header.c

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#define _FILE_OFFSET_BITS 64

#include "util.h"
#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 <linux/bitops.h>
#include <sys/utsname.h>

#include "evlist.h"
#include "evsel.h"
#include "header.h"
#include "../perf.h"
#include "trace-event.h"
#include "session.h"
#include "symbol.h"
#include "debug.h"
#include "cpumap.h"
#include "pmu.h"
#include "vdso.h"
#include "strbuf.h"

static bool no_buildid_cache = false;

static int trace_event_count;
static struct perf_trace_event_type *trace_events;

static u32 header_argc;
static const char **header_argv;

int perf_header__push_event(u64 id, const char *name)
{
    struct perf_trace_event_type *nevents;

    if (strlen(name) > MAX_EVENT_NAME)
        pr_warning("Event %s will be truncated\n", name);

    nevents = realloc(trace_events, (trace_event_count + 1) * sizeof(*trace_events));
    if (nevents == NULL)
        return -ENOMEM;
    trace_events = nevents;

    memset(&trace_events[trace_event_count], 0, sizeof(struct perf_trace_event_type));
    trace_events[trace_event_count].event_id = id;
    strncpy(trace_events[trace_event_count].name, name, MAX_EVENT_NAME - 1);
    trace_event_count++;
    return 0;
}

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

/*
 * magic2 = "PERFILE2"
 * must be a numerical value to let the endianness
 * determine the memory layout. That way we are able
 * to detect endianness when reading the perf.data file
 * back.
 *
 * we check for legacy (PERFFILE) format.
 */
static const char *__perf_magic1 = "PERFFILE";
static const u64 __perf_magic2    = 0x32454c4946524550ULL;
static const u64 __perf_magic2_sw = 0x50455246494c4532ULL;

#define PERF_MAGIC  __perf_magic2

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

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

void perf_header__clear_feat(struct perf_header *header, int feat)
{
    clear_bit(feat, header->adds_features);
}

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

static int do_write_string(int fd, const char *str)
{
    u32 len, olen;
    int ret;

    olen = strlen(str) + 1;
    len = PERF_ALIGN(olen, NAME_ALIGN);

    /* write len, incl. \0 */
    ret = do_write(fd, &len, sizeof(len));
    if (ret < 0)
        return ret;

    return write_padded(fd, str, olen, len);
}

static char *do_read_string(int fd, struct perf_header *ph)
{
    ssize_t sz, ret;
    u32 len;
    char *buf;

    sz = read(fd, &len, sizeof(len));
    if (sz < (ssize_t)sizeof(len))
        return NULL;

    if (ph->needs_swap)
        len = bswap_32(len);

    buf = malloc(len);
    if (!buf)
        return NULL;

    ret = read(fd, buf, len);
    if (ret == (ssize_t)len) {
        /*
         * strings are padded by zeroes
         * thus the actual strlen of buf
         * may be less than len
         */
        return buf;
    }

    free(buf);
    return NULL;
}

int
perf_header__set_cmdline(int argc, const char **argv)
{
    int i;

    /*
     * If header_argv has already been set, do not override it.
     * This allows a command to set the cmdline, parse args and
     * then call another builtin function that implements a
     * command -- e.g, cmd_kvm calling cmd_record.
     */
    if (header_argv)
        return 0;

    header_argc = (u32)argc;

    /* do not include NULL termination */
    header_argv = calloc(argc, sizeof(char *));
    if (!header_argv)
        return -ENOMEM;

    /*
     * must copy argv contents because it gets moved
     * around during option parsing
     */
    for (i = 0; i < argc ; i++)
        header_argv[i] = argv[i];

    return 0;
}

#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 write_buildid(char *name, size_t name_len, u8 *build_id,
             pid_t pid, u16 misc, int fd)
{
    int err;
    struct build_id_event b;
    size_t len;

    len = name_len + 1;
    len = PERF_ALIGN(len, NAME_ALIGN);

    memset(&b, 0, sizeof(b));
    memcpy(&b.build_id, build_id, BUILD_ID_SIZE);
    b.pid = pid;
    b.header.misc = misc;
    b.header.size = sizeof(b) + len;

    err = do_write(fd, &b, sizeof(b));
    if (err < 0)
        return err;

    return write_padded(fd, name, name_len + 1, len);
}

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

    dsos__for_each_with_build_id(pos, head) {
        int err;
        char  *name;
        size_t name_len;

        if (!pos->hit)
            continue;

        if (is_vdso_map(pos->short_name)) {
            name = (char *) VDSO__MAP_NAME;
            name_len = sizeof(VDSO__MAP_NAME) + 1;
        } else {
            name = pos->long_name;
            name_len = pos->long_name_len + 1;
        }

        err = write_buildid(name, name_len, pos->build_id,
                    pid, misc, fd);
        if (err)
            return err;
    }

    return 0;
}

static int machine__write_buildid_table(struct machine *machine, int fd)
{
    int err;
    u16 kmisc = PERF_RECORD_MISC_KERNEL,
        umisc = PERF_RECORD_MISC_USER;

    if (!machine__is_host(machine)) {
        kmisc = PERF_RECORD_MISC_GUEST_KERNEL;
        umisc = PERF_RECORD_MISC_GUEST_USER;
    }

    err = __dsos__write_buildid_table(&machine->kernel_dsos, machine->pid,
                      kmisc, fd);
    if (err == 0)
        err = __dsos__write_buildid_table(&machine->user_dsos,
                          machine->pid, umisc, fd);
    return err;
}

static int dsos__write_buildid_table(struct perf_header *header, int fd)
{
    struct perf_session *session = container_of(header,
            struct perf_session, header);
    struct rb_node *nd;
    int err = machine__write_buildid_table(&session->host_machine, fd);

    if (err)
        return err;

    for (nd = rb_first(&session->machines); nd; nd = rb_next(nd)) {
        struct machine *pos = rb_entry(nd, struct machine, rb_node);
        err = machine__write_buildid_table(pos, fd);
        if (err)
            break;
    }
    return err;
}

