Re: [PATCH 7/3] signal: Deliver all of the perf_data in si_perf

On Sun, 2 May 2021 at 20:39, Eric W. Biederman [off-list ref] wrote:

Marco Elver [off-list ref] writes:

quoted

On Sat, 1 May 2021 at 01:44, Eric W. Biederman [off-list ref] wrote:

quoted

Don't abuse si_errno and deliver all of the perf data in si_perf.

Signed-off-by: "Eric W. Biederman" <redacted>
---

Thank you for the fix, this looks cleaner.

Just note that this patch needs to include updates to
tools/testing/selftests/perf_events. This should do it:

quoted

 sed -i 's/si_perf/si_perf.data/g; s/si_errno/si_perf.type/g' tools/testing/selftests/perf_events/*.c

Subject: s/perf_data/perf data/ ?

For uapi, need to switch to __u32, see below.

Good point.

The one thing that this doesn't do is give you a 64bit field
on 32bit architectures.

On 32bit builds the layout is:

        int si_signo;
        int si_errno;
        int si_code;
        void __user *_addr;

So I believe if the first 3 fields were moved into the _sifields union
si_perf could define a 64bit field as it's first member and it would not
break anything else.

Given that the data field is 64bit that seems desirable.

Yes, it's quite unfortunate -- it was __u64 at first, but then we
noticed it broke 32-bit architectures like arm:
https://lore.kernel.org/linux-arch/20210422191823.79012-1-elver@google.com/ (local)

Thanks,
-- Marco