DT(4) - Device Drivers Manual #
DT(4) - Device Drivers Manual
NAME #
dt - dynamic tracer
SYNOPSIS #
pseudo-device dt
DESCRIPTION #
System and application tracing can happen in the kernel. It has to be configured and enabled through the ioctl(2) interface exposed by the pseudo-device /dev/dt.
This device can only be opened when the kern.allowdt sysctl(2) variable is set.
IOCTL INTERFACE #
The ioctl(2) command codes below are defined in <dev/dt/dtvar.h>.
DTIOCGPLIST struct dtioc_probe *dtpr
Get available probe entries.
struct dtioc_probe { size_t dtpr_size; struct dtioc_probe_info *dtpr_probes; };
If dtpr_size is non-zero, as many probes as possible that can fit into this size will be copied into the supplied buffer. On exit, dtpr_size is always set to the total size required to hold all probe entries (i.e., it is set to
sizeof(struct dtioc_probe_info) * dt_nprobes).
DTIOCGSTATS struct dtioc_stat *dtst
Get statistics for current recording.
struct dtioc_stat { uint64_t dtst_readevt; uint64_t dtst_dropevt; };
DTIOCRECORD int on
Start or stop recording.
DTIOCPRBENABLE struct dtioc_req *dtrq
Enable the given probe for recording.
struct dtioc_req { uint32_t dtrq_pbn; struct dt_filter dtrq_filter; uint32_t dtrq_rate; uint64_t dtrq_evtflags; };
FILES #
/dev/dt
dynamic tracing device.
ERRORS #
An open of /dev/dt will fail if:
[EPERM]
the kern.allowdt sysctl(2) variable wasn’t set.
[ENOMEM]
not enough memory space was available.
SEE ALSO #
HISTORY #
The dt dynamic tracing mechanism first appeared in OpenBSD 6.7.
OpenBSD 7.5 - December 2, 2020