header.c

#define _FILE_OFFSET_BITS 64

#include <sys/types.h>
#include <byteswap.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <linux/list.h>
#include <linux/kernel.h>

#include "util.h"
#include "header.h"
#include "../perf.h"
#include "trace-event.h"
#include "session.h"
#include "symbol.h"
#include "debug.h"

/*
 * Create new perf.data header attribute:
 */
struct perf_header_attr *perf_header_attr__new(struct perf_event_attr *attr)
{
	struct perf_header_attr *self = malloc(sizeof(*self));

	if (self != NULL) {
		self->attr = *attr;
		self->ids  = 0;
		self->size = 1;
		self->id   = malloc(sizeof(u64));
		if (self->id == NULL) {
			free(self);
			self = NULL;
		}
	}

	return self;
}

void perf_header_attr__delete(struct perf_header_attr *self)
{
	free(self->id);
	free(self);
}

int perf_header_attr__add_id(struct perf_header_attr *self, u64 id)
{
	int pos = self->ids;

	self->ids++;
	if (self->ids > self->size) {
		int nsize = self->size * 2;
		u64 *nid = realloc(self->id, nsize * sizeof(u64));

		if (nid == NULL)
			return -1;

		self->size = nsize;
		self->id = nid;
	}
	self->id[pos] = id;
	return 0;
}

int perf_header__init(struct perf_header *self)
{
	self->size = 1;
	self->attr = malloc(sizeof(void *));
	return self->attr == NULL ? -ENOMEM : 0;
}

void perf_header__exit(struct perf_header *self)
{
	int i;
	for (i = 0; i < self->attrs; ++i)
                perf_header_attr__delete(self->attr[i]);
	free(self->attr);
}

int perf_header__add_attr(struct perf_header *self,
			  struct perf_header_attr *attr)
{
	if (self->frozen)
		return -1;

	if (self->attrs == self->size) {
		int nsize = self->size * 2;
		struct perf_header_attr **nattr;

		nattr = realloc(self->attr, nsize * sizeof(void *));
		if (nattr == NULL)
			return -1;

		self->size = nsize;
		self->attr = nattr;
	}

	self->attr[self->attrs++] = attr;
	return 0;
}

static int event_count;
static struct perf_trace_event_type *events;

int perf_header__push_event(u64 id, const char *name)
{
	if (strlen(name) > MAX_EVENT_NAME)
		pr_warning("Event %s will be truncated\n", name);

	if (!events) {
		events = malloc(sizeof(struct perf_trace_event_type));
		if (events == NULL)
			return -ENOMEM;
	} else {
		struct perf_trace_event_type *nevents;

		nevents = realloc(events, (event_count + 1) * sizeof(*events));
		if (nevents == NULL)
			return -ENOMEM;
		events = nevents;
	}
	memset(&events[event_count], 0, sizeof(struct perf_trace_event_type));
	events[event_count].event_id = id;
	strncpy(events[event_count].name, name, MAX_EVENT_NAME - 1);
	event_count++;
	return 0;
}

char *perf_header__find_event(u64 id)
{
	int i;
	for (i = 0 ; i < event_count; i++) {
		if (events[i].event_id == id)
			return events[i].name;
	}
	return NULL;
}

static const char *__perf_magic = "PERFFILE";

#define PERF_MAGIC	(*(u64 *)__perf_magic)

struct perf_file_attr {
	struct perf_event_attr	attr;
	struct perf_file_section	ids;
};

void perf_header__set_feat(struct perf_header *self, int feat)
{
	set_bit(feat, self->adds_features);
}

bool perf_header__has_feat(const struct perf_header *self, int feat)
{
	return test_bit(feat, self->adds_features);
}

static int do_write(int fd, const void *buf, size_t size)
{
	while (size) {
		int ret = write(fd, buf, size);

		if (ret < 0)
			return -errno;

