libipt/src/pt_insn_decoder.c

/*
 * Copyright (c) 2013-2018, 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_insn_decoder.h"
#include "pt_insn.h"
#include "pt_config.h"
#include "pt_asid.h"
#include "pt_compiler.h"

#include "intel-pt.h"

#include <string.h>
#include <stdlib.h>


static int pt_insn_check_ip_event(struct pt_insn_decoder *,
				  const struct pt_insn *,
				  const struct pt_insn_ext *);


static void pt_insn_reset(struct pt_insn_decoder *decoder)
{
	if (!decoder)
		return;

	decoder->mode = ptem_unknown;
	decoder->ip = 0ull;
	decoder->status = 0;
	decoder->enabled = 0;
	decoder->process_event = 0;
	decoder->speculative = 0;
	decoder->process_insn = 0;
	decoder->bound_paging = 0;
	decoder->bound_vmcs = 0;
	decoder->bound_ptwrite = 0;

	pt_retstack_init(&decoder->retstack);
	pt_asid_init(&decoder->asid);
}

static int pt_insn_status(const struct pt_insn_decoder *decoder, int flags)
{
	int status;

	if (!decoder)
		return -pte_internal;

	status = decoder->status;

	/* Indicate whether tracing is disabled or enabled.
	 *
	 * This duplicates the indication in struct pt_insn and covers the case
	 * where we indicate the status after synchronizing.
	 */
	if (!decoder->enabled)
		flags |= pts_ip_suppressed;

	/* Forward end-of-trace indications.
	 *
	 * Postpone it as long as we're still processing events, though.
	 */
	if ((status & pts_eos) && !decoder->process_event)
		flags |= pts_eos;

	return flags;
}

/* Initialize the query decoder flags based on our flags. */

static int pt_insn_init_qry_flags(struct pt_conf_flags *qflags,
				  const struct pt_conf_flags *flags)
{
	if (!qflags || !flags)
		return -pte_internal;

	memset(qflags, 0, sizeof(*qflags));

	return 0;
}

int pt_insn_decoder_init(struct pt_insn_decoder *decoder,
			 const struct pt_config *uconfig)
{
	struct pt_config config;
	int errcode;

	if (!decoder)
		return -pte_internal;

	errcode = pt_config_from_user(&config, uconfig);
	if (errcode < 0)
		return errcode;

	/* The user supplied decoder flags. */
	decoder->flags = config.flags;

	/* Set the flags we need for the query decoder we use. */
	errcode = pt_insn_init_qry_flags(&config.flags, &decoder->flags);
	if (errcode < 0)
		return errcode;

	errcode = pt_qry_decoder_init(&decoder->query, &config);
	if (errcode < 0)
		return errcode;

	pt_image_init(&decoder->default_image, NULL);
	decoder->image = &decoder->default_image;

	errcode = pt_msec_cache_init(&decoder->scache);
	if (errcode < 0)
		return errcode;

	pt_insn_reset(decoder);

	return 0;
}

void pt_insn_decoder_fini(struct pt_insn_decoder *decoder)
{
	if (!decoder)
		return;

	pt_msec_cache_fini(&decoder->scache);
	pt_image_fini(&decoder->default_image);
	pt_qry_decoder_fini(&decoder->query);
}

struct pt_insn_decoder *pt_insn_alloc_decoder(const struct pt_config *config)
{
	struct pt_insn_decoder *decoder;
	int errcode;

	decoder = malloc(sizeof(*decoder));
	if (!decoder)
		return NULL;

	errcode = pt_insn_decoder_init(decoder, config);
	if (errcode < 0) {
		free(decoder);
		return NULL;
	}

	return decoder;
}

void pt_insn_free_decoder(struct pt_insn_decoder *decoder)
{
	if (!decoder)
		return;

	pt_insn_decoder_fini(decoder);
	free(decoder);
}

/* Maybe synthesize a tick event.
 *
 * If we're not already processing events, check the current time against the
 * last event's time.  If it changed, synthesize a tick event with the new time.
 *
 * Returns zero if no tick event has been created.
 * Returns a positive integer if a tick event has been created.
 * Returns a negative error code otherwise.
 */
static int pt_insn_tick(struct pt_insn_decoder *decoder, uint64_t ip)
{
	struct pt_event *ev;
	uint64_t tsc;
	uint32_t lost_mtc, lost_cyc;
	int errcode;

	if (!decoder)
		return -pte_internal;

	/* We're not generating tick events if tracing is disabled. */
	if (!decoder->enabled)
		return -pte_internal;

	/* Events already provide a timestamp so there is no need to synthesize
	 * an artificial tick event.  There's no room, either, since this would
	 * overwrite the in-progress event.
	 *
	 * In rare cases where we need to proceed to an event location using
	 * trace this may cause us to miss a timing update if the event is not
	 * forwarded to the user.
	 *
	 * The only case I can come up with at the moment is a MODE.EXEC binding
	 * to the TIP IP of a far branch.
	 */
	if (decoder->process_event)
		return 0;

	errcode = pt_qry_time(&decoder->query, &tsc, &lost_mtc, &lost_cyc);
	if (errcode < 0) {
		/* If we don't have wall-clock time, we use relative time. */
		if (errcode != -pte_no_time)
			return errcode;
	}

	ev = &decoder->event;

	/* We're done if time has not changed since the last event. */
	if (tsc == ev->tsc)
		return 0;

	/* Time has changed so we create a new tick event. */
	memset(ev, 0, sizeof(*ev));
	ev->type = ptev_tick;
	ev->variant.tick.ip = ip;

