1 files changed, 898 insertions, 0 deletions

diff --git a/tools/perf/arch/arm/util/cs-etm.c b/tools/perf/arch/arm/util/cs-etm.c
new file mode 100644
index 000000000..cad7bf783
--- /dev/null
+++ b/tools/perf/arch/arm/util/cs-etm.c
@@ -0,0 +1,898 @@
+// SPDX-License-Identifier: GPL-2.0
+/*
+ * Copyright(C) 2015 Linaro Limited. All rights reserved.
+ * Author: Mathieu Poirier <mathieu.poirier@linaro.org>
+ */
+
+#include <api/fs/fs.h>
+#include <linux/bits.h>
+#include <linux/bitops.h>
+#include <linux/compiler.h>
+#include <linux/coresight-pmu.h>
+#include <linux/kernel.h>
+#include <linux/log2.h>
+#include <linux/string.h>
+#include <linux/types.h>
+#include <linux/zalloc.h>
+
+#include "cs-etm.h"
+#include "../../util/debug.h"
+#include "../../util/record.h"
+#include "../../util/auxtrace.h"
+#include "../../util/cpumap.h"
+#include "../../util/event.h"
+#include "../../util/evlist.h"
+#include "../../util/evsel.h"
+#include "../../util/perf_api_probe.h"
+#include "../../util/evsel_config.h"
+#include "../../util/pmu.h"
+#include "../../util/cs-etm.h"
+#include <internal/lib.h> // page_size
+#include "../../util/session.h"
+
+#include <errno.h>
+#include <stdlib.h>
+#include <sys/stat.h>
+
+struct cs_etm_recording {
+	struct auxtrace_record	itr;
+	struct perf_pmu		*cs_etm_pmu;
+	struct evlist		*evlist;
+	int			wrapped_cnt;
+	bool			*wrapped;
+	bool			snapshot_mode;
+	size_t			snapshot_size;
+};
+
+static const char *metadata_etmv3_ro[CS_ETM_PRIV_MAX] = {
+	[CS_ETM_ETMCCER]	= "mgmt/etmccer",
+	[CS_ETM_ETMIDR]		= "mgmt/etmidr",
+};
+
+static const char *metadata_etmv4_ro[CS_ETMV4_PRIV_MAX] = {
+	[CS_ETMV4_TRCIDR0]		= "trcidr/trcidr0",
+	[CS_ETMV4_TRCIDR1]		= "trcidr/trcidr1",
+	[CS_ETMV4_TRCIDR2]		= "trcidr/trcidr2",
+	[CS_ETMV4_TRCIDR8]		= "trcidr/trcidr8",
+	[CS_ETMV4_TRCAUTHSTATUS]	= "mgmt/trcauthstatus",
+};
+
+static bool cs_etm_is_etmv4(struct auxtrace_record *itr, int cpu);
+
+static int cs_etm_set_context_id(struct auxtrace_record *itr,
+				 struct evsel *evsel, int cpu)
+{
+	struct cs_etm_recording *ptr;
+	struct perf_pmu *cs_etm_pmu;
+	char path[PATH_MAX];
+	int err = -EINVAL;
+	u32 val;
+
+	ptr = container_of(itr, struct cs_etm_recording, itr);
+	cs_etm_pmu = ptr->cs_etm_pmu;
+
+	if (!cs_etm_is_etmv4(itr, cpu))
+		goto out;
+
+	/* Get a handle on TRCIRD2 */
+	snprintf(path, PATH_MAX, "cpu%d/%s",
+		 cpu, metadata_etmv4_ro[CS_ETMV4_TRCIDR2]);
+	err = perf_pmu__scan_file(cs_etm_pmu, path, "%x", &val);
+
+	/* There was a problem reading the file, bailing out */
+	if (err != 1) {
+		pr_err("%s: can't read file %s\n",
+		       CORESIGHT_ETM_PMU_NAME, path);
+		goto out;
+	}
+
+	/*
+	 * TRCIDR2.CIDSIZE, bit [9-5], indicates whether contextID tracing
+	 * is supported:
+	 *  0b00000 Context ID tracing is not supported.
+	 *  0b00100 Maximum of 32-bit Context ID size.
+	 *  All other values are reserved.
