intel-pt-decoder.c

/*
 * intel_pt_decoder.c: Intel Processor Trace support
 * Copyright (c) 2013-2014, Intel Corporation.
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms and conditions of the GNU General Public License,
 * version 2, as published by the Free Software Foundation.
 *
 * This program is distributed in the hope it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License for
 * more details.
 *
 */

#ifndef _GNU_SOURCE
#define _GNU_SOURCE
#endif
#include <stdlib.h>
#include <stdbool.h>
#include <string.h>
#include <errno.h>
#include <stdint.h>
#include <inttypes.h>

#include "../cache.h"
#include "../util.h"

#include "intel-pt-insn-decoder.h"
#include "intel-pt-pkt-decoder.h"
#include "intel-pt-decoder.h"
#include "intel-pt-log.h"

#define INTEL_PT_BLK_SIZE 1024

#define BIT63 (((uint64_t)1 << 63))

#define INTEL_PT_RETURN 1

/* Maximum number of loops with no packets consumed i.e. stuck in a loop */
#define INTEL_PT_MAX_LOOPS 10000

struct intel_pt_blk {
	struct intel_pt_blk *prev;
	uint64_t ip[INTEL_PT_BLK_SIZE];
};

struct intel_pt_stack {
	struct intel_pt_blk *blk;
	struct intel_pt_blk *spare;
	int pos;
};

enum intel_pt_pkt_state {
	INTEL_PT_STATE_NO_PSB,
	INTEL_PT_STATE_NO_IP,
	INTEL_PT_STATE_ERR_RESYNC,
	INTEL_PT_STATE_IN_SYNC,
	INTEL_PT_STATE_TNT,
	INTEL_PT_STATE_TIP,
	INTEL_PT_STATE_TIP_PGD,
	INTEL_PT_STATE_FUP,
	INTEL_PT_STATE_FUP_NO_TIP,
};

#ifdef INTEL_PT_STRICT
#define INTEL_PT_STATE_ERR1	INTEL_PT_STATE_NO_PSB
#define INTEL_PT_STATE_ERR2	INTEL_PT_STATE_NO_PSB
#define INTEL_PT_STATE_ERR3	INTEL_PT_STATE_NO_PSB
#define INTEL_PT_STATE_ERR4	INTEL_PT_STATE_NO_PSB
#else
#define INTEL_PT_STATE_ERR1	(decoder->pkt_state)
#define INTEL_PT_STATE_ERR2	INTEL_PT_STATE_NO_IP
#define INTEL_PT_STATE_ERR3	INTEL_PT_STATE_ERR_RESYNC
#define INTEL_PT_STATE_ERR4	INTEL_PT_STATE_IN_SYNC
#endif

struct intel_pt_decoder {
	int (*get_trace)(struct intel_pt_buffer *buffer, void *data);
	int (*walk_insn)(struct intel_pt_insn *intel_pt_insn,
			 uint64_t *insn_cnt_ptr, uint64_t *ip, uint64_t to_ip,
			 uint64_t max_insn_cnt, void *data);
	void *data;
	struct intel_pt_state state;
	const unsigned char *buf;
	size_t len;
	bool return_compression;
	bool pge;
	uint64_t pos;
	uint64_t last_ip;
	uint64_t ip;
	uint64_t cr3;
	uint64_t timestamp;
	uint64_t tsc_timestamp;
	uint64_t ref_timestamp;
	uint64_t ret_addr;
	struct intel_pt_stack stack;
	enum intel_pt_pkt_state pkt_state;
	struct intel_pt_pkt packet;
	struct intel_pt_pkt tnt;
	int pkt_step;
	int pkt_len;
	unsigned int cbr;
	unsigned int max_non_turbo_ratio;
	int exec_mode;
	unsigned int insn_bytes;
	uint64_t sign_bit;
	uint64_t sign_bits;
	uint64_t period;
	enum intel_pt_period_type period_type;
	uint64_t tot_insn_cnt;
	uint64_t period_insn_cnt;
	uint64_t period_mask;
	uint64_t period_ticks;
	uint64_t last_masked_timestamp;
	bool continuous_period;
	bool overflow;
	bool set_fup_tx_flags;
	unsigned int fup_tx_flags;
	unsigned int tx_flags;
	uint64_t timestamp_insn_cnt;
	uint64_t stuck_ip;
	int no_progress;
	int stuck_ip_prd;
	int stuck_ip_cnt;
	const unsigned char *next_buf;
	size_t next_len;
	unsigned char temp_buf[INTEL_PT_PKT_MAX_SZ];
};

static uint64_t intel_pt_lower_power_of_2(uint64_t x)
{
	int i;

	for (i = 0; x != 1; i++)
		x >>= 1;

	return x << i;
}

static void intel_pt_setup_period(struct intel_pt_decoder *decoder)
{
	if (decoder->period_type == INTEL_PT_PERIOD_TICKS) {
		uint64_t period;

		period = intel_pt_lower_power_of_2(decoder->period);
		decoder->period_mask  = ~(period - 1);
		decoder->period_ticks = period;
	}
}

struct intel_pt_decoder *intel_pt_decoder_new(struct intel_pt_params *params)
{
	struct intel_pt_decoder *decoder;

	if (!params->get_trace || !params->walk_insn)
		return NULL;

	decoder = zalloc(sizeof(struct intel_pt_decoder));
	if (!decoder)
		return NULL;

	decoder->get_trace          = params->get_trace;
	decoder->walk_insn          = params->walk_insn;
	decoder->data               = params->data;
	decoder->return_compression = params->return_compression;

	decoder->sign_bit           = (uint64_t)1 << 47;
	decoder->sign_bits          = ~(((uint64_t)1 << 48) - 1);

	decoder->period             = params->period;
	decoder->period_type        = params->period_type;

	decoder->max_non_turbo_ratio = params->max_non_turbo_ratio;

	intel_pt_setup_period(decoder);

	return decoder;
}

static void intel_pt_pop_blk(struct intel_pt_stack *stack)
{
	struct intel_pt_blk *blk = stack->blk;

	stack->blk = blk->prev;
	if (!stack->spare)
		stack->spare = blk;
	else
		free(blk);
}

static uint64_t intel_pt_pop(struct intel_pt_stack *stack)
{
	if (!stack->pos) {
		if (!stack->blk)
			return 0;
		intel_pt_pop_blk(stack);
		if (!stack->blk)
			return 0;
		stack->pos = INTEL_PT_BLK_SIZE;
	}
	return stack->blk->ip[--stack->pos];
}

static int intel_pt_alloc_blk(struct intel_pt_stack *stack)
{
	struct intel_pt_blk *blk;

	if (stack->spare) {
		blk = stack->spare;
		stack->spare = NULL;
	} else {
		blk = malloc(sizeof(struct intel_pt_blk));
		if (!blk)
			return -ENOMEM;
	}

	blk->prev = stack->blk;
	stack->blk = blk;
	stack->pos = 0;
	return 0;
}

static int intel_pt_push(struct intel_pt_stack *stack, uint64_t ip)
{
	int err;

	if (!stack->blk || stack->pos == INTEL_PT_BLK_SIZE) {
		err = intel_pt_alloc_blk(stack);
		if (err)
			return err;
	}

