Re: Loading splash ok -> <reset>, how to debug?

On Sun, 8 Jun 2025 at 10:47, Bjoern A. Zeeb <[email protected]>
wrote:

> On Sun, 8 Jun 2025, Warner Losh wrote:
>
> > On Sun, Jun 8, 2025, 10:08 AM Tomek CEDRO <[email protected]> wrote:
> >
> >> On Sun, Jun 8, 2025 at 5:10 PM Bjoern A. Zeeb
> >> <[email protected]> wrote:
> >>> Hi,
> >>> is there any good way to debug early kernel kabooms (or maybe efi
> loader
> >>> handover) without JTAG in place?
> >>> I have a SoC using U-Boot and often after a cold start it goes like
> >>> this:
> >>>
> ------------------------------------------------------------------------
> >>> Hit [Enter] to boot immediately, or any other key for command prompt.
> >>> Booting [/boot/kernel/kernel]...
> >>> Using DTB provided by EFI at 0x3e6c3000.
> >>> Loading splash ok
> >>> <reset>
> >>>
> ------------------------------------------------------------------------
> >>> Once it's been looping for a few iterations eventually it starts
> >>> booting.
> >>> Given there is zero output of the error, is there aything one could try
> >>> to do to debug this (remotely)?
> >>> I can netboot it and change laoder/kernel.
> >>
> >> DDB?
> >>
> https://docs.freebsd.org/en/books/developers-handbook/kerneldebug/#kerneldebug-online-ddb
> >>
> >> KGDB?
> >>
> https://docs.freebsd.org/en/books/developers-handbook/kerneldebug/#kerneldebug-online-gdb
> >>
> >> over the Serial Port? :-)
> >>
> >
> > I think he's not even getting to the handoff. Best to toss out all
>
> hmm..
>
> > graphical things that are configured and see if that gets us to the
> handoff
> > point... get rid of the splash screen first of all..
>
> How?  I do not have boot_mute="YES" set.
>
> I tried setting console to just efi manually; that didn't help. Also on
> first attempt I got an error, typing it again worked (but I didn't
> re-validate).
>
> I have the following in loader.conf and I tried various combinations
> without
> success to see ... I also tried to fdt ls to make sure fdt is all right
> and there...
>

You may need to do some gross early book hacks to print out like a forever
string of 'A's to see if you're even ending up in the kernel start routine
or not.



-adrian