	/* Indicate if we have wall-clock time or only relative time. */
	if (errcode != -pte_no_time)
		ev->has_tsc = 1;
	ev->tsc = tsc;
	ev->lost_mtc = lost_mtc;
	ev->lost_cyc = lost_cyc;

	/* We now have an event to process. */
	decoder->process_event = 1;

	return 1;
}

/* Query an indirect branch.
 *
 * Returns zero on success, a negative error code otherwise.
 */
static int pt_insn_indirect_branch(struct pt_insn_decoder *decoder,
				   uint64_t *ip)
{
	uint64_t evip;
	int status, errcode;

	if (!decoder)
		return -pte_internal;

	evip = decoder->ip;

	status = pt_qry_indirect_branch(&decoder->query, ip);
	if (status < 0)
		return status;

	if (decoder->flags.variant.insn.enable_tick_events) {
		errcode = pt_insn_tick(decoder, evip);
		if (errcode < 0)
			return errcode;
	}

	return status;
}

/* Query a conditional branch.
 *
 * Returns zero on success, a negative error code otherwise.
 */
static int pt_insn_cond_branch(struct pt_insn_decoder *decoder, int *taken)
{
	int status, errcode;

	if (!decoder)
		return -pte_internal;

	status = pt_qry_cond_branch(&decoder->query, taken);
	if (status < 0)
		return status;

	if (decoder->flags.variant.insn.enable_tick_events) {
		errcode = pt_insn_tick(decoder, decoder->ip);
		if (errcode < 0)
			return errcode;
	}

	return status;
}

static int pt_insn_start(struct pt_insn_decoder *decoder, int status)
{
	if (!decoder)
		return -pte_internal;

	if (status < 0)
		return status;

	decoder->status = status;

	if (!(status & pts_ip_suppressed))
		decoder->enabled = 1;

	/* Process any initial events.
	 *
	 * Some events are processed after proceeding to the next IP in order to
	 * indicate things like tracing disable or trace stop in the preceding
	 * instruction.  Those events will be processed without such an
	 * indication before decoding the current instruction.
	 *
	 * We do this already here so we can indicate user-events that precede
	 * the first instruction.
	 */
	return pt_insn_check_ip_event(decoder, NULL, NULL);
}

int pt_insn_sync_forward(struct pt_insn_decoder *decoder)
{
	int status;

	if (!decoder)
		return -pte_invalid;

	pt_insn_reset(decoder);

	status = pt_qry_sync_forward(&decoder->query, &decoder->ip);

	return pt_insn_start(decoder, status);
}

int pt_insn_sync_backward(struct pt_insn_decoder *decoder)
{
	int status;

	if (!decoder)
		return -pte_invalid;

	pt_insn_reset(decoder);

	status = pt_qry_sync_backward(&decoder->query, &decoder->ip);

	return pt_insn_start(decoder, status);
}

int pt_insn_sync_set(struct pt_insn_decoder *decoder, uint64_t offset)
{
	int status;

	if (!decoder)
		return -pte_invalid;

	pt_insn_reset(decoder);

	status = pt_qry_sync_set(&decoder->query, &decoder->ip, offset);

	return pt_insn_start(decoder, status);
}

int pt_insn_get_offset(const struct pt_insn_decoder *decoder, uint64_t *offset)
{
	if (!decoder)
		return -pte_invalid;

	return pt_qry_get_offset(&decoder->query, offset);
}

int pt_insn_get_sync_offset(const struct pt_insn_decoder *decoder,
			    uint64_t *offset)
{
	if (!decoder)
		return -pte_invalid;

	return pt_qry_get_sync_offset(&decoder->query, offset);
}

struct pt_image *pt_insn_get_image(struct pt_insn_decoder *decoder)
{
	if (!decoder)
		return NULL;

	return decoder->image;
}

int pt_insn_set_image(struct pt_insn_decoder *decoder,
		      struct pt_image *image)
{
	if (!decoder)
		return -pte_invalid;

	if (!image)
		image = &decoder->default_image;

	decoder->image = image;
	return 0;
}

const struct pt_config *
pt_insn_get_config(const struct pt_insn_decoder *decoder)
{
	if (!decoder)
		return NULL;

	return pt_qry_get_config(&decoder->query);
}

int pt_insn_time(struct pt_insn_decoder *decoder, uint64_t *time,
		 uint32_t *lost_mtc, uint32_t *lost_cyc)
{
	if (!decoder || !time)
		return -pte_invalid;

	return pt_qry_time(&decoder->query, time, lost_mtc, lost_cyc);
}

int pt_insn_core_bus_ratio(struct pt_insn_decoder *decoder, uint32_t *cbr)
{
	if (!decoder || !cbr)
		return -pte_invalid;

	return pt_qry_core_bus_ratio(&decoder->query, cbr);
}

int pt_insn_asid(const struct pt_insn_decoder *decoder, struct pt_asid *asid,
		 size_t size)
{
	if (!decoder || !asid)
		return -pte_invalid;

	return pt_asid_to_user(asid, &decoder->asid, size);
}

static inline int event_pending(struct pt_insn_decoder *decoder)
{
	int status;

	if (!decoder)
		return -pte_invalid;

	if (decoder->process_event)
		return 1;

	status = decoder->status;
	if (!(status & pts_event_pending))
		return 0;

	status = pt_qry_event(&decoder->query, &decoder->event,
			      sizeof(decoder->event));
	if (status < 0)
		return status;

