ├── grub-mkstandalone.sh
> >>>>> ├── grubx64.efi
> >>>>> └── iso
> >>>>>        ├── deepin-desktop-community-23-Beta-amd64.iso
> >>>>>        ├── rescatux-0.74.iso
> >>>>>        ├── supergrub2-2.06s1-beta2-multiarch-CD.iso
> >>>>>        ├── systemrescue-10.01-amd64.iso
> >>>>>        ├── ubuntu-23.04-desktop-amd64.iso
> >>>>>        └── ubuntukylin-23.04-desktop-amd64.iso
> >>>>>
> >>>>> 1 directory, 9 files
> >>>>>
> >>>>> Regards,
> >>>>> Zhao