linux-kernel - Re: [RFC][PATCH] x86/mm: Sync all vmalloc mappings before text

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Date:   Wed, 29 Apr 2020 18:20:26 +0200
From:   Joerg Roedel <jroedel@...e.de>
To:     Steven Rostedt <rostedt@...dmis.org>
Cc:     LKML <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Peter Zijlstra <peterz@...radead.org>,
        Borislav Petkov <bp@...en8.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Shile Zhang <shile.zhang@...ux.alibaba.com>,
        Andy Lutomirski <luto@...capital.net>,
        "Rafael J. Wysocki" <rafael.j.wysocki@...el.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Tzvetomir Stoyanov <tz.stoyanov@...il.com>,
        Mathieu Desnoyers <mathieu.desnoyers@...icios.com>
Subject: Re: [RFC][PATCH] x86/mm: Sync all vmalloc mappings before text_poke()

On Wed, Apr 29, 2020 at 06:17:47PM +0200, Joerg Roedel wrote:
> On Wed, Apr 29, 2020 at 10:07:31AM -0400, Steven Rostedt wrote:
> > Talking with Mathieu about this on IRC, he pointed out that my code does
> > have a vzalloc() that is called:
> > 
> > in trace_pid_write()
> > 
> > 	pid_list->pids = vzalloc((pid_list->pid_max + 7) >> 3);
> > 
> > This is done when -P1,2 is on the trace-cmd command line.
> 
> And that buffer is written to at any function entry?

What I meant to say, is it possible that the page-fault handler does not
complete because at its beginning it calls into trace-code and faults
again on the same address?

Regards,

	Joerg