Re: [PATCH 0/5] x86: CVE-2017-5715, aka Spectre

On Sun, 2018-01-07 at 16:36 -0700, Jeff Law wrote: > > My fundamental problem with this patchkit is that it is 100% x86/x86_64 > specific. > > ISTM we want a target independent mechanism (ie, new standard patterns, > options, etc) then an x86/x86_64 implementation using that target > independent

Re: [PATCH 3/5] x86: Add -mfunction-return=

On Mon, 2018-01-08 at 03:59 -0800, H.J. Lu wrote: > On Mon, Jan 8, 2018 at 1:56 AM, Martin Liška wrote: > > > > On 01/07/2018 11:59 PM, H.J. Lu wrote: > > > > > > Function return thunk is the same as memory thunk for -mindirect-branch= > > > where the return address is at the

Re: [PATCH 1/5] x86: Add -mindirect-branch=

On Mon, 2018-01-08 at 13:32 -0800, H.J. Lu wrote: > On Mon, Jan 8, 2018 at 8:46 AM, Andi Kleen wrote: > > > > "H.J. Lu" writes: > > > > > > > > > > > > > > > Talking about PIC thunks, those have I believe . character in their > > > > symbols, > > >

Re: [PATCH 0/5] x86: CVE-2017-5715, aka Spectre

On Mon, 2018-01-08 at 09:27 +0100, Florian Weimer wrote: > * H. J. Lu: > > > > > This set of patches for GCC 8 mitigates variant #2 of the > > speculative execution vulnerabilities on x86 processors identified > > by CVE-2017-5715, aka Spectre.  They convert indirect branches to > > call and

Re: [PATCH 2/5] x86: Add -mindirect-branch-loop=

On Mon, 2018-01-08 at 09:20 +0100, Florian Weimer wrote: > * H. J. Lu: > > > Add -mindirect-branch-loop= option to control loop filler in call and > > return thunks generated by -mindirect-branch=.  'lfence' uses "lfence" > > as loop filler.  'pause' uses "pause" as loop filler.  'nop' uses "nop"

Re: [PATCH 1/5] x86: Add -mindirect-branch=

On Mon, 2018-01-08 at 14:27 -0800, Andi Kleen wrote: > On Mon, Jan 08, 2018 at 09:35:26PM +0000, David Woodhouse wrote: > > On Mon, 2018-01-08 at 13:32 -0800, H.J. Lu wrote: > > > On Mon, Jan 8, 2018 at 8:46 AM, Andi Kleen <a...@linux.intel.com> wrote: > >

Re: [PATCH 0/5] x86: CVE-2017-5715, aka Spectre

On Sun, 2018-01-14 at 14:03 -0800, H.J. Lu wrote: > > > And *that* was the point at which I asked HJ to just use the proper > > bloody register names :) > > Please let me know if I should make the change to ax,..., r8,..r15. This is what I'm building my compiler with now, to make that change:

Re: [PATCH 0/5] x86: CVE-2017-5715, aka Spectre

On Sun, 2018-01-14 at 15:02 -0800, Linus Torvalds wrote: > On Sun, Jan 14, 2018 at 2:39 PM, David Woodhouse <dw...@infradead.org > > wrote: > > > > I'm not convinced we want to do this, but I'll defer to Linus. > > Well, I guess we have no choice, if gcc en

[PATCH] x86/retpoline: Switch thunk names to match final GCC patches

At the last minute, they were switched from __x86_indirect_thunk_rax to __x86_indirect_thunk_ax without the 'r' or 'e' on the register name. Except for the _r[89..] versions, obviously. This is not entirely an improvement, IMO. Reluctantly-signed-off-by: David Woodhouse <d...@amazon.co.uk>

Re: [PATCH 0/5] x86: CVE-2017-5715, aka Spectre

On Sun, 2018-01-14 at 13:07 -0800, Linus Torvalds wrote: > On Sun, Jan 14, 2018 at 1:02 PM, David Woodhouse <dw...@infradead.org> wrote: > > > > Review on the GCC patches has led to a request that the thunk symbols > > be changed from e.g. __x86_indirect_thunk_rax to

Re: [PATCH 1/5] x86: Add -mindirect-branch=

On Sat, 2018-01-13 at 09:17 -0700, Jeff Law wrote: > On 01/13/2018 02:03 AM, David Woodhouse wrote: > > On Fri, 2018-01-12 at 10:57 -0700, Jeff Law wrote: > > As things stand with retpoline in the kernel, userspace  processes > > aren't protected from each other. The a

