1PT_BLK_SYNC_FORWARD(3) PT_BLK_SYNC_FORWARD(3)
2
6 pt_blk_sync_forward, pt_blk_sync_backward, pt_blk_sync_set - synchro‐
7 nize an Intel(R) Processor Trace block decoder
8
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 Link with -lipt.
17
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 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 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 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 pt_blk_sync_set() searches at offset bytes from the beginning of its
40 trace buffer.
41
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 On success, a bit-vector of pt_status_flag enumeration constants is re‐
48 turned. The pt_status_flag enumeration is declared as:
49 /** Decoder status flags. */
51 enum pt_status_flag {
52 /** There is an event pending. */
53 pts_event_pending = 1 << 0,
54 /** The address has been suppressed. */
56 pts_ip_suppressed = 1 << 1,
57 /** There is no more trace data available. */
59 pts_eos = 1 << 2
60 };
61 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 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
72 pte_invalid
73 The decoder argument is NULL.
74 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 pte_nosync
81 There is no PSB packet at offset bytes from the beginning of the
82 trace (pt_blk_sync_set() only).
83 pte_bad_opc
85 The decoder encountered an unsupported Intel PT packet opcode.
86 pte_bad_packet
88 The decoder encountered an unsupported Intel PT packet payload.
89
91 The following example re-synchronizes an Intel PT block decoder after
92 decode errors:
93 int foo(struct pt_block_decoder *decoder) {
95 for (;;) {
96 int errcode;
97 errcode = pt_blk_sync_forward(decoder);
99 if (errcode < 0)
100 return errcode;
101 do {
103 errcode = decode(decoder);
104 } while (errcode >= 0);
105 }
106 }
107
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)
112 PT_BLK_SYNC_FORWARD(3)