		size -= ret;
		buf += ret;
	}

	return 0;
}

#define NAME_ALIGN 64

static int write_padded(int fd, const void *bf, size_t count,
			size_t count_aligned)
{
	static const char zero_buf[NAME_ALIGN];
	int err = do_write(fd, bf, count);

	if (!err)
		err = do_write(fd, zero_buf, count_aligned - count);

	return err;
}

#define dsos__for_each_with_build_id(pos, head)	\
	list_for_each_entry(pos, head, node)	\
		if (!pos->has_build_id)		\
			continue;		\
		else

static int __dsos__write_buildid_table(struct list_head *head, u16 misc, int fd)
{
	struct dso *pos;

	dsos__for_each_with_build_id(pos, head) {
		int err;
		struct build_id_event b;
		size_t len;

		if (!pos->hit)
			continue;
		len = pos->long_name_len + 1;
		len = ALIGN(len, NAME_ALIGN);
		memset(&b, 0, sizeof(b));
		memcpy(&b.build_id, pos->build_id, sizeof(pos->build_id));
		b.header.misc = misc;
		b.header.size = sizeof(b) + len;
		err = do_write(fd, &b, sizeof(b));
		if (err < 0)
			return err;
		err = write_padded(fd, pos->long_name,
				   pos->long_name_len + 1, len);
		if (err < 0)
			return err;
	}

	return 0;
}

static int dsos__write_buildid_table(int fd)
{
	int err = __dsos__write_buildid_table(&dsos__kernel,
					      PERF_RECORD_MISC_KERNEL, fd);
	if (err == 0)
		err = __dsos__write_buildid_table(&dsos__user,
						  PERF_RECORD_MISC_USER, fd);
	return err;
}

int build_id_cache__add_s(const char *sbuild_id, const char *debugdir,
			  const char *name, bool is_kallsyms)
{
	const size_t size = PATH_MAX;
	char *filename = malloc(size),
	     *linkname = malloc(size), *targetname;
	int len, err = -1;

	if (filename == NULL || linkname == NULL)
		goto out_free;

	len = snprintf(filename, size, "%s%s%s",
		       debugdir, is_kallsyms ? "/" : "", name);
	if (mkdir_p(filename, 0755))
		goto out_free;

	snprintf(filename + len, sizeof(filename) - len, "/%s", sbuild_id);

	if (access(filename, F_OK)) {
		if (is_kallsyms) {
			 if (copyfile("/proc/kallsyms", filename))
				goto out_free;
		} else if (link(name, filename) && copyfile(name, filename))
			goto out_free;
	}

	len = snprintf(linkname, size, "%s/.build-id/%.2s",
		       debugdir, sbuild_id);

	if (access(linkname, X_OK) && mkdir_p(linkname, 0755))
		goto out_free;

	snprintf(linkname + len, size - len, "/%s", sbuild_id + 2);
	targetname = filename + strlen(debugdir) - 5;
	memcpy(targetname, "../..", 5);

	if (symlink(targetname, linkname) == 0)
		err = 0;
out_free:
	free(filename);
	free(linkname);
	return err;
}

static int build_id_cache__add_b(const u8 *build_id, size_t build_id_size,
				 const char *name, const char *debugdir,
				 bool is_kallsyms)
{
	char sbuild_id[BUILD_ID_SIZE * 2 + 1];

	build_id__sprintf(build_id, build_id_size, sbuild_id);

	return build_id_cache__add_s(sbuild_id, debugdir, name, is_kallsyms);
}

int build_id_cache__remove_s(const char *sbuild_id, const char *debugdir)
{
	const size_t size = PATH_MAX;
	char *filename = malloc(size),
	     *linkname = malloc(size);
	int err = -1;

	if (filename == NULL || linkname == NULL)
		goto out_free;

	snprintf(linkname, size, "%s/.build-id/%.2s/%s",
		 debugdir, sbuild_id, sbuild_id + 2);

	if (access(linkname, F_OK))
		goto out_free;

	if (readlink(linkname, filename, size) < 0)
		goto out_free;

	if (unlink(linkname))
		goto out_free;

