% PT_QRY_SYNC_FORWARD(3)

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# NAME

pt_qry_sync_forward, pt_qry_sync_backward, pt_qry_sync_set - synchronize an

Intel(R) Processor Trace query decoder

# SYNOPSIS

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

|

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

|                         **uint64_t \**ip*);**

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

|                          **uint64_t \**ip*);**

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

|                     **uint64_t \**ip*, uint64_t *offset*);**

Link with *-lipt*.

# DESCRIPTION

These functions synchronize an Intel Processor Trace (Intel PT) query decoder

pointed to by *decoder* onto the trace stream in *decoder*'s trace buffer.

They search for a Packet Stream Boundary (PSB) packet in the trace stream and,

if successful, set *decoder*'s current position and synchronization position to

that packet and start processing packets.  For synchronization to be

successfull, there must be a full PSB+ header in the trace stream.

If the *ip* argument is not NULL, these functions provide the code memory

address at which tracing starts in the variable pointed to by *ip*.  If tracing

is disabled at the synchronization point, the lack of an IP is indicated in the

return value by setting the *pts_ip_suppressed* bit.

**pt_qry_sync_forward**() searches in forward direction from *decoder*'s current

position towards the end of the trace buffer.  If *decoder* has been newly

allocated and has not been synchronized yet, the search starts from the

beginning of the trace.

**pt_qry_sync_backward**() searches in backward direction from *decoder*'s

current position towards the beginning of the trace buffer.  If *decoder* has

been newly allocated and has not been synchronized yet, the search starts from

the end of the trace.

**pt_qry_sync_set**() searches at *offset* bytes from the beginning of its trace

buffer.

# RETURN VALUE

All synchronization functions return 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* argument is NULL.

pte_eos

:   There is no (further) PSB+ header in the trace stream

    (**pt_qry_sync_forward**() and **pt_qry_sync_backward**()) or at *offset*

    bytes into the trace buffer (**pt_qry_sync_set**()).

pte_nosync

:   There is no PSB packet at *offset* bytes from the beginning of the trace

    (**pt_qry_sync_set**() only).

pte_bad_opc

:   The decoder encountered an unsupported Intel PT packet opcode.

pte_bad_packet

:   The decoder encountered an unsupported Intel PT packet payload.

# EXAMPLE

The following example re-synchronizes an Intel PT query decoder after decode

errors:

~~~{.c}

int foo(struct pt_query_decoder *decoder) {

	for (;;) {

		int errcode;

		errcode = pt_qry_sync_forward(decoder);

		if (errcode < 0)

			return errcode;

		do {

			errcode = decode(decoder);

		} while (errcode >= 0);

	}

}

~~~

# SEE ALSO

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

**pt_qry_get_offset**(3), **pt_qry_get_sync_offset**(3),

**pt_qry_get_config**(3), **pt_qry_cond_branch**(3),

**pt_qry_indirect_branch**(3), **pt_qry_event**(3), **pt_qry_time**(3),

**pt_qry_core_bus_ratio**(3)