Re: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f

On Thu, Feb 08, 2018 at 09:31:46PM +0100, Borislav Petkov wrote: > On Thu, Feb 08, 2018 at 08:44:06PM +0100, Peter Zijlstra wrote: > > + * Since various instruction decoders/specs disagree on the encoding of > > + * UD0/UD1, >^ > > Does that comma mean the sentence continues

Re: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f

On Thu, Feb 08, 2018 at 09:31:46PM +0100, Borislav Petkov wrote: > On Thu, Feb 08, 2018 at 08:44:06PM +0100, Peter Zijlstra wrote: > > + * Since various instruction decoders/specs disagree on the encoding of > > + * UD0/UD1, >^ > > Does that comma mean the sentence continues

Re: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f

On Thu, Feb 08, 2018 at 08:44:06PM +0100, Peter Zijlstra wrote: > /* > - * Since some emulators terminate on UD2, we cannot use it for WARN. > - * Since various instruction decoders disagree on the length of UD1, > - * we cannot use it either. So use UD0 for WARN. > + * Despite that some

Re: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f

On Thu, Feb 08, 2018 at 08:44:06PM +0100, Peter Zijlstra wrote: > /* > - * Since some emulators terminate on UD2, we cannot use it for WARN. > - * Since various instruction decoders disagree on the length of UD1, > - * we cannot use it either. So use UD0 for WARN. > + * Despite that some

Re: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f

On Thu, Feb 8, 2018 at 11:44 AM, Peter Zijlstra wrote: > > OK, here's the patch.. It leaves the UD0 in traps.c such that people > could recompile their kernel with a simple change. Ack, that seems about the best we can do. Linus

Re: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f

On Thu, Feb 8, 2018 at 11:44 AM, Peter Zijlstra wrote: > > OK, here's the patch.. It leaves the UD0 in traps.c such that people > could recompile their kernel with a simple change. Ack, that seems about the best we can do. Linus

Re: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f

On Thu, Feb 08, 2018 at 10:15:30AM -0800, Linus Torvalds wrote: > On Thu, Feb 8, 2018 at 10:03 AM, Peter Zijlstra wrote: > > > > But yes, for our purposes UD2 is perfectly fine too, it will just mess > > up the people doing bringup and the like. > > Oh, we'll inconvenience

Re: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f

On Thu, Feb 08, 2018 at 10:15:30AM -0800, Linus Torvalds wrote: > On Thu, Feb 8, 2018 at 10:03 AM, Peter Zijlstra wrote: > > > > But yes, for our purposes UD2 is perfectly fine too, it will just mess > > up the people doing bringup and the like. > > Oh, we'll inconvenience people inside Intel? >

Re: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f

On Thu, Feb 8, 2018 at 10:03 AM, Peter Zijlstra wrote: > > But yes, for our purposes UD2 is perfectly fine too, it will just mess > up the people doing bringup and the like. Oh, we'll inconvenience people inside Intel? The same people who changed and screwed up the

Re: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f

On Thu, Feb 8, 2018 at 10:03 AM, Peter Zijlstra wrote: > > But yes, for our purposes UD2 is perfectly fine too, it will just mess > up the people doing bringup and the like. Oh, we'll inconvenience people inside Intel? The same people who changed and screwed up the definition of UD0 just a

Re: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f

On Thu, Feb 08, 2018 at 09:27:56AM -0800, Linus Torvalds wrote: > On Thu, Feb 8, 2018 at 1:13 AM, Peter Zijlstra wrote: > > > > _The_ problem is that new binutils cannot sanely decode any function > > that has a WARN in (this very much includes perf annotate): > > Ugh. > >

Re: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f

On Thu, Feb 08, 2018 at 09:27:56AM -0800, Linus Torvalds wrote: > On Thu, Feb 8, 2018 at 1:13 AM, Peter Zijlstra wrote: > > > > _The_ problem is that new binutils cannot sanely decode any function > > that has a WARN in (this very much includes perf annotate): > > Ugh. > > Is there any reason

Re: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f

On Thu, Feb 8, 2018 at 1:13 AM, Peter Zijlstra wrote: > > _The_ problem is that new binutils cannot sanely decode any function > that has a WARN in (this very much includes perf annotate): Ugh. Is there any reason why we don't just use UD2 and avoid this whole issue? Do