	stack->blk->ip[stack->pos++] = ip;
	return 0;
}

static void intel_pt_clear_stack(struct intel_pt_stack *stack)
{
	while (stack->blk)
		intel_pt_pop_blk(stack);
	stack->pos = 0;
}

static void intel_pt_free_stack(struct intel_pt_stack *stack)
{
	intel_pt_clear_stack(stack);
	zfree(&stack->blk);
	zfree(&stack->spare);
}

void intel_pt_decoder_free(struct intel_pt_decoder *decoder)
{
	intel_pt_free_stack(&decoder->stack);
	free(decoder);
}

static int intel_pt_ext_err(int code)
{
	switch (code) {
	case -ENOMEM:
		return INTEL_PT_ERR_NOMEM;
	case -ENOSYS:
		return INTEL_PT_ERR_INTERN;
	case -EBADMSG:
		return INTEL_PT_ERR_BADPKT;
	case -ENODATA:
		return INTEL_PT_ERR_NODATA;
	case -EILSEQ:
		return INTEL_PT_ERR_NOINSN;
	case -ENOENT:
		return INTEL_PT_ERR_MISMAT;
	case -EOVERFLOW:
		return INTEL_PT_ERR_OVR;
	case -ENOSPC:
		return INTEL_PT_ERR_LOST;
	case -ELOOP:
		return INTEL_PT_ERR_NELOOP;
	default:
		return INTEL_PT_ERR_UNK;
	}
}

static const char *intel_pt_err_msgs[] = {
	[INTEL_PT_ERR_NOMEM]  = "Memory allocation failed",
	[INTEL_PT_ERR_INTERN] = "Internal error",
	[INTEL_PT_ERR_BADPKT] = "Bad packet",
	[INTEL_PT_ERR_NODATA] = "No more data",
	[INTEL_PT_ERR_NOINSN] = "Failed to get instruction",
	[INTEL_PT_ERR_MISMAT] = "Trace doesn't match instruction",
	[INTEL_PT_ERR_OVR]    = "Overflow packet",
	[INTEL_PT_ERR_LOST]   = "Lost trace data",
	[INTEL_PT_ERR_UNK]    = "Unknown error!",
	[INTEL_PT_ERR_NELOOP] = "Never-ending loop",
};

int intel_pt__strerror(int code, char *buf, size_t buflen)
{
	if (code < 1 || code > INTEL_PT_ERR_MAX)
		code = INTEL_PT_ERR_UNK;
	strlcpy(buf, intel_pt_err_msgs[code], buflen);
	return 0;
}

static uint64_t intel_pt_calc_ip(struct intel_pt_decoder *decoder,
				 const struct intel_pt_pkt *packet,
				 uint64_t last_ip)
{
	uint64_t ip;

	switch (packet->count) {
	case 2:
		ip = (last_ip & (uint64_t)0xffffffffffff0000ULL) |
		     packet->payload;
		break;
	case 4:
		ip = (last_ip & (uint64_t)0xffffffff00000000ULL) |
		     packet->payload;
		break;
	case 6:
		ip = packet->payload;
		break;
	default:
		return 0;
	}

	if (ip & decoder->sign_bit)
		return ip | decoder->sign_bits;

	return ip;
}

static inline void intel_pt_set_last_ip(struct intel_pt_decoder *decoder)
{
	decoder->last_ip = intel_pt_calc_ip(decoder, &decoder->packet,
					    decoder->last_ip);
}

static inline void intel_pt_set_ip(struct intel_pt_decoder *decoder)
{
	intel_pt_set_last_ip(decoder);
	decoder->ip = decoder->last_ip;
}

static void intel_pt_decoder_log_packet(struct intel_pt_decoder *decoder)
{
	intel_pt_log_packet(&decoder->packet, decoder->pkt_len, decoder->pos,
			    decoder->buf);
}

static int intel_pt_bug(struct intel_pt_decoder *decoder)
{
	intel_pt_log("ERROR: Internal error\n");
	decoder->pkt_state = INTEL_PT_STATE_NO_PSB;
	return -ENOSYS;
}

static inline void intel_pt_clear_tx_flags(struct intel_pt_decoder *decoder)
{
	decoder->tx_flags = 0;
}

static inline void intel_pt_update_in_tx(struct intel_pt_decoder *decoder)
{
	decoder->tx_flags = decoder->packet.payload & INTEL_PT_IN_TX;
}

static int intel_pt_bad_packet(struct intel_pt_decoder *decoder)
{
	intel_pt_clear_tx_flags(decoder);
	decoder->pkt_len = 1;
	decoder->pkt_step = 1;
	intel_pt_decoder_log_packet(decoder);
	if (decoder->pkt_state != INTEL_PT_STATE_NO_PSB) {
		intel_pt_log("ERROR: Bad packet\n");
		decoder->pkt_state = INTEL_PT_STATE_ERR1;
	}
	return -EBADMSG;
}

static int intel_pt_get_data(struct intel_pt_decoder *decoder)
{
	struct intel_pt_buffer buffer = { .buf = 0, };
	int ret;

	decoder->pkt_step = 0;

	intel_pt_log("Getting more data\n");
	ret = decoder->get_trace(&buffer, decoder->data);
	if (ret)
		return ret;
	decoder->buf = buffer.buf;
	decoder->len = buffer.len;
	if (!decoder->len) {
		intel_pt_log("No more data\n");
		return -ENODATA;
	}
	if (!buffer.consecutive) {
		decoder->ip = 0;
		decoder->pkt_state = INTEL_PT_STATE_NO_PSB;
		decoder->ref_timestamp = buffer.ref_timestamp;
		decoder->timestamp = 0;
		decoder->state.trace_nr = buffer.trace_nr;
		intel_pt_log("Reference timestamp 0x%" PRIx64 "\n",
			     decoder->ref_timestamp);
		return -ENOLINK;
	}

	return 0;
}

static int intel_pt_get_next_data(struct intel_pt_decoder *decoder)
{
	if (!decoder->next_buf)
		return intel_pt_get_data(decoder);

	decoder->buf = decoder->next_buf;
	decoder->len = decoder->next_len;
	decoder->next_buf = 0;
	decoder->next_len = 0;
	return 0;
}

static int intel_pt_get_split_packet(struct intel_pt_decoder *decoder)
{
	unsigned char *buf = decoder->temp_buf;
	size_t old_len, len, n;
	int ret;

	old_len = decoder->len;
	len = decoder->len;
	memcpy(buf, decoder->buf, len);

	ret = intel_pt_get_data(decoder);
	if (ret) {
		decoder->pos += old_len;
		return ret < 0 ? ret : -EINVAL;
	}

	n = INTEL_PT_PKT_MAX_SZ - len;
	if (n > decoder->len)
		n = decoder->len;
	memcpy(buf + len, decoder->buf, n);
	len += n;

	ret = intel_pt_get_packet(buf, len, &decoder->packet);
	if (ret < (int)old_len) {
		decoder->next_buf = decoder->buf;
		decoder->next_len = decoder->len;
		decoder->buf = buf;
		decoder->len = old_len;
		return intel_pt_bad_packet(decoder);
	}

	decoder->next_buf = decoder->buf + (ret - old_len);
	decoder->next_len = decoder->len - (ret - old_len);

	decoder->buf = buf;
	decoder->len = ret;

