The pid field corresponds to the result of gettid() in userspace.
However, userspace cannot reliably attribute PTE events to processes
with just the thread id. This patch allows userspace to easily
attribute PTE update events to specific processes by comparing this
field with the result of getpid().

For attributing events to specific threads, the thread id is also
contained in the common fields of each trace event.
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Friedrich Vock <friedrich.vock@gmx.de>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>