Date: Mon, 8 Jan 2018 12:03:09 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: David Woodhouse <dwmw2@infradead.org>
Cc: Andi Kleen <ak@linux.intel.com>, Paul Turner <pjt@google.com>,
        LKML <linux-kernel@vger.kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Greg Kroah-Hartman <gregkh@linux-foundation.org>,
        Tim Chen <tim.c.chen@linux.intel.com>,
        Dave Hansen <dave.hansen@intel.com>, tglx@linutronix.de,
        Kees Cook <keescook@google.com>,
        Rik van Riel <riel@redhat.com>,
        Andy Lutomirski <luto@amacapital.net>,
        Jiri Kosina <jikos@kernel.org>, gnomes@lxorguk.ukuu.org.uk
Subject: Re: [PATCH v6 01/10] x86/retpoline: Add initial retpoline support
Message-ID: <20180108110309.GH3040@hirez.programming.kicks-ass.net>
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On Mon, Jan 08, 2018 at 10:53:02AM +0000, David Woodhouse wrote:
> On Mon, 2018-01-08 at 11:45 +0100, Peter Zijlstra wrote:
> > 
> > 
> > Should this not use local name labels instead?
> > 
> > .macro RETPOLINE_JMP reg:req
> > ????????call????.Ldo_rop_\@
> > .Lspec_trap_\@:
> > ????????pause
> > ????????jmp .Lspec_trap_\@
> > .Ldo_rop_\@:
> > ????????mov?????\reg, (%_ASM_SP)
> > ????????ret
> > .endm
> 
> Not if you want to be able to use them twice in the same .S file.

Should work fine, the \@ expands to a per-instance magic thing IIRC. All
the PTI helpers do this too and that works just fine, see
arch/x86/entry/calling.h