+	 */
+	val = BMVAL(val, 5, 9);
+	if (!val || val != 0x4) {
+		err = -EINVAL;
+		goto out;
+	}
+
+	/* All good, let the kernel know */
+	evsel->core.attr.config |= (1 << ETM_OPT_CTXTID);
+	err = 0;
+
+out:
+
+	return err;
+}
+
+static int cs_etm_set_timestamp(struct auxtrace_record *itr,
+				struct evsel *evsel, int cpu)
+{
+	struct cs_etm_recording *ptr;
+	struct perf_pmu *cs_etm_pmu;
+	char path[PATH_MAX];
+	int err = -EINVAL;
+	u32 val;
+
+	ptr = container_of(itr, struct cs_etm_recording, itr);
+	cs_etm_pmu = ptr->cs_etm_pmu;
+
+	if (!cs_etm_is_etmv4(itr, cpu))
+		goto out;
+
+	/* Get a handle on TRCIRD0 */
+	snprintf(path, PATH_MAX, "cpu%d/%s",
+		 cpu, metadata_etmv4_ro[CS_ETMV4_TRCIDR0]);
+	err = perf_pmu__scan_file(cs_etm_pmu, path, "%x", &val);
+
+	/* There was a problem reading the file, bailing out */
+	if (err != 1) {
+		pr_err("%s: can't read file %s\n",
+		       CORESIGHT_ETM_PMU_NAME, path);
+		goto out;
+	}
+
+	/*
+	 * TRCIDR0.TSSIZE, bit [28-24], indicates whether global timestamping
+	 * is supported:
+	 *  0b00000 Global timestamping is not implemented
+	 *  0b00110 Implementation supports a maximum timestamp of 48bits.
+	 *  0b01000 Implementation supports a maximum timestamp of 64bits.
+	 */
+	val &= GENMASK(28, 24);
+	if (!val) {
+		err = -EINVAL;
+		goto out;
+	}
+
+	/* All good, let the kernel know */
+	evsel->core.attr.config |= (1 << ETM_OPT_TS);
+	err = 0;
+
+out:
+	return err;
+}
+
+static int cs_etm_set_option(struct auxtrace_record *itr,
+			     struct evsel *evsel, u32 option)
+{
+	int i, err = -EINVAL;
+	struct perf_cpu_map *event_cpus = evsel->evlist->core.cpus;
+	struct perf_cpu_map *online_cpus = perf_cpu_map__new(NULL);
+
+	/* Set option of each CPU we have */
+	for (i = 0; i < cpu__max_cpu(); i++) {
+		if (!cpu_map__has(event_cpus, i) ||
+		    !cpu_map__has(online_cpus, i))
+			continue;
+
+		if (option & ETM_OPT_CTXTID) {
+			err = cs_etm_set_context_id(itr, evsel, i);
+			if (err)
+				goto out;
+		}
+		if (option & ETM_OPT_TS) {
+			err = cs_etm_set_timestamp(itr, evsel, i);
+			if (err)
+				goto out;
+		}
+		if (option & ~(ETM_OPT_CTXTID | ETM_OPT_TS))
+			/* Nothing else is currently supported */
+			goto out;
+	}
+
+	err = 0;
+out:
+	perf_cpu_map__put(online_cpus);
+	return err;
+}
+
+static int cs_etm_parse_snapshot_options(struct auxtrace_record *itr,
+					 struct record_opts *opts,
+					 const char *str)
+{
+	struct cs_etm_recording *ptr =
+				container_of(itr, struct cs_etm_recording, itr);
+	unsigned long long snapshot_size = 0;
+	char *endptr;
+
+	if (str) {
+		snapshot_size = strtoull(str, &endptr, 0);
+		if (*endptr || snapshot_size > SIZE_MAX)
+			return -1;
+	}
+
+	opts->auxtrace_snapshot_mode = true;
+	opts->auxtrace_snapshot_size = snapshot_size;
+	ptr->snapshot_size = snapshot_size;
+
+	return 0;
+}
+
+static int cs_etm_set_sink_attr(struct perf_pmu *pmu,
+				struct evsel *evsel)
+{
+	char msg[BUFSIZ], path[PATH_MAX], *sink;
+	struct evsel_config_term *term;
+	int ret = -EINVAL;
+	u32 hash;
+
+	if (evsel->core.attr.config2 & GENMASK(31, 0))
