linux-kernel - Re: [RFC][PATCH] objtool: STAC/CLAC validation

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Message-ID: <CAHk-=wiHS_Dk2A7NPWi1KWGf5Ds1Yha_LnsjrWSF84+TyG54xA@mail.gmail.com>
Date:   Fri, 22 Feb 2019 15:34:00 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     Peter Zijlstra <peterz@...radead.org>
Cc:     Thomas Gleixner <tglx@...utronix.de>,
        Julien Thierry <julien.thierry@....com>,
        "H. Peter Anvin" <hpa@...or.com>,
        Will Deacon <will.deacon@....com>,
        Andy Lutomirski <luto@...capital.net>,
        Ingo Molnar <mingo@...nel.org>,
        Linux List Kernel Mailing <linux-kernel@...r.kernel.org>,
        "linux-alpha@...r.kernel.org" <linux-arm-kernel@...ts.infradead.org>,
        Ingo Molnar <mingo@...hat.com>,
        Catalin Marinas <catalin.marinas@....com>,
        James Morse <james.morse@....com>, valentin.schneider@....com,
        Brian Gerst <brgerst@...il.com>,
        Josh Poimboeuf <jpoimboe@...hat.com>,
        Andrew Lutomirski <luto@...nel.org>,
        Borislav Petkov <bp@...en8.de>,
        Denys Vlasenko <dvlasenk@...hat.com>
Subject: Re: [RFC][PATCH] objtool: STAC/CLAC validation

On Fri, Feb 22, 2019 at 2:26 PM Peter Zijlstra <peterz@...radead.org> wrote:
>
> So find the below patch -- which spotted fail in ptrace.c
>
> It has an AC_SAFE(func) annotation which allows marking specific
> functions as safe to call. The patch includes 2 instances which were
> required to make arch/x86 'build':

Looks sane enough to me.

Can you make it do DF too while at it? I really think AC and DF are
the same in this context. If you call an arbitrary function with DF
set, things will very quickly go sideways (even if it might work in
practice as long as the function just doesn't do a memcpy or similar)

              Linus