linux-kernel - Re: [RFC][PATCH 4/7] x86/debug: Move historical SYSENTER junk into exc_debug

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Message-ID: <20200821101903.GK1362448@hirez.programming.kicks-ass.net>
Date:   Fri, 21 Aug 2020 12:19:03 +0200
From:   peterz@...radead.org
To:     Daniel Thompson <daniel.thompson@...aro.org>
Cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        Kyle Huey <me@...ehuey.com>,
        Alexandre Chartre <alexandre.chartre@...cle.com>,
        Robert O'Callahan <rocallahan@...il.com>,
        "Paul E. McKenney" <paulmck@...nel.org>,
        Frederic Weisbecker <frederic@...nel.org>,
        Paolo Bonzini <pbonzini@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>,
        Masami Hiramatsu <mhiramat@...nel.org>,
        Petr Mladek <pmladek@...e.com>,
        Steven Rostedt <rostedt@...dmis.org>,
        Joel Fernandes <joel@...lfernandes.org>,
        Boris Ostrovsky <boris.ostrovsky@...cle.com>,
        Juergen Gross <jgross@...e.com>,
        Brian Gerst <brgerst@...il.com>,
        Andy Lutomirski <luto@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>
Subject: Re: [RFC][PATCH 4/7] x86/debug: Move historical SYSENTER junk into
 exc_debug_kernel()

On Thu, Aug 20, 2020 at 04:28:28PM +0100, Daniel Thompson wrote:

> Specifically I've entered the kdb in pretty much the simplest way
> possible: a direct call to kgdb_breakpoint() from a task context. I
> generate a backtrace to illustrate this, just to give you a better
> understanding of what might be happening) and then ran the single step.


> + make -C .. O=$PWD x86_64_defconfig
> + ../scripts/config --enable RUNTIME_TESTING_MENU
> + ../scripts/config --enable DEBUG_INFO --enable DEBUG_FS --enable KALLSYMS_ALL --enable MAGIC_SYSRQ --enable KGDB --enable KGDB_TESTS --enable KGDB_KDB --enable KDB_KEYBOARD --enable LKDTM
> + ../scripts/config --enable PROVE_LOCKING --enable DEBUG_ATOMIC_SLEEP
> + make olddefconfig


That asked me about a kgdb boottime selftest, which I figured was a good
idea, but even without my patches that seems to fail, and fail so that
it doesn't boot :/

> # echo g > /proc/sysrq-trigger

OK, I think I got that working with the latest set.

Thanks!