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/openbmc/linux/tools/testing/selftests/bpf/prog_tests/
H A Dexhandler.cc23551c9 Fri Nov 05 11:50:46 CDT 2021 Alan Maguire <alan.maguire@oracle.com> selftests/bpf: Add exception handling selftests for tp_bpf program

Exception handling is triggered in BPF tracing programs when a NULL pointer
is dereferenced; the exception handler zeroes the target register and
execution of the BPF program progresses.

To test exception handling then, we need to trigger a NULL pointer dereference
for a field which should never be zero; if it is, the only explanation is the
exception handler ran. task->task_works is the NULL pointer chosen (for a new
task from fork() no work is associated), and the task_works->func field should
not be zero if task_works is non-NULL. The test verifies that task_works and
task_works->func are 0.

Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/1636131046-5982-3-git-send-email-alan.maguire@oracle.com
/openbmc/linux/tools/testing/selftests/bpf/progs/
H A Dexhandler_kern.cc23551c9 Fri Nov 05 11:50:46 CDT 2021 Alan Maguire <alan.maguire@oracle.com> selftests/bpf: Add exception handling selftests for tp_bpf program

Exception handling is triggered in BPF tracing programs when a NULL pointer
is dereferenced; the exception handler zeroes the target register and
execution of the BPF program progresses.

To test exception handling then, we need to trigger a NULL pointer dereference
for a field which should never be zero; if it is, the only explanation is the
exception handler ran. task->task_works is the NULL pointer chosen (for a new
task from fork() no work is associated), and the task_works->func field should
not be zero if task_works is non-NULL. The test verifies that task_works and
task_works->func are 0.

Signed-off-by: Alan Maguire <alan.maguire@oracle.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/1636131046-5982-3-git-send-email-alan.maguire@oracle.com