On Thu, May 14, 2020 at 10:40:44AM +0200, Arnd Bergmann wrote:
> On Thu, May 14, 2020 at 7:22 AM Arvind Sankar wrote:
> > On Wed, May 13, 2020 at 09:52:07PM -0700, Linus Torvalds wrote:
> > > On Wed, May 13, 2020, 20:50 Andy Lutomirski wrote:
> > The gcc docs [1,2] at least don't inspire much con
Kalle Valo [13.05.2020 17:31]:
> Great, so it's not a problem due to my setup.
I see the same thing on two machines, using a self-compiled gcc 10.1.0.
Glad to hear it's not just me. Switched back to 9.3.0 for the time being.
--
Hilsen Harald
On Thu, May 14, 2020 at 7:22 AM Arvind Sankar wrote:
> On Wed, May 13, 2020 at 09:52:07PM -0700, Linus Torvalds wrote:
> > On Wed, May 13, 2020, 20:50 Andy Lutomirski wrote:
> The gcc docs [1,2] at least don't inspire much confidence that this will
> continue working with plain asm("") though:
>
From: Linus Torvalds
> Sent: 14 May 2020 03:20
> On Wed, May 13, 2020 at 5:51 PM Nick Desaulniers
> wrote:
> >
> > Are you sure LTO treats empty asm statements differently than full
> > memory barriers in regards to preventing tail calls?
>
> It had better.
>
> At link-time, there is nothing lef
On Wed, May 13, 2020 at 09:52:07PM -0700, Linus Torvalds wrote:
> On Wed, May 13, 2020, 20:50 Andy Lutomirski wrote:
>
> >
> > LTO isn’t a linker taking regular .o files full of regular machine
> > code and optimizing it. That’s nuts.
> >
>
> Yeah, you're right. I wear originally thinking just a
> On May 13, 2020, at 7:20 PM, Linus Torvalds
> wrote:
>
> On Wed, May 13, 2020 at 5:51 PM Nick Desaulniers
> wrote:
>>
>> Are you sure LTO treats empty asm statements differently than full
>> memory barriers in regards to preventing tail calls?
>
> It had better.
>
> At link-time, there is not
On Wed, May 13, 2020 at 5:51 PM Nick Desaulniers
wrote:
>
> Are you sure LTO treats empty asm statements differently than full
> memory barriers in regards to preventing tail calls?
It had better.
At link-time, there is nothing left of an empty asm statement. So by
the time the linker runs, it o
On Wed, May 13, 2020 at 5:11 PM Linus Torvalds
wrote:
>
> On Wed, May 13, 2020 at 4:36 PM Borislav Petkov wrote:
> >
> >
> > Looking at them, they do have an mb() too so how about this then
> > instead?
> >
> > #define prevent_tail_call_optimization()mb()
>
> Yeah, I think a full mb() is
On Wed, May 13, 2020 at 4:36 PM Borislav Petkov wrote:
>
>
> Looking at them, they do have an mb() too so how about this then
> instead?
>
> #define prevent_tail_call_optimization()mb()
Yeah, I think a full mb() is likely safe, because that's pretty much
always going to be a real instruct
On Wed, May 13, 2020 at 04:13:53PM -0700, Linus Torvalds wrote:
> The check itself doesn't seem worth it. If your worry is that an empty
> asm() can be optimized away, then don't use an empty asm!
gcc guys said we should use that since the first attempt using
__attribute__((optimize("-fno-stack-p
On Wed, May 13, 2020 at 3:20 PM Borislav Petkov wrote:
>
> Linus, shout if you'd prefer only the last three commits there:
>
> 950a37078aa0 x86/build: Use $(CONFIG_SHELL)
> f670269a42bf x86: Fix early boot crash on gcc-10, next try
> 73da86741e7f x86/build: Check whether the compiler is sane
Do w
On Wed, May 13, 2020 at 2:50 PM Arnd Bergmann wrote:
>
> Right, in particular since Linus started building with gcc-10 already and
> would likely soon run into that problem if he hasn't already ;-)
I don't happen to have stack canaries on the configs I actually boot,
so I didn't notice.
