linux-kernel - Re: [PATCH 3/4] x86/intel lbr: down with test_thread_flag(TIF

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <20160420112152.GA3408@twins.programming.kicks-ass.net>
Date:	Wed, 20 Apr 2016 13:21:52 +0200
From:	Peter Zijlstra <peterz@...radead.org>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Dmitry Safonov <dsafonov@...tuozzo.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>, X86 ML <x86@...nel.org>,
	Robert Richter <rric@...nel.org>, oprofile-list@...ts.sf.net,
	Dmitry Safonov <0x7f454c46@...il.com>
Subject: Re: [PATCH 3/4] x86/intel lbr: down with test_thread_flag(TIF_IA32)

On Thu, Apr 14, 2016 at 12:29:12PM -0700, Andy Lutomirski wrote:
> On Thu, Apr 14, 2016 at 11:10 AM, Dmitry Safonov <dsafonov@...tuozzo.com> wrote:

> > @@ -724,7 +727,7 @@ static int branch_type(unsigned long from, unsigned long to, int abort)
> >          * on 64-bit systems running 32-bit apps
> >          */
> >  #ifdef CONFIG_X86_64
> > -       is64 = kernel_ip((unsigned long)addr) || !test_thread_flag(TIF_IA32);
> > +       is64 = kernel_ip((unsigned long)addr) || user_64bit_mode(regs);
> 
> Peterz, looking at this some more, would it make sense to pass
> user_regs and interrupt_regs (or whatever we'd call it) all the way
> through to here?

Urgh; again, wtf wasn't I Cc'ed to these patches?

And not sure; if we never need the user regs, calling
perf_get_user_regs() to set all that up seems like a massive waste of
cycles.