+		return 0;
+
+	list_for_each_entry(term, &evsel->config_terms, list) {
+		if (term->type != EVSEL__CONFIG_TERM_DRV_CFG)
+			continue;
+
+		sink = term->val.str;
+		snprintf(path, PATH_MAX, "sinks/%s", sink);
+
+		ret = perf_pmu__scan_file(pmu, path, "%x", &hash);
+		if (ret != 1) {
+			pr_err("failed to set sink \"%s\" on event %s with %d (%s)\n",
+			       sink, evsel__name(evsel), errno,
+			       str_error_r(errno, msg, sizeof(msg)));
+			return ret;
+		}
+
+		evsel->core.attr.config2 |= hash;
+		return 0;
+	}
+
+	/*
+	 * No sink was provided on the command line - allow the CoreSight
+	 * system to look for a default
+	 */
+	return 0;
+}
+
+static int cs_etm_recording_options(struct auxtrace_record *itr,
+				    struct evlist *evlist,
+				    struct record_opts *opts)
+{
+	int ret;
+	struct cs_etm_recording *ptr =
+				container_of(itr, struct cs_etm_recording, itr);
+	struct perf_pmu *cs_etm_pmu = ptr->cs_etm_pmu;
+	struct evsel *evsel, *cs_etm_evsel = NULL;
+	struct perf_cpu_map *cpus = evlist->core.cpus;
+	bool privileged = perf_event_paranoid_check(-1);
+	int err = 0;
+
+	ptr->evlist = evlist;
+	ptr->snapshot_mode = opts->auxtrace_snapshot_mode;
+
+	if (!record_opts__no_switch_events(opts) &&
+	    perf_can_record_switch_events())
+		opts->record_switch_events = true;
+
+	evlist__for_each_entry(evlist, evsel) {
+		if (evsel->core.attr.type == cs_etm_pmu->type) {
+			if (cs_etm_evsel) {
+				pr_err("There may be only one %s event\n",
+				       CORESIGHT_ETM_PMU_NAME);
+				return -EINVAL;
+			}
+			evsel->core.attr.freq = 0;
+			evsel->core.attr.sample_period = 1;
+			cs_etm_evsel = evsel;
+			opts->full_auxtrace = true;
+		}
+	}
+
+	/* no need to continue if at least one event of interest was found */
+	if (!cs_etm_evsel)
+		return 0;
+
+	ret = cs_etm_set_sink_attr(cs_etm_pmu, cs_etm_evsel);
+	if (ret)
+		return ret;
+
+	if (opts->use_clockid) {
+		pr_err("Cannot use clockid (-k option) with %s\n",
+		       CORESIGHT_ETM_PMU_NAME);
+		return -EINVAL;
+	}
+
+	/* we are in snapshot mode */
+	if (opts->auxtrace_snapshot_mode) {
+		/*
+		 * No size were given to '-S' or '-m,', so go with
+		 * the default
+		 */
+		if (!opts->auxtrace_snapshot_size &&
+		    !opts->auxtrace_mmap_pages) {
+			if (privileged) {
+				opts->auxtrace_mmap_pages = MiB(4) / page_size;
+			} else {
+				opts->auxtrace_mmap_pages =
+							KiB(128) / page_size;
+				if (opts->mmap_pages == UINT_MAX)
+					opts->mmap_pages = KiB(256) / page_size;
+			}
+		} else if (!opts->auxtrace_mmap_pages && !privileged &&
+						opts->mmap_pages == UINT_MAX) {
+			opts->mmap_pages = KiB(256) / page_size;
+		}
+
+		/*
+		 * '-m,xyz' was specified but no snapshot size, so make the
+		 * snapshot size as big as the auxtrace mmap area.
+		 */
+		if (!opts->auxtrace_snapshot_size) {
+			opts->auxtrace_snapshot_size =
+				opts->auxtrace_mmap_pages * (size_t)page_size;
+		}
+
+		/*
+		 * -Sxyz was specified but no auxtrace mmap area, so make the
+		 * auxtrace mmap area big enough to fit the requested snapshot
+		 * size.