	return ret;
}

static int intel_pt_get_next_packet(struct intel_pt_decoder *decoder)
{
	int ret;

	do {
		decoder->pos += decoder->pkt_step;
		decoder->buf += decoder->pkt_step;
		decoder->len -= decoder->pkt_step;

		if (!decoder->len) {
			ret = intel_pt_get_next_data(decoder);
			if (ret)
				return ret;
		}

		ret = intel_pt_get_packet(decoder->buf, decoder->len,
					  &decoder->packet);
		if (ret == INTEL_PT_NEED_MORE_BYTES &&
		    decoder->len < INTEL_PT_PKT_MAX_SZ && !decoder->next_buf) {
			ret = intel_pt_get_split_packet(decoder);
			if (ret < 0)
				return ret;
		}
		if (ret <= 0)
			return intel_pt_bad_packet(decoder);

		decoder->pkt_len = ret;
		decoder->pkt_step = ret;
		intel_pt_decoder_log_packet(decoder);
	} while (decoder->packet.type == INTEL_PT_PAD);

	return 0;
}

static uint64_t intel_pt_next_period(struct intel_pt_decoder *decoder)
{
	uint64_t timestamp, masked_timestamp;

	timestamp = decoder->timestamp + decoder->timestamp_insn_cnt;
	masked_timestamp = timestamp & decoder->period_mask;
	if (decoder->continuous_period) {
		if (masked_timestamp != decoder->last_masked_timestamp)
			return 1;
	} else {
		timestamp += 1;
		masked_timestamp = timestamp & decoder->period_mask;
		if (masked_timestamp != decoder->last_masked_timestamp) {
			decoder->last_masked_timestamp = masked_timestamp;
			decoder->continuous_period = true;
		}
	}
	return decoder->period_ticks - (timestamp - masked_timestamp);
}

static uint64_t intel_pt_next_sample(struct intel_pt_decoder *decoder)
{
	switch (decoder->period_type) {
	case INTEL_PT_PERIOD_INSTRUCTIONS:
		return decoder->period - decoder->period_insn_cnt;
	case INTEL_PT_PERIOD_TICKS:
		return intel_pt_next_period(decoder);
	case INTEL_PT_PERIOD_NONE:
	default:
		return 0;
	}
}

static void intel_pt_sample_insn(struct intel_pt_decoder *decoder)
{
	uint64_t timestamp, masked_timestamp;

	switch (decoder->period_type) {
	case INTEL_PT_PERIOD_INSTRUCTIONS:
		decoder->period_insn_cnt = 0;
		break;
	case INTEL_PT_PERIOD_TICKS:
		timestamp = decoder->timestamp + decoder->timestamp_insn_cnt;
		masked_timestamp = timestamp & decoder->period_mask;
		decoder->last_masked_timestamp = masked_timestamp;
		break;
	case INTEL_PT_PERIOD_NONE:
	default:
		break;
	}

	decoder->state.type |= INTEL_PT_INSTRUCTION;
}

static int intel_pt_walk_insn(struct intel_pt_decoder *decoder,
			      struct intel_pt_insn *intel_pt_insn, uint64_t ip)
{
	uint64_t max_insn_cnt, insn_cnt = 0;
	int err;

	max_insn_cnt = intel_pt_next_sample(decoder);

	err = decoder->walk_insn(intel_pt_insn, &insn_cnt, &decoder->ip, ip,
				 max_insn_cnt, decoder->data);

	decoder->tot_insn_cnt += insn_cnt;
	decoder->timestamp_insn_cnt += insn_cnt;
	decoder->period_insn_cnt += insn_cnt;

	if (err) {
		decoder->no_progress = 0;
		decoder->pkt_state = INTEL_PT_STATE_ERR2;
		intel_pt_log_at("ERROR: Failed to get instruction",
				decoder->ip);
		if (err == -ENOENT)
			return -ENOLINK;
		return -EILSEQ;
	}

	if (ip && decoder->ip == ip) {
		err = -EAGAIN;
		goto out;
	}

	if (max_insn_cnt && insn_cnt >= max_insn_cnt)
		intel_pt_sample_insn(decoder);

	if (intel_pt_insn->branch == INTEL_PT_BR_NO_BRANCH) {
		decoder->state.type = INTEL_PT_INSTRUCTION;
		decoder->state.from_ip = decoder->ip;
		decoder->state.to_ip = 0;
		decoder->ip += intel_pt_insn->length;
		err = INTEL_PT_RETURN;
		goto out;
	}

	if (intel_pt_insn->op == INTEL_PT_OP_CALL) {
		/* Zero-length calls are excluded */
		if (intel_pt_insn->branch != INTEL_PT_BR_UNCONDITIONAL ||
		    intel_pt_insn->rel) {
			err = intel_pt_push(&decoder->stack, decoder->ip +
					    intel_pt_insn->length);
			if (err)
				goto out;
		}
	} else if (intel_pt_insn->op == INTEL_PT_OP_RET) {
		decoder->ret_addr = intel_pt_pop(&decoder->stack);
	}

	if (intel_pt_insn->branch == INTEL_PT_BR_UNCONDITIONAL) {
		int cnt = decoder->no_progress++;

		decoder->state.from_ip = decoder->ip;
		decoder->ip += intel_pt_insn->length +
				intel_pt_insn->rel;
		decoder->state.to_ip = decoder->ip;
		err = INTEL_PT_RETURN;

		/*
		 * Check for being stuck in a loop.  This can happen if a
		 * decoder error results in the decoder erroneously setting the
		 * ip to an address that is itself in an infinite loop that
		 * consumes no packets.  When that happens, there must be an
		 * unconditional branch.
		 */
		if (cnt) {
			if (cnt == 1) {
				decoder->stuck_ip = decoder->state.to_ip;
				decoder->stuck_ip_prd = 1;
				decoder->stuck_ip_cnt = 1;
			} else if (cnt > INTEL_PT_MAX_LOOPS ||
				   decoder->state.to_ip == decoder->stuck_ip) {
				intel_pt_log_at("ERROR: Never-ending loop",
						decoder->state.to_ip);
				decoder->pkt_state = INTEL_PT_STATE_ERR_RESYNC;
				err = -ELOOP;
				goto out;
			} else if (!--decoder->stuck_ip_cnt) {
				decoder->stuck_ip_prd += 1;
				decoder->stuck_ip_cnt = decoder->stuck_ip_prd;
				decoder->stuck_ip = decoder->state.to_ip;
			}
		}
		goto out_no_progress;
	}
out:
	decoder->no_progress = 0;
out_no_progress:
	decoder->state.insn_op = intel_pt_insn->op;
	decoder->state.insn_len = intel_pt_insn->length;

	if (decoder->tx_flags & INTEL_PT_IN_TX)
		decoder->state.flags |= INTEL_PT_IN_TX;

	return err;
}

static int intel_pt_walk_fup(struct intel_pt_decoder *decoder)
{
	struct intel_pt_insn intel_pt_insn;
	uint64_t ip;
	int err;

	ip = decoder->last_ip;