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

    if (is_kallsyms) {
        if (symbol_conf.kptr_restrict) {
            pr_debug("Not caching a kptr_restrict'ed /proc/kallsyms\n");
            return 0;
        }
        realname = (char *) name;
    } else
        realname = realpath(name, NULL);

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

    len = scnprintf(filename, size, "%s%s%s",
               debugdir, slash ? "/" : "",
               is_vdso ? VDSO__MAP_NAME : realname);
    if (mkdir_p(filename, 0755))
        goto out_free;

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

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

    len = scnprintf(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:
    if (!is_kallsyms)
        free(realname);
    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, bool is_vdso)
{
    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, is_vdso);
}

int build_id_cache__remove_s(const char *sbuild_id, const char *debugdir)
{
    const size_t size = PATH_MAX;
    char *filename = zalloc(size),
         *linkname = zalloc(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 - 1) < 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 *dso, const char *debugdir)
{
    bool is_kallsyms = dso->kernel && dso->long_name[0] != '/';
    bool is_vdso = is_vdso_map(dso->short_name);

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

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 machine__cache_build_ids(struct machine *machine, const char *debugdir)
{
    int ret = __dsos__cache_build_ids(&machine->kernel_dsos, debugdir);
    ret |= __dsos__cache_build_ids(&machine->user_dsos, debugdir);
    return ret;
}

static int perf_session__cache_build_ids(struct perf_session *session)
{
    struct rb_node *nd;
    int ret;
    char debugdir[PATH_MAX];

    snprintf(debugdir, sizeof(debugdir), "%s", buildid_dir);

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

    ret = machine__cache_build_ids(&session->host_machine, debugdir);

    for (nd = rb_first(&session->machines); nd; nd = rb_next(nd)) {
        struct machine *pos = rb_entry(nd, struct machine, rb_node);
        ret |= machine__cache_build_ids(pos, debugdir);
    }
    return ret ? -1 : 0;
}

static bool machine__read_build_ids(struct machine *machine, bool with_hits)
{
    bool ret = __dsos__read_build_ids(&machine->kernel_dsos, with_hits);
    ret |= __dsos__read_build_ids(&machine->user_dsos, with_hits);
    return ret;
}

static bool perf_session__read_build_ids(struct perf_session *session, bool with_hits)
{
    struct rb_node *nd;
    bool ret = machine__read_build_ids(&session->host_machine, with_hits);

    for (nd = rb_first(&session->machines); nd; nd = rb_next(nd)) {
        struct machine *pos = rb_entry(nd, struct machine, rb_node);
        ret |= machine__read_build_ids(pos, with_hits);
    }

    return ret;
}

static int write_tracing_data(int fd, struct perf_header *h __maybe_unused,
                struct perf_evlist *evlist)
{
    return read_tracing_data(fd, &evlist->entries);
}


static int write_build_id(int fd, struct perf_header *h,
              struct perf_evlist *evlist __maybe_unused)
{
    struct perf_session *session;
    int err;

    session = container_of(h, struct perf_session, header);

    if (!perf_session__read_build_ids(session, true))
        return -1;

    err = dsos__write_buildid_table(h, fd);
    if (err < 0) {
        pr_debug("failed to write buildid table\n");
        return err;
    }
    if (!no_buildid_cache)
        perf_session__cache_build_ids(session);

    return 0;
}

static int write_hostname(int fd, struct perf_header *h __maybe_unused,
              struct perf_evlist *evlist __maybe_unused)
{
    struct utsname uts;
    int ret;

    ret = uname(&uts);
    if (ret < 0)
        return -1;

    return do_write_string(fd, uts.nodename);
}

static int write_osrelease(int fd, struct perf_header *h __maybe_unused,
               struct perf_evlist *evlist __maybe_unused)
{
    struct utsname uts;
    int ret;

    ret = uname(&uts);
    if (ret < 0)
        return -1;

    return do_write_string(fd, uts.release);
}

static int write_arch(int fd, struct perf_header *h __maybe_unused,
              struct perf_evlist *evlist __maybe_unused)
{
    struct utsname uts;
    int ret;

    ret = uname(&uts);
    if (ret < 0)
        return -1;

    return do_write_string(fd, uts.machine);
}

static int write_version(int fd, struct perf_header *h __maybe_unused,
             struct perf_evlist *evlist __maybe_unused)
{
    return do_write_string(fd, perf_version_string);
}

static int write_cpudesc(int fd, struct perf_header *h __maybe_unused,
               struct perf_evlist *evlist __maybe_unused)
{
#ifndef CPUINFO_PROC
#define CPUINFO_PROC NULL
#endif
    FILE *file;
    char *buf = NULL;
    char *s, *p;
    const char *search = CPUINFO_PROC;
    size_t len = 0;
    int ret = -1;

    if (!search)
        return -1;

    file = fopen("/proc/cpuinfo", "r");
    if (!file)
        return -1;

    while (getline(&buf, &len, file) > 0) {
        ret = strncmp(buf, search, strlen(search));
        if (!ret)
            break;
    }

    if (ret)
        goto done;

    s = buf;

    p = strchr(buf, ':');
    if (p && *(p+1) == ' ' && *(p+2))
        s = p + 2;
    p = strchr(s, '\n');
    if (p)
        *p = '\0';

