--- man2/perf_event_open.2 | 37 +++++++++++++++++++++++++++++++++++++ 1 file changed, 37 insertions(+) diff --git a/man2/perf_event_open.2 b/man2/perf_event_open.2 index 65239e6..ad2c596 100644 --- a/man2/perf_event_open.2 +++ b/man2/perf_event_open.2 @@ -1338,6 +1338,43 @@ includes .BR PERF_SAMPLE_CALLCHAIN , this field specifies how many stack frames to report when generating the callchain. +.SS Interaction with execve(2) +It is important to separate the consideration of a file descriptor obtained +from +.BR perf_event_open +and that of the underlying performance counters. The two may be, but often +aren't, associated with the same task. With the exception of the +.BR PERF_FLAG_FD_CLOEXEC +flag (see above) there is nothing special about the file descriptors, so this +section will discuss the underlying performance counters. + +When +.BR perf_event_open +is called, in addition to the file descriptor, the underlying performance counters +are created and associated with each thread in the specified process's thread group. +This association ends whenever the task exits, but generally persists across +.BR execve(2) +(unless of course, the execve causes the last file descriptor referencing these counters +to close). However, for security reasons, the association is broken if the +.BR execve(2) +causes the task's "dumpable", flag to be reset (see +.BR prctl(2) +). + +If the +.IR inherit +option is specified, new children of any task already associated with these performance counters, +will inherit this association. + +Once all associations are broken, no further events are counted. However, the file descriptor +will not indicate this condition through an error return +(i.e. +.BR read(2) +and +.BR mmap(2) +will still succeed +). + .SS Reading results Once a .BR perf_event_open () -- 2.8.1 -- To unsubscribe from this list: send the line "unsubscribe linux-man" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