Re: [PATCH 2/5] x86: Add -mindirect-branch-loop=

On Sat, 2018-01-13 at 03:11 +, Kumar, Venkataramanan wrote: > > > My original patch uses "lfence".  I was asked to use "pause": > >  > > https://gcc.gnu.org/ml/gcc-patches/2018-01/msg00969.html > > If everyone is ok, my suggestion is to use  "lfence" as the default > loop filler for

Re: [PATCH 3/4] x86: Add -mindirect-branch-register

On Sat, 2018-01-13 at 08:46 -0800, H.J. Lu wrote: > > >> +@item -mindirect-branch-register > >> +@opindex -mindirect-branch-register > >> +Force indirect call and jump via register. > > > > Again I think this option needs better documentation.  It is not quite > > clear to me why > > it is

Re: [PATCH 0/5] x86: CVE-2017-5715, aka Spectre

On Sun, 2018-01-14 at 21:21 +0100, Uros Bizjak wrote: > A quick look through latest x86/pti update [1] shows: > > +#ifdef CONFIG_X86_32 > +#define INDIRECT_THUNK(reg) extern asmlinkage void > __x86_indirect_thunk_e ## reg(void); > +#else > +#define INDIRECT_THUNK(reg) extern asmlinkage void >

Re: [PATCH 1/5] x86: Add -mindirect-branch=

On Sun, 2018-01-14 at 12:06 +0100, Jan Hubicka wrote: > > Yes, according to my understanding we want both pause and lefence by default > (it is expensive anyway) + command line option to control which one to use? > > Probably thus the first patch should default to both. In the kernel we're

Re: [PATCH 0/5] x86: CVE-2017-5715, aka Spectre

On Sun, 2018-01-14 at 21:52 +0100, Uros Bizjak wrote: > On Sun, Jan 14, 2018 at 9:34 PM, David Woodhouse <dw...@infradead.org> wrote: > > But sure, right now it isn't that might of a difference for me; my > > implementation has changed since I made that reqeust. I have no >

Re: [PATCH 0/5] x86: CVE-2017-5715, aka Spectre

On Sun, 2018-01-14 at 13:07 -0800, Linus Torvalds wrote: > On Sun, Jan 14, 2018 at 1:02 PM, David Woodhouse <dw...@infradead.org> wrote: > > Review on the GCC patches has led to a request that the thunk symbols > > be changed from e.g. __x86_indirect_thunk_rax to > &

Re: [PATCH 0/5] x86: CVE-2017-5715, aka Spectre

e _ASM_AX etc. macros in *addition* to the bare "ax" that goes in the symbol names. I'm not convinced we want to do this, but I'll defer to Linus. From 755f50731a99b0ce0890e478e6a2d6ebd647da15 Mon Sep 17 00:00:00 2001 From: David Woodhouse <d...@amazon.co.uk> Date: Sun, 14 Jan 2018 2

Re: [PATCH 0/5] x86: CVE-2017-5715, aka Spectre

On Sun, 2018-01-14 at 21:52 +0100, Uros Bizjak wrote: > > Well, you did say that these are strange times ;) > > From the user perspective, it would be more convenient to use the > thunk names that are the same for 32bit and 64bit targets. If we > ignore this fact, the difference is only a couple

Re: [PATCH 0/5] x86: CVE-2017-5715, aka Spectre

On Thu, 2018-01-11 at 22:17 +0100, Florian Weimer wrote: > * David Woodhouse: > > > > > On Sun, 2018-01-07 at 16:36 -0700, Jeff Law wrote: > > > > > > > > > My fundamental problem with this patchkit is that it is 100% x86/x86_64 > > > sp

Re: [PATCH 1/5] x86: Add -mindirect-branch=

On Fri, 2018-01-12 at 10:57 -0700, Jeff Law wrote: > > WRT text relocs, yea that sucks, but if we're going to have user space > mitigations, then we're likely going to need those relocs so that the > thunks can be patched out.  I'm actually hoping we're not going to need > user space mitigations

Re: [PATCH 0/5] x86: CVE-2017-5715, aka Spectre

On Sat, 2018-01-13 at 13:01 +0100, Florian Weimer wrote: > * David Woodhouse: > > > > > > > > > Do you assume that you will eventually apply run-time patching to > > > thunks (in case they aren't needed)? > > "eventually"? We've b

Re: [PATCH 2/5] x86: Add -mindirect-branch-loop=

On Sat, 2018-01-13 at 03:11 +, Kumar, Venkataramanan wrote: > > > My original patch uses "lfence".  I was asked to use "pause": > >  > > https://gcc.gnu.org/ml/gcc-patches/2018-01/msg00969.html > > If everyone is ok, my suggestion is to use  "lfence" as the default > loop filler for