/*

 * Copyright (c) 2013-2017, Intel Corporation

 *

 * 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.

 */

#include "pt_sync.h"

#include "pt_packet.h"

#include "intel-pt.h"

/* A psb packet contains a unique 2-byte repeating pattern.

 *

 * There are only two ways to fill up a 64bit work with such a pattern.

 */

const uint64_t psb_pattern[] = {

	((uint64_t) pt_psb_lohi		| (uint64_t) pt_psb_lohi << 16 |

	 (uint64_t) pt_psb_lohi << 32	| (uint64_t) pt_psb_lohi << 48),

	((uint64_t) pt_psb_hilo		| (uint64_t) pt_psb_hilo << 16 |

	 (uint64_t) pt_psb_hilo << 32	| (uint64_t) pt_psb_hilo << 48)

};

static const uint8_t *truncate(const uint8_t *pointer, size_t alignment)

{

	uintptr_t raw = (uintptr_t) pointer;

	raw /= alignment;

	raw *= alignment;

	return (const uint8_t *) raw;

}

static const uint8_t *align(const uint8_t *pointer, size_t alignment)

{

	return truncate(pointer + alignment - 1, alignment);

}

/* Find a psb packet given a position somewhere in the payload.

 *

 * Return the position of the psb packet.

 * Return NULL, if this is not a psb packet.

 */

static const uint8_t *pt_find_psb(const uint8_t *pos,

				  const struct pt_config *config)

{

	const uint8_t *begin, *end;

	int errcode;

	if (!pos || !config)

		return NULL;

	begin = config->begin;

	end = config->end;

	/* Navigate to the end of the psb payload pattern.

	 *

	 * Beware that PSB is an extended opcode. We must not confuse the extend

	 * opcode of the following packet as belonging to the PSB.

	 */

	if (*pos != pt_psb_hi)

		pos++;

	for (; (pos + 1) < end; pos += 2) {

		uint8_t hi, lo;

		hi = pos[0];

		lo = pos[1];

		if (hi != pt_psb_hi)

			break;

		if (lo != pt_psb_lo)

			break;

	}

	/*

	 * We're right after the psb payload and within the buffer.

	 * Navigate to the expected beginning of the psb packet.

	 */

	pos -= ptps_psb;

	/* Check if we're still inside the buffer. */

	if (pos < begin)

		return NULL;

	/* Check that this is indeed a psb packet we're at. */

	if (pos[0] != pt_opc_psb || pos[1] != pt_ext_psb)

		return NULL;

	errcode = pt_pkt_read_psb(pos, config);

	if (errcode < 0)

		return NULL;

	return pos;

}

static int pt_sync_within_bounds(const uint8_t *pos, const uint8_t *begin,

				 const uint8_t *end)

{

	/* We allow @pos == @end representing the very end of the trace.

	 *

	 * This will result in -pte_eos when we actually try to read from @pos.

	 */

	return (begin <= pos) && (pos <= end);

}

int pt_sync_set(const uint8_t **sync, const uint8_t *pos,

		const struct pt_config *config)

{

	const uint8_t *begin, *end;

	int errcode;

	if (!sync || !pos || !config)

		return -pte_internal;

	begin = config->begin;

	end = config->end;

	if (!pt_sync_within_bounds(pos, begin, end))

		return -pte_eos;

	if (end < pos + 2)

		return -pte_eos;

	/* Check that this is indeed a psb packet we're at. */

	if (pos[0] != pt_opc_psb || pos[1] != pt_ext_psb)

		return -pte_nosync;

	errcode = pt_pkt_read_psb(pos, config);

	if (errcode < 0)

		return errcode;

	*sync = pos;

	return 0;

}

int pt_sync_forward(const uint8_t **sync, const uint8_t *pos,

		    const struct pt_config *config)

{

	const uint8_t *begin, *end;

	if (!sync || !pos || !config)

		return -pte_internal;

	begin = config->begin;

	end = config->end;

	if (!pt_sync_within_bounds(pos, begin, end))

		return -pte_internal;

	/* We search for a full 64bit word. It's OK to skip the current one. */

	pos = align(pos, sizeof(*psb_pattern));

	/* Search for the psb payload pattern in the buffer. */

	for (;;) {

		const uint8_t *current = pos;

		uint64_t val;

		pos += sizeof(uint64_t);

		if (end < pos)

			return -pte_eos;

		val = * (const uint64_t *) current;

		if ((val != psb_pattern[0]) && (val != psb_pattern[1]))

			continue;

		/* We found a 64bit word's worth of psb payload pattern. */

		current = pt_find_psb(pos, config);

		if (!current)

			continue;

		*sync = current;

		return 0;

	}

}

int pt_sync_backward(const uint8_t **sync, const uint8_t *pos,

		    const struct pt_config *config)

{

	const uint8_t *begin, *end;

	if (!sync || !pos || !config)

		return -pte_internal;

	begin = config->begin;

	end = config->end;

	if (!pt_sync_within_bounds(pos, begin, end))

		return -pte_internal;

	/* We search for a full 64bit word. It's OK to skip the current one. */

	pos = truncate(pos, sizeof(*psb_pattern));

	/* Search for the psb payload pattern in the buffer. */

	for (;;) {

		const uint8_t *next = pos;

		uint64_t val;

		pos -= sizeof(uint64_t);

		if (pos < begin)

			return -pte_eos;

		val = * (const uint64_t *) pos;

		if ((val != psb_pattern[0]) && (val != psb_pattern[1]))

			continue;

		/* We found a 64bit word's worth of psb payload pattern. */

		next = pt_find_psb(next, config);

		if (!next)

			continue;

		*sync = next;

		return 0;

	}

}