linux-kernel - Re: [PATCH v1 tip/master 0/3] kprobes/x86: retpoline: Fix kprobes for retpoline

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Date:   Fri, 19 Jan 2018 00:36:52 +0900
From:   Masami Hiramatsu <mhiramat@...nel.org>
To:     Andi Kleen <ak@...ux.intel.com>
Cc:     mhiramat@...nel.org, Ingo Molnar <mingo@...nel.org>,
        David Woodhouse <dwmw@...zon.co.uk>,
        linux-kernel@...r.kernel.org,
        Greg Kroah-Hartman <gregkh@...ux-foundation.org>,
        Arjan van de Ven <arjan@...ux.intel.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Ananth N Mavinakayanahalli <ananth@...ux.vnet.ibm.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        "H . Peter Anvin" <hpa@...or.com>
Subject: Re: [PATCH v1 tip/master 0/3] kprobes/x86: retpoline: Fix kprobes
 for retpoline

On Thu, 18 Jan 2018 05:01:57 -0800
Andi Kleen <ak@...ux.intel.com> wrote:

> > Side effect: [1/3] will move __x86_indirect_thunk_* functions
> > in kernel text area. Of course those functions were in the
> > .text area, but placed in right after _etext. This just moves
> > it right before the _etext.
> 
> I assume you tested that with page table isolation on?
> 
> The thunks need to be accessible from the trampoline.

Yes, I've tested the kernel with CONFIG_PAGE_TABLE_ISOLATION=y.
As David pointed, maybe all those points are using JMP/CALL_NOSPEC macro directly?

Thanks,

> 
> -Andi


-- 
Masami Hiramatsu <mhiramat@...nel.org>