    /* squash extra space characters (branding string) */
    p = s;
    while (*p) {
        if (isspace(*p)) {
            char *r = p + 1;
            char *q = r;
            *p = ' ';
            while (*q && isspace(*q))
                q++;
            if (q != (p+1))
                while ((*r++ = *q++));
        }
        p++;
    }
    ret = do_write_string(fd, s);
done:
    free(buf);
    fclose(file);
    return ret;
}

static int write_nrcpus(int fd, struct perf_header *h __maybe_unused,
            struct perf_evlist *evlist __maybe_unused)
{
    long nr;
    u32 nrc, nra;
    int ret;

    nr = sysconf(_SC_NPROCESSORS_CONF);
    if (nr < 0)
        return -1;

    nrc = (u32)(nr & UINT_MAX);

    nr = sysconf(_SC_NPROCESSORS_ONLN);
    if (nr < 0)
        return -1;

    nra = (u32)(nr & UINT_MAX);

    ret = do_write(fd, &nrc, sizeof(nrc));
    if (ret < 0)
        return ret;

    return do_write(fd, &nra, sizeof(nra));
}

static int write_event_desc(int fd, struct perf_header *h __maybe_unused,
                struct perf_evlist *evlist)
{
    struct perf_evsel *evsel;
    u32 nre, nri, sz;
    int ret;

    nre = evlist->nr_entries;

    /*
     * write number of events
     */
    ret = do_write(fd, &nre, sizeof(nre));
    if (ret < 0)
        return ret;

    /*
     * size of perf_event_attr struct
     */
    sz = (u32)sizeof(evsel->attr);
    ret = do_write(fd, &sz, sizeof(sz));
    if (ret < 0)
        return ret;

    list_for_each_entry(evsel, &evlist->entries, node) {

        ret = do_write(fd, &evsel->attr, sz);
        if (ret < 0)
            return ret;
        /*
         * write number of unique id per event
         * there is one id per instance of an event
         *
         * copy into an nri to be independent of the
         * type of ids,
         */
        nri = evsel->ids;
        ret = do_write(fd, &nri, sizeof(nri));
        if (ret < 0)
            return ret;

        /*
         * write event string as passed on cmdline
         */
        ret = do_write_string(fd, perf_evsel__name(evsel));
        if (ret < 0)
            return ret;
        /*
         * write unique ids for this event
         */
        ret = do_write(fd, evsel->id, evsel->ids * sizeof(u64));
        if (ret < 0)
            return ret;
    }
    return 0;
}

static int write_cmdline(int fd, struct perf_header *h __maybe_unused,
             struct perf_evlist *evlist __maybe_unused)
{
    char buf[MAXPATHLEN];
    char proc[32];
    u32 i, n;
    int ret;

    /*
     * actual atual path to perf binary
     */
    sprintf(proc, "/proc/%d/exe", getpid());
    ret = readlink(proc, buf, sizeof(buf));
    if (ret <= 0)
        return -1;

    /* readlink() does not add null termination */
    buf[ret] = '\0';

    /* account for binary path */
    n = header_argc + 1;

    ret = do_write(fd, &n, sizeof(n));
    if (ret < 0)
        return ret;

    ret = do_write_string(fd, buf);
    if (ret < 0)
        return ret;

    for (i = 0 ; i < header_argc; i++) {
        ret = do_write_string(fd, header_argv[i]);
        if (ret < 0)
            return ret;
    }
    return 0;
}

#define CORE_SIB_FMT \
    "/sys/devices/system/cpu/cpu%d/topology/core_siblings_list"
#define THRD_SIB_FMT \
    "/sys/devices/system/cpu/cpu%d/topology/thread_siblings_list"

struct cpu_topo {
    u32 core_sib;
    u32 thread_sib;
    char **core_siblings;
    char **thread_siblings;
};

static int build_cpu_topo(struct cpu_topo *tp, int cpu)
{
    FILE *fp;
    char filename[MAXPATHLEN];
    char *buf = NULL, *p;
    size_t len = 0;
    u32 i = 0;
    int ret = -1;

    sprintf(filename, CORE_SIB_FMT, cpu);
    fp = fopen(filename, "r");
    if (!fp)
        return -1;

    if (getline(&buf, &len, fp) <= 0)
        goto done;

    fclose(fp);

    p = strchr(buf, '\n');
    if (p)
        *p = '\0';