	while (1) {
		err = intel_pt_walk_insn(decoder, &intel_pt_insn, ip);
		if (err == INTEL_PT_RETURN)
			return 0;
		if (err == -EAGAIN) {
			if (decoder->set_fup_tx_flags) {
				decoder->set_fup_tx_flags = false;
				decoder->tx_flags = decoder->fup_tx_flags;
				decoder->state.type = INTEL_PT_TRANSACTION;
				decoder->state.from_ip = decoder->ip;
				decoder->state.to_ip = 0;
				decoder->state.flags = decoder->fup_tx_flags;
				return 0;
			}
			return err;
		}
		decoder->set_fup_tx_flags = false;
		if (err)
			return err;

		if (intel_pt_insn.branch == INTEL_PT_BR_INDIRECT) {
			intel_pt_log_at("ERROR: Unexpected indirect branch",
					decoder->ip);
			decoder->pkt_state = INTEL_PT_STATE_ERR_RESYNC;
			return -ENOENT;
		}

		if (intel_pt_insn.branch == INTEL_PT_BR_CONDITIONAL) {
			intel_pt_log_at("ERROR: Unexpected conditional branch",
					decoder->ip);
			decoder->pkt_state = INTEL_PT_STATE_ERR_RESYNC;
			return -ENOENT;
		}

		intel_pt_bug(decoder);
	}
}

static int intel_pt_walk_tip(struct intel_pt_decoder *decoder)
{
	struct intel_pt_insn intel_pt_insn;
	int err;

	err = intel_pt_walk_insn(decoder, &intel_pt_insn, 0);
	if (err == INTEL_PT_RETURN)
		return 0;
	if (err)
		return err;

	if (intel_pt_insn.branch == INTEL_PT_BR_INDIRECT) {
		if (decoder->pkt_state == INTEL_PT_STATE_TIP_PGD) {
			decoder->pge = false;
			decoder->continuous_period = false;
			decoder->pkt_state = INTEL_PT_STATE_IN_SYNC;
			decoder->state.from_ip = decoder->ip;
			decoder->state.to_ip = 0;
			if (decoder->packet.count != 0)
				decoder->ip = decoder->last_ip;
		} else {
			decoder->pkt_state = INTEL_PT_STATE_IN_SYNC;
			decoder->state.from_ip = decoder->ip;
			if (decoder->packet.count == 0) {
				decoder->state.to_ip = 0;
			} else {
				decoder->state.to_ip = decoder->last_ip;
				decoder->ip = decoder->last_ip;
			}
		}
		return 0;
	}

	if (intel_pt_insn.branch == INTEL_PT_BR_CONDITIONAL) {
		intel_pt_log_at("ERROR: Conditional branch when expecting indirect branch",
				decoder->ip);
		decoder->pkt_state = INTEL_PT_STATE_ERR_RESYNC;
		return -ENOENT;
	}

	return intel_pt_bug(decoder);
}

static int intel_pt_walk_tnt(struct intel_pt_decoder *decoder)
{
	struct intel_pt_insn intel_pt_insn;
	int err;

	while (1) {
		err = intel_pt_walk_insn(decoder, &intel_pt_insn, 0);
		if (err == INTEL_PT_RETURN)
			return 0;
		if (err)
			return err;

		if (intel_pt_insn.op == INTEL_PT_OP_RET) {
			if (!decoder->return_compression) {
				intel_pt_log_at("ERROR: RET when expecting conditional branch",
						decoder->ip);
				decoder->pkt_state = INTEL_PT_STATE_ERR3;
				return -ENOENT;
			}
			if (!decoder->ret_addr) {
				intel_pt_log_at("ERROR: Bad RET compression (stack empty)",
						decoder->ip);
				decoder->pkt_state = INTEL_PT_STATE_ERR3;
				return -ENOENT;
			}
			if (!(decoder->tnt.payload & BIT63)) {
				intel_pt_log_at("ERROR: Bad RET compression (TNT=N)",
						decoder->ip);
				decoder->pkt_state = INTEL_PT_STATE_ERR3;
				return -ENOENT;
			}
			decoder->tnt.count -= 1;
			if (!decoder->tnt.count)
				decoder->pkt_state = INTEL_PT_STATE_IN_SYNC;
			decoder->tnt.payload <<= 1;
			decoder->state.from_ip = decoder->ip;
			decoder->ip = decoder->ret_addr;
			decoder->state.to_ip = decoder->ip;
			return 0;
		}

		if (intel_pt_insn.branch == INTEL_PT_BR_INDIRECT) {
			/* Handle deferred TIPs */
			err = intel_pt_get_next_packet(decoder);
			if (err)
				return err;
			if (decoder->packet.type != INTEL_PT_TIP ||
			    decoder->packet.count == 0) {
				intel_pt_log_at("ERROR: Missing deferred TIP for indirect branch",
						decoder->ip);
				decoder->pkt_state = INTEL_PT_STATE_ERR3;
				decoder->pkt_step = 0;
				return -ENOENT;
			}
			intel_pt_set_last_ip(decoder);
			decoder->state.from_ip = decoder->ip;
			decoder->state.to_ip = decoder->last_ip;
			decoder->ip = decoder->last_ip;
			return 0;
		}

		if (intel_pt_insn.branch == INTEL_PT_BR_CONDITIONAL) {
			decoder->tnt.count -= 1;
			if (!decoder->tnt.count)
				decoder->pkt_state = INTEL_PT_STATE_IN_SYNC;
			if (decoder->tnt.payload & BIT63) {
				decoder->tnt.payload <<= 1;
				decoder->state.from_ip = decoder->ip;
				decoder->ip += intel_pt_insn.length +
					       intel_pt_insn.rel;
				decoder->state.to_ip = decoder->ip;
				return 0;
			}
			/* Instruction sample for a non-taken branch */
			if (decoder->state.type & INTEL_PT_INSTRUCTION) {
				decoder->tnt.payload <<= 1;
				decoder->state.type = INTEL_PT_INSTRUCTION;
				decoder->state.from_ip = decoder->ip;
				decoder->state.to_ip = 0;
				decoder->ip += intel_pt_insn.length;
				return 0;
			}
			decoder->ip += intel_pt_insn.length;
			if (!decoder->tnt.count)
				return -EAGAIN;
			decoder->tnt.payload <<= 1;
			continue;
		}

		return intel_pt_bug(decoder);
	}
}

static int intel_pt_mode_tsx(struct intel_pt_decoder *decoder, bool *no_tip)
{
	unsigned int fup_tx_flags;
	int err;

	fup_tx_flags = decoder->packet.payload &
		       (INTEL_PT_IN_TX | INTEL_PT_ABORT_TX);
	err = intel_pt_get_next_packet(decoder);
	if (err)
		return err;
	if (decoder->packet.type == INTEL_PT_FUP) {
		decoder->fup_tx_flags = fup_tx_flags;
		decoder->set_fup_tx_flags = true;
		if (!(decoder->fup_tx_flags & INTEL_PT_ABORT_TX))
			*no_tip = true;
	} else {
		intel_pt_log_at("ERROR: Missing FUP after MODE.TSX",
				decoder->pos);
		intel_pt_update_in_tx(decoder);
	}
	return 0;
}

static void intel_pt_calc_tsc_timestamp(struct intel_pt_decoder *decoder)
{
	uint64_t timestamp;