	/*
	 * Since the link is relative, we must make it absolute:
	 */
	snprintf(linkname, size, "%s/.build-id/%.2s/%s",
		 debugdir, sbuild_id, filename);

	if (unlink(linkname))
		goto out_free;

	err = 0;
out_free:
	free(filename);
	free(linkname);
	return err;
}

static int dso__cache_build_id(struct dso *self, const char *debugdir)
{
	bool is_kallsyms = self->kernel && self->long_name[0] != '/';

	return build_id_cache__add_b(self->build_id, sizeof(self->build_id),
				     self->long_name, debugdir, is_kallsyms);
}

static int __dsos__cache_build_ids(struct list_head *head, const char *debugdir)
{
	struct dso *pos;
	int err = 0;

	dsos__for_each_with_build_id(pos, head)
		if (dso__cache_build_id(pos, debugdir))
			err = -1;

	return err;
}

static int dsos__cache_build_ids(void)
{
	int err_kernel, err_user;
	char debugdir[PATH_MAX];

	snprintf(debugdir, sizeof(debugdir), "%s/%s", getenv("HOME"),
		 DEBUG_CACHE_DIR);

	if (mkdir(debugdir, 0755) != 0 && errno != EEXIST)
		return -1;

	err_kernel = __dsos__cache_build_ids(&dsos__kernel, debugdir);
	err_user   = __dsos__cache_build_ids(&dsos__user, debugdir);
	return err_kernel || err_user ? -1 : 0;
}

static int perf_header__adds_write(struct perf_header *self, int fd)
{
	int nr_sections;
	struct perf_file_section *feat_sec;
	int sec_size;
	u64 sec_start;
	int idx = 0, err;

	if (dsos__read_build_ids(true))
		perf_header__set_feat(self, HEADER_BUILD_ID);

	nr_sections = bitmap_weight(self->adds_features, HEADER_FEAT_BITS);
	if (!nr_sections)
		return 0;

	feat_sec = calloc(sizeof(*feat_sec), nr_sections);
	if (feat_sec == NULL)
		return -ENOMEM;

	sec_size = sizeof(*feat_sec) * nr_sections;

	sec_start = self->data_offset + self->data_size;
	lseek(fd, sec_start + sec_size, SEEK_SET);

	if (perf_header__has_feat(self, HEADER_TRACE_INFO)) {
		struct perf_file_section *trace_sec;

		trace_sec = &feat_sec[idx++];

		/* Write trace info */
		trace_sec->offset = lseek(fd, 0, SEEK_CUR);
		read_tracing_data(fd, attrs, nr_counters);
		trace_sec->size = lseek(fd, 0, SEEK_CUR) - trace_sec->offset;
	}


	if (perf_header__has_feat(self, HEADER_BUILD_ID)) {
		struct perf_file_section *buildid_sec;

		buildid_sec = &feat_sec[idx++];

		/* Write build-ids */
		buildid_sec->offset = lseek(fd, 0, SEEK_CUR);
		err = dsos__write_buildid_table(fd);
		if (err < 0) {
			pr_debug("failed to write buildid table\n");
			goto out_free;
		}
		buildid_sec->size = lseek(fd, 0, SEEK_CUR) -
					  buildid_sec->offset;
		dsos__cache_build_ids();
	}

	lseek(fd, sec_start, SEEK_SET);
	err = do_write(fd, feat_sec, sec_size);
	if (err < 0)
		pr_debug("failed to write feature section\n");
out_free:
	free(feat_sec);
	return err;
}

int perf_header__write_pipe(int fd)
{
	struct perf_pipe_file_header f_header;
	int err;

	f_header = (struct perf_pipe_file_header){
		.magic	   = PERF_MAGIC,
		.size	   = sizeof(f_header),
	};