    for (i = 0; i < tp->core_sib; i++) {
        if (!strcmp(buf, tp->core_siblings[i]))
            break;
    }
    if (i == tp->core_sib) {
        tp->core_siblings[i] = buf;
        tp->core_sib++;
        buf = NULL;
        len = 0;
    }

    sprintf(filename, THRD_SIB_FMT, cpu);
    fp = fopen(filename, "r");
    if (!fp)
        goto done;

    if (getline(&buf, &len, fp) <= 0)
        goto done;

    p = strchr(buf, '\n');
    if (p)
        *p = '\0';

    for (i = 0; i < tp->thread_sib; i++) {
        if (!strcmp(buf, tp->thread_siblings[i]))
            break;
    }
    if (i == tp->thread_sib) {
        tp->thread_siblings[i] = buf;
        tp->thread_sib++;
        buf = NULL;
    }
    ret = 0;
done:
    if(fp)
        fclose(fp);
    free(buf);
    return ret;
}

static void free_cpu_topo(struct cpu_topo *tp)
{
    u32 i;

    if (!tp)
        return;

    for (i = 0 ; i < tp->core_sib; i++)
        free(tp->core_siblings[i]);

    for (i = 0 ; i < tp->thread_sib; i++)
        free(tp->thread_siblings[i]);

    free(tp);
}

static struct cpu_topo *build_cpu_topology(void)
{
    struct cpu_topo *tp;
    void *addr;
    u32 nr, i;
    size_t sz;
    long ncpus;
    int ret = -1;

    ncpus = sysconf(_SC_NPROCESSORS_CONF);
    if (ncpus < 0)
        return NULL;

    nr = (u32)(ncpus & UINT_MAX);

    sz = nr * sizeof(char *);

    addr = calloc(1, sizeof(*tp) + 2 * sz);
    if (!addr)
        return NULL;

    tp = addr;

    addr += sizeof(*tp);
    tp->core_siblings = addr;
    addr += sz;
    tp->thread_siblings = addr;

    for (i = 0; i < nr; i++) {
        ret = build_cpu_topo(tp, i);
        if (ret < 0)
            break;
    }
    if (ret) {
        free_cpu_topo(tp);
        tp = NULL;
    }
    return tp;
}

static int write_cpu_topology(int fd, struct perf_header *h __maybe_unused,
              struct perf_evlist *evlist __maybe_unused)
{
    struct cpu_topo *tp;
    u32 i;
    int ret;

    tp = build_cpu_topology();
    if (!tp)
        return -1;

    ret = do_write(fd, &tp->core_sib, sizeof(tp->core_sib));
    if (ret < 0)
        goto done;

    for (i = 0; i < tp->core_sib; i++) {
        ret = do_write_string(fd, tp->core_siblings[i]);
        if (ret < 0)
            goto done;
    }
    ret = do_write(fd, &tp->thread_sib, sizeof(tp->thread_sib));
    if (ret < 0)
        goto done;

    for (i = 0; i < tp->thread_sib; i++) {
        ret = do_write_string(fd, tp->thread_siblings[i]);
        if (ret < 0)
            break;
    }
done:
    free_cpu_topo(tp);
    return ret;
}



static int write_total_mem(int fd, struct perf_header *h __maybe_unused,
              struct perf_evlist *evlist __maybe_unused)
{
    char *buf = NULL;
    FILE *fp;
    size_t len = 0;
    int ret = -1, n;
    uint64_t mem;

    fp = fopen("/proc/meminfo", "r");
    if (!fp)
        return -1;

    while (getline(&buf, &len, fp) > 0) {
        ret = strncmp(buf, "MemTotal:", 9);
        if (!ret)
            break;
    }
    if (!ret) {
        n = sscanf(buf, "%*s %"PRIu64, &mem);
        if (n == 1)
            ret = do_write(fd, &mem, sizeof(mem));
    }
    free(buf);
    fclose(fp);
    return ret;
}

static int write_topo_node(int fd, int node)
{
    char str[MAXPATHLEN];
    char field[32];
    char *buf = NULL, *p;
    size_t len = 0;
    FILE *fp;
    u64 mem_total, mem_free, mem;
    int ret = -1;

    sprintf(str, "/sys/devices/system/node/node%d/meminfo", node);
    fp = fopen(str, "r");
    if (!fp)
        return -1;

    while (getline(&buf, &len, fp) > 0) {
        /* skip over invalid lines */
        if (!strchr(buf, ':'))
            continue;
        if (sscanf(buf, "%*s %*d %s %"PRIu64, field, &mem) != 2)
            goto done;
        if (!strcmp(field, "MemTotal:"))
            mem_total = mem;
        if (!strcmp(field, "MemFree:"))
            mem_free = mem;
    }

    fclose(fp);

    ret = do_write(fd, &mem_total, sizeof(u64));
    if (ret)
        goto done;

    ret = do_write(fd, &mem_free, sizeof(u64));
    if (ret)
        goto done;

    ret = -1;
    sprintf(str, "/sys/devices/system/node/node%d/cpulist", node);

    fp = fopen(str, "r");
    if (!fp)
        goto done;

    if (getline(&buf, &len, fp) <= 0)
        goto done;

    p = strchr(buf, '\n');
    if (p)
        *p = '\0';

    ret = do_write_string(fd, buf);
done:
    free(buf);
    fclose(fp);
    return ret;
}

