From: Peter Zijlstra <peterz@infradead.org>
To: daniel.thompson@linaro.org, x86@kernel.org
Cc: sumit.garg@linaro.org, jason.wessel@windriver.com,
dianders@chromium.org, kgdb-bugreport@lists.sourceforge.net,
linux-kernel@vger.kernel.org, pmladek@suse.com,
sergey.senozhatsky@gmail.com, will@kernel.org
Subject: Re: x86/entry vs kgdb
Date: Mon, 25 May 2020 11:18:32 +0200 [thread overview]
Message-ID: <20200525091832.GE325303@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20200525083605.GB317569@hirez.programming.kicks-ass.net>
On Mon, May 25, 2020 at 10:36:05AM +0200, Peter Zijlstra wrote:
> Hi!
>
> Since you seem to care about kgdb, I figured you might want to fix this
> before I mark it broken on x86 (we've been considering doing that for a
> while).
>
> AFAICT the whole debugreg usage of kgdb-x86_64 is completely hosed; it
> doesn't respsect the normal exclusion zones as per arch_build_bp_info().
>
> That is, breakpoints must never be in:
>
> - in the cpu_entry_area
> - in .entry.text
> - in .noinstr.text
> - in anything else marked NOKPROBE
>
> by not respecting these constraints it is trivial to completely and
> utterly hose the machine. The entry rework that is current underway will
> explicitly not deal with #DB triggering in any of those places.
This also very much includes single stepping those bits. Which KGDB
obviously also does not respects.
next prev parent reply other threads:[~2020-05-25 9:18 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-05-25 8:36 x86/entry vs kgdb Peter Zijlstra
2020-05-25 9:18 ` Peter Zijlstra [this message]
2020-05-26 16:16 ` Daniel Thompson
2020-05-26 16:28 ` Peter Zijlstra
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