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% PT_EVT_SYNC_FORWARD(3)
<!---
! Copyright (c) 2015-2025, Intel Corporation
! SPDX-License-Identifier: BSD-3-Clause
!
! Redistribution and use in source and binary forms, with or without
! modification, are permitted provided that the following conditions are met:
!
! * Redistributions of source code must retain the above copyright notice,
! this list of conditions and the following disclaimer.
! * Redistributions in binary form must reproduce the above copyright notice,
! this list of conditions and the following disclaimer in the documentation
! and/or other materials provided with the distribution.
! * Neither the name of Intel Corporation nor the names of its contributors
! may be used to endorse or promote products derived from this software
! without specific prior written permission.
!
! THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
! AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
! IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
! ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
! LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
! CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
! SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
! INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
! CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
! ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
! POSSIBILITY OF SUCH DAMAGE.
!-->
# NAME
pt_evt_sync_forward, pt_evt_sync_backward, pt_evt_sync_set - synchronize an
Intel(R) Processor Trace event decoder
# SYNOPSIS
| **\#include `<intel-pt.h>`**
|
| **int pt_evt_sync_forward(struct pt_event_decoder \**decoder*);**
| **int pt_evt_sync_backward(struct pt_event_decoder \**decoder*);**
| **int pt_evt_sync_set(struct pt_event_decoder \**decoder*,**
| **uint64_t *offset*);**
Link with *-lipt*.
# DESCRIPTION
These functions synchronize an Intel Processor Trace (Intel PT) event 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
successful, there must be a full PSB+ header in the trace stream.
**pt_evt_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_evt_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_evt_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.
# ERRORS
pte_invalid
: The *decoder* argument is NULL.
pte_eos
: There is no (further) PSB+ header in the trace stream
(**pt_evt_sync_forward**() and **pt_evt_sync_backward**()) or at *offset*
bytes into the trace buffer (**pt_evt_sync_set**()).
pte_nosync
: There is no PSB packet at *offset* bytes from the beginning of the trace
(**pt_evt_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 event decoder after decode
errors:
~~~{.c}
int foo(struct pt_event_decoder *decoder) {
for (;;) {
int errcode;
errcode = pt_evt_sync_forward(decoder);
if (errcode < 0)
return errcode;
do {
errcode = decode(decoder);
} while (errcode >= 0);
}
}
~~~
# SEE ALSO
**pt_evt_alloc_decoder**(3), **pt_evt_free_decoder**(3),
**pt_evt_get_offset**(3), **pt_evt_get_sync_offset**(3),
**pt_evt_get_config**(3), **pt_evt_next**(3)
|
