perf tools: Add documentation for BPF event selection

Add documentation for how to pass a BPF program as a perf event.

Signed-off-by: Changbin Du <changbin.du@gmail.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Link: http://lkml.kernel.org/r/20190201134651.12373-1-changbin.du@gmail.com
Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>

1 files changed, 14 insertions, 0 deletions

diff --git a/tools/perf/Documentation/perf-record.txt b/tools/perf/Documentation/perf-record.txt
index d232b13ea713..02b4aa2621e7 100644
--- a/tools/perf/Documentation/perf-record.txt
+++ b/tools/perf/Documentation/perf-record.txt
@@ -88,6 +88,20 @@ OPTIONS
           If you want to profile write accesses in [0x1000~1008), just set
           'mem:0x1000/8:w'.
 
+        - a BPF source file (ending in .c) or a precompiled object file (ending
+          in .o) selects one or more BPF events.
+          The BPF program can attach to various perf events based on the ELF section
+          names.
+
+          When processing a '.c' file, perf searches an installed LLVM to compile it
+          into an object file first. Optional clang options can be passed via the
+          '--clang-opt' command line option, e.g.:
+
+            perf record --clang-opt "-DLINUX_VERSION_CODE=0x50000" \
+                        -e tests/bpf-script-example.c
+
+          Note: '--clang-opt' must be placed before '--event/-e'.
+
 	- a group of events surrounded by a pair of brace ("{event1,event2,...}").
 	  Each event is separated by commas and the group should be quoted to
 	  prevent the shell interpretation.  You also need to use --group on