	err = do_write(fd, &f_header, sizeof(f_header));
	if (err < 0) {
		pr_debug("failed to write perf pipe header\n");
		return err;
	}

	return 0;
}

int perf_header__write(struct perf_header *self, int fd, bool at_exit)
{
	struct perf_file_header f_header;
	struct perf_file_attr   f_attr;
	struct perf_header_attr	*attr;
	int i, err;

	lseek(fd, sizeof(f_header), SEEK_SET);


	for (i = 0; i < self->attrs; i++) {
		attr = self->attr[i];

		attr->id_offset = lseek(fd, 0, SEEK_CUR);
		err = do_write(fd, attr->id, attr->ids * sizeof(u64));
		if (err < 0) {
			pr_debug("failed to write perf header\n");
			return err;
		}
	}


	self->attr_offset = lseek(fd, 0, SEEK_CUR);

	for (i = 0; i < self->attrs; i++) {
		attr = self->attr[i];

		f_attr = (struct perf_file_attr){
			.attr = attr->attr,
			.ids  = {
				.offset = attr->id_offset,
				.size   = attr->ids * sizeof(u64),
			}
		};
		err = do_write(fd, &f_attr, sizeof(f_attr));
		if (err < 0) {
			pr_debug("failed to write perf header attribute\n");
			return err;
		}
	}

	self->event_offset = lseek(fd, 0, SEEK_CUR);
	self->event_size = event_count * sizeof(struct perf_trace_event_type);
	if (events) {
		err = do_write(fd, events, self->event_size);
		if (err < 0) {
			pr_debug("failed to write perf header events\n");
			return err;
		}
	}

	self->data_offset = lseek(fd, 0, SEEK_CUR);

	if (at_exit) {
		err = perf_header__adds_write(self, fd);
		if (err < 0)
			return err;
	}

	f_header = (struct perf_file_header){
		.magic	   = PERF_MAGIC,
		.size	   = sizeof(f_header),
		.attr_size = sizeof(f_attr),
		.attrs = {
			.offset = self->attr_offset,
			.size   = self->attrs * sizeof(f_attr),
		},
		.data = {
			.offset = self->data_offset,
			.size	= self->data_size,
		},
		.event_types = {
			.offset = self->event_offset,
			.size	= self->event_size,
		},
	};

	memcpy(&f_header.adds_features, &self->adds_features, sizeof(self->adds_features));

	lseek(fd, 0, SEEK_SET);
	err = do_write(fd, &f_header, sizeof(f_header));
	if (err < 0) {
		pr_debug("failed to write perf header\n");
		return err;
	}
	lseek(fd, self->data_offset + self->data_size, SEEK_SET);

	self->frozen = 1;
	return 0;
}

static int perf_header__getbuffer64(struct perf_header *self,
				    int fd, void *buf, size_t size)
{
	if (do_read(fd, buf, size) <= 0)
		return -1;

	if (self->needs_swap)
		mem_bswap_64(buf, size);

	return 0;
}

int perf_header__process_sections(struct perf_header *self, int fd,
				  int (*process)(struct perf_file_section *self,
						 struct perf_header *ph,
						 int feat, int fd))
{
	struct perf_file_section *feat_sec;
	int nr_sections;
	int sec_size;
	int idx = 0;
	int err = -1, feat = 1;

	nr_sections = bitmap_weight(self->adds_features, HEADER_FEAT_BITS);
	if (!nr_sections)
		return 0;

	feat_sec = calloc(sizeof(*feat_sec), nr_sections);
	if (!feat_sec)
		return -1;

	sec_size = sizeof(*feat_sec) * nr_sections;

	lseek(fd, self->data_offset + self->data_size, SEEK_SET);

	if (perf_header__getbuffer64(self, fd, feat_sec, sec_size))
		goto out_free;

	err = 0;
	while (idx < nr_sections && feat < HEADER_LAST_FEATURE) {
		if (perf_header__has_feat(self, feat)) {
			struct perf_file_section *sec = &feat_sec[idx++];

