linux-kernel - Re: [patch V2 28/29] x86/irq/64: Remap the IRQ stack with guard pages

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Message-ID: <CALCETrX_Pyo-H8H2feZz1+hiz_E99ZqVBqb+xvZfZ+gvFGL5gw@mail.gmail.com>
Date:   Mon, 8 Apr 2019 09:18:00 -0700
From:   Andy Lutomirski <luto@...nel.org>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Andy Lutomirski <luto@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>, X86 ML <x86@...nel.org>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Sean Christopherson <sean.j.christopherson@...el.com>
Subject: Re: [patch V2 28/29] x86/irq/64: Remap the IRQ stack with guard pages

On Sun, Apr 7, 2019 at 11:46 PM Thomas Gleixner <tglx@...utronix.de> wrote:
>
> On Sun, 7 Apr 2019, Andy Lutomirski wrote:
> > On Sun, Apr 7, 2019 at 3:44 PM Thomas Gleixner <tglx@...utronix.de> wrote:
> > > Actually we have: save_stack_trace()
> > >
> >
> > Like I did here:
> >
> > https://git.kernel.org/pub/scm/linux/kernel/git/luto/linux.git/log/?h=WIP.x86/stackguards
>
> Kinda, but what that code wants is to skip any entry before 'caller'. So we
> either add something like save_stack_trace_from() which is trivial on x86
> because unwind_start() already has an argument to hand in the start of
> stack or we filter out the entries up to 'caller' in that code.
>
>

Whoops!

I could add a save_stack_trace_from() or I could add a "caller"
argument to struct stack_trace.  Any preference as to which looks
better?  The latter seems a little nicer to me.