[PATCH v17 0/3] arm64: expose FAR_EL1 tag bits in siginfo

[Peter Collingbourne]

On Tue, Nov 17, 2020 at 10:17 AM Eric W. Biederman
<ebiederm at xmission.com> wrote:
>
> Peter Collingbourne <pcc at google.com> writes:
>
> > The kernel currently clears the tag bits (i.e. bits 56-63) in the fault
> > address exposed via siginfo.si_addr and sigcontext.fault_address. However,
> > the tag bits may be needed by tools in order to accurately diagnose
> > memory errors, such as HWASan [1] or future tools based on the Memory
> > Tagging Extension (MTE).
> >
> > We should not stop clearing these bits in the existing fault address
> > fields, because there may be existing userspace applications that are
> > expecting the tag bits to be cleared. Instead, introduce a flag in
> > sigaction.sa_flags, SA_EXPOSE_TAGBITS, and only expose the tag bits
> > there if the signal handler has this flag set.
> >
> > In order to allow userspace to determine whether SA_EXPOSE_TAGBITS
> > is supported, we first introduce a mechanism for userspace to detect
> > kernel support for SA_* flags.
> >
> > These patches need to be applied on top of:
> > https://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace.git signal-for-v5.11
>
> The first two patches look good and I have applied them.
>
> While I was at it I added Link tags to the LKML postings to the entire
> series.  I don't think anyone has merged my branch into another so it
> should still be safe.

Thanks!

Peter