% PT_QRY_EVENT(3)

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# NAME

pt_qry_event - query an Intel(R) Processor Trace query decoder for an asynchronous event

# SYNOPSIS

| **\#include `<intel-pt.h>`**

|

| **int pt_qry_event(struct pt_query_decoder \**decoder*,**

|                  **struct pt_event \**event*, size_t *size*);**

Link with *-lipt*.

# DESCRIPTION

**pt_qry_event**() provides the next pending asynchronous event in *decoder*'s

Intel Processor Trace (Intel PT) decode in the *pt_event* object pointed to by

the *event* argument.

The *size* argument must be set to *sizeof(struct pt_event)*.  The function will

provide at most *size* bytes of the *pt_event* structure.  A newer decoder

library may provide event types that are not yet defined.  Those events may be

truncated.

On success, detailed information about the event is provided in the *pt_event*

object pointed to by the *event* argument.  The *pt_event* structure is declared

as:

~~~{.c}

/** An event. */

struct pt_event {

	/** The type of the event. */

	enum pt_event_type type;

	/** A flag indicating that the event IP has been

	 * suppressed.

	 */

	uint32_t ip_suppressed:1;

	/** A flag indicating that the event is for status update. */

	uint32_t status_update:1;

	/** A flag indicating that the event has timing

	 * information.

	 */

	uint32_t has_tsc:1;

	/** The time stamp count of the event.

	 *

	 * This field is only valid if \@has_tsc is set.

	 */

	uint64_t tsc;

	/** The number of lost mtc and cyc packets.

	 *

	 * This gives an idea about the quality of the \@tsc.  The

	 * more packets were dropped, the less precise timing is.

	 */

	uint32_t lost_mtc;

	uint32_t lost_cyc;

	/* Reserved space for future extensions. */

	uint64_t reserved[2];

	/** Event specific data. */

	union {

		/** Event: enabled. */

		struct {

			/** The address at which tracing resumes. */

			uint64_t ip;

		} enabled;

		/** Event: disabled. */

		struct {

			/** The destination of the first branch inside a

			 * filtered area.

			 *

			 * This field is not valid if \@ip_suppressed is set.

			 */

			uint64_t ip;

			/* The exact source ip needs to be determined using

			 * disassembly and the filter configuration.

			 */

		} disabled;

		[...]

	} variant;

};

~~~

See the *intel-pt.h* header file for more detail.  The common fields of the

*pt_event* structure are described in more detail below:

type

:   The type of the event as a *pt_event_type* enumeration, which is declared

    as:

~~~{.c}

/** Event types. */

enum pt_event_type {

	/* Tracing has been enabled/disabled. */

	ptev_enabled,

	ptev_disabled,

	/* Tracing has been disabled asynchronously. */

	ptev_async_disabled,

	/* An asynchronous branch, e.g. interrupt. */

	ptev_async_branch,

	/* A synchronous paging event. */

	ptev_paging,

	/* An asynchronous paging event. */

	ptev_async_paging,

	/* Trace overflow. */

	ptev_overflow,

	/* An execution mode change. */

	ptev_exec_mode,

	/* A transactional execution state change. */

	ptev_tsx,

	/* Trace Stop. */

	ptev_stop,

	/* A synchronous vmcs event. */

	ptev_vmcs,

	/* An asynchronous vmcs event. */

	ptev_async_vmcs

};

~~~

ip_suppressed

:   A flag indicating whether the *ip* field in the event-dependent part is not

    valid because the value has been suppressed in the trace.

status_update

:   A flag indicating whether the event is for updating the decoder's status.

    Status update events originate from Intel PT packets in PSB+.

has_tsc

:   A flag indicating that the event's timing-related fields *tsc*, *lost_mtc*,

    and *lost_cyc* are valid.

tsc

:   The last time stamp count before the event.  Depending on the timing

    configuration, the timestamp can be more or less precise.  For

    cycle-accurate tracing, event packets are typically CYC-eligible so the

    timestamp should be cycle-accurate.

lost_mtc, lost_cyc

:   The number of lost MTC and CYC updates.  An update is lost if the decoder

    was not able to process an MTC or CYC packet due to missing information.

    This can be either missing calibration or missing configuration information.

    The number of lost MTC and CYC updates gives a rough idea about the quality

    of the *tsc* field.

variant

:   This field contains event-specific information.  See the *intel-pt.h* header

    file for details.

# RETURN VALUE

**pt_qry_event**() returns zero or a positive value on success or a negative

*pt_error_code* enumeration constant in case of an error.

On success, a bit-vector of *pt_status_flag* enumeration constants is returned.

The *pt_status_flag* enumeration is declared as:

~~~{.c}

/** Decoder status flags. */

enum pt_status_flag {

	/** There is an event pending. */

	pts_event_pending	= 1 << 0,

	/** The address has been suppressed. */

	pts_ip_suppressed	= 1 << 1,

	/** There is no more trace data available. */

	pts_eos				= 1 << 2

};

~~~

# ERRORS

pte_invalid

:   The *decoder* or *event* argument is NULL or the *size* argument is too

    small.

pte_eos

:   Decode reached the end of the trace stream.

pte_nosync

:   The decoder has not been synchronized onto the trace stream.  Use

    **pt_qry_sync_forward**(3), **pt_qry_sync_backward**(3), or

    **pt_qry_sync_set**(3) to synchronize *decoder*.

pte_bad_opc

:   The decoder encountered an unsupported Intel PT packet opcode.

pte_bad_packet

:   The decoder encountered an unsupported Intel PT packet payload.

pte_bad_query

:   The query does not match the data provided in the Intel PT stream.  Based on

    the trace, the decoder expected a call to **pt_qry_cond_branch**(3) or

    **pt_qry_indirect_branch**(3).  This usually means that execution flow

    reconstruction and trace got out of sync.

# SEE ALSO

**pt_qry_alloc_decoder**(3), **pt_qry_free_decoder**(3),

**pt_qry_cond_branch**(3), **pt_qry_indirect_branch**(3), **pt_qry_time**(3),

**pt_qry_core_bus_ratio**(3)