linux-kernel - Re: [PATCH v7 03/14] x86/cet/ibt: Add IBT legacy code bitmap setup function

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Message-ID: <d699f179b7daefc6269174867a04868c9157ebe4.camel@intel.com>
Date:   Mon, 10 Jun 2019 09:03:04 -0700
From:   Yu-cheng Yu <yu-cheng.yu@...el.com>
To:     Andy Lutomirski <luto@...capital.net>,
        Dave Hansen <dave.hansen@...el.com>
Cc:     Peter Zijlstra <peterz@...radead.org>, x86@...nel.org,
        "H. Peter Anvin" <hpa@...or.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>, linux-kernel@...r.kernel.org,
        linux-doc@...r.kernel.org, linux-mm@...ck.org,
        linux-arch@...r.kernel.org, linux-api@...r.kernel.org,
        Arnd Bergmann <arnd@...db.de>,
        Balbir Singh <bsingharora@...il.com>,
        Borislav Petkov <bp@...en8.de>,
        Cyrill Gorcunov <gorcunov@...il.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        Eugene Syromiatnikov <esyr@...hat.com>,
        Florian Weimer <fweimer@...hat.com>,
        "H.J. Lu" <hjl.tools@...il.com>, Jann Horn <jannh@...gle.com>,
        Jonathan Corbet <corbet@....net>,
        Kees Cook <keescook@...omium.org>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Nadav Amit <nadav.amit@...il.com>,
        Oleg Nesterov <oleg@...hat.com>, Pavel Machek <pavel@....cz>,
        Randy Dunlap <rdunlap@...radead.org>,
        "Ravi V. Shankar" <ravi.v.shankar@...el.com>,
        Vedvyas Shanbhogue <vedvyas.shanbhogue@...el.com>,
        Dave Martin <Dave.Martin@....com>
Subject: Re: [PATCH v7 03/14] x86/cet/ibt: Add IBT legacy code bitmap setup
 function

On Fri, 2019-06-07 at 15:27 -0700, Andy Lutomirski wrote:
> > On Jun 7, 2019, at 2:09 PM, Dave Hansen <dave.hansen@...el.com> wrote:
> > 
> > On 6/7/19 1:06 PM, Yu-cheng Yu wrote:
> > > > Huh, how does glibc know about all possible past and future legacy code
> > > > in the application?
> > > 
> > > When dlopen() gets a legacy binary and the policy allows that, it will
> > > manage
> > > the bitmap:
> > > 
> > >  If a bitmap has not been created, create one.
> > >  Set bits for the legacy code being loaded.
> > 
> > I was thinking about code that doesn't go through GLIBC like JITs.
> 
> CRIU is another consideration: it would be rather annoying if CET programs
> can’t migrate between LA57 and normal machines.

When a machine migrates, does its applications' addresses change?
If no, then the bitmap should still work, right?

Yu-cheng