linux-kernel - Re: [PATCH] Documentation/livepatch: remove the limitation for schedule() patching

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Message-ID: <20170109145433.xiopfww5q37ndzdz@treble>
Date:   Mon, 9 Jan 2017 08:54:33 -0600
From:   Josh Poimboeuf <jpoimboe@...hat.com>
To:     Miroslav Benes <mbenes@...e.cz>
Cc:     jeyu@...hat.com, jikos@...nel.org, pmladek@...e.com,
        corbet@....net, live-patching@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Documentation/livepatch: remove the limitation for
 schedule() patching

On Mon, Jan 09, 2017 at 01:50:19PM +0100, Miroslav Benes wrote:
> There is still one thing which I don't understand. Why __schedule() 
> (patched or the original) is not on the stack. The actual "sleep" 
> should happen in __switch_to_asm() which is C function now. And there is a 
> call to __switch_to_asm() in __schedule(). __schedule() thus should be on 
> the stack, shouldn't it? What am I missing? __switch_to_asm() pushes %rbp 
> on the stack...

Ah, this is an unwinder bug.  get_frame_pointer() needs to be fixed so
that for an inactive task it returns a pointer to inactive_task_frame.bp
rather than the value of inactive_task_frame.bp itself.  Will fix it.

-- 
Josh