	decoder->process_event = 1;
	decoder->status = status;
	return 1;
}

static int check_erratum_skd022(struct pt_insn_decoder *decoder)
{
	struct pt_insn_ext iext;
	struct pt_insn insn;
	int errcode;

	if (!decoder)
		return -pte_internal;

	insn.mode = decoder->mode;
	insn.ip = decoder->ip;

	errcode = pt_insn_decode(&insn, &iext, decoder->image, &decoder->asid);
	if (errcode < 0)
		return 0;

	switch (iext.iclass) {
	default:
		return 0;

	case PTI_INST_VMLAUNCH:
	case PTI_INST_VMRESUME:
		return 1;
	}
}

static inline int handle_erratum_skd022(struct pt_insn_decoder *decoder)
{
	struct pt_event *ev;
	uint64_t ip;
	int errcode;

	if (!decoder)
		return -pte_internal;

	errcode = check_erratum_skd022(decoder);
	if (errcode <= 0)
		return errcode;

	/* We turn the async disable into a sync disable.  It will be processed
	 * after decoding the instruction.
	 */
	ev = &decoder->event;

	ip = ev->variant.async_disabled.ip;

	ev->type = ptev_disabled;
	ev->variant.disabled.ip = ip;

	return 1;
}

static int pt_insn_proceed(struct pt_insn_decoder *decoder,
			   const struct pt_insn *insn,
			   const struct pt_insn_ext *iext)
{
	if (!decoder || !insn || !iext)
		return -pte_internal;

	/* Branch displacements apply to the next instruction. */
	decoder->ip += insn->size;

	/* We handle non-branches, non-taken conditional branches, and
	 * compressed returns directly in the switch and do some pre-work for
	 * calls.
	 *
	 * All kinds of branches are handled below the switch.
	 */
	switch (insn->iclass) {
	case ptic_ptwrite:
	case ptic_other:
		return 0;

	case ptic_cond_jump: {
		int status, taken;

		status = pt_insn_cond_branch(decoder, &taken);
		if (status < 0)
			return status;

		decoder->status = status;
		if (!taken)
			return 0;

		break;
	}

	case ptic_call:
		/* Log the call for return compression.
		 *
		 * Unless this is a call to the next instruction as is used
		 * for position independent code.
		 */
		if (iext->variant.branch.displacement ||
		    !iext->variant.branch.is_direct)
			pt_retstack_push(&decoder->retstack, decoder->ip);

		break;

	case ptic_return: {
		int taken, status;

		/* Check for a compressed return. */
		status = pt_insn_cond_branch(decoder, &taken);
		if (status >= 0) {
			decoder->status = status;

			/* A compressed return is indicated by a taken
			 * conditional branch.
			 */
			if (!taken)
				return -pte_bad_retcomp;

			return pt_retstack_pop(&decoder->retstack,
					       &decoder->ip);
		}

		break;
	}

	case ptic_jump:
	case ptic_far_call:
	case ptic_far_return:
	case ptic_far_jump:
		break;

	case ptic_error:
		return -pte_bad_insn;
	}

	/* Process a direct or indirect branch.
	 *
	 * This combines calls, uncompressed returns, taken conditional jumps,
	 * and all flavors of far transfers.
	 */
	if (iext->variant.branch.is_direct)
		decoder->ip += iext->variant.branch.displacement;
	else {
		int status;

		status = pt_insn_indirect_branch(decoder, &decoder->ip);

		if (status < 0)
			return status;

		decoder->status = status;

		/* We do need an IP to proceed. */
		if (status & pts_ip_suppressed)
			return -pte_noip;
	}

	return 0;
}

static int pt_insn_at_skl014(const struct pt_event *ev,
			     const struct pt_insn *insn,
			     const struct pt_insn_ext *iext,
			     const struct pt_config *config)
{
	uint64_t ip;
	int status;

	if (!ev || !insn || !iext || !config)
		return -pte_internal;

	if (!ev->ip_suppressed)
		return 0;

	switch (insn->iclass) {
	case ptic_call:
	case ptic_jump:
		/* The erratum only applies to unconditional direct branches. */
		if (!iext->variant.branch.is_direct)
			break;

		/* Check the filter against the branch target. */
		ip = insn->ip;
		ip += insn->size;
		ip += iext->variant.branch.displacement;

		status = pt_filter_addr_check(&config->addr_filter, ip);
		if (status <= 0) {
			if (status < 0)
				return status;

			return 1;
		}
		break;

	default:
		break;
	}

	return 0;
}

static int pt_insn_at_disabled_event(const struct pt_event *ev,
				     const struct pt_insn *insn,
				     const struct pt_insn_ext *iext,
				     const struct pt_config *config)
{
	if (!ev || !insn || !iext || !config)
		return -pte_internal;

	if (ev->ip_suppressed) {
		if (pt_insn_is_far_branch(insn, iext) ||
		    pt_insn_changes_cpl(insn, iext) ||
		    pt_insn_changes_cr3(insn, iext))
			return 1;

