Re: after trivial update, 15.0 ARM64 system no longer boots

On Mar 25, 2024, at 00:51, Lexi Winter <lexi@le-fay.org> wrote:

> Lexi Winter:
>> . . .
> 
> . . .
> 
> - even with the working keyboard, ctrl+alt+esc doesn't seem to work to
>  break into kdb when the problem occurs.  i'm not sure if i'm doing
>  something wrong here or that key sequence doesn't work over USB, so i
>  wanted to try it via a serial console instead, which led to...
> 
> . . .

https://man.freebsd.org/cgi/man.cgi?ddb(4) reports:

QUOTE
Serial consoles can break to the debugger by sending a BREAK condition
on the serial line. This requires a kernel built with options
BREAK_TO_DEBUGGER is specified in the kernel. Most terminal emulation
programs can send a break sequence with a special key sequence or menu
selection. Sending the break can be difficult or even happen spuri-
ously in some setups. An alternative method is to build a kernel with
options ALT_BREAK_TO_DEBUGGER then the sequence of CR TILDE CTRL-B en-
ters the debugger; CR TILDE CTRL-P causes a panic; and CR TILDE CTRL-R
causes an immediate reboot. In all these sequences, CR represents Car-
riage Return and is usually sent by pressing the Enter or Return key.
TILDE is the ASCII tilde character (~). CTRL-x is Control x, sent by
pressing the Control key, then x, then releasing both.
END QUOTE

Note the lack of mention of the ctrl+alt+esc .

I expect that the:

https://docs.freebsd.org/en/books/developers-handbook/kerneldebug/

reference to "The default break-to-debugger sequence is Ctrl+Alt+ESC"
may be x86/i386 specific (historical tier 1) or have some other
specific type of context it applies to.

I've historically used ALT_BREAK_TO_DEBUGGER and its CR TILDE CTRL-B
on everything to get to the ddb> prompt via keyboards, including the
serial console. (But, thinking about it, I've not used that in some
time.)

===
Mark Millard
marklmi at yahoo.com