But yes,
On Thu, May 14, 2020 at 12:20:38AM +0200, Borislav Petkov wrote:
> On Wed, May 13, 2020 at 11:49:49PM +0200, Arnd Bergmann wrote:
> > Right, in particular since Linus started building with gcc-10 already and
> > would likely soon run into that problem if he hasn't already ;-)
>
> Oh noo, we don't
On Wed, May 13, 2020 at 11:49:49PM +0200, Arnd Bergmann wrote:
> Right, in particular since Linus started building with gcc-10 already and
> would likely soon run into that problem if he hasn't already ;-)
Oh noo, we don't want Linus' kernel broken. ;-)
We will send him the fix this weekend.
Loo
On Wed, May 13, 2020 at 11:41 PM Borislav Petkov wrote:
>
> On Wed, May 13, 2020 at 11:28:09PM +0200, Arnd Bergmann wrote:
> > I see the patch in linux-next but not in mainline. I suppose we want
> > it in v5.7 and backported to stable kernels so they can boot when
> > built with gcc-10?
>
> It is
On Wed, May 13, 2020 at 11:28:09PM +0200, Arnd Bergmann wrote:
> I see the patch in linux-next but not in mainline. I suppose we want
> it in v5.7 and backported to stable kernels so they can boot when
> built with gcc-10?
It is queued for 5.8. For a good reason, if you read the whole thread
Arvin
On Wed, May 13, 2020 at 5:48 PM Arvind Sankar wrote:
>
> On Wed, May 13, 2020 at 09:50:03AM +0300, Kalle Valo wrote:
> > And now I have a problem :) I first noticed that my x86 testbox is not
> > booting when I compile the kernel with GCC 10.1.0 from crosstool. I
> > didn't get any error messages
From: Arnd Bergmann
> Sent: 13 May 2020 17:00
> On Wed, May 13, 2020 at 5:31 PM Kalle Valo wrote:
...
> I investigated a little more: This does happen with 'defconfig'
> after all, in my first try I must have missed the '-smp 2' argument
> to qemu, and it ended up working correctly with just one C
On Wed, May 13, 2020 at 5:31 PM Kalle Valo wrote:
> Arnd Bergmann writes:
> > On Wed, May 13, 2020 at 2:57 PM Kalle Valo wrote:
> >>
> >> Arnd Bergmann writes:
> >>
> >> > If you share your .config, I can try reproducing with that as well.
> >> > Once there is a reproducer in qemu, it should be
On Wed, May 13, 2020 at 09:50:03AM +0300, Kalle Valo wrote:
> (trimming CC, changing title)
>
> Kalle Valo writes:
>
> > Kalle Valo writes:
> >
> >> Arnd Bergmann writes:
> >>
> >>> gcc-10 correctly points out a bug with a zero-length array in
> >>> struct ath10k_pci:
> >>>
> >>> drivers/net/w
Arnd Bergmann writes:
> On Wed, May 13, 2020 at 2:57 PM Kalle Valo wrote:
>>
>> Arnd Bergmann writes:
>>
>> > On Wed, May 13, 2020 at 8:50 AM Kalle Valo wrote:
>> >>
>> >> Kalle Valo writes:
>> >
>> > At least if it fails reproducibly, it's probably not too hard to drill
>> > down further. So
On Wed, May 13, 2020 at 2:57 PM Kalle Valo wrote:
>
> Arnd Bergmann writes:
>
> > On Wed, May 13, 2020 at 8:50 AM Kalle Valo wrote:
> >>
> >> Kalle Valo writes:
> >
> > At least if it fails reproducibly, it's probably not too hard to drill
> > down further. Some ideas:
> >
> > * I'd first try t
Arnd Bergmann writes:
> On Wed, May 13, 2020 at 8:50 AM Kalle Valo wrote:
>>
>> Kalle Valo writes:
>>
>> > This motivated me to switch to using GCC 10.x and I noticed that you had
>> > already upgraded crosstool so it was a trivial thing to do, awesome :)
>> >
>> > https://mirrors.edge.kernel.o
On Wed, May 13, 2020 at 8:50 AM Kalle Valo wrote:
>
> Kalle Valo writes:
>
> > This motivated me to switch to using GCC 10.x and I noticed that you had
> > already upgraded crosstool so it was a trivial thing to do, awesome :)
> >
> > https://mirrors.edge.kernel.org/pub/tools/crosstool/
>
> And n
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