		/* If we don't have a filter configuration we assume that no
		 * address filters were used and the erratum does not apply.
		 *
		 * We might otherwise disable tracing too early.
		 */
		if (config->addr_filter.config.addr_cfg &&
		    config->errata.skl014 &&
		    pt_insn_at_skl014(ev, insn, iext, config))
			return 1;
	} else {
		switch (insn->iclass) {
		case ptic_ptwrite:
		case ptic_other:
			break;

		case ptic_call:
		case ptic_jump:
			/* If we got an IP with the disabled event, we may
			 * ignore direct branches that go to a different IP.
			 */
			if (iext->variant.branch.is_direct) {
				uint64_t ip;

				ip = insn->ip;
				ip += insn->size;
				ip += iext->variant.branch.displacement;

				if (ip != ev->variant.disabled.ip)
					break;
			}

			fallthrough;
		case ptic_return:
		case ptic_far_call:
		case ptic_far_return:
		case ptic_far_jump:
		case ptic_cond_jump:
			return 1;

		case ptic_error:
			return -pte_bad_insn;
		}
	}

	return 0;
}

/* Postpone proceeding past @insn/@iext and indicate a pending event.
 *
 * There may be further events pending on @insn/@iext.  Postpone proceeding past
 * @insn/@iext until we processed all events that bind to it.
 *
 * Returns a non-negative pt_status_flag bit-vector indicating a pending event
 * on success, a negative pt_error_code otherwise.
 */
static int pt_insn_postpone(struct pt_insn_decoder *decoder,
			    const struct pt_insn *insn,
			    const struct pt_insn_ext *iext)
{
	if (!decoder || !insn || !iext)
		return -pte_internal;

	if (!decoder->process_insn) {
		decoder->process_insn = 1;
		decoder->insn = *insn;
		decoder->iext = *iext;
	}

	return pt_insn_status(decoder, pts_event_pending);
}

/* Remove any postponed instruction from @decoder.
 *
 * Returns zero on success, a negative pt_error_code otherwise.
 */
static int pt_insn_clear_postponed(struct pt_insn_decoder *decoder)
{
	if (!decoder)
		return -pte_internal;

	decoder->process_insn = 0;
	decoder->bound_paging = 0;
	decoder->bound_vmcs = 0;
	decoder->bound_ptwrite = 0;

	return 0;
}

/* Proceed past a postponed instruction.
 *
 * Returns zero on success, a negative pt_error_code otherwise.
 */
static int pt_insn_proceed_postponed(struct pt_insn_decoder *decoder)
{
	int status;

	if (!decoder)
		return -pte_internal;

	if (!decoder->process_insn)
		return -pte_internal;

	/* There's nothing to do if tracing got disabled. */
	if (!decoder->enabled)
		return pt_insn_clear_postponed(decoder);

	status = pt_insn_proceed(decoder, &decoder->insn, &decoder->iext);
	if (status < 0)
		return status;

	return pt_insn_clear_postponed(decoder);
}

/* Check for events that bind to instruction.
 *
 * Check whether an event is pending that binds to @insn/@iext, and, if that is
 * the case, proceed past @insn/@iext and indicate the event by setting
 * pts_event_pending.
 *
 * If that is not the case, we return zero.  This is what pt_insn_status() would
 * return since:
 *
 *   - we suppress pts_eos as long as we're processing events
 *   - we do not set pts_ip_suppressed since tracing must be enabled
 *
 * Returns a non-negative pt_status_flag bit-vector on success, a negative error
 * code otherwise.
 */
static int pt_insn_check_insn_event(struct pt_insn_decoder *decoder,
				    const struct pt_insn *insn,
				    const struct pt_insn_ext *iext)
{
	struct pt_event *ev;
	int status;

	if (!decoder)
		return -pte_internal;

	status = event_pending(decoder);
	if (status <= 0)
		return status;

	ev = &decoder->event;
	switch (ev->type) {
	case ptev_enabled:
	case ptev_overflow:
	case ptev_async_paging:
	case ptev_async_vmcs:
	case ptev_async_disabled:
	case ptev_async_branch:
	case ptev_exec_mode:
	case ptev_tsx:
	case ptev_stop:
	case ptev_exstop:
	case ptev_mwait:
	case ptev_pwre:
	case ptev_pwrx:
	case ptev_tick:
	case ptev_cbr:
	case ptev_mnt:
		/* We're only interested in events that bind to instructions. */
		return 0;

	case ptev_disabled:
		status = pt_insn_at_disabled_event(ev, insn, iext,
						   &decoder->query.config);
		if (status <= 0)
			return status;

		/* We're at a synchronous disable event location.
		 *
		 * Let's determine the IP at which we expect tracing to resume.
		 */
		status = pt_insn_next_ip(&decoder->ip, insn, iext);
		if (status < 0) {
			/* We don't know the IP on error. */
			decoder->ip = 0ull;

			/* For indirect calls, assume that we return to the next
			 * instruction.
			 *
			 * We only check the instruction class, not the
			 * is_direct property, since direct calls would have
			 * been handled by pt_insn_nex_ip() or would have
			 * provoked a different error.
			 */
			if (status != -pte_bad_query)
				return status;

			switch (insn->iclass) {
			case ptic_call:
			case ptic_far_call:
				decoder->ip = insn->ip + insn->size;
				break;

			default:
				break;
			}
		}

		break;

	case ptev_paging:
		/* We bind at most one paging event to an instruction. */
		if (decoder->bound_paging)
			return 0;

		if (!pt_insn_binds_to_pip(insn, iext))
			return 0;

		/* We bound a paging event.  Make sure we do not bind further
		 * paging events to this instruction.
		 */
		decoder->bound_paging = 1;

		return pt_insn_postpone(decoder, insn, iext);

	case ptev_vmcs:
		/* We bind at most one vmcs event to an instruction. */
		if (decoder->bound_vmcs)
			return 0;

		if (!pt_insn_binds_to_vmcs(insn, iext))
			return 0;

