[PATCH v21 1/2] signal: define the SA_EXPOSE_TAGBITS bit in sa_flags

[Eric W. Biederman]

Catalin Marinas <catalin.marinas at arm.com> writes:

> On Mon, Nov 23, 2020 at 09:53:13AM -0600, Eric W. Biederman wrote:
>> Catalin Marinas <catalin.marinas at arm.com> writes:
>> > On Fri, Nov 20, 2020 at 05:22:58PM -0600, Eric W. Biederman wrote:
>> >> Peter Collingbourne <pcc at google.com> writes:
>> >> > Architectures that support address tagging, such as arm64, may want to
>> >> > expose fault address tag bits to the signal handler to help diagnose
>> >> > memory errors. However, these bits have not been previously set,
>> >> > and their presence may confuse unaware user applications. Therefore,
>> >> > introduce a SA_EXPOSE_TAGBITS flag bit in sa_flags that a signal
>> >> > handler may use to explicitly request that the bits are set.
>> >> >
>> >> > The generic signal handler APIs expect to receive tagged addresses.
>> >> > Architectures may specify how to untag addresses in the case where
>> >> > SA_EXPOSE_TAGBITS is clear by defining the arch_untagged_si_addr
>> >> > function.
>> >> >
>> >> > Signed-off-by: Peter Collingbourne <pcc at google.com>
>> >> > Acked-by: "Eric W. Biederman" <ebiederm at xmission.com>
>> >> > Link: https://linux-review.googlesource.com/id/I16dd0ed2081f091fce97be0190cb8caa874c26cb
>> >> > ---
>> >> > To be applied on top of:
>> >> > https://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace.git signal-for-v5.11
>> >> 
>> >> I have merged this first patch into signal-for-v5.11 and pushed
>> >> everything out to linux-next.
>> >
>> > Thank you Eric. Assuming this branch won't be rebased, I'll apply the
>> > arm64 changes on top (well, if you rebase it, just let me know so that
>> > we don't end up with duplicate commits in mainline).
>> 
>> No.  I won't be rebasing it.  Not unless something serious problem shows
>> up, and at that point I will be more likely to apply a corrective change
>> on top that you can also grab.
>
> Thanks Eric. During the merging window, I'll probably wait for you to
> send the pull request first just to keep the arm64 diffstat simpler.
>
> BTW, did you mean to base them on v5.10-rc3-391-g9cfd9c45994b or just
> v5.10-rc3? It doesn't matter much as I'll generate the diffstat manually
> anyway in my pull request as I have different bases in other branches.

Crap.  How did that happen?  I thought for certain I had based them on
v5.10-rc3.  Some random git commit is not a good base.  I think the
better part of valor is to just admit I goofed and not rebase even now.

It it would make your life easier I will be happy to rebase (onto
v5.10-rc3?).  I just wanted to get these into my tree so that we could
incremetnally commit to the changes that makes sense and be certain not
to loose them.

Eric