Re: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f

On Thu, Feb 8, 2018 at 1:13 AM, Peter Zijlstra wrote: > > _The_ problem is that new binutils cannot sanely decode any function > that has a WARN in (this very much includes perf annotate): Ugh. Is there any reason why we don't just use UD2 and avoid this whole issue? Do we even *do* anything

Re: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f

On Thu, Feb 08, 2018 at 09:47:53AM +, David Laight wrote: > From: Peter Zijlstra > > I went through the register opcodes and matched it against the ModR/M > > encoding, and the best option I've found so far is using 0xd6 as the > > next byte. > > Wouldn't 0xc3 work as well. > A retq is

Re: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f

On Thu, Feb 08, 2018 at 09:47:53AM +, David Laight wrote: > From: Peter Zijlstra > > I went through the register opcodes and matched it against the ModR/M > > encoding, and the best option I've found so far is using 0xd6 as the > > next byte. > > Wouldn't 0xc3 work as well. > A retq is

RE: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f

From: Peter Zijlstra > Sent: 08 February 2018 09:13 ... > > > Yeah, note says UD0 didn't eat a ModRM byte on old CPUs. But then that > > > changed too. Fun stuff changing insn encoding underway. > > > > > > So if we opt for adding a ModRM byte, could a 0x90 NOP work so that it > > > doesn't shit

RE: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f

From: Peter Zijlstra > Sent: 08 February 2018 09:13 ... > > > Yeah, note says UD0 didn't eat a ModRM byte on old CPUs. But then that > > > changed too. Fun stuff changing insn encoding underway. > > > > > > So if we opt for adding a ModRM byte, could a 0x90 NOP work so that it > > > doesn't shit

Re: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f

On Thu, Feb 08, 2018 at 10:13:02AM +0100, Peter Zijlstra wrote: > diff --git a/arch/x86/include/asm/bug.h b/arch/x86/include/asm/bug.h > index 34d99af43994..f0d5b4a1512d 100644 > --- a/arch/x86/include/asm/bug.h > +++ b/arch/x86/include/asm/bug.h > @@ -12,16 +12,21 @@ > * (binutils knows about

Re: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f

On Thu, Feb 08, 2018 at 10:13:02AM +0100, Peter Zijlstra wrote: > diff --git a/arch/x86/include/asm/bug.h b/arch/x86/include/asm/bug.h > index 34d99af43994..f0d5b4a1512d 100644 > --- a/arch/x86/include/asm/bug.h > +++ b/arch/x86/include/asm/bug.h > @@ -12,16 +12,21 @@ > * (binutils knows about

Re: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f

On Thu, Feb 08, 2018 at 10:13:02AM +0100, Peter Zijlstra wrote: > _The_ problem is that new binutils cannot sanely decode any function > that has a WARN in (this very much includes perf annotate): > new: > > 16a0 : > 16a0: 48 89 f2mov%rsi,%rdx >

Re: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f

On Thu, Feb 08, 2018 at 10:13:02AM +0100, Peter Zijlstra wrote: > _The_ problem is that new binutils cannot sanely decode any function > that has a WARN in (this very much includes perf annotate): > new: > > 16a0 : > 16a0: 48 89 f2mov%rsi,%rdx >

Re: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f

On Wed, Feb 07, 2018 at 11:43:37AM -0800, Linus Torvalds wrote: > On Wed, Feb 7, 2018 at 11:28 AM, Borislav Petkov wrote: > > On Wed, Feb 07, 2018 at 08:14:51PM +0100, Peter Zijlstra wrote: > >> Then someone went and wrecked it. > > > > Yeah, note says UD0 didn't eat a ModRM byte

Re: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f

On Wed, Feb 07, 2018 at 11:43:37AM -0800, Linus Torvalds wrote: > On Wed, Feb 7, 2018 at 11:28 AM, Borislav Petkov wrote: > > On Wed, Feb 07, 2018 at 08:14:51PM +0100, Peter Zijlstra wrote: > >> Then someone went and wrecked it. > > > > Yeah, note says UD0 didn't eat a ModRM byte on old CPUs. But

Re: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f

On Wed, Feb 07, 2018 at 11:43:37AM -0800, Linus Torvalds wrote: > We could just also decide that the only thing that the modrm bytes of > UD0 actually *affect* is how the CPU might act for a page-crossing > instruction. > > Because I think that's the only semantic difference: if it's a >

