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Date:   Wed, 6 May 2020 17:42:53 +0200
From:   Peter Zijlstra <peterz@infradead.org>
To:     Brian Gerst <brgerst@gmail.com>
Cc:     Thomas Gleixner <tglx@linutronix.de>,
        LKML <linux-kernel@vger.kernel.org>,
        the arch/x86 maintainers <x86@kernel.org>,
        "Paul E. McKenney" <paulmck@kernel.org>,
        Andy Lutomirski <luto@kernel.org>,
        Alexandre Chartre <alexandre.chartre@oracle.com>,
        Frederic Weisbecker <frederic@kernel.org>,
        Paolo Bonzini <pbonzini@redhat.com>,
        Sean Christopherson <sean.j.christopherson@intel.com>,
        Masami Hiramatsu <mhiramat@kernel.org>,
        Petr Mladek <pmladek@suse.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Joel Fernandes <joel@joelfernandes.org>,
        Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        Juergen Gross <jgross@suse.com>,
        Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
        Josh Poimboeuf <jpoimboe@redhat.com>,
        Will Deacon <will@kernel.org>
Subject: Re: [patch V4 part 1 19/36] x86/entry: Exclude low level entry code
 from sanitizing
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On Tue, May 05, 2020 at 04:39:01PM -0400, Brian Gerst wrote:
> On Tue, May 5, 2020 at 10:13 AM Thomas Gleixner <tglx@linutronix.de> wrote:
> >
> > The sanitizers are not really applicable to the fragile low level entry
> > code. code. Entry code needs to carefully setup a normal 'runtime'
> > environment.
> >
> > Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
> > Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
> > ---
> >  arch/x86/entry/Makefile |    8 ++++++++
> >  1 file changed, 8 insertions(+)
> >
> > --- a/arch/x86/entry/Makefile
> > +++ b/arch/x86/entry/Makefile
> > @@ -3,6 +3,14 @@
> >  # Makefile for the x86 low level entry code
> >  #
> >
> > +KASAN_SANITIZE := n
> > +UBSAN_SANITIZE := n
> > +KCOV_INSTRUMENT := n
> > +
> > +CFLAGS_REMOVE_common.o = $(CC_FLAGS_FTRACE) -fstack-protector -fstack-protector-strong
> > +CFLAGS_REMOVE_syscall_32.o = $(CC_FLAGS_FTRACE) -fstack-protector -fstack-protector-strong
> > +CFLAGS_REMOVE_syscall_64.o = $(CC_FLAGS_FTRACE) -fstack-protector -fstack-protector-strong
> 
> Is this necessary for syscall_*.o?  They just contain the syscall
> tables (ie. data).

Proabaly not, but I just made sure to kill everything, less chance an
accident happens.