+		 */
+		if (!opts->auxtrace_mmap_pages) {
+			size_t sz = opts->auxtrace_snapshot_size;
+
+			sz = round_up(sz, page_size) / page_size;
+			opts->auxtrace_mmap_pages = roundup_pow_of_two(sz);
+		}
+
+		/* Snapshost size can't be bigger than the auxtrace area */
+		if (opts->auxtrace_snapshot_size >
+				opts->auxtrace_mmap_pages * (size_t)page_size) {
+			pr_err("Snapshot size %zu must not be greater than AUX area tracing mmap size %zu\n",
+			       opts->auxtrace_snapshot_size,
+			       opts->auxtrace_mmap_pages * (size_t)page_size);
+			return -EINVAL;
+		}
+
+		/* Something went wrong somewhere - this shouldn't happen */
+		if (!opts->auxtrace_snapshot_size ||
+		    !opts->auxtrace_mmap_pages) {
+			pr_err("Failed to calculate default snapshot size and/or AUX area tracing mmap pages\n");
+			return -EINVAL;
+		}
+	}
+
+	/* We are in full trace mode but '-m,xyz' wasn't specified */
+	if (opts->full_auxtrace && !opts->auxtrace_mmap_pages) {
+		if (privileged) {
+			opts->auxtrace_mmap_pages = MiB(4) / page_size;
+		} else {
+			opts->auxtrace_mmap_pages = KiB(128) / page_size;
+			if (opts->mmap_pages == UINT_MAX)
+				opts->mmap_pages = KiB(256) / page_size;
+		}
+
+	}
+
+	/* Validate auxtrace_mmap_pages provided by user */
+	if (opts->auxtrace_mmap_pages) {
+		unsigned int max_page = (KiB(128) / page_size);
+		size_t sz = opts->auxtrace_mmap_pages * (size_t)page_size;
+
+		if (!privileged &&
+		    opts->auxtrace_mmap_pages > max_page) {
+			opts->auxtrace_mmap_pages = max_page;
+			pr_err("auxtrace too big, truncating to %d\n",
+			       max_page);
+		}
+
+		if (!is_power_of_2(sz)) {
+			pr_err("Invalid mmap size for %s: must be a power of 2\n",
+			       CORESIGHT_ETM_PMU_NAME);
+			return -EINVAL;
+		}
+	}
+
+	if (opts->auxtrace_snapshot_mode)
+		pr_debug2("%s snapshot size: %zu\n", CORESIGHT_ETM_PMU_NAME,
+			  opts->auxtrace_snapshot_size);
+
+	/*
+	 * To obtain the auxtrace buffer file descriptor, the auxtrace
+	 * event must come first.
+	 */
+	perf_evlist__to_front(evlist, cs_etm_evsel);
+
+	/*
+	 * In the case of per-cpu mmaps, we need the CPU on the
+	 * AUX event.  We also need the contextID in order to be notified
+	 * when a context switch happened.
+	 */
+	if (!perf_cpu_map__empty(cpus)) {
+		evsel__set_sample_bit(cs_etm_evsel, CPU);
+
+		err = cs_etm_set_option(itr, cs_etm_evsel,
+					ETM_OPT_CTXTID | ETM_OPT_TS);
+		if (err)
+			goto out;
+	}
+
+	/* Add dummy event to keep tracking */
+	if (opts->full_auxtrace) {
+		struct evsel *tracking_evsel;
+
+		err = parse_events(evlist, "dummy:u", NULL);
+		if (err)
+			goto out;
+
+		tracking_evsel = evlist__last(evlist);
+		perf_evlist__set_tracking_event(evlist, tracking_evsel);
+
+		tracking_evsel->core.attr.freq = 0;
+		tracking_evsel->core.attr.sample_period = 1;
+
+		/* In per-cpu case, always need the time of mmap events etc */
+		if (!perf_cpu_map__empty(cpus))
+			evsel__set_sample_bit(tracking_evsel, TIME);
+	}
+
+out:
+	return err;
+}
+
+static u64 cs_etm_get_config(struct auxtrace_record *itr)
+{
+	u64 config = 0;
+	struct cs_etm_recording *ptr =
+			container_of(itr, struct cs_etm_recording, itr);
+	struct perf_pmu *cs_etm_pmu = ptr->cs_etm_pmu;
+	struct evlist *evlist = ptr->evlist;
+	struct evsel *evsel;
+
+	evlist__for_each_entry(evlist, evsel) {
+		if (evsel->core.attr.type == cs_etm_pmu->type) {
+			/*
+			 * Variable perf_event_attr::config is assigned to
+			 * ETMv3/PTM.  The bit fields have been made to match
+			 * the ETMv3.5 ETRMCR register specification.  See the
+			 * PMU_FORMAT_ATTR() declarations in
+			 * drivers/hwtracing/coresight/coresight-perf.c for
+			 * details.