Re: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f

On Wed, Feb 07, 2018 at 11:43:37AM -0800, Linus Torvalds wrote: > We could just also decide that the only thing that the modrm bytes of > UD0 actually *affect* is how the CPU might act for a page-crossing > instruction. > > Because I think that's the only semantic difference: if it's a >

Re: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f

On Wed, Feb 7, 2018 at 11:28 AM, Borislav Petkov wrote: > On Wed, Feb 07, 2018 at 08:14:51PM +0100, Peter Zijlstra wrote: >> Then someone went and wrecked it. > > Yeah, note says UD0 didn't eat a ModRM byte on old CPUs. But then that > changed too. Fun stuff changing insn encoding

Re: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f

On Wed, Feb 7, 2018 at 11:28 AM, Borislav Petkov wrote: > On Wed, Feb 07, 2018 at 08:14:51PM +0100, Peter Zijlstra wrote: >> Then someone went and wrecked it. > > Yeah, note says UD0 didn't eat a ModRM byte on old CPUs. But then that > changed too. Fun stuff changing insn encoding underway. > >

Re: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f

On Wed, Feb 07, 2018 at 08:14:51PM +0100, Peter Zijlstra wrote: > Then someone went and wrecked it. Yeah, note says UD0 didn't eat a ModRM byte on old CPUs. But then that changed too. Fun stuff changing insn encoding underway. So if we opt for adding a ModRM byte, could a 0x90 NOP work so that

Re: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f

On Wed, Feb 07, 2018 at 08:14:51PM +0100, Peter Zijlstra wrote: > Then someone went and wrecked it. Yeah, note says UD0 didn't eat a ModRM byte on old CPUs. But then that changed too. Fun stuff changing insn encoding underway. So if we opt for adding a ModRM byte, could a 0x90 NOP work so that

Re: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f

On Wed, Feb 07, 2018 at 11:03:42AM -0800, Linus Torvalds wrote: > On Wed, Feb 7, 2018 at 10:49 AM, Peter Zijlstra wrote: > > > > Right, we picked UD0 because we _thought_ everybody agreed it being 2 > > bytes, just like UD2. This is now not true anymore? > > Both UD0 and

Re: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f

On Wed, Feb 07, 2018 at 11:03:42AM -0800, Linus Torvalds wrote: > On Wed, Feb 7, 2018 at 10:49 AM, Peter Zijlstra wrote: > > > > Right, we picked UD0 because we _thought_ everybody agreed it being 2 > > bytes, just like UD2. This is now not true anymore? > > Both UD0 and UD1 are documented to

Re: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f

On Wed, Feb 07, 2018 at 08:06:51PM +0100, Peter Zijlstra wrote: > On Wed, Feb 07, 2018 at 11:01:29AM -0800, Linus Torvalds wrote: > > On Wed, Feb 7, 2018 at 10:38 AM, Randy Dunlap wrote: > > > On 02/07/2018 10:13 AM, Linus Torvalds wrote: > > >> > > >> That said, intel only

Re: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f

On Wed, Feb 07, 2018 at 08:06:51PM +0100, Peter Zijlstra wrote: > On Wed, Feb 07, 2018 at 11:01:29AM -0800, Linus Torvalds wrote: > > On Wed, Feb 7, 2018 at 10:38 AM, Randy Dunlap wrote: > > > On 02/07/2018 10:13 AM, Linus Torvalds wrote: > > >> > > >> That said, intel only _documents_ UD2 (0f

Re: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f

On Wed, Feb 07, 2018 at 11:01:29AM -0800, Linus Torvalds wrote: > On Wed, Feb 7, 2018 at 10:38 AM, Randy Dunlap wrote: > > On 02/07/2018 10:13 AM, Linus Torvalds wrote: > >> > >> That said, intel only _documents_ UD2 (0f 0b). > > > > Intel Order Number: 325383-064US,

Re: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f

On Wed, Feb 07, 2018 at 11:01:29AM -0800, Linus Torvalds wrote: > On Wed, Feb 7, 2018 at 10:38 AM, Randy Dunlap wrote: > > On 02/07/2018 10:13 AM, Linus Torvalds wrote: > >> > >> That said, intel only _documents_ UD2 (0f 0b). > > > > Intel Order Number: 325383-064US, October 2017, documents UD0,

