On Tue, Nov 15, 2022 at 03:09:37PM +0000, Catalin Marinas wrote:
> > On ARM platforms is_default_overflow_handler() is used to determine if
> > hw_breakpoint code should single-step over the watchpoint trigger or
> > let the custom handler deal with it.
> >
> > Attaching a BPF program to a watchpoint replaces the handler with
> > bpf_overflow_handler, which isn't recognized as a default handler so we
> > never step over the instruction triggering the data abort exception (the
> > watchpoint keeps firing):
> >
> > # bpftrace -e 'watchpoint:0x10000000:4:w { printf("hit\n"); }' ./wp_test
> > Attaching 1 probe...
> > hit
> > hit
> > hit
> > [...]
> >
> > (wp_test performs a single 4-byte store to address 0x10000000)
> >
> > This patch replaces the check with uses_default_overflow_handler(), which
> > accounts for the bpf_overflow_handler() case by also testing if the handler
> > invokes one of the perf_event_output functions via orig_default_handler.
> >
> > Signed-off-by: Tomislav Novak <tnovak@xxxxxx>
> > Tested-by: Samuel Gosselin <sgosselin@xxxxxx> # arm64
> > ---
> > arch/arm/kernel/hw_breakpoint.c | 8 ++++----
> > arch/arm64/kernel/hw_breakpoint.c | 4 ++--
> > include/linux/perf_event.h | 22 +++++++++++++++++++---
> > 3 files changed, 25 insertions(+), 9 deletions(-)
>
> It looks like this slipped through the cracks. I'm fine with the patch
> but could you split the arm and arm64 parts in separate patches? Unless
> rmk acks it and we can take the patch through the arm64 (or perf) tree.
Thanks for reviewing!
Given the changes in the arch-independent perf_event.h, I think merging it
as a single commit may be easiest (assuming rmk acks it).
Alternatively I could move arm changes into a separate patch, keeping arm64
and perf_event.h in this one (possibly splitting out the latter into its own
commit). One that's merged, the arm patch could be submitted to linux-arm.
What would you prefer?
--
T.