+			 */
+			config = evsel->core.attr.config;
+			break;
+		}
+	}
+
+	return config;
+}
+
+#ifndef BIT
+#define BIT(N) (1UL << (N))
+#endif
+
+static u64 cs_etmv4_get_config(struct auxtrace_record *itr)
+{
+	u64 config = 0;
+	u64 config_opts = 0;
+
+	/*
+	 * The perf event variable config bits represent both
+	 * the command line options and register programming
+	 * bits in ETMv3/PTM. For ETMv4 we must remap options
+	 * to real bits
+	 */
+	config_opts = cs_etm_get_config(itr);
+	if (config_opts & BIT(ETM_OPT_CYCACC))
+		config |= BIT(ETM4_CFG_BIT_CYCACC);
+	if (config_opts & BIT(ETM_OPT_CTXTID))
+		config |= BIT(ETM4_CFG_BIT_CTXTID);
+	if (config_opts & BIT(ETM_OPT_TS))
+		config |= BIT(ETM4_CFG_BIT_TS);
+	if (config_opts & BIT(ETM_OPT_RETSTK))
+		config |= BIT(ETM4_CFG_BIT_RETSTK);
+
+	return config;
+}
+
+static size_t
+cs_etm_info_priv_size(struct auxtrace_record *itr __maybe_unused,
+		      struct evlist *evlist __maybe_unused)
+{
+	int i;
+	int etmv3 = 0, etmv4 = 0;
+	struct perf_cpu_map *event_cpus = evlist->core.cpus;
+	struct perf_cpu_map *online_cpus = perf_cpu_map__new(NULL);
+
+	/* cpu map is not empty, we have specific CPUs to work with */
+	if (!perf_cpu_map__empty(event_cpus)) {
+		for (i = 0; i < cpu__max_cpu(); i++) {
+			if (!cpu_map__has(event_cpus, i) ||
+			    !cpu_map__has(online_cpus, i))
+				continue;
+
+			if (cs_etm_is_etmv4(itr, i))
+				etmv4++;
+			else
+				etmv3++;
+		}
+	} else {
+		/* get configuration for all CPUs in the system */
+		for (i = 0; i < cpu__max_cpu(); i++) {
+			if (!cpu_map__has(online_cpus, i))
+				continue;
+
+			if (cs_etm_is_etmv4(itr, i))
+				etmv4++;
+			else
+				etmv3++;
+		}
+	}
+
+	perf_cpu_map__put(online_cpus);
+
+	return (CS_ETM_HEADER_SIZE +
+	       (etmv4 * CS_ETMV4_PRIV_SIZE) +
+	       (etmv3 * CS_ETMV3_PRIV_SIZE));
+}
+
+static bool cs_etm_is_etmv4(struct auxtrace_record *itr, int cpu)
+{
+	bool ret = false;
+	char path[PATH_MAX];
+	int scan;
+	unsigned int val;
+	struct cs_etm_recording *ptr =
+			container_of(itr, struct cs_etm_recording, itr);
+	struct perf_pmu *cs_etm_pmu = ptr->cs_etm_pmu;
+
+	/* Take any of the RO files for ETMv4 and see if it present */
+	snprintf(path, PATH_MAX, "cpu%d/%s",
+		 cpu, metadata_etmv4_ro[CS_ETMV4_TRCIDR0]);
+	scan = perf_pmu__scan_file(cs_etm_pmu, path, "%x", &val);
+
+	/* The file was read successfully, we have a winner */
+	if (scan == 1)
+		ret = true;
+
+	return ret;
+}
+
+static int cs_etm_get_ro(struct perf_pmu *pmu, int cpu, const char *path)
+{
+	char pmu_path[PATH_MAX];
+	int scan;
+	unsigned int val = 0;
+
+	/* Get RO metadata from sysfs */
+	snprintf(pmu_path, PATH_MAX, "cpu%d/%s", cpu, path);
+
+	scan = perf_pmu__scan_file(pmu, pmu_path, "%x", &val);
+	if (scan != 1)
+		pr_err("%s: error reading: %s\n", __func__, pmu_path);
+
+	return val;
+}
+
+static void cs_etm_get_metadata(int cpu, u32 *offset,
+				struct auxtrace_record *itr,
+				struct perf_record_auxtrace_info *info)
+{
+	u32 increment;
+	u64 magic;
+	struct cs_etm_recording *ptr =
+			container_of(itr, struct cs_etm_recording, itr);