Re: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f

On Wed, Feb 7, 2018 at 10:49 AM, Peter Zijlstra wrote: > > Right, we picked UD0 because we _thought_ everybody agreed it being 2 > bytes, just like UD2. This is now not true anymore? Both UD0 and UD1 are documented to have modrm in the latest Intel SDM I can find (Order

Re: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f

On Wed, Feb 7, 2018 at 10:49 AM, Peter Zijlstra wrote: > > Right, we picked UD0 because we _thought_ everybody agreed it being 2 > bytes, just like UD2. This is now not true anymore? Both UD0 and UD1 are documented to have modrm in the latest Intel SDM I can find (Order number 325462-065US,

Re: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f

On Wed, Feb 7, 2018 at 10:38 AM, Randy Dunlap wrote: > On 02/07/2018 10:13 AM, Linus Torvalds wrote: >> >> That said, intel only _documents_ UD2 (0f 0b). > > Intel Order Number: 325383-064US, October 2017, documents UD0, UD1, and UD2. > Section A.2.5, Table A-1, says: Ahh,

Re: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f

On Wed, Feb 7, 2018 at 10:38 AM, Randy Dunlap wrote: > On 02/07/2018 10:13 AM, Linus Torvalds wrote: >> >> That said, intel only _documents_ UD2 (0f 0b). > > Intel Order Number: 325383-064US, October 2017, documents UD0, UD1, and UD2. > Section A.2.5, Table A-1, says: Ahh, I had an older

Re: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f

On Wed, Feb 07, 2018 at 07:35:43PM +0100, Borislav Petkov wrote: > On Wed, Feb 07, 2018 at 10:13:35AM -0800, Linus Torvalds wrote: > > Adding more people for this funky warning from the kbuild robot. > > > > Something is confused. UD0 is 0f ff, the bytes after that shouldn't > > matter. But I

Re: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f

On Wed, Feb 07, 2018 at 07:35:43PM +0100, Borislav Petkov wrote: > On Wed, Feb 07, 2018 at 10:13:35AM -0800, Linus Torvalds wrote: > > Adding more people for this funky warning from the kbuild robot. > > > > Something is confused. UD0 is 0f ff, the bytes after that shouldn't > > matter. But I

Re: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f

On 02/07/2018 10:13 AM, Linus Torvalds wrote: > Adding more people for this funky warning from the kbuild robot. > > Something is confused. UD0 is 0f ff, the bytes after that shouldn't > matter. But I guess they can be interpreted as modrm bytes, and > somebody started doing that. > > That said,

Re: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f

On 02/07/2018 10:13 AM, Linus Torvalds wrote: > Adding more people for this funky warning from the kbuild robot. > > Something is confused. UD0 is 0f ff, the bytes after that shouldn't > matter. But I guess they can be interpreted as modrm bytes, and > somebody started doing that. > > That said,

Re: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f

On Wed, Feb 07, 2018 at 10:13:35AM -0800, Linus Torvalds wrote: > Adding more people for this funky warning from the kbuild robot. > > Something is confused. UD0 is 0f ff, the bytes after that shouldn't > matter. But I guess they can be interpreted as modrm bytes, and > somebody started doing

Re: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f

On Wed, Feb 07, 2018 at 10:13:35AM -0800, Linus Torvalds wrote: > Adding more people for this funky warning from the kbuild robot. > > Something is confused. UD0 is 0f ff, the bytes after that shouldn't > matter. But I guess they can be interpreted as modrm bytes, and > somebody started doing

Re: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f

Adding more people for this funky warning from the kbuild robot. Something is confused. UD0 is 0f ff, the bytes after that shouldn't matter. But I guess they can be interpreted as modrm bytes, and somebody started doing that. That said, intel only _documents_ UD2 (0f 0b). Maybe we should avoid

Re: [linus:master] BUILD REGRESSION a2e5790d841658485d642196dbb0927303d6c22f

Adding more people for this funky warning from the kbuild robot. Something is confused. UD0 is 0f ff, the bytes after that shouldn't matter. But I guess they can be interpreted as modrm bytes, and somebody started doing that. That said, intel only _documents_ UD2 (0f 0b). Maybe we should avoid