	if (decoder->ref_timestamp) {
		timestamp = decoder->packet.payload |
			    (decoder->ref_timestamp & (0xffULL << 56));
		if (timestamp < decoder->ref_timestamp) {
			if (decoder->ref_timestamp - timestamp > (1ULL << 55))
				timestamp += (1ULL << 56);
		} else {
			if (timestamp - decoder->ref_timestamp > (1ULL << 55))
				timestamp -= (1ULL << 56);
		}
		decoder->tsc_timestamp = timestamp;
		decoder->timestamp = timestamp;
		decoder->ref_timestamp = 0;
		decoder->timestamp_insn_cnt = 0;
	} else if (decoder->timestamp) {
		timestamp = decoder->packet.payload |
			    (decoder->timestamp & (0xffULL << 56));
		if (timestamp < decoder->timestamp &&
		    decoder->timestamp - timestamp < 0x100) {
			intel_pt_log_to("ERROR: Suppressing backwards timestamp",
					timestamp);
			timestamp = decoder->timestamp;
		}
		while (timestamp < decoder->timestamp) {
			intel_pt_log_to("Wraparound timestamp", timestamp);
			timestamp += (1ULL << 56);
		}
		decoder->tsc_timestamp = timestamp;
		decoder->timestamp = timestamp;
		decoder->timestamp_insn_cnt = 0;
	}

	intel_pt_log_to("Setting timestamp", decoder->timestamp);
}

static int intel_pt_overflow(struct intel_pt_decoder *decoder)
{
	intel_pt_log("ERROR: Buffer overflow\n");
	intel_pt_clear_tx_flags(decoder);
	decoder->pkt_state = INTEL_PT_STATE_ERR_RESYNC;
	decoder->overflow = true;
	return -EOVERFLOW;
}

/* Walk PSB+ packets when already in sync. */
static int intel_pt_walk_psbend(struct intel_pt_decoder *decoder)
{
	int err;

	while (1) {
		err = intel_pt_get_next_packet(decoder);
		if (err)
			return err;

		switch (decoder->packet.type) {
		case INTEL_PT_PSBEND:
			return 0;

		case INTEL_PT_TIP_PGD:
		case INTEL_PT_TIP_PGE:
		case INTEL_PT_TIP:
		case INTEL_PT_TNT:
		case INTEL_PT_BAD:
		case INTEL_PT_PSB:
			intel_pt_log("ERROR: Unexpected packet\n");
			return -EAGAIN;

		case INTEL_PT_OVF:
			return intel_pt_overflow(decoder);

		case INTEL_PT_TSC:
			intel_pt_calc_tsc_timestamp(decoder);
			break;

		case INTEL_PT_CBR:
			decoder->cbr = decoder->packet.payload;
			break;

		case INTEL_PT_MODE_EXEC:
			decoder->exec_mode = decoder->packet.payload;
			break;

		case INTEL_PT_PIP:
			decoder->cr3 = decoder->packet.payload;
			break;

		case INTEL_PT_FUP:
			decoder->pge = true;
			intel_pt_set_last_ip(decoder);
			break;

		case INTEL_PT_MODE_TSX:
			intel_pt_update_in_tx(decoder);
			break;

		case INTEL_PT_PAD:
		default:
			break;
		}
	}
}

static int intel_pt_walk_fup_tip(struct intel_pt_decoder *decoder)
{
	int err;

	if (decoder->tx_flags & INTEL_PT_ABORT_TX) {
		decoder->tx_flags = 0;
		decoder->state.flags &= ~INTEL_PT_IN_TX;
		decoder->state.flags |= INTEL_PT_ABORT_TX;
	} else {
		decoder->state.flags |= INTEL_PT_ASYNC;
	}

	while (1) {
		err = intel_pt_get_next_packet(decoder);
		if (err)
			return err;

		switch (decoder->packet.type) {
		case INTEL_PT_TNT:
		case INTEL_PT_FUP:
		case INTEL_PT_PSB:
		case INTEL_PT_TSC:
		case INTEL_PT_CBR:
		case INTEL_PT_MODE_TSX:
		case INTEL_PT_BAD:
		case INTEL_PT_PSBEND:
			intel_pt_log("ERROR: Missing TIP after FUP\n");
			decoder->pkt_state = INTEL_PT_STATE_ERR3;
			return -ENOENT;

		case INTEL_PT_OVF:
			return intel_pt_overflow(decoder);

		case INTEL_PT_TIP_PGD:
			decoder->state.from_ip = decoder->ip;
			decoder->state.to_ip = 0;
			if (decoder->packet.count != 0) {
				intel_pt_set_ip(decoder);
				intel_pt_log("Omitting PGD ip " x64_fmt "\n",
					     decoder->ip);
			}
			decoder->pge = false;
			decoder->continuous_period = false;
			return 0;

		case INTEL_PT_TIP_PGE:
			decoder->pge = true;
			intel_pt_log("Omitting PGE ip " x64_fmt "\n",
				     decoder->ip);
			decoder->state.from_ip = 0;
			if (decoder->packet.count == 0) {
				decoder->state.to_ip = 0;
			} else {
				intel_pt_set_ip(decoder);
				decoder->state.to_ip = decoder->ip;
			}
			return 0;

		case INTEL_PT_TIP:
			decoder->state.from_ip = decoder->ip;
			if (decoder->packet.count == 0) {
				decoder->state.to_ip = 0;
			} else {
				intel_pt_set_ip(decoder);
				decoder->state.to_ip = decoder->ip;
			}
			return 0;

		case INTEL_PT_PIP:
			decoder->cr3 = decoder->packet.payload;
			break;

		case INTEL_PT_MODE_EXEC:
			decoder->exec_mode = decoder->packet.payload;
			break;

		case INTEL_PT_PAD:
			break;

		default:
			return intel_pt_bug(decoder);
		}
	}
}

static int intel_pt_walk_trace(struct intel_pt_decoder *decoder)
{
	bool no_tip = false;
	int err;

	while (1) {
		err = intel_pt_get_next_packet(decoder);
		if (err)
			return err;
next:
		switch (decoder->packet.type) {
		case INTEL_PT_TNT:
			if (!decoder->packet.count)
				break;
			decoder->tnt = decoder->packet;
			decoder->pkt_state = INTEL_PT_STATE_TNT;
			err = intel_pt_walk_tnt(decoder);
			if (err == -EAGAIN)
				break;
			return err;

		case INTEL_PT_TIP_PGD:
			if (decoder->packet.count != 0)
				intel_pt_set_last_ip(decoder);
			decoder->pkt_state = INTEL_PT_STATE_TIP_PGD;
			return intel_pt_walk_tip(decoder);

		case INTEL_PT_TIP_PGE: {
			decoder->pge = true;
			if (decoder->packet.count == 0) {
				intel_pt_log_at("Skipping zero TIP.PGE",
						decoder->pos);
				break;
			}
			intel_pt_set_ip(decoder);
			decoder->state.from_ip = 0;
			decoder->state.to_ip = decoder->ip;
			return 0;
		}

		case INTEL_PT_OVF:
			return intel_pt_overflow(decoder);

		case INTEL_PT_TIP:
			if (decoder->packet.count != 0)
				intel_pt_set_last_ip(decoder);
			decoder->pkt_state = INTEL_PT_STATE_TIP;
			return intel_pt_walk_tip(decoder);