+	struct perf_pmu *cs_etm_pmu = ptr->cs_etm_pmu;
+
+	/* first see what kind of tracer this cpu is affined to */
+	if (cs_etm_is_etmv4(itr, cpu)) {
+		magic = __perf_cs_etmv4_magic;
+		/* Get trace configuration register */
+		info->priv[*offset + CS_ETMV4_TRCCONFIGR] =
+						cs_etmv4_get_config(itr);
+		/* Get traceID from the framework */
+		info->priv[*offset + CS_ETMV4_TRCTRACEIDR] =
+						coresight_get_trace_id(cpu);
+		/* Get read-only information from sysFS */
+		info->priv[*offset + CS_ETMV4_TRCIDR0] =
+			cs_etm_get_ro(cs_etm_pmu, cpu,
+				      metadata_etmv4_ro[CS_ETMV4_TRCIDR0]);
+		info->priv[*offset + CS_ETMV4_TRCIDR1] =
+			cs_etm_get_ro(cs_etm_pmu, cpu,
+				      metadata_etmv4_ro[CS_ETMV4_TRCIDR1]);
+		info->priv[*offset + CS_ETMV4_TRCIDR2] =
+			cs_etm_get_ro(cs_etm_pmu, cpu,
+				      metadata_etmv4_ro[CS_ETMV4_TRCIDR2]);
+		info->priv[*offset + CS_ETMV4_TRCIDR8] =
+			cs_etm_get_ro(cs_etm_pmu, cpu,
+				      metadata_etmv4_ro[CS_ETMV4_TRCIDR8]);
+		info->priv[*offset + CS_ETMV4_TRCAUTHSTATUS] =
+			cs_etm_get_ro(cs_etm_pmu, cpu,
+				      metadata_etmv4_ro
+				      [CS_ETMV4_TRCAUTHSTATUS]);
+
+		/* How much space was used */
+		increment = CS_ETMV4_PRIV_MAX;
+	} else {
+		magic = __perf_cs_etmv3_magic;
+		/* Get configuration register */
+		info->priv[*offset + CS_ETM_ETMCR] = cs_etm_get_config(itr);
+		/* Get traceID from the framework */
+		info->priv[*offset + CS_ETM_ETMTRACEIDR] =
+						coresight_get_trace_id(cpu);
+		/* Get read-only information from sysFS */
+		info->priv[*offset + CS_ETM_ETMCCER] =
+			cs_etm_get_ro(cs_etm_pmu, cpu,
+				      metadata_etmv3_ro[CS_ETM_ETMCCER]);
+		info->priv[*offset + CS_ETM_ETMIDR] =
+			cs_etm_get_ro(cs_etm_pmu, cpu,
+				      metadata_etmv3_ro[CS_ETM_ETMIDR]);
+
+		/* How much space was used */
+		increment = CS_ETM_PRIV_MAX;
+	}
+
+	/* Build generic header portion */
+	info->priv[*offset + CS_ETM_MAGIC] = magic;
+	info->priv[*offset + CS_ETM_CPU] = cpu;
+	/* Where the next CPU entry should start from */
+	*offset += increment;
+}
+
+static int cs_etm_info_fill(struct auxtrace_record *itr,
+			    struct perf_session *session,
+			    struct perf_record_auxtrace_info *info,
+			    size_t priv_size)
+{
+	int i;
+	u32 offset;
+	u64 nr_cpu, type;
+	struct perf_cpu_map *cpu_map;
+	struct perf_cpu_map *event_cpus = session->evlist->core.cpus;
+	struct perf_cpu_map *online_cpus = perf_cpu_map__new(NULL);
+	struct cs_etm_recording *ptr =
+			container_of(itr, struct cs_etm_recording, itr);
+	struct perf_pmu *cs_etm_pmu = ptr->cs_etm_pmu;
+
+	if (priv_size != cs_etm_info_priv_size(itr, session->evlist))
+		return -EINVAL;
+
+	if (!session->evlist->core.nr_mmaps)
+		return -EINVAL;
+
+	/* If the cpu_map is empty all online CPUs are involved */
+	if (perf_cpu_map__empty(event_cpus)) {
+		cpu_map = online_cpus;
+	} else {
+		/* Make sure all specified CPUs are online */
+		for (i = 0; i < perf_cpu_map__nr(event_cpus); i++) {
+			if (cpu_map__has(event_cpus, i) &&
+			    !cpu_map__has(online_cpus, i))
+				return -EINVAL;
