Date: Thu, 07 Feb 2002 12:32:46 +0100 From: Gary Jennejohn <garyj@jennejohn.org> To: Peter Jeremy <peter.jeremy@alcatel.com.au> Cc: freebsd-hackers@freebsd.org Subject: Re: Patching a kernel Message-ID: <200202071132.g17BWkL52065@peedub.jennejohn.org> In-Reply-To: Your message of "Wed, 06 Feb 2002 07:37:13 %2B1100." <20020206073713.Z7444@gsmx07.alcatel.com.au>
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Peter Jeremy writes:
> I'd like to patch a running kernel to disable an annoying
non-rate-limited
> message but gdb won't let me. (For various reasons, I don't want to have
> to build a new kernel and reboot).
>
> aalp03# chflags noschg /kernel
> aalp03# gdb -k /kernel /dev/mem
> GNU gdb 4.18
> ...
> IdlePTD 3457024
> initial pcb at 4d40000
> panic messages:
> ---
> ---
> #0 0xc0159bf0 in mi_switch ()
> (kgdb) set write on
> (kgdb) print {int}0xc01fffa4 = 0x00004eb8
> kvm_write:write failed
> (kgdb) show write
> Writing into executable and core files is on.
> (kgdb)
>
> 0xc01fffa4 is in the kernel text area.
>
> This is 4.4-STABLE from mid-December running at securelevel -1.
>
> Is there any way around this?
>
RTFM :) You have to use the wcore option to turn on writing in kgdb mode.
The ``show write'' command is totally unrelated to this and only shows
what's set for _normal_ debugging. There's no way to tell from within
gdb whether wcore was used or not.
Unfortunately, the -w option is overloaded. Normally it means ``use
a windowing system''. In FreeBSD it's an alias for wcore.
---
Gary Jennejohn / garyj@jennejohn.org gj@freebsd.org
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