			err = process(sec, self, feat, fd);
			if (err < 0)
				break;
		}
		++feat;
	}
out_free:
	free(feat_sec);
	return err;
}

int perf_file_header__read(struct perf_file_header *self,
			   struct perf_header *ph, int fd)
{
	lseek(fd, 0, SEEK_SET);

	if (do_read(fd, self, sizeof(*self)) <= 0 ||
	    memcmp(&self->magic, __perf_magic, sizeof(self->magic)))
		return -1;

	if (self->attr_size != sizeof(struct perf_file_attr)) {
		u64 attr_size = bswap_64(self->attr_size);

		if (attr_size != sizeof(struct perf_file_attr))
			return -1;

		mem_bswap_64(self, offsetof(struct perf_file_header,
					    adds_features));
		ph->needs_swap = true;
	}

	if (self->size != sizeof(*self)) {
		/* Support the previous format */
		if (self->size == offsetof(typeof(*self), adds_features))
			bitmap_zero(self->adds_features, HEADER_FEAT_BITS);
		else
			return -1;
	}

	memcpy(&ph->adds_features, &self->adds_features,
	       sizeof(ph->adds_features));
	/*
	 * FIXME: hack that assumes that if we need swap the perf.data file
	 * may be coming from an arch with a different word-size, ergo different
	 * DEFINE_BITMAP format, investigate more later, but for now its mostly
	 * safe to assume that we have a build-id section. Trace files probably
	 * have several other issues in this realm anyway...
	 */
	if (ph->needs_swap) {
		memset(&ph->adds_features, 0, sizeof(ph->adds_features));
		perf_header__set_feat(ph, HEADER_BUILD_ID);
	}

	ph->event_offset = self->event_types.offset;
	ph->event_size   = self->event_types.size;
	ph->data_offset  = self->data.offset;
	ph->data_size	 = self->data.size;
	return 0;
}

static int perf_file_section__process(struct perf_file_section *self,
				      struct perf_header *ph,
				      int feat, int fd)
{
	if (lseek(fd, self->offset, SEEK_SET) == (off_t)-1) {
		pr_debug("Failed to lseek to %Ld offset for feature %d, "
			 "continuing...\n", self->offset, feat);
		return 0;
	}

	switch (feat) {
	case HEADER_TRACE_INFO:
		trace_report(fd);
		break;

	case HEADER_BUILD_ID:
		if (perf_header__read_build_ids(ph, fd, self->offset, self->size))
			pr_debug("Failed to read buildids, continuing...\n");
		break;
	default:
		pr_debug("unknown feature %d, continuing...\n", feat);
	}

	return 0;
}

static int perf_file_header__read_pipe(struct perf_pipe_file_header *self,
				       struct perf_header *ph, int fd)
{
	if (do_read(fd, self, sizeof(*self)) <= 0 ||
	    memcmp(&self->magic, __perf_magic, sizeof(self->magic)))
		return -1;

	if (self->size != sizeof(*self)) {
		u64 size = bswap_64(self->size);

		if (size != sizeof(*self))
			return -1;

		ph->needs_swap = true;
	}

	return 0;
}

static int perf_header__read_pipe(struct perf_session *session, int fd)
{
	struct perf_header *self = &session->header;
	struct perf_pipe_file_header f_header;

	if (perf_file_header__read_pipe(&f_header, self, fd) < 0) {
		pr_debug("incompatible file format\n");
		return -EINVAL;
	}

	session->fd = fd;

	return 0;
}

int perf_header__read(struct perf_session *session, int fd)
{
	struct perf_header *self = &session->header;
	struct perf_file_header	f_header;
	struct perf_file_attr	f_attr;
	u64			f_id;
	int nr_attrs, nr_ids, i, j;

	if (session->fd_pipe)
		return perf_header__read_pipe(session, fd);