+		}
+
+		cpu_map = event_cpus;
+	}
+
+	nr_cpu = perf_cpu_map__nr(cpu_map);
+	/* Get PMU type as dynamically assigned by the core */
+	type = cs_etm_pmu->type;
+
+	/* First fill out the session header */
+	info->type = PERF_AUXTRACE_CS_ETM;
+	info->priv[CS_HEADER_VERSION_0] = 0;
+	info->priv[CS_PMU_TYPE_CPUS] = type << 32;
+	info->priv[CS_PMU_TYPE_CPUS] |= nr_cpu;
+	info->priv[CS_ETM_SNAPSHOT] = ptr->snapshot_mode;
+
+	offset = CS_ETM_SNAPSHOT + 1;
+
+	for (i = 0; i < cpu__max_cpu() && offset < priv_size; i++)
+		if (cpu_map__has(cpu_map, i))
+			cs_etm_get_metadata(i, &offset, itr, info);
+
+	perf_cpu_map__put(online_cpus);
+
+	return 0;
+}
+
+static int cs_etm_alloc_wrapped_array(struct cs_etm_recording *ptr, int idx)
+{
+	bool *wrapped;
+	int cnt = ptr->wrapped_cnt;
+
+	/* Make @ptr->wrapped as big as @idx */
+	while (cnt <= idx)
+		cnt++;
+
+	/*
+	 * Free'ed in cs_etm_recording_free().  Using realloc() to avoid
+	 * cross compilation problems where the host's system supports
+	 * reallocarray() but not the target.
+	 */
+	wrapped = realloc(ptr->wrapped, cnt * sizeof(bool));
+	if (!wrapped)
+		return -ENOMEM;
+
+	wrapped[cnt - 1] = false;
+	ptr->wrapped_cnt = cnt;
+	ptr->wrapped = wrapped;
+
+	return 0;
+}
+
+static bool cs_etm_buffer_has_wrapped(unsigned char *buffer,
+				      size_t buffer_size, u64 head)
+{
+	u64 i, watermark;
+	u64 *buf = (u64 *)buffer;
+	size_t buf_size = buffer_size;
+
+	/*
+	 * We want to look the very last 512 byte (chosen arbitrarily) in
+	 * the ring buffer.
+	 */
+	watermark = buf_size - 512;
+
+	/*
+	 * @head is continuously increasing - if its value is equal or greater
+	 * than the size of the ring buffer, it has wrapped around.
+	 */
+	if (head >= buffer_size)
+		return true;
+
+	/*
+	 * The value of @head is somewhere within the size of the ring buffer.
+	 * This can be that there hasn't been enough data to fill the ring
+	 * buffer yet or the trace time was so long that @head has numerically
+	 * wrapped around.  To find we need to check if we have data at the very
+	 * end of the ring buffer.  We can reliably do this because mmap'ed
+	 * pages are zeroed out and there is a fresh mapping with every new
+	 * session.
+	 */
+
+	/* @head is less than 512 byte from the end of the ring buffer */
+	if (head > watermark)
+		watermark = head;
+
+	/*
+	 * Speed things up by using 64 bit transactions (see "u64 *buf" above)
+	 */
+	watermark >>= 3;
+	buf_size >>= 3;
+
+	/*
+	 * If we find trace data at the end of the ring buffer, @head has
+	 * been there and has numerically wrapped around at least once.
+	 */
+	for (i = watermark; i < buf_size; i++)
+		if (buf[i])
+			return true;
+
+	return false;
+}
+
+static int cs_etm_find_snapshot(struct auxtrace_record *itr,
+				int idx, struct auxtrace_mmap *mm,
+				unsigned char *data,
+				u64 *head, u64 *old)
+{
+	int err;
+	bool wrapped;
+	struct cs_etm_recording *ptr =
+			container_of(itr, struct cs_etm_recording, itr);
+
+	/*
+	 * Allocate memory to keep track of wrapping if this is the first
+	 * time we deal with this *mm.