		case INTEL_PT_FUP:
			if (decoder->packet.count == 0) {
				intel_pt_log_at("Skipping zero FUP",
						decoder->pos);
				no_tip = false;
				break;
			}
			intel_pt_set_last_ip(decoder);
			err = intel_pt_walk_fup(decoder);
			if (err != -EAGAIN) {
				if (err)
					return err;
				if (no_tip)
					decoder->pkt_state =
						INTEL_PT_STATE_FUP_NO_TIP;
				else
					decoder->pkt_state = INTEL_PT_STATE_FUP;
				return 0;
			}
			if (no_tip) {
				no_tip = false;
				break;
			}
			return intel_pt_walk_fup_tip(decoder);

		case INTEL_PT_PSB:
			intel_pt_clear_stack(&decoder->stack);
			err = intel_pt_walk_psbend(decoder);
			if (err == -EAGAIN)
				goto next;
			if (err)
				return err;
			break;

		case INTEL_PT_PIP:
			decoder->cr3 = decoder->packet.payload;
			break;

		case INTEL_PT_TSC:
			intel_pt_calc_tsc_timestamp(decoder);
			break;

		case INTEL_PT_CBR:
			decoder->cbr = decoder->packet.payload;
			break;

		case INTEL_PT_MODE_EXEC:
			decoder->exec_mode = decoder->packet.payload;
			break;

		case INTEL_PT_MODE_TSX:
			/* MODE_TSX need not be followed by FUP */
			if (!decoder->pge) {
				intel_pt_update_in_tx(decoder);
				break;
			}
			err = intel_pt_mode_tsx(decoder, &no_tip);
			if (err)
				return err;
			goto next;

		case INTEL_PT_BAD: /* Does not happen */
			return intel_pt_bug(decoder);

		case INTEL_PT_PSBEND:
		case INTEL_PT_PAD:
			break;

		default:
			return intel_pt_bug(decoder);
		}
	}
}

/* Walk PSB+ packets to get in sync. */
static int intel_pt_walk_psb(struct intel_pt_decoder *decoder)
{
	int err;

	while (1) {
		err = intel_pt_get_next_packet(decoder);
		if (err)
			return err;

		switch (decoder->packet.type) {
		case INTEL_PT_TIP_PGD:
			decoder->continuous_period = false;
		case INTEL_PT_TIP_PGE:
		case INTEL_PT_TIP:
			intel_pt_log("ERROR: Unexpected packet\n");
			return -ENOENT;

		case INTEL_PT_FUP:
			decoder->pge = true;
			if (decoder->last_ip || decoder->packet.count == 6 ||
			    decoder->packet.count == 0) {
				uint64_t current_ip = decoder->ip;

				intel_pt_set_ip(decoder);
				if (current_ip)
					intel_pt_log_to("Setting IP",
							decoder->ip);
			}
			break;

		case INTEL_PT_TSC:
			intel_pt_calc_tsc_timestamp(decoder);
			break;

		case INTEL_PT_CBR:
			decoder->cbr = decoder->packet.payload;
			break;

		case INTEL_PT_PIP:
			decoder->cr3 = decoder->packet.payload;
			break;

		case INTEL_PT_MODE_EXEC:
			decoder->exec_mode = decoder->packet.payload;
			break;

		case INTEL_PT_MODE_TSX:
			intel_pt_update_in_tx(decoder);
			break;

		case INTEL_PT_TNT:
			intel_pt_log("ERROR: Unexpected packet\n");
			if (decoder->ip)
				decoder->pkt_state = INTEL_PT_STATE_ERR4;
			else
				decoder->pkt_state = INTEL_PT_STATE_ERR3;
			return -ENOENT;

		case INTEL_PT_BAD: /* Does not happen */
			return intel_pt_bug(decoder);

		case INTEL_PT_OVF:
			return intel_pt_overflow(decoder);

		case INTEL_PT_PSBEND:
			return 0;

		case INTEL_PT_PSB:
		case INTEL_PT_PAD:
		default:
			break;
		}
	}
}

static int intel_pt_walk_to_ip(struct intel_pt_decoder *decoder)
{
	int err;

	while (1) {
		err = intel_pt_get_next_packet(decoder);
		if (err)
			return err;

		switch (decoder->packet.type) {
		case INTEL_PT_TIP_PGD:
			decoder->continuous_period = false;
		case INTEL_PT_TIP_PGE:
		case INTEL_PT_TIP:
			decoder->pge = decoder->packet.type != INTEL_PT_TIP_PGD;
			if (decoder->last_ip || decoder->packet.count == 6 ||
			    decoder->packet.count == 0)
				intel_pt_set_ip(decoder);
			if (decoder->ip)
				return 0;
			break;

		case INTEL_PT_FUP:
			if (decoder->overflow) {
				if (decoder->last_ip ||
				    decoder->packet.count == 6 ||
				    decoder->packet.count == 0)
					intel_pt_set_ip(decoder);
				if (decoder->ip)
					return 0;
			}
			if (decoder->packet.count)
				intel_pt_set_last_ip(decoder);
			break;

		case INTEL_PT_TSC:
			intel_pt_calc_tsc_timestamp(decoder);
			break;

		case INTEL_PT_CBR:
			decoder->cbr = decoder->packet.payload;
			break;

		case INTEL_PT_PIP:
			decoder->cr3 = decoder->packet.payload;
			break;

		case INTEL_PT_MODE_EXEC:
			decoder->exec_mode = decoder->packet.payload;
			break;

		case INTEL_PT_MODE_TSX:
			intel_pt_update_in_tx(decoder);
			break;

		case INTEL_PT_OVF:
			return intel_pt_overflow(decoder);

		case INTEL_PT_BAD: /* Does not happen */
			return intel_pt_bug(decoder);

		case INTEL_PT_PSB:
			err = intel_pt_walk_psb(decoder);
			if (err)
				return err;
			if (decoder->ip) {
				/* Do not have a sample */
				decoder->state.type = 0;
				return 0;
			}
			break;

		case INTEL_PT_TNT:
		case INTEL_PT_PSBEND:
		case INTEL_PT_PAD:
		default:
			break;
		}
	}
}

static int intel_pt_sync_ip(struct intel_pt_decoder *decoder)
{
	int err;

	intel_pt_log("Scanning for full IP\n");
	err = intel_pt_walk_to_ip(decoder);
	if (err)
		return err;

	decoder->pkt_state = INTEL_PT_STATE_IN_SYNC;
	decoder->overflow = false;

	decoder->state.from_ip = 0;
	decoder->state.to_ip = decoder->ip;
	intel_pt_log_to("Setting IP", decoder->ip);

	return 0;
}

static int intel_pt_part_psb(struct intel_pt_decoder *decoder)
{
	const unsigned char *end = decoder->buf + decoder->len;
	size_t i;

	for (i = INTEL_PT_PSB_LEN - 1; i; i--) {
		if (i > decoder->len)
			continue;
		if (!memcmp(end - i, INTEL_PT_PSB_STR, i))
			return i;
	}
	return 0;
}

static int intel_pt_rest_psb(struct intel_pt_decoder *decoder, int part_psb)
{
	size_t rest_psb = INTEL_PT_PSB_LEN - part_psb;
	const char *psb = INTEL_PT_PSB_STR;

