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perf_event_open.2: Document the PERF_EVENT_IOC_QUERY_BPF ioctl 

The PERF_EVENT_IOC_QUERY_BPF ioctl was introduced in Linux 4.16.

Signed-off-by: Vince Weaver <vincent.weaver@maine.edu>
Signed-off-by: Michael Kerrisk <mtk.manpages@gmail.com>
This commit is contained in:
Vince Weaver 2018-08-13 16:27:01 +02:00 committed by Michael Kerrisk
parent 92e696b95d
commit 43cc0d8ab1
1 changed files with 41 additions and 0 deletions
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41
man2/perf_event_open.2
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@ -2953,6 +2953,47 @@ Currently this is supported only for breakpoint events.
The argument is a pointer to a
.I perf_event_attr
structure containing the updated event settings.
.TP
.BR PERF_EVENT_IOC_QUERY_BPF " (since Linux 4.16)"
.\" commit f371b304f12e31fe30207c41ca7754564e0ea4dc
This allows querying which Berkeley Packet Filter (BPF)
programs are attached to an existing kprobe tracepoint.
You can only attach one BPF program per event, but you can
have multiple events attached to a tracepoint.
Querying this value on one tracepoint event returns the id
of all BPF programs in all events attached to the tracepoint.
You need
.B CAP_SYS_ADMIN
privileges to use this ioctl.
.IP
The argument is a pointer to a structure
.in +4n
.EX
struct perf_event_query_bpf {
__u32 ids_len;
__u32 prog_cnt;
__u32 ids[0];
};
.EE
.IP
The
.I ids_len
field indicates the number of ids that can fit in the provided
.I ids
array.
The
.I prog_cnt
value is filled in by the kernel with the number of attached
BPF programs.
The
.I ids
array is filled with the id of each attached BPF program.
If there are more programs than will fit in the array, then the
kernel will return
.B ENOSPC
and
.I ids_len
will indicate the number of program IDs that were successfully copied.
.\"
.SS Using prctl(2)
A process can enable or disable all currently open event groups