static int write_numa_topology(int fd, struct perf_header *h __maybe_unused,
              struct perf_evlist *evlist __maybe_unused)
{
    char *buf = NULL;
    size_t len = 0;
    FILE *fp;
    struct cpu_map *node_map = NULL;
    char *c;
    u32 nr, i, j;
    int ret = -1;

    fp = fopen("/sys/devices/system/node/online", "r");
    if (!fp)
        return -1;

    if (getline(&buf, &len, fp) <= 0)
        goto done;

    c = strchr(buf, '\n');
    if (c)
        *c = '\0';

    node_map = cpu_map__new(buf);
    if (!node_map)
        goto done;

    nr = (u32)node_map->nr;

    ret = do_write(fd, &nr, sizeof(nr));
    if (ret < 0)
        goto done;

    for (i = 0; i < nr; i++) {
        j = (u32)node_map->map[i];
        ret = do_write(fd, &j, sizeof(j));
        if (ret < 0)
            break;

        ret = write_topo_node(fd, i);
        if (ret < 0)
            break;
    }
done:
    free(buf);
    fclose(fp);
    free(node_map);
    return ret;
}

/*
 * File format:
 *
 * struct pmu_mappings {
 *  u32 pmu_num;
 *  struct pmu_map {
 *      u32 type;
 *      char    name[];
 *  }[pmu_num];
 * };
 */

static int write_pmu_mappings(int fd, struct perf_header *h __maybe_unused,
                  struct perf_evlist *evlist __maybe_unused)
{
    struct perf_pmu *pmu = NULL;
    off_t offset = lseek(fd, 0, SEEK_CUR);
    __u32 pmu_num = 0;

    /* write real pmu_num later */
    do_write(fd, &pmu_num, sizeof(pmu_num));

    while ((pmu = perf_pmu__scan(pmu))) {
        if (!pmu->name)
            continue;
        pmu_num++;
        do_write(fd, &pmu->type, sizeof(pmu->type));
        do_write_string(fd, pmu->name);
    }

    if (pwrite(fd, &pmu_num, sizeof(pmu_num), offset) != sizeof(pmu_num)) {
        /* discard all */
        lseek(fd, offset, SEEK_SET);
        return -1;
    }

    return 0;
}

/*
 * default get_cpuid(): nothing gets recorded
 * actual implementation must be in arch/$(ARCH)/util/header.c
 */
int __attribute__ ((weak)) get_cpuid(char *buffer __maybe_unused,
                     size_t sz __maybe_unused)
{
    return -1;
}

static int write_cpuid(int fd, struct perf_header *h __maybe_unused,
               struct perf_evlist *evlist __maybe_unused)
{
    char buffer[64];
    int ret;

    ret = get_cpuid(buffer, sizeof(buffer));
    if (!ret)
        goto write_it;

    return -1;
write_it:
    return do_write_string(fd, buffer);
}

static int write_branch_stack(int fd __maybe_unused,
                  struct perf_header *h __maybe_unused,
               struct perf_evlist *evlist __maybe_unused)
{
    return 0;
}

static void print_hostname(struct perf_header *ph, int fd __maybe_unused,
               FILE *fp)
{
    fprintf(fp, "# hostname : %s\n", ph->env.hostname);
}

static void print_osrelease(struct perf_header *ph, int fd __maybe_unused,
                FILE *fp)
{
    fprintf(fp, "# os release : %s\n", ph->env.os_release);
}

static void print_arch(struct perf_header *ph, int fd __maybe_unused, FILE *fp)
{
    fprintf(fp, "# arch : %s\n", ph->env.arch);
}

static void print_cpudesc(struct perf_header *ph, int fd __maybe_unused,
              FILE *fp)
{
    fprintf(fp, "# cpudesc : %s\n", ph->env.cpu_desc);
}

static void print_nrcpus(struct perf_header *ph, int fd __maybe_unused,
             FILE *fp)
{
    fprintf(fp, "# nrcpus online : %u\n", ph->env.nr_cpus_online);
    fprintf(fp, "# nrcpus avail : %u\n", ph->env.nr_cpus_avail);
}

static void print_version(struct perf_header *ph, int fd __maybe_unused,
              FILE *fp)
{
    fprintf(fp, "# perf version : %s\n", ph->env.version);
}

static void print_cmdline(struct perf_header *ph, int fd __maybe_unused,
              FILE *fp)
{
    int nr, i;
    char *str;

    nr = ph->env.nr_cmdline;
    str = ph->env.cmdline;

    fprintf(fp, "# cmdline : ");

    for (i = 0; i < nr; i++) {
        fprintf(fp, "%s ", str);
        str += strlen(str) + 1;
    }
    fputc('\n', fp);
}

static void print_cpu_topology(struct perf_header *ph, int fd __maybe_unused,
                   FILE *fp)
{
    int nr, i;
    char *str;

    nr = ph->env.nr_sibling_cores;
    str = ph->env.sibling_cores;

    for (i = 0; i < nr; i++) {
        fprintf(fp, "# sibling cores   : %s\n", str);
        str += strlen(str) + 1;
    }

    nr = ph->env.nr_sibling_threads;
    str = ph->env.sibling_threads;

    for (i = 0; i < nr; i++) {
        fprintf(fp, "# sibling threads : %s\n", str);
        str += strlen(str) + 1;
    }
}

static void free_event_desc(struct perf_evsel *events)
{
    struct perf_evsel *evsel;

    if (!events)
        return;

    for (evsel = events; evsel->attr.size; evsel++) {
        if (evsel->name)
            free(evsel->name);
        if (evsel->id)
            free(evsel->id);
    }

    free(events);
}

static struct perf_evsel *
read_event_desc(struct perf_header *ph, int fd)
{
    struct perf_evsel *evsel, *events = NULL;
    u64 *id;
    void *buf = NULL;
    u32 nre, sz, nr, i, j;
    ssize_t ret;
    size_t msz;