	if (rest_psb > decoder->len ||
	    memcmp(decoder->buf, psb + part_psb, rest_psb))
		return 0;

	return rest_psb;
}

static int intel_pt_get_split_psb(struct intel_pt_decoder *decoder,
				  int part_psb)
{
	int rest_psb, ret;

	decoder->pos += decoder->len;
	decoder->len = 0;

	ret = intel_pt_get_next_data(decoder);
	if (ret)
		return ret;

	rest_psb = intel_pt_rest_psb(decoder, part_psb);
	if (!rest_psb)
		return 0;

	decoder->pos -= part_psb;
	decoder->next_buf = decoder->buf + rest_psb;
	decoder->next_len = decoder->len - rest_psb;
	memcpy(decoder->temp_buf, INTEL_PT_PSB_STR, INTEL_PT_PSB_LEN);
	decoder->buf = decoder->temp_buf;
	decoder->len = INTEL_PT_PSB_LEN;

	return 0;
}

static int intel_pt_scan_for_psb(struct intel_pt_decoder *decoder)
{
	unsigned char *next;
	int ret;

	intel_pt_log("Scanning for PSB\n");
	while (1) {
		if (!decoder->len) {
			ret = intel_pt_get_next_data(decoder);
			if (ret)
				return ret;
		}

		next = memmem(decoder->buf, decoder->len, INTEL_PT_PSB_STR,
			      INTEL_PT_PSB_LEN);
		if (!next) {
			int part_psb;

			part_psb = intel_pt_part_psb(decoder);
			if (part_psb) {
				ret = intel_pt_get_split_psb(decoder, part_psb);
				if (ret)
					return ret;
			} else {
				decoder->pos += decoder->len;
				decoder->len = 0;
			}
			continue;
		}

		decoder->pkt_step = next - decoder->buf;
		return intel_pt_get_next_packet(decoder);
	}
}

static int intel_pt_sync(struct intel_pt_decoder *decoder)
{
	int err;

	decoder->pge = false;
	decoder->continuous_period = false;
	decoder->last_ip = 0;
	decoder->ip = 0;
	intel_pt_clear_stack(&decoder->stack);

	err = intel_pt_scan_for_psb(decoder);
	if (err)
		return err;

	decoder->pkt_state = INTEL_PT_STATE_NO_IP;

	err = intel_pt_walk_psb(decoder);
	if (err)
		return err;

	if (decoder->ip) {
		decoder->state.type = 0; /* Do not have a sample */
		decoder->pkt_state = INTEL_PT_STATE_IN_SYNC;
	} else {
		return intel_pt_sync_ip(decoder);
	}

	return 0;
}

static uint64_t intel_pt_est_timestamp(struct intel_pt_decoder *decoder)
{
	uint64_t est = decoder->timestamp_insn_cnt << 1;

	if (!decoder->cbr || !decoder->max_non_turbo_ratio)
		goto out;

	est *= decoder->max_non_turbo_ratio;
	est /= decoder->cbr;
out:
	return decoder->timestamp + est;
}

const struct intel_pt_state *intel_pt_decode(struct intel_pt_decoder *decoder)
{
	int err;

	do {
		decoder->state.type = INTEL_PT_BRANCH;
		decoder->state.flags = 0;

		switch (decoder->pkt_state) {
		case INTEL_PT_STATE_NO_PSB:
			err = intel_pt_sync(decoder);
			break;
		case INTEL_PT_STATE_NO_IP:
			decoder->last_ip = 0;
			/* Fall through */
		case INTEL_PT_STATE_ERR_RESYNC:
			err = intel_pt_sync_ip(decoder);
			break;
		case INTEL_PT_STATE_IN_SYNC:
			err = intel_pt_walk_trace(decoder);
			break;
		case INTEL_PT_STATE_TNT:
			err = intel_pt_walk_tnt(decoder);
			if (err == -EAGAIN)
				err = intel_pt_walk_trace(decoder);
			break;
		case INTEL_PT_STATE_TIP:
		case INTEL_PT_STATE_TIP_PGD:
			err = intel_pt_walk_tip(decoder);
			break;
		case INTEL_PT_STATE_FUP:
			decoder->pkt_state = INTEL_PT_STATE_IN_SYNC;
			err = intel_pt_walk_fup(decoder);
			if (err == -EAGAIN)
				err = intel_pt_walk_fup_tip(decoder);
			else if (!err)
				decoder->pkt_state = INTEL_PT_STATE_FUP;
			break;
		case INTEL_PT_STATE_FUP_NO_TIP:
			decoder->pkt_state = INTEL_PT_STATE_IN_SYNC;
			err = intel_pt_walk_fup(decoder);
			if (err == -EAGAIN)
				err = intel_pt_walk_trace(decoder);
			break;
		default:
			err = intel_pt_bug(decoder);
			break;
		}
	} while (err == -ENOLINK);

	decoder->state.err = err ? intel_pt_ext_err(err) : 0;
	decoder->state.timestamp = decoder->timestamp;
	decoder->state.est_timestamp = intel_pt_est_timestamp(decoder);
	decoder->state.cr3 = decoder->cr3;
	decoder->state.tot_insn_cnt = decoder->tot_insn_cnt;

	if (err)
		decoder->state.from_ip = decoder->ip;

	return &decoder->state;
}

static bool intel_pt_at_psb(unsigned char *buf, size_t len)
{
	if (len < INTEL_PT_PSB_LEN)
		return false;
	return memmem(buf, INTEL_PT_PSB_LEN, INTEL_PT_PSB_STR,
		      INTEL_PT_PSB_LEN);
}

/**
 * intel_pt_next_psb - move buffer pointer to the start of the next PSB packet.
 * @buf: pointer to buffer pointer
 * @len: size of buffer
 *
 * Updates the buffer pointer to point to the start of the next PSB packet if
 * there is one, otherwise the buffer pointer is unchanged.  If @buf is updated,
 * @len is adjusted accordingly.
 *
 * Return: %true if a PSB packet is found, %false otherwise.
 */
static bool intel_pt_next_psb(unsigned char **buf, size_t *len)
{
	unsigned char *next;

	next = memmem(*buf, *len, INTEL_PT_PSB_STR, INTEL_PT_PSB_LEN);
	if (next) {
		*len -= next - *buf;
		*buf = next;
		return true;
	}
	return false;
}

/**
 * intel_pt_step_psb - move buffer pointer to the start of the following PSB
 *                     packet.
 * @buf: pointer to buffer pointer
 * @len: size of buffer
 *
 * Updates the buffer pointer to point to the start of the following PSB packet
 * (skipping the PSB at @buf itself) if there is one, otherwise the buffer
 * pointer is unchanged.  If @buf is updated, @len is adjusted accordingly.
 *
 * Return: %true if a PSB packet is found, %false otherwise.
 */
static bool intel_pt_step_psb(unsigned char **buf, size_t *len)
{
	unsigned char *next;

	if (!*len)
		return false;

	next = memmem(*buf + 1, *len - 1, INTEL_PT_PSB_STR, INTEL_PT_PSB_LEN);
	if (next) {
		*len -= next - *buf;
		*buf = next;
		return true;
	}
	return false;
}

