[RFC PATCH] perf/arm64: Add BRBE support for bpf_get_branch_snapshot()

[Puranjay Mohan]

On Mon, Jan 5, 2026 at 9:22 PM Leo Yan <leo.yan at arm.com> wrote:
>
> Hi,
>
> On Fri, Jan 02, 2026 at 09:51:15PM +0000, Puranjay Mohan wrote:
> > Hi Catalin, Will, Mark, and Rob.
> >
> > I don't have access to BRBE enabled hardware and Qemu doesn't support
> > this as well therefore I just sent the compile tested version.
> >
> > Can you help me with testing this:
> >
> > The relevant bpf self test is:
> >
> > ./test_progs -t get_branch_snapshot
> > #132     get_branch_snapshot:SKIP
> > Summary: 1/0 PASSED, 1 SKIPPED, 0 FAILED
> >
> > skipped for my setup as it is not supported.
>
> eBPF selftest build is quite heavy (many dependencies), finally I built
> it cleanly.
>
> I did a test on FVP RevC, the test hit NULL pointer deference and kernel
> panic in armv8pmu_sched_task().  See https://termbin.com/peg4, the
> backtrace should can give you hints for the issue.
>
> Thanks,
> Leo
>
> P.s. some logs are duplicate, this might be caused by two cores both hit
> the NULL pointer issue ?

Thanks for running the test, it will help me debug it better. But as
Mark pointer out this has fundamental problems which I will try to fix
first.

P.S. - The test on FVP RevC, does this need special hardware or this
is an emulation platform, in the later case, can I do the test myself
somehow?

Thanks,
Puranjay