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Date: Mon, 1 Aug 2022 15:58:24 +0200 From: Daniel Vacek <neelx@...hat.com> To: Jiri Olsa <olsajiri@...il.com> Cc: Artem Savkov <asavkov@...hat.com>, Alexei Starovoitov <ast@...nel.org>, Daniel Borkmann <daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>, bpf@...r.kernel.org, netdev@...r.kernel.org, linux-kernel@...r.kernel.org, Andrea Arcangeli <aarcange@...hat.com> Subject: Re: [RFC PATCH bpf-next 0/4] bpf_panic() helper On Mon, Jul 11, 2022 at 12:51 PM Jiri Olsa <olsajiri@...il.com> wrote: > > On Mon, Jul 11, 2022 at 10:32:16AM +0200, Artem Savkov wrote: > > eBPF is often used for kernel debugging, and one of the widely used and > > powerful debugging techniques is post-mortem debugging with a full memory dump. > > Triggering a panic at exactly the right moment allows the user to get such a > > dump and thus a better view at the system's state. This patchset adds > > bpf_panic() helper to do exactly that. > > FWIW I was asked for such helper some time ago from Daniel Vacek, cc-ed Nice :-) This is totally welcome. Though, IIRC, I was asking if I could do a NULL pointer dereference within perf probe (or ftrace) back then. Still, the outcome is similar. So kudos to Artem. --nX > jirka > > > > > I realize that even though there are multiple guards present, a helper like > > this is contrary to BPF being "safe", so this is sent as RFC to have a > > discussion on whether adding destructive capabilities is deemed acceptable. > > > > Artem Savkov (4): > > bpf: add a sysctl to enable destructive bpf helpers > > bpf: add BPF_F_DESTRUCTIVE flag for BPF_PROG_LOAD > > bpf: add bpf_panic() helper > > selftests/bpf: bpf_panic selftest > > > > include/linux/bpf.h | 8 + > > include/uapi/linux/bpf.h | 13 ++ > > kernel/bpf/core.c | 1 + > > kernel/bpf/helpers.c | 13 ++ > > kernel/bpf/syscall.c | 33 +++- > > kernel/bpf/verifier.c | 7 + > > kernel/trace/bpf_trace.c | 2 + > > tools/include/uapi/linux/bpf.h | 13 ++ > > .../selftests/bpf/prog_tests/bpf_panic.c | 144 ++++++++++++++++++ > > 9 files changed, 233 insertions(+), 1 deletion(-) > > create mode 100644 tools/testing/selftests/bpf/prog_tests/bpf_panic.c > > > > -- > > 2.35.3 > > >
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