		/* We bound a vmcs event.  Make sure we do not bind further vmcs
		 * events to this instruction.
		 */
		decoder->bound_vmcs = 1;

		return pt_insn_postpone(decoder, insn, iext);

	case ptev_ptwrite:
		/* We bind at most one ptwrite event to an instruction. */
		if (decoder->bound_ptwrite)
			return 0;

		if (ev->ip_suppressed) {
			if (!pt_insn_is_ptwrite(insn, iext))
				return 0;

			/* Fill in the event IP.  Our users will need them to
			 * make sense of the PTWRITE payload.
			 */
			ev->variant.ptwrite.ip = decoder->ip;
			ev->ip_suppressed = 0;
		} else {
			/* The ptwrite event contains the IP of the ptwrite
			 * instruction (CLIP) unlike most events that contain
			 * the IP of the first instruction that did not complete
			 * (NLIP).
			 *
			 * It's easier to handle this case here, as well.
			 */
			if (decoder->ip != ev->variant.ptwrite.ip)
				return 0;
		}

		/* We bound a ptwrite event.  Make sure we do not bind further
		 * ptwrite events to this instruction.
		 */
		decoder->bound_ptwrite = 1;

		return pt_insn_postpone(decoder, insn, iext);
	}

	return pt_insn_status(decoder, pts_event_pending);
}

enum {
	/* The maximum number of steps to take when determining whether the
	 * event location can be reached.
	 */
	bdm64_max_steps	= 0x100
};

/* Try to work around erratum BDM64.
 *
 * If we got a transaction abort immediately following a branch that produced
 * trace, the trace for that branch might have been corrupted.
 *
 * Returns a positive integer if the erratum was handled.
 * Returns zero if the erratum does not seem to apply.
 * Returns a negative error code otherwise.
 */
static int handle_erratum_bdm64(struct pt_insn_decoder *decoder,
				const struct pt_event *ev,
				const struct pt_insn *insn,
				const struct pt_insn_ext *iext)
{
	int status;

	if (!decoder || !ev || !insn || !iext)
		return -pte_internal;

	/* This only affects aborts. */
	if (!ev->variant.tsx.aborted)
		return 0;

	/* This only affects branches. */
	if (!pt_insn_is_branch(insn, iext))
		return 0;

	/* Let's check if we can reach the event location from here.
	 *
	 * If we can, let's assume the erratum did not hit.  We might still be
	 * wrong but we're not able to tell.
	 */
	status = pt_insn_range_is_contiguous(decoder->ip, ev->variant.tsx.ip,
					     decoder->mode, decoder->image,
					     &decoder->asid, bdm64_max_steps);
	if (status > 0)
		return 0;

	/* We can't reach the event location.  This could either mean that we
	 * stopped too early (and status is zero) or that the erratum hit.
	 *
	 * We assume the latter and pretend that the previous branch brought us
	 * to the event location, instead.
	 */
	decoder->ip = ev->variant.tsx.ip;

	return 1;
}

/* Check whether a peek TSX event should be postponed.
 *
 * This involves handling erratum BDM64.
 *
 * Returns a positive integer if the event is to be postponed.
 * Returns zero if the event should be processed.
 * Returns a negative error code otherwise.
 */
static inline int pt_insn_postpone_tsx(struct pt_insn_decoder *decoder,
				       const struct pt_insn *insn,
				       const struct pt_insn_ext *iext,
				       const struct pt_event *ev)
{
	int status;

	if (!decoder || !ev)
		return -pte_internal;

	if (ev->ip_suppressed)
		return 0;

	if (insn && iext && decoder->query.config.errata.bdm64) {
		status = handle_erratum_bdm64(decoder, ev, insn, iext);
		if (status < 0)
			return status;
	}

	if (decoder->ip != ev->variant.tsx.ip)
		return 1;

	return 0;
}

/* Check for events that bind to an IP.
 *
 * Check whether an event is pending that binds to @decoder->ip, and, if that is
 * the case, indicate the event by setting pt_pts_event_pending.
 *
 * Returns a non-negative pt_status_flag bit-vector on success, a negative error
 * code otherwise.
 */
static int pt_insn_check_ip_event(struct pt_insn_decoder *decoder,
				  const struct pt_insn *insn,
				  const struct pt_insn_ext *iext)
{
	struct pt_event *ev;
	int status;

	if (!decoder)
		return -pte_internal;

	status = event_pending(decoder);
	if (status <= 0) {
		if (status < 0)
			return status;

		return pt_insn_status(decoder, 0);
	}

	ev = &decoder->event;
	switch (ev->type) {
	case ptev_disabled:
		break;

	case ptev_enabled:
		return pt_insn_status(decoder, pts_event_pending);

	case ptev_async_disabled:
		if (ev->variant.async_disabled.at != decoder->ip)
			break;

		if (decoder->query.config.errata.skd022) {
			int errcode;

			errcode = handle_erratum_skd022(decoder);
			if (errcode != 0) {
				if (errcode < 0)
					return errcode;

