Documentation/trace/user_events.rst

2 user_events: User-based Event Tracing
8 --------
10 that can be viewed via existing tools, such as ftrace and perf.
20 requires CAP_PERFMON due to the event persisting, otherwise -EPERM is returned.
23 tools that can read trace_events (such as ftrace and perf). The registration
36 -----------
44         /* Input: Size of the user_reg structure being used */
45         __u32 size;
50         /* Input: Enable size in bytes at address */
68 + size: This must be set to sizeof(struct user_reg).
73 + enable_size: The size of the value specified by enable_addr.
74   This must be 4 (32-bit) or 8 (64-bit). 64-bit values are only allowed to be
75   used on 64-bit kernels, however, 32-bit can be used on all kernels.
79   support for lower versions of the kernel. If a flag is not supported -EINVAL
93   -EPERM is returned.
104 or perf record -e user_events:[name] when attaching/recording.
108 future to change the subsystem name per-process to accommodate event isolation.
124   type name [size]
129 **NOTE:** *Long is not supported since size can vary between user and kernel.*
131 The size is only valid for types that start with a struct prefix.
145 --------
155 **NOTE:** By default events will auto-delete when there are no references left
156 to the event. If programs do not want auto-delete, they must use the
159 event that persists requires CAP_PERFMON, otherwise -EPERM is returned.
162 -------------
172         /* Input: Size of the user_unreg structure being used */
173         __u32 size;
190 + size: This must be set to sizeof(struct user_unreg).
203 ------
228 If a user enables the user event via ftrace, the output would change to this::
230   test # Used by ftrace
236 ------------
242 payload of the event. Then the data would have to be 8 bytes (2 ints) in size,
278 ------------