/**
 * intel_pt_last_psb - find the last PSB packet in a buffer.
 * @buf: buffer
 * @len: size of buffer
 *
 * This function finds the last PSB in a buffer.
 *
 * Return: A pointer to the last PSB in @buf if found, %NULL otherwise.
 */
static unsigned char *intel_pt_last_psb(unsigned char *buf, size_t len)
{
	const char *n = INTEL_PT_PSB_STR;
	unsigned char *p;
	size_t k;

	if (len < INTEL_PT_PSB_LEN)
		return NULL;

	k = len - INTEL_PT_PSB_LEN + 1;
	while (1) {
		p = memrchr(buf, n[0], k);
		if (!p)
			return NULL;
		if (!memcmp(p + 1, n + 1, INTEL_PT_PSB_LEN - 1))
			return p;
		k = p - buf;
		if (!k)
			return NULL;
	}
}

/**
 * intel_pt_next_tsc - find and return next TSC.
 * @buf: buffer
 * @len: size of buffer
 * @tsc: TSC value returned
 *
 * Find a TSC packet in @buf and return the TSC value.  This function assumes
 * that @buf starts at a PSB and that PSB+ will contain TSC and so stops if a
 * PSBEND packet is found.
 *
 * Return: %true if TSC is found, false otherwise.
 */
static bool intel_pt_next_tsc(unsigned char *buf, size_t len, uint64_t *tsc)
{
	struct intel_pt_pkt packet;
	int ret;

	while (len) {
		ret = intel_pt_get_packet(buf, len, &packet);
		if (ret <= 0)
			return false;
		if (packet.type == INTEL_PT_TSC) {
			*tsc = packet.payload;
			return true;
		}
		if (packet.type == INTEL_PT_PSBEND)
			return false;
		buf += ret;
		len -= ret;
	}
	return false;
}

/**
 * intel_pt_tsc_cmp - compare 7-byte TSCs.
 * @tsc1: first TSC to compare
 * @tsc2: second TSC to compare
 *
 * This function compares 7-byte TSC values allowing for the possibility that
 * TSC wrapped around.  Generally it is not possible to know if TSC has wrapped
 * around so for that purpose this function assumes the absolute difference is
 * less than half the maximum difference.
 *
 * Return: %-1 if @tsc1 is before @tsc2, %0 if @tsc1 == @tsc2, %1 if @tsc1 is
 * after @tsc2.
 */
static int intel_pt_tsc_cmp(uint64_t tsc1, uint64_t tsc2)
{
	const uint64_t halfway = (1ULL << 55);

	if (tsc1 == tsc2)
		return 0;

	if (tsc1 < tsc2) {
		if (tsc2 - tsc1 < halfway)
			return -1;
		else
			return 1;
	} else {
		if (tsc1 - tsc2 < halfway)
			return 1;
		else
			return -1;
	}
}

/**
 * intel_pt_find_overlap_tsc - determine start of non-overlapped trace data
 *                             using TSC.
 * @buf_a: first buffer
 * @len_a: size of first buffer
 * @buf_b: second buffer
 * @len_b: size of second buffer
 *
 * If the trace contains TSC we can look at the last TSC of @buf_a and the
 * first TSC of @buf_b in order to determine if the buffers overlap, and then
 * walk forward in @buf_b until a later TSC is found.  A precondition is that
 * @buf_a and @buf_b are positioned at a PSB.
 *
 * Return: A pointer into @buf_b from where non-overlapped data starts, or
 * @buf_b + @len_b if there is no non-overlapped data.
 */
static unsigned char *intel_pt_find_overlap_tsc(unsigned char *buf_a,
						size_t len_a,
						unsigned char *buf_b,
						size_t len_b)
{
	uint64_t tsc_a, tsc_b;
	unsigned char *p;
	size_t len;

	p = intel_pt_last_psb(buf_a, len_a);
	if (!p)
		return buf_b; /* No PSB in buf_a => no overlap */

	len = len_a - (p - buf_a);
	if (!intel_pt_next_tsc(p, len, &tsc_a)) {
		/* The last PSB+ in buf_a is incomplete, so go back one more */
		len_a -= len;
		p = intel_pt_last_psb(buf_a, len_a);
		if (!p)
			return buf_b; /* No full PSB+ => assume no overlap */
		len = len_a - (p - buf_a);
		if (!intel_pt_next_tsc(p, len, &tsc_a))
			return buf_b; /* No TSC in buf_a => assume no overlap */
	}

	while (1) {
		/* Ignore PSB+ with no TSC */
		if (intel_pt_next_tsc(buf_b, len_b, &tsc_b) &&
		    intel_pt_tsc_cmp(tsc_a, tsc_b) < 0)
			return buf_b; /* tsc_a < tsc_b => no overlap */

		if (!intel_pt_step_psb(&buf_b, &len_b))
			return buf_b + len_b; /* No PSB in buf_b => no data */
	}
}

/**
 * intel_pt_find_overlap - determine start of non-overlapped trace data.
 * @buf_a: first buffer
 * @len_a: size of first buffer
 * @buf_b: second buffer
 * @len_b: size of second buffer
 * @have_tsc: can use TSC packets to detect overlap
 *
 * When trace samples or snapshots are recorded there is the possibility that
 * the data overlaps.  Note that, for the purposes of decoding, data is only
 * useful if it begins with a PSB packet.
 *
 * Return: A pointer into @buf_b from where non-overlapped data starts, or
 * @buf_b + @len_b if there is no non-overlapped data.
 */
unsigned char *intel_pt_find_overlap(unsigned char *buf_a, size_t len_a,
				     unsigned char *buf_b, size_t len_b,
				     bool have_tsc)
{
	unsigned char *found;

	/* Buffer 'b' must start at PSB so throw away everything before that */
	if (!intel_pt_next_psb(&buf_b, &len_b))
		return buf_b + len_b; /* No PSB */

	if (!intel_pt_next_psb(&buf_a, &len_a))
		return buf_b; /* No overlap */

	if (have_tsc) {
		found = intel_pt_find_overlap_tsc(buf_a, len_a, buf_b, len_b);
		if (found)
			return found;
	}

	/*
	 * Buffer 'b' cannot end within buffer 'a' so, for comparison purposes,
	 * we can ignore the first part of buffer 'a'.
	 */
	while (len_b < len_a) {
		if (!intel_pt_step_psb(&buf_a, &len_a))
			return buf_b; /* No overlap */
	}

	/* Now len_b >= len_a */
	if (len_b > len_a) {
		/* The leftover buffer 'b' must start at a PSB */
		while (!intel_pt_at_psb(buf_b + len_a, len_b - len_a)) {
			if (!intel_pt_step_psb(&buf_a, &len_a))
				return buf_b; /* No overlap */
		}
	}

	while (1) {
		/* Potential overlap so check the bytes */
		found = memmem(buf_a, len_a, buf_b, len_a);
		if (found)
			return buf_b + len_a;

		/* Try again at next PSB in buffer 'a' */
		if (!intel_pt_step_psb(&buf_a, &len_a))
			return buf_b; /* No overlap */

		/* The leftover buffer 'b' must start at a PSB */
		while (!intel_pt_at_psb(buf_b + len_a, len_b - len_a)) {
			if (!intel_pt_step_psb(&buf_a, &len_a))
				return buf_b; /* No overlap */
		}
	}
}