				/* If the erratum applies, we postpone the
				 * modified event to the next call to
				 * pt_insn_next().
				 */
				break;
			}
		}

		return pt_insn_status(decoder, pts_event_pending);

	case ptev_tsx:
		status = pt_insn_postpone_tsx(decoder, insn, iext, ev);
		if (status != 0) {
			if (status < 0)
				return status;

			break;
		}

		return pt_insn_status(decoder, pts_event_pending);

	case ptev_async_branch:
		if (ev->variant.async_branch.from != decoder->ip)
			break;

		return pt_insn_status(decoder, pts_event_pending);

	case ptev_overflow:
		return pt_insn_status(decoder, pts_event_pending);

	case ptev_exec_mode:
		if (!ev->ip_suppressed &&
		    ev->variant.exec_mode.ip != decoder->ip)
			break;

		return pt_insn_status(decoder, pts_event_pending);

	case ptev_paging:
		if (decoder->enabled)
			break;

		return pt_insn_status(decoder, pts_event_pending);

	case ptev_async_paging:
		if (!ev->ip_suppressed &&
		    ev->variant.async_paging.ip != decoder->ip)
			break;

		return pt_insn_status(decoder, pts_event_pending);

	case ptev_vmcs:
		if (decoder->enabled)
			break;

		return pt_insn_status(decoder, pts_event_pending);

	case ptev_async_vmcs:
		if (!ev->ip_suppressed &&
		    ev->variant.async_vmcs.ip != decoder->ip)
			break;

		return pt_insn_status(decoder, pts_event_pending);

	case ptev_stop:
		return pt_insn_status(decoder, pts_event_pending);

	case ptev_exstop:
		if (!ev->ip_suppressed && decoder->enabled &&
		    decoder->ip != ev->variant.exstop.ip)
			break;

		return pt_insn_status(decoder, pts_event_pending);

	case ptev_mwait:
		if (!ev->ip_suppressed && decoder->enabled &&
		    decoder->ip != ev->variant.mwait.ip)
			break;

		return pt_insn_status(decoder, pts_event_pending);

	case ptev_pwre:
	case ptev_pwrx:
		return pt_insn_status(decoder, pts_event_pending);

	case ptev_ptwrite:
		/* Any event binding to the current PTWRITE instruction is
		 * handled in pt_insn_check_insn_event().
		 *
		 * Any subsequent ptwrite event binds to a different instruction
		 * and must wait until the next iteration - as long as tracing
		 * is enabled.
		 *
		 * When tracing is disabled, we forward all ptwrite events
		 * immediately to the user.
		 */
		if (decoder->enabled)
			break;

		return pt_insn_status(decoder, pts_event_pending);

	case ptev_tick:
	case ptev_cbr:
	case ptev_mnt:
		return pt_insn_status(decoder, pts_event_pending);
	}

	return pt_insn_status(decoder, 0);
}

static inline int insn_to_user(struct pt_insn *uinsn, size_t size,
			       const struct pt_insn *insn)
{
	if (!uinsn || !insn)
		return -pte_internal;

	if (uinsn == insn)
		return 0;

	/* Zero out any unknown bytes. */
	if (sizeof(*insn) < size) {
		memset(uinsn + sizeof(*insn), 0, size - sizeof(*insn));

		size = sizeof(*insn);
	}

	memcpy(uinsn, insn, size);

	return 0;
}

static int pt_insn_decode_cached(struct pt_insn_decoder *decoder,
				 const struct pt_mapped_section *msec,
				 struct pt_insn *insn, struct pt_insn_ext *iext)
{
	int status;

	if (!decoder || !insn || !iext)
		return -pte_internal;

	/* Try reading the memory containing @insn from the cached section.  If
	 * that fails, if we don't have a cached section, or if decode fails
	 * later on, fall back to decoding @insn from @decoder->image.
	 *
	 * The latter will also handle truncated instructions that cross section
	 * boundaries.
	 */

	if (!msec)
		return pt_insn_decode(insn, iext, decoder->image,
				      &decoder->asid);

	status = pt_msec_read(msec, insn->raw, sizeof(insn->raw), insn->ip);
	if (status < 0) {
		if (status != -pte_nomap)
			return status;

		return pt_insn_decode(insn, iext, decoder->image,
				      &decoder->asid);
	}

	/* We initialize @insn->size to the maximal possible size.  It will be
	 * set to the actual size during instruction decode.
	 */
	insn->size = (uint8_t) status;

	status = pt_ild_decode(insn, iext);
	if (status < 0) {
		if (status != -pte_bad_insn)
			return status;

		return pt_insn_decode(insn, iext, decoder->image,
				      &decoder->asid);
	}

	return status;
}

static int pt_insn_msec_lookup(struct pt_insn_decoder *decoder,
			       const struct pt_mapped_section **pmsec)
{
	struct pt_msec_cache *scache;
	struct pt_image *image;
	uint64_t ip;
	int isid;

	if (!decoder || !pmsec)
		return -pte_internal;

	scache = &decoder->scache;
	image = decoder->image;
	ip = decoder->ip;

	isid = pt_msec_cache_read(scache, pmsec, image, ip);
	if (isid < 0) {
		if (isid != -pte_nomap)
			return isid;

		return pt_msec_cache_fill(scache, pmsec, image,
					  &decoder->asid, ip);
	}

	return isid;
}

int pt_insn_next(struct pt_insn_decoder *decoder, struct pt_insn *uinsn,
		 size_t size)
{
	const struct pt_mapped_section *msec;
	struct pt_insn_ext iext;
	struct pt_insn insn, *pinsn;
	int status, isid;

	if (!uinsn || !decoder)
		return -pte_invalid;

	/* Tracing must be enabled.
	 *
	 * If it isn't we should be processing events until we either run out of
	 * trace or process a tracing enabled event.
	 */
	if (!decoder->enabled) {
		if (decoder->status & pts_eos)
			return -pte_eos;

		return -pte_no_enable;
	}

	pinsn = size == sizeof(insn) ? uinsn : &insn;

	/* Zero-initialize the instruction in case of error returns. */
	memset(pinsn, 0, sizeof(*pinsn));

