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Diffstat (limited to 'docs/reference_guide.md')
| -rw-r--r-- | docs/reference_guide.md | 11 |
1 files changed, 9 insertions, 2 deletions
diff --git a/docs/reference_guide.md b/docs/reference_guide.md index 96e8a3f2..ff18ab93 100644 --- a/docs/reference_guide.md +++ b/docs/reference_guide.md @@ -202,6 +202,9 @@ Syntax: TRACEPOINT_PROBE(*category*, *event*) This is a macro that instruments the tracepoint defined by *category*:*event*. +The tracepoint name is `<category>:<event>`. +The probe function name is `tracepoint__<category>__<event>`. + Arguments are available in an ```args``` struct, which are the tracepoint arguments. One way to list these is to cat the relevant format file under /sys/kernel/debug/tracing/events/*category*/*event*/format. The ```args``` struct can be used in place of ``ctx`` in each functions requiring a context as an argument. This includes notably [perf_submit()](#3-perf_submit). @@ -216,7 +219,11 @@ TRACEPOINT_PROBE(random, urandom_read) { } ``` -This instruments the random:urandom_read tracepoint, and prints the tracepoint argument ```got_bits```. +This instruments the tracepoint `random:urandom_read tracepoint`, and prints the tracepoint argument ```got_bits```. +When using Python API, this probe is automatically attached to the right tracepoint target. +For C++, this tracepoint probe can be attached by specifying the tracepoint target and function name explicitly: +`BPF::attach_tracepoint("random:urandom_read", "tracepoint__random__urandom_read")` +Note the name of the probe function defined above is `tracepoint__random__urandom_read`. Examples in situ: [code](https://github.com/iovisor/bcc/blob/a4159da8c4ea8a05a3c6e402451f530d6e5a8b41/examples/tracing/urandomread.py#L19) ([output](https://github.com/iovisor/bcc/commit/e422f5e50ecefb96579b6391a2ada7f6367b83c4#diff-41e5ecfae4a3b38de5f4e0887ed160e5R10)), @@ -1825,7 +1832,7 @@ XDP_FLAGS_REPLACE = (1 << 4) You can use flags like this ```BPF.attach_xdp(dev="device", fn=b.load_func("fn_name",BPF.XDP), flags=BPF.XDP_FLAGS_UPDATE_IF_NOEXIST)``` -The default value of flgas is 0. This means if there is no xdp program with `device`, the fn will run with that device. If there is an xdp program running with device, the old program will be replaced with new fn program. +The default value of flags is 0. This means if there is no xdp program with `device`, the fn will run with that device. If there is an xdp program running with device, the old program will be replaced with new fn program. Currently, bcc does not support XDP_FLAGS_REPLACE flag. The following are the descriptions of other flags. |