linux-kernel - Re: [PATCH v2 12/39] x86/ibt,ftrace: Search for __fentry_

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Message-ID: <202202241654.1D43F008@keescook>
Date:   Thu, 24 Feb 2022 16:55:08 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     x86@...nel.org, joao@...rdrivepizza.com, hjl.tools@...il.com,
        jpoimboe@...hat.com, andrew.cooper3@...rix.com,
        linux-kernel@...r.kernel.org, ndesaulniers@...gle.com,
        samitolvanen@...gle.com, mark.rutland@....com,
        alyssa.milburn@...el.com, mbenes@...e.cz, rostedt@...dmis.org,
        mhiramat@...nel.org, alexei.starovoitov@...il.com
Subject: Re: [PATCH v2 12/39] x86/ibt,ftrace: Search for __fentry__ location

On Thu, Feb 24, 2022 at 03:51:50PM +0100, Peter Zijlstra wrote:
> Have ftrace_location() search the symbol for the __fentry__ location
> when it isn't at func+0 and use this for {,un}register_ftrace_direct().
> 
> This avoids a whole bunch of assumptions about __fentry__ being at
> func+0.
> 
> Suggested-by: Steven Rostedt <rostedt@...dmis.org>
> Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>

Cool. This should help with anything using __fentry__ tricks (i.e.
future CFI...), yes?

Reviewed-by: Kees Cook <keescook@...omium.org>

-- 
Kees Cook