+	 */
+	if (idx >= ptr->wrapped_cnt) {
+		err = cs_etm_alloc_wrapped_array(ptr, idx);
+		if (err)
+			return err;
+	}
+
+	/*
+	 * Check to see if *head has wrapped around.  If it hasn't only the
+	 * amount of data between *head and *old is snapshot'ed to avoid
+	 * bloating the perf.data file with zeros.  But as soon as *head has
+	 * wrapped around the entire size of the AUX ring buffer it taken.
+	 */
+	wrapped = ptr->wrapped[idx];
+	if (!wrapped && cs_etm_buffer_has_wrapped(data, mm->len, *head)) {
+		wrapped = true;
+		ptr->wrapped[idx] = true;
+	}
+
+	pr_debug3("%s: mmap index %d old head %zu new head %zu size %zu\n",
+		  __func__, idx, (size_t)*old, (size_t)*head, mm->len);
+
+	/* No wrap has occurred, we can just use *head and *old. */
+	if (!wrapped)
+		return 0;
+
+	/*
+	 * *head has wrapped around - adjust *head and *old to pickup the
+	 * entire content of the AUX buffer.
+	 */
+	if (*head >= mm->len) {
+		*old = *head - mm->len;
+	} else {
+		*head += mm->len;
+		*old = *head - mm->len;
+	}
+
+	return 0;
+}
+
+static int cs_etm_snapshot_start(struct auxtrace_record *itr)
+{
+	struct cs_etm_recording *ptr =
+			container_of(itr, struct cs_etm_recording, itr);
+	struct evsel *evsel;
+
+	evlist__for_each_entry(ptr->evlist, evsel) {
+		if (evsel->core.attr.type == ptr->cs_etm_pmu->type)
+			return evsel__disable(evsel);
+	}
+	return -EINVAL;
+}
+
+static int cs_etm_snapshot_finish(struct auxtrace_record *itr)
+{
+	struct cs_etm_recording *ptr =
+			container_of(itr, struct cs_etm_recording, itr);
+	struct evsel *evsel;
+
+	evlist__for_each_entry(ptr->evlist, evsel) {
+		if (evsel->core.attr.type == ptr->cs_etm_pmu->type)
+			return evsel__enable(evsel);
+	}
+	return -EINVAL;
+}
+
+static u64 cs_etm_reference(struct auxtrace_record *itr __maybe_unused)
+{
+	return (((u64) rand() <<  0) & 0x00000000FFFFFFFFull) |
+		(((u64) rand() << 32) & 0xFFFFFFFF00000000ull);
+}
+
+static void cs_etm_recording_free(struct auxtrace_record *itr)
+{
+	struct cs_etm_recording *ptr =
+			container_of(itr, struct cs_etm_recording, itr);
+
+	zfree(&ptr->wrapped);
+	free(ptr);
+}
+
+struct auxtrace_record *cs_etm_record_init(int *err)
+{
+	struct perf_pmu *cs_etm_pmu;
+	struct cs_etm_recording *ptr;
+
+	cs_etm_pmu = perf_pmu__find(CORESIGHT_ETM_PMU_NAME);
+
+	if (!cs_etm_pmu) {
+		*err = -EINVAL;
+		goto out;
+	}
+
+	ptr = zalloc(sizeof(struct cs_etm_recording));
+	if (!ptr) {
+		*err = -ENOMEM;
+		goto out;
+	}
+
+	ptr->cs_etm_pmu			= cs_etm_pmu;
+	ptr->itr.pmu			= cs_etm_pmu;
+	ptr->itr.parse_snapshot_options	= cs_etm_parse_snapshot_options;
+	ptr->itr.recording_options	= cs_etm_recording_options;
+	ptr->itr.info_priv_size		= cs_etm_info_priv_size;
+	ptr->itr.info_fill		= cs_etm_info_fill;
+	ptr->itr.find_snapshot		= cs_etm_find_snapshot;
+	ptr->itr.snapshot_start		= cs_etm_snapshot_start;
+	ptr->itr.snapshot_finish	= cs_etm_snapshot_finish;
+	ptr->itr.reference		= cs_etm_reference;
+	ptr->itr.free			= cs_etm_recording_free;
+	ptr->itr.read_finish		= auxtrace_record__read_finish;
+
+	*err = 0;
+	return &ptr->itr;
+out:
+	return NULL;
+}