    /* number of events */
    ret = read(fd, &nre, sizeof(nre));
    if (ret != (ssize_t)sizeof(nre))
        goto error;

    if (ph->needs_swap)
        nre = bswap_32(nre);

    ret = read(fd, &sz, sizeof(sz));
    if (ret != (ssize_t)sizeof(sz))
        goto error;

    if (ph->needs_swap)
        sz = bswap_32(sz);

    /* buffer to hold on file attr struct */
    buf = malloc(sz);
    if (!buf)
        goto error;

    /* the last event terminates with evsel->attr.size == 0: */
    events = calloc(nre + 1, sizeof(*events));
    if (!events)
        goto error;

    msz = sizeof(evsel->attr);
    if (sz < msz)
        msz = sz;

    for (i = 0, evsel = events; i < nre; evsel++, i++) {
        evsel->idx = i;

        /*
         * must read entire on-file attr struct to
         * sync up with layout.
         */
        ret = read(fd, buf, sz);
        if (ret != (ssize_t)sz)
            goto error;

        if (ph->needs_swap)
            perf_event__attr_swap(buf);

        memcpy(&evsel->attr, buf, msz);

        ret = read(fd, &nr, sizeof(nr));
        if (ret != (ssize_t)sizeof(nr))
            goto error;

        if (ph->needs_swap) {
            nr = bswap_32(nr);
            evsel->needs_swap = true;
        }

        evsel->name = do_read_string(fd, ph);

        if (!nr)
            continue;

        id = calloc(nr, sizeof(*id));
        if (!id)
            goto error;
        evsel->ids = nr;
        evsel->id = id;

        for (j = 0 ; j < nr; j++) {
            ret = read(fd, id, sizeof(*id));
            if (ret != (ssize_t)sizeof(*id))
                goto error;
            if (ph->needs_swap)
                *id = bswap_64(*id);
            id++;
        }
    }
out:
    if (buf)
        free(buf);
    return events;
error:
    if (events)
        free_event_desc(events);
    events = NULL;
    goto out;
}

static void print_event_desc(struct perf_header *ph, int fd, FILE *fp)
{
    struct perf_evsel *evsel, *events = read_event_desc(ph, fd);
    u32 j;
    u64 *id;

    if (!events) {
        fprintf(fp, "# event desc: not available or unable to read\n");
        return;
    }

    for (evsel = events; evsel->attr.size; evsel++) {
        fprintf(fp, "# event : name = %s, ", evsel->name);

        fprintf(fp, "type = %d, config = 0x%"PRIx64
                ", config1 = 0x%"PRIx64", config2 = 0x%"PRIx64,
                evsel->attr.type,
                (u64)evsel->attr.config,
                (u64)evsel->attr.config1,
                (u64)evsel->attr.config2);

        fprintf(fp, ", excl_usr = %d, excl_kern = %d",
                evsel->attr.exclude_user,
                evsel->attr.exclude_kernel);

        fprintf(fp, ", excl_host = %d, excl_guest = %d",
                evsel->attr.exclude_host,
                evsel->attr.exclude_guest);

        fprintf(fp, ", precise_ip = %d", evsel->attr.precise_ip);

        if (evsel->ids) {
            fprintf(fp, ", id = {");
            for (j = 0, id = evsel->id; j < evsel->ids; j++, id++) {
                if (j)
                    fputc(',', fp);
                fprintf(fp, " %"PRIu64, *id);
            }
            fprintf(fp, " }");
        }

        fputc('\n', fp);
    }

    free_event_desc(events);
}

static void print_total_mem(struct perf_header *ph, int fd __maybe_unused,
                FILE *fp)
{
    fprintf(fp, "# total memory : %Lu kB\n", ph->env.total_mem);
}

static void print_numa_topology(struct perf_header *ph, int fd __maybe_unused,
                FILE *fp)
{
    u32 nr, c, i;
    char *str, *tmp;
    uint64_t mem_total, mem_free;