	/* Fill in a few things from the current decode state.
	 *
	 * This reflects the state of the last pt_insn_next(), pt_insn_event()
	 * or pt_insn_start() call.
	 */
	if (decoder->speculative)
		pinsn->speculative = 1;
	pinsn->ip = decoder->ip;
	pinsn->mode = decoder->mode;

	isid = pt_insn_msec_lookup(decoder, &msec);
	if (isid < 0) {
		if (isid != -pte_nomap)
			return isid;

		msec = NULL;
	}

	/* We set an incorrect isid if @msec is NULL.  This will be corrected
	 * when we read the memory from the image later on.
	 */
	pinsn->isid = isid;

	status = pt_insn_decode_cached(decoder, msec, pinsn, &iext);
	if (status < 0) {
		/* Provide the incomplete instruction - the IP and mode fields
		 * are valid and may help diagnose the error.
		 */
		(void) insn_to_user(uinsn, size, pinsn);
		return status;
	}

	/* Provide the decoded instruction to the user.  It won't change during
	 * event processing.
	 */
	status = insn_to_user(uinsn, size, pinsn);
	if (status < 0)
		return status;

	/* Check for events that bind to the current instruction.
	 *
	 * If an event is indicated, we're done.
	 */
	status = pt_insn_check_insn_event(decoder, pinsn, &iext);
	if (status != 0) {
		if (status < 0)
			return status;

		if (status & pts_event_pending)
			return status;
	}

	/* Determine the next instruction's IP. */
	status = pt_insn_proceed(decoder, pinsn, &iext);
	if (status < 0)
		return status;

	/* Indicate events that bind to the new IP.
	 *
	 * Although we only look at the IP for binding events, we pass the
	 * decoded instruction in order to handle errata.
	 */
	return pt_insn_check_ip_event(decoder, pinsn, &iext);
}

static int pt_insn_process_enabled(struct pt_insn_decoder *decoder)
{
	struct pt_event *ev;

	if (!decoder)
		return -pte_internal;

	ev = &decoder->event;

	/* This event can't be a status update. */
	if (ev->status_update)
		return -pte_bad_context;

	/* We must have an IP in order to start decoding. */
	if (ev->ip_suppressed)
		return -pte_noip;

	/* We must currently be disabled. */
	if (decoder->enabled)
		return -pte_bad_context;

	decoder->ip = ev->variant.enabled.ip;
	decoder->enabled = 1;

	return 0;
}

static int pt_insn_process_disabled(struct pt_insn_decoder *decoder)
{
	struct pt_event *ev;

	if (!decoder)
		return -pte_internal;

	ev = &decoder->event;

	/* This event can't be a status update. */
	if (ev->status_update)
		return -pte_bad_context;

	/* We must currently be enabled. */
	if (!decoder->enabled)
		return -pte_bad_context;

	/* We preserve @decoder->ip.  This is where we expect tracing to resume
	 * and we'll indicate that on the subsequent enabled event if tracing
	 * actually does resume from there.
	 */
	decoder->enabled = 0;

	return 0;
}

static int pt_insn_process_async_branch(struct pt_insn_decoder *decoder)
{
	struct pt_event *ev;

	if (!decoder)
		return -pte_internal;

	ev = &decoder->event;

	/* This event can't be a status update. */
	if (ev->status_update)
		return -pte_bad_context;

	/* Tracing must be enabled in order to make sense of the event. */
	if (!decoder->enabled)
		return -pte_bad_context;

	decoder->ip = ev->variant.async_branch.to;

	return 0;
}

static int pt_insn_process_paging(struct pt_insn_decoder *decoder)
{
	uint64_t cr3;
	int errcode;

	if (!decoder)
		return -pte_internal;

	cr3 = decoder->event.variant.paging.cr3;
	if (decoder->asid.cr3 != cr3) {
		errcode = pt_msec_cache_invalidate(&decoder->scache);
		if (errcode < 0)
			return errcode;

		decoder->asid.cr3 = cr3;
	}

	return 0;
}

static int pt_insn_process_overflow(struct pt_insn_decoder *decoder)
{
	struct pt_event *ev;

	if (!decoder)
		return -pte_internal;

	ev = &decoder->event;

	/* This event can't be a status update. */
	if (ev->status_update)
		return -pte_bad_context;

	/* If the IP is suppressed, the overflow resolved while tracing was
	 * disabled.  Otherwise it resolved while tracing was enabled.
	 */
	if (ev->ip_suppressed) {
		/* Tracing is disabled.
		 *
		 * It doesn't make sense to preserve the previous IP.  This will
		 * just be misleading.  Even if tracing had been disabled
		 * before, as well, we might have missed the re-enable in the
		 * overflow.
		 */
		decoder->enabled = 0;
		decoder->ip = 0ull;
	} else {
		/* Tracing is enabled and we're at the IP at which the overflow
		 * resolved.
		 */
		decoder->ip = ev->variant.overflow.ip;
		decoder->enabled = 1;
	}

	/* We don't know the TSX state.  Let's assume we execute normally.
	 *
	 * We also don't know the execution mode.  Let's keep what we have
	 * in case we don't get an update before we have to decode the next
	 * instruction.
	 */
	decoder->speculative = 0;

	return 0;
}

static int pt_insn_process_exec_mode(struct pt_insn_decoder *decoder)
{
	enum pt_exec_mode mode;
	struct pt_event *ev;

	if (!decoder)
		return -pte_internal;

	ev = &decoder->event;
	mode = ev->variant.exec_mode.mode;

