On Wed, Apr 14, 2021 at 01:30:43PM +0200, Florian Weimer wrote:
> Is this discussion about better behavior (at least diagnostics) for
> existing applications, without any code changes? Or an alternative
> programming model?
Former.
> Does noavx512 acutally reduce the XSAVE size to AVX2 levels?
* Borislav Petkov:
> On Mon, Apr 12, 2021 at 10:30:23PM +, Bae, Chang Seok wrote:
>> On Mar 26, 2021, at 03:30, Borislav Petkov wrote:
>> > On Thu, Mar 25, 2021 at 09:56:53PM -0700, Andy Lutomirski wrote:
>> >> We really ought to have a SIGSIGFAIL signal that's sent, double-fault
>> >>
On Mon, Apr 12, 2021 at 10:30:23PM +, Bae, Chang Seok wrote:
> On Mar 26, 2021, at 03:30, Borislav Petkov wrote:
> > On Thu, Mar 25, 2021 at 09:56:53PM -0700, Andy Lutomirski wrote:
> >> We really ought to have a SIGSIGFAIL signal that's sent, double-fault
> >> style, when we fail to send a
On Mar 26, 2021, at 03:30, Borislav Petkov wrote:
> On Thu, Mar 25, 2021 at 09:56:53PM -0700, Andy Lutomirski wrote:
>> We really ought to have a SIGSIGFAIL signal that's sent, double-fault
>> style, when we fail to send a signal.
>
> Yeap, we should be able to tell userspace that we couldn't
On Thu, Mar 25, 2021 at 09:56:53PM -0700, Andy Lutomirski wrote:
> Nope. on_sig_stack() is a horrible kludge and won't work here. We
> could have something like __on_sig_stack() or sp_is_on_sig_stack() or
> something, though.
Yeah, see my other reply. Ack to either of those carved out helpers.
I forgot to mention why I cc'd all you fine Xen folk:
On Thu, Mar 25, 2021 at 11:13 AM Andy Lutomirski wrote:
>
> > } else if (IS_ENABLED(CONFIG_X86_32) &&
> >!onsigstack &&
> >regs->ss != __USER_DS &&
This bit here seems really dubious on Xen
On Thu, Mar 25, 2021 at 11:54 AM Borislav Petkov wrote:
>
> On Thu, Mar 25, 2021 at 11:13:12AM -0700, Andy Lutomirski wrote:
> > diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
> > index ea794a083c44..53781324a2d3 100644
> > --- a/arch/x86/kernel/signal.c
> > +++
On Thu, Mar 25, 2021 at 09:11:56PM +, Bae, Chang Seok wrote:
> But if sigaltstack()’ed with the SS_AUTODISARM flag, both on_sig_stack() and
> sas_ss_flags() return 0 [1]. Then, segfault always here. v5 had the exact
> issue before [2].
Ah, there's that SS_AUTODISARM check above it which I
On Mar 25, 2021, at 11:54, Borislav Petkov wrote:
> On Thu, Mar 25, 2021 at 11:13:12AM -0700, Andy Lutomirski wrote:
>> diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
>> index ea794a083c44..53781324a2d3 100644
>> --- a/arch/x86/kernel/signal.c
>> +++ b/arch/x86/kernel/signal.c
* Chang Seok via Libc-alpha Bae:
> On Mar 25, 2021, at 09:20, Borislav Petkov wrote:
>>
>> $ gcc tst-minsigstksz-2.c -DMY_MINSIGSTKSZ=3453 -o tst-minsigstksz-2
>> $ ./tst-minsigstksz-2
>> tst-minsigstksz-2: changed byte 50 bytes below configured stack
>>
>> Whoops.
>>
>> And the debug print
On Thu, Mar 25, 2021 at 11:13:12AM -0700, Andy Lutomirski wrote:
> diff --git a/arch/x86/kernel/signal.c b/arch/x86/kernel/signal.c
> index ea794a083c44..53781324a2d3 100644
> --- a/arch/x86/kernel/signal.c
> +++ b/arch/x86/kernel/signal.c
> @@ -237,7 +237,8 @@ get_sigframe(struct k_sigaction *ka,
On Mon, Mar 15, 2021 at 11:57 PM Chang S. Bae wrote:
>
> The kernel pushes context on to the userspace stack to prepare for the
> user's signal handler. When the user has supplied an alternate signal
> stack, via sigaltstack(2), it is easy for the kernel to verify that the
> stack size is
On Mar 25, 2021, at 09:20, Borislav Petkov wrote:
>
> $ gcc tst-minsigstksz-2.c -DMY_MINSIGSTKSZ=3453 -o tst-minsigstksz-2
> $ ./tst-minsigstksz-2
> tst-minsigstksz-2: changed byte 50 bytes below configured stack
>
> Whoops.
>
> And the debug print said:
>
> [ 5395.252884] signal:
On Tue, Mar 16, 2021 at 06:26:46PM +, Bae, Chang Seok wrote:
> I suspect the AVX-512 states not enabled there.
Ok, I found a machine which has AVX-512:
[0.00] x86/fpu: Supporting XSAVE feature 0x001: 'x87 floating point
registers'
[0.00] x86/fpu: Supporting XSAVE feature
On Mar 16, 2021, at 04:52, Borislav Petkov wrote:
> On Mon, Mar 15, 2021 at 11:52:14PM -0700, Chang S. Bae wrote:
>> @@ -272,7 +275,8 @@ get_sigframe(struct k_sigaction *ka, struct pt_regs
>> *regs, size_t frame_size,
>> * If we are on the alternate signal stack and would overflow it,
On Mon, Mar 15, 2021 at 11:52:14PM -0700, Chang S. Bae wrote:
> @@ -272,7 +275,8 @@ get_sigframe(struct k_sigaction *ka, struct pt_regs
> *regs, size_t frame_size,
>* If we are on the alternate signal stack and would overflow it, don't.
>* Return an always-bogus address instead so
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