    /* nr nodes */
    nr = ph->env.nr_numa_nodes;
    str = ph->env.numa_nodes;

    for (i = 0; i < nr; i++) {
        /* node number */
        c = strtoul(str, &tmp, 0);
        if (*tmp != ':')
            goto error;

        str = tmp + 1;
        mem_total = strtoull(str, &tmp, 0);
        if (*tmp != ':')
            goto error;

        str = tmp + 1;
        mem_free = strtoull(str, &tmp, 0);
        if (*tmp != ':')
            goto error;

        fprintf(fp, "# node%u meminfo  : total = %"PRIu64" kB,"
                " free = %"PRIu64" kB\n",
            c, mem_total, mem_free);

        str = tmp + 1;
        fprintf(fp, "# node%u cpu list : %s\n", c, str);

        str += strlen(str) + 1;
    }
    return;
error:
    fprintf(fp, "# numa topology : not available\n");
}

static void print_cpuid(struct perf_header *ph, int fd __maybe_unused, FILE *fp)
{
    fprintf(fp, "# cpuid : %s\n", ph->env.cpuid);
}

static void print_branch_stack(struct perf_header *ph __maybe_unused,
                   int fd __maybe_unused, FILE *fp)
{
    fprintf(fp, "# contains samples with branch stack\n");
}

static void print_pmu_mappings(struct perf_header *ph, int fd __maybe_unused,
                   FILE *fp)
{
    const char *delimiter = "# pmu mappings: ";
    char *str, *tmp;
    u32 pmu_num;
    u32 type;

    pmu_num = ph->env.nr_pmu_mappings;
    if (!pmu_num) {
        fprintf(fp, "# pmu mappings: not available\n");
        return;
    }

    str = ph->env.pmu_mappings;

    while (pmu_num) {
        type = strtoul(str, &tmp, 0);
        if (*tmp != ':')
            goto error;

        str = tmp + 1;
        fprintf(fp, "%s%s = %" PRIu32, delimiter, str, type);

        delimiter = ", ";
        str += strlen(str) + 1;
        pmu_num--;
    }

    fprintf(fp, "\n");

    if (!pmu_num)
        return;
error:
    fprintf(fp, "# pmu mappings: unable to read\n");
}

static int __event_process_build_id(struct build_id_event *bev,
                    char *filename,
                    struct perf_session *session)
{
    int err = -1;
    struct list_head *head;
    struct machine *machine;
    u16 misc;
    struct dso *dso;
    enum dso_kernel_type dso_type;

    machine = perf_session__findnew_machine(session, bev->pid);
    if (!machine)
        goto out;

    misc = bev->header.misc & PERF_RECORD_MISC_CPUMODE_MASK;

    switch (misc) {
    case PERF_RECORD_MISC_KERNEL:
        dso_type = DSO_TYPE_KERNEL;
        head = &machine->kernel_dsos;
        break;
    case PERF_RECORD_MISC_GUEST_KERNEL:
        dso_type = DSO_TYPE_GUEST_KERNEL;
        head = &machine->kernel_dsos;
        break;
    case PERF_RECORD_MISC_USER:
    case PERF_RECORD_MISC_GUEST_USER:
        dso_type = DSO_TYPE_USER;
        head = &machine->user_dsos;
        break;
    default:
        goto out;
    }

    dso = __dsos__findnew(head, filename);
    if (dso != NULL) {
        char sbuild_id[BUILD_ID_SIZE * 2 + 1];

        dso__set_build_id(dso, &bev->build_id);

        if (filename[0] == '[')
            dso->kernel = dso_type;

        build_id__sprintf(dso->build_id, sizeof(dso->build_id),
                  sbuild_id);
        pr_debug("build id event received for %s: %s\n",
             dso->long_name, sbuild_id);
    }

    err = 0;
out:
    return err;
}

static int perf_header__read_build_ids_abi_quirk(struct perf_header *header,
                         int input, u64 offset, u64 size)
{
    struct perf_session *session = container_of(header, struct perf_session, header);
    struct {
        struct perf_event_header   header;
        u8             build_id[PERF_ALIGN(BUILD_ID_SIZE, sizeof(u64))];
        char               filename[0];
    } old_bev;
    struct build_id_event bev;
    char filename[PATH_MAX];
    u64 limit = offset + size;

    while (offset < limit) {
        ssize_t len;

        if (read(input, &old_bev, sizeof(old_bev)) != sizeof(old_bev))
            return -1;

        if (header->needs_swap)
            perf_event_header__bswap(&old_bev.header);

        len = old_bev.header.size - sizeof(old_bev);
        if (read(input, filename, len) != len)
            return -1;

        bev.header = old_bev.header;

        /*
         * As the pid is the missing value, we need to fill
         * it properly. The header.misc value give us nice hint.
         */
        bev.pid = HOST_KERNEL_ID;
        if (bev.header.misc == PERF_RECORD_MISC_GUEST_USER ||
            bev.header.misc == PERF_RECORD_MISC_GUEST_KERNEL)
            bev.pid = DEFAULT_GUEST_KERNEL_ID;

        memcpy(bev.build_id, old_bev.build_id, sizeof(bev.build_id));
        __event_process_build_id(&bev, filename, session);

        offset += bev.header.size;
    }

    return 0;
}

static int perf_header__read_build_ids(struct perf_header *header,
                       int input, u64 offset, u64 size)
{
    struct perf_session *session = container_of(header, struct perf_session, header);
    struct build_id_event bev;
    char filename[PATH_MAX];
    u64 limit = offset + size, orig_offset = offset;
    int err = -1;

    while (offset < limit) {
        ssize_t len;

        if (read(input, &bev, sizeof(bev)) != sizeof(bev))
            goto out;

        if (header->needs_swap)
            perf_event_header__bswap(&bev.header);

        len = bev.header.size - sizeof(bev);
        if (read(input, filename, len) != len)
            goto out;
        /*
         * The a1645ce1 changeset:
         *
         * "perf: 'perf kvm' tool for monitoring guest performance from host"
         *
         * Added a field to struct build_id_event that broke the file
         * format.
         *
         * Since the kernel build-id is the first entry, process the
         * table using the old format if the well known
         * '[kernel.kallsyms]' string for the kernel build-id has the
         * first 4 characters chopped off (where the pid_t sits).
         */
        if (memcmp(filename, "nel.kallsyms]", 13) == 0) {
            if (lseek(input, orig_offset, SEEK_SET) == (off_t)-1)
                return -1;
            return perf_header__read_build_ids_abi_quirk(header, input, offset, size);
        }