	/* Use status update events to diagnose inconsistencies. */
	if (ev->status_update && decoder->enabled &&
	    decoder->mode != ptem_unknown && decoder->mode != mode)
		return -pte_bad_status_update;

	decoder->mode = mode;

	return 0;
}

static int pt_insn_process_tsx(struct pt_insn_decoder *decoder)
{
	if (!decoder)
		return -pte_internal;

	decoder->speculative = decoder->event.variant.tsx.speculative;

	return 0;
}

static int pt_insn_process_stop(struct pt_insn_decoder *decoder)
{
	struct pt_event *ev;

	if (!decoder)
		return -pte_internal;

	ev = &decoder->event;

	/* This event can't be a status update. */
	if (ev->status_update)
		return -pte_bad_context;

	/* Tracing is always disabled before it is stopped. */
	if (decoder->enabled)
		return -pte_bad_context;

	return 0;
}

static int pt_insn_process_vmcs(struct pt_insn_decoder *decoder)
{
	uint64_t vmcs;
	int errcode;

	if (!decoder)
		return -pte_internal;

	vmcs = decoder->event.variant.vmcs.base;
	if (decoder->asid.vmcs != vmcs) {
		errcode = pt_msec_cache_invalidate(&decoder->scache);
		if (errcode < 0)
			return errcode;

		decoder->asid.vmcs = vmcs;
	}

	return 0;
}

int pt_insn_event(struct pt_insn_decoder *decoder, struct pt_event *uevent,
		  size_t size)
{
	struct pt_event *ev;
	int status;

	if (!decoder || !uevent)
		return -pte_invalid;

	/* We must currently process an event. */
	if (!decoder->process_event)
		return -pte_bad_query;

	ev = &decoder->event;
	switch (ev->type) {
	default:
		/* This is not a user event.
		 *
		 * We either indicated it wrongly or the user called
		 * pt_insn_event() without a pts_event_pending indication.
		 */
		return -pte_bad_query;

	case ptev_enabled:
		/* Indicate that tracing resumes from the IP at which tracing
		 * had been disabled before (with some special treatment for
		 * calls).
		 */
		if (decoder->ip == ev->variant.enabled.ip)
			ev->variant.enabled.resumed = 1;

		status = pt_insn_process_enabled(decoder);
		if (status < 0)
			return status;

		break;

	case ptev_async_disabled:
		if (!ev->ip_suppressed &&
		    decoder->ip != ev->variant.async_disabled.at)
			return -pte_bad_query;

		fallthrough;
	case ptev_disabled:
		status = pt_insn_process_disabled(decoder);
		if (status < 0)
			return status;

		break;

	case ptev_async_branch:
		if (decoder->ip != ev->variant.async_branch.from)
			return -pte_bad_query;

		status = pt_insn_process_async_branch(decoder);
		if (status < 0)
			return status;

		break;

	case ptev_async_paging:
		if (!ev->ip_suppressed &&
		    decoder->ip != ev->variant.async_paging.ip)
			return -pte_bad_query;

		fallthrough;
	case ptev_paging:
		status = pt_insn_process_paging(decoder);
		if (status < 0)
			return status;

		break;

	case ptev_async_vmcs:
		if (!ev->ip_suppressed &&
		    decoder->ip != ev->variant.async_vmcs.ip)
			return -pte_bad_query;

		fallthrough;
	case ptev_vmcs:
		status = pt_insn_process_vmcs(decoder);
		if (status < 0)
			return status;

		break;

	case ptev_overflow:
		status = pt_insn_process_overflow(decoder);
		if (status < 0)
			return status;

		break;

	case ptev_exec_mode:
		status = pt_insn_process_exec_mode(decoder);
		if (status < 0)
			return status;

		break;

	case ptev_tsx:
		status = pt_insn_process_tsx(decoder);
		if (status < 0)
			return status;

		break;

	case ptev_stop:
		status = pt_insn_process_stop(decoder);
		if (status < 0)
			return status;

		break;

	case ptev_exstop:
		if (!ev->ip_suppressed && decoder->enabled &&
		    decoder->ip != ev->variant.exstop.ip)
			return -pte_bad_query;

		break;

	case ptev_mwait:
		if (!ev->ip_suppressed && decoder->enabled &&
		    decoder->ip != ev->variant.mwait.ip)
			return -pte_bad_query;

		break;

	case ptev_pwre:
	case ptev_pwrx:
	case ptev_ptwrite:
	case ptev_tick:
	case ptev_cbr:
	case ptev_mnt:
		break;
	}

	/* Copy the event to the user.  Make sure we're not writing beyond the
	 * memory provided by the user.
	 *
	 * We might truncate details of an event but only for those events the
	 * user can't know about, anyway.
	 */
	if (sizeof(*ev) < size)
		size = sizeof(*ev);

	memcpy(uevent, ev, size);

	/* This completes processing of the current event. */
	decoder->process_event = 0;

	/* If we just handled an instruction event, check for further events
	 * that bind to this instruction.
	 *
	 * If we don't have further events, proceed beyond the instruction so we
	 * can check for IP events, as well.
	 */
	if (decoder->process_insn) {
		status = pt_insn_check_insn_event(decoder, &decoder->insn,
						  &decoder->iext);

		if (status != 0) {
			if (status < 0)
				return status;

			if (status & pts_event_pending)
				return status;
		}

		/* Proceed to the next instruction. */
		status = pt_insn_proceed_postponed(decoder);
		if (status < 0)
			return status;
	}

	/* Indicate further events that bind to the same IP. */
	return pt_insn_check_ip_event(decoder, NULL, NULL);
}