	if (perf_file_header__read(&f_header, self, fd) < 0) {
		pr_debug("incompatible file format\n");
		return -EINVAL;
	}

	nr_attrs = f_header.attrs.size / sizeof(f_attr);
	lseek(fd, f_header.attrs.offset, SEEK_SET);

	for (i = 0; i < nr_attrs; i++) {
		struct perf_header_attr *attr;
		off_t tmp;

		if (perf_header__getbuffer64(self, fd, &f_attr, sizeof(f_attr)))
			goto out_errno;

		tmp = lseek(fd, 0, SEEK_CUR);

		attr = perf_header_attr__new(&f_attr.attr);
		if (attr == NULL)
			 return -ENOMEM;

		nr_ids = f_attr.ids.size / sizeof(u64);
		lseek(fd, f_attr.ids.offset, SEEK_SET);

		for (j = 0; j < nr_ids; j++) {
			if (perf_header__getbuffer64(self, fd, &f_id, sizeof(f_id)))
				goto out_errno;

			if (perf_header_attr__add_id(attr, f_id) < 0) {
				perf_header_attr__delete(attr);
				return -ENOMEM;
			}
		}
		if (perf_header__add_attr(self, attr) < 0) {
			perf_header_attr__delete(attr);
			return -ENOMEM;
		}

		lseek(fd, tmp, SEEK_SET);
	}

	if (f_header.event_types.size) {
		lseek(fd, f_header.event_types.offset, SEEK_SET);
		events = malloc(f_header.event_types.size);
		if (events == NULL)
			return -ENOMEM;
		if (perf_header__getbuffer64(self, fd, events,
					     f_header.event_types.size))
			goto out_errno;
		event_count =  f_header.event_types.size / sizeof(struct perf_trace_event_type);
	}

	perf_header__process_sections(self, fd, perf_file_section__process);

	lseek(fd, self->data_offset, SEEK_SET);

	self->frozen = 1;
	return 0;
out_errno:
	return -errno;
}

u64 perf_header__sample_type(struct perf_header *header)
{
	u64 type = 0;
	int i;

	for (i = 0; i < header->attrs; i++) {
		struct perf_header_attr *attr = header->attr[i];

		if (!type)
			type = attr->attr.sample_type;
		else if (type != attr->attr.sample_type)
			die("non matching sample_type");
	}

	return type;
}

struct perf_event_attr *
perf_header__find_attr(u64 id, struct perf_header *header)
{
	int i;

	for (i = 0; i < header->attrs; i++) {
		struct perf_header_attr *attr = header->attr[i];
		int j;

		for (j = 0; j < attr->ids; j++) {
			if (attr->id[j] == id)
				return &attr->attr;
		}
	}

	return NULL;
}

int event__synthesize_attr(struct perf_event_attr *attr, u16 ids, u64 *id,
			   event__handler_t process,
			   struct perf_session *session)
{
	event_t *ev;
	size_t size;
	int err;

	size = sizeof(struct perf_event_attr);
	size = ALIGN(size, sizeof(u64));
	size += sizeof(struct perf_event_header);
	size += ids * sizeof(u64);

	ev = malloc(size);

	ev->attr.attr = *attr;
	memcpy(ev->attr.id, id, ids * sizeof(u64));

	ev->attr.header.type = PERF_RECORD_HEADER_ATTR;
	ev->attr.header.size = size;

	err = process(ev, session);

	free(ev);

	return err;
}

int event__synthesize_attrs(struct perf_header *self,
			    event__handler_t process,
			    struct perf_session *session)
{
	struct perf_header_attr	*attr;
	int i, err = 0;

	for (i = 0; i < self->attrs; i++) {
		attr = self->attr[i];

		err = event__synthesize_attr(&attr->attr, attr->ids, attr->id,
					     process, session);
		if (err) {
			pr_debug("failed to create perf header attribute\n");
			return err;
		}
	}

