PT_BLK_SYNC_FORWARD(3)

NAME

pt_blk_sync_forward, pt_blk_sync_backward, pt_blk_sync_set - synchronize an Intel(R) Processor Trace block decoder

SYNOPSIS

#include <intel-pt.h>
int pt_blk_sync_forward(struct pt_block_decoder *decoder);
int pt_blk_sync_backward(struct pt_block_decoder *decoder);
int pt_blk_sync_set(struct pt_block_decoder *decoder,
uint64_t offset);

Link with -lipt.

DESCRIPTION

These functions synchronize an Intel Processor Trace (Intel PT) block 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.

pt_blk_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_blk_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_blk_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:

    /** 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
    };

The pts_event_pending flag indicates that one or more events are pending. Use pt_blk_event(3) to process pending events before calling pt_blk_next(3).

The pt_eos flag indicates that the information contained in the Intel PT stream has been consumed. Calls to pt_blk_next() will provide blocks for instructions as long as the instruction’s addresses can be determined without further trace.

ERRORS

pte_invalid
    The decoder argument is NULL.

pte_eos
    There is no (further) PSB+ header in the trace stream (pt_blk_sync_forward() and pt_blk_sync_backward()) or at offset bytes into the trace buffer (pt_blk_sync_set()).

pte_nosync
    There is no PSB packet at offset bytes from the beginning of the trace (pt_blk_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 block decoder after decode errors:

    int foo(struct pt_block_decoder *decoder) {
        for (;;) {
            int errcode;
            errcode = pt_blk_sync_forward(decoder);
            if (errcode < 0)
                return errcode;
            do {
                errcode = decode(decoder);
            } while (errcode >= 0);
        }
    }

SEE ALSO

pt_blk_alloc_decoder(3), pt_blk_free_decoder(3), pt_blk_get_offset(3), pt_blk_get_sync_offset(3), pt_blk_get_config(3), pt_blk_time(3), pt_blk_core_bus_ratio(3), pt_blk_next(3), pt_blk_event(3)