1PT_BLK_SYNC_FORWARD(3)                                  PT_BLK_SYNC_FORWARD(3)
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NAME

6       pt_blk_sync_forward,  pt_blk_sync_backward,  pt_blk_sync_set - synchro‐
7       nize an Intel(R) Processor Trace block decoder
8

SYNOPSIS

10       #include <intel-pt.h>
11       int pt_blk_sync_forward(struct pt_block_decoder *decoder);
12       int pt_blk_sync_backward(struct pt_block_decoder *decoder);
13       int pt_blk_sync_set(struct pt_block_decoder *decoder,
14                           uint64_t offset);
15
16       Link with -lipt.
17

DESCRIPTION

19       These functions synchronize an Intel Processor Trace (Intel  PT)  block
20       decoder  pointed to by decoder onto the trace stream in decoder's trace
21       buffer.
22
23       They search for a Packet Stream Boundary  (PSB)  packet  in  the  trace
24       stream  and, if successful, set decoder's current position and synchro‐
25       nization position to that packet and  start  processing  packets.   For
26       synchronization  to be successfull, there must be a full PSB+ header in
27       the trace stream.
28
29       pt_blk_sync_forward() searches in forward direction from decoder's cur‐
30       rent position towards the end of the trace buffer.  If decoder has been
31       newly allocated and has not been synchronized yet,  the  search  starts
32       from the beginning of the trace.
33
34       pt_blk_sync_backward()  searches  in  backward direction from decoder's
35       current position towards the beginning of the trace buffer.  If decoder
36       has  been newly allocated and has not been synchronized yet, the search
37       starts from the end of the trace.
38
39       pt_blk_sync_set() searches at offset bytes from the  beginning  of  its
40       trace buffer.
41

RETURN VALUE

43       All  synchronization  functions return zero or a positive value on suc‐
44       cess or a negative pt_error_code enumeration constant in case of an er‐
45       ror.
46
47       On success, a bit-vector of pt_status_flag enumeration constants is re‐
48       turned.  The pt_status_flag enumeration is declared as:
49
50              /** Decoder status flags. */
51              enum pt_status_flag {
52                  /** There is an event pending. */
53                  pts_event_pending    = 1 << 0,
54
55                  /** The address has been suppressed. */
56                  pts_ip_suppressed    = 1 << 1,
57
58                  /** There is no more trace data available. */
59                  pts_eos              = 1 << 2
60              };
61
62       The pts_event_pending flag indicates that one or more events are  pend‐
63       ing.   Use  pt_blk_event(3)  to  process  pending events before calling
64       pt_blk_next(3).
65
66       The pt_eos flag indicates that the information contained in  the  Intel
67       PT  stream  has  been  consumed.   Calls  to pt_blk_next() will provide
68       blocks for instructions as long as the instruction's addresses  can  be
69       determined without further trace.
70

ERRORS

72       pte_invalid
73              The decoder argument is NULL.
74
75       pte_eos
76              There   is   no  (further)  PSB+  header  in  the  trace  stream
77              (pt_blk_sync_forward() and pt_blk_sync_backward()) or at  offset
78              bytes into the trace buffer (pt_blk_sync_set()).
79
80       pte_nosync
81              There is no PSB packet at offset bytes from the beginning of the
82              trace (pt_blk_sync_set() only).
83
84       pte_bad_opc
85              The decoder encountered an unsupported Intel PT packet opcode.
86
87       pte_bad_packet
88              The decoder encountered an unsupported Intel PT packet payload.
89

EXAMPLE

91       The following example re-synchronizes an Intel PT block  decoder  after
92       decode errors:
93
94              int foo(struct pt_block_decoder *decoder) {
95                  for (;;) {
96                      int errcode;
97
98                      errcode = pt_blk_sync_forward(decoder);
99                      if (errcode < 0)
100                          return errcode;
101
102                      do {
103                          errcode = decode(decoder);
104                      } while (errcode >= 0);
105                  }
106              }
107

SEE ALSO

109       pt_blk_alloc_decoder(3),  pt_blk_free_decoder(3), pt_blk_get_offset(3),
110       pt_blk_get_sync_offset(3),    pt_blk_get_config(3),     pt_blk_time(3),
111       pt_blk_core_bus_ratio(3), pt_blk_next(3), pt_blk_event(3)
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115                                                        PT_BLK_SYNC_FORWARD(3)
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