	return err;
}

int event__process_attr(event_t *self, struct perf_session *session)
{
	struct perf_header_attr *attr;
	unsigned int i, ids, n_ids;

	attr = perf_header_attr__new(&self->attr.attr);
	if (attr == NULL)
		return -ENOMEM;

	ids = self->header.size;
	ids -= (void *)&self->attr.id - (void *)self;
	n_ids = ids / sizeof(u64);

	for (i = 0; i < n_ids; i++) {
		if (perf_header_attr__add_id(attr, self->attr.id[i]) < 0) {
			perf_header_attr__delete(attr);
			return -ENOMEM;
		}
	}

	if (perf_header__add_attr(&session->header, attr) < 0) {
		perf_header_attr__delete(attr);
		return -ENOMEM;
	}

	perf_session__update_sample_type(session);

	return 0;
}

int event__synthesize_event_type(u64 event_id, char *name,
				 event__handler_t process,
				 struct perf_session *session)
{
	event_t ev;
	size_t size = 0;
	int err = 0;

	memset(&ev, 0, sizeof(ev));

	ev.event_type.event_type.event_id = event_id;
	memset(ev.event_type.event_type.name, 0, MAX_EVENT_NAME);
	strncpy(ev.event_type.event_type.name, name, MAX_EVENT_NAME - 1);

	ev.event_type.header.type = PERF_RECORD_HEADER_EVENT_TYPE;
	size = strlen(name);
	size = ALIGN(size, sizeof(u64));
	ev.event_type.header.size = sizeof(ev.event_type) -
		(sizeof(ev.event_type.event_type.name) - size);

	err = process(&ev, session);

	return err;
}

int event__synthesize_event_types(event__handler_t process,
				  struct perf_session *session)
{
	struct perf_trace_event_type *type;
	int i, err = 0;

	for (i = 0; i < event_count; i++) {
		type = &events[i];

		err = event__synthesize_event_type(type->event_id, type->name,
						   process, session);
		if (err) {
			pr_debug("failed to create perf header event type\n");
			return err;
		}
	}

	return err;
}

int event__process_event_type(event_t *self,
			      struct perf_session *session __unused)
{
	if (perf_header__push_event(self->event_type.event_type.event_id,
				    self->event_type.event_type.name) < 0)
		return -ENOMEM;

	return 0;
}

int event__synthesize_tracing_data(int fd, struct perf_event_attr *pattrs,
				   int nb_events,
				   event__handler_t process,
				   struct perf_session *session __unused)
{
	event_t ev;
	ssize_t size = 0, aligned_size = 0, padding;
	int err = 0;

	memset(&ev, 0, sizeof(ev));

	ev.tracing_data.header.type = PERF_RECORD_HEADER_TRACING_DATA;
	size = read_tracing_data_size(fd, pattrs, nb_events);
	if (size <= 0)
		return size;
	aligned_size = ALIGN(size, sizeof(u64));
	padding = aligned_size - size;
	ev.tracing_data.header.size = sizeof(ev.tracing_data);
	ev.tracing_data.size = aligned_size;

	process(&ev, session);

	err = read_tracing_data(fd, pattrs, nb_events);
	write_padded(fd, NULL, 0, padding);

	return aligned_size;
}

int event__process_tracing_data(event_t *self,
				struct perf_session *session)
{
	ssize_t size_read, padding, size = self->tracing_data.size;
	off_t offset = lseek(session->fd, 0, SEEK_CUR);
	char buf[BUFSIZ];

	/* setup for reading amidst mmap */
	lseek(session->fd, offset + sizeof(struct tracing_data_event),
	      SEEK_SET);

	size_read = trace_report(session->fd);

	padding = ALIGN(size_read, sizeof(u64)) - size_read;

	if (read(session->fd, buf, padding) < 0)
		die("reading input file");

	if (size_read + padding != size)
		die("tracing data size mismatch");

	return size_read + padding;
}