        __event_process_build_id(&bev, filename, session);

        offset += bev.header.size;
    }
    err = 0;
out:
    return err;
}

static int process_tracing_data(struct perf_file_section *section __maybe_unused,
                struct perf_header *ph __maybe_unused,
                int fd, void *data)
{
    trace_report(fd, data, false);
    return 0;
}

static int process_build_id(struct perf_file_section *section,
                struct perf_header *ph, int fd,
                void *data __maybe_unused)
{
    if (perf_header__read_build_ids(ph, fd, section->offset, section->size))
        pr_debug("Failed to read buildids, continuing...\n");
    return 0;
}

static int process_hostname(struct perf_file_section *section __maybe_unused,
                struct perf_header *ph, int fd,
                void *data __maybe_unused)
{
    ph->env.hostname = do_read_string(fd, ph);
    return ph->env.hostname ? 0 : -ENOMEM;
}

static int process_osrelease(struct perf_file_section *section __maybe_unused,
                 struct perf_header *ph, int fd,
                 void *data __maybe_unused)
{
    ph->env.os_release = do_read_string(fd, ph);
    return ph->env.os_release ? 0 : -ENOMEM;
}

static int process_version(struct perf_file_section *section __maybe_unused,
               struct perf_header *ph, int fd,
               void *data __maybe_unused)
{
    ph->env.version = do_read_string(fd, ph);
    return ph->env.version ? 0 : -ENOMEM;
}

static int process_arch(struct perf_file_section *section __maybe_unused,
            struct perf_header *ph, int fd,
            void *data __maybe_unused)
{
    ph->env.arch = do_read_string(fd, ph);
    return ph->env.arch ? 0 : -ENOMEM;
}

static int process_nrcpus(struct perf_file_section *section __maybe_unused,
              struct perf_header *ph, int fd,
              void *data __maybe_unused)
{
    size_t ret;
    u32 nr;

    ret = read(fd, &nr, sizeof(nr));
    if (ret != sizeof(nr))
        return -1;

    if (ph->needs_swap)
        nr = bswap_32(nr);

    ph->env.nr_cpus_online = nr;

    ret = read(fd, &nr, sizeof(nr));
    if (ret != sizeof(nr))
        return -1;

    if (ph->needs_swap)
        nr = bswap_32(nr);

    ph->env.nr_cpus_avail = nr;
    return 0;
}

static int process_cpudesc(struct perf_file_section *section __maybe_unused,
               struct perf_header *ph, int fd,
               void *data __maybe_unused)
{
    ph->env.cpu_desc = do_read_string(fd, ph);
    return ph->env.cpu_desc ? 0 : -ENOMEM;
}

static int process_cpuid(struct perf_file_section *section __maybe_unused,
             struct perf_header *ph,  int fd,
             void *data __maybe_unused)
{
    ph->env.cpuid = do_read_string(fd, ph);
    return ph->env.cpuid ? 0 : -ENOMEM;
}

static int process_total_mem(struct perf_file_section *section __maybe_unused,
                 struct perf_header *ph, int fd,
                 void *data __maybe_unused)
{
    uint64_t mem;
    size_t ret;

    ret = read(fd, &mem, sizeof(mem));
    if (ret != sizeof(mem))
        return -1;

    if (ph->needs_swap)
        mem = bswap_64(mem);

    ph->env.total_mem = mem;
    return 0;
}

static struct perf_evsel *
perf_evlist__find_by_index(struct perf_evlist *evlist, int idx)
{
    struct perf_evsel *evsel;

    list_for_each_entry(evsel, &evlist->entries, node) {
        if (evsel->idx == idx)
            return evsel;
    }

    return NULL;
}

static void
perf_evlist__set_event_name(struct perf_evlist *evlist,
                struct perf_evsel *event)
{
    struct perf_evsel *evsel;

    if (!event->name)
        return;

    evsel = perf_evlist__find_by_index(evlist, event->idx);
    if (!evsel)
        return;

    if (evsel->name)
        return;

    evsel->name = strdup(event->name);
}

static int
process_event_desc(struct perf_file_section *section __maybe_unused,
           struct perf_header *header, int fd,
           void *data __maybe_unused)
{
    struct perf_session *session;
    struct perf_evsel *evsel, *events = read_event_desc(header, fd);

    if (!events)
        return 0;

    session = container_of(header, struct perf_session, header);
    for (evsel = events; evsel->attr.size; evsel++)
        perf_evlist__set_event_name(session->evlist, evsel);

    free_event_desc(events);

    return 0;
}

static int process_cmdline(struct perf_file_section *section __maybe_unused,
               struct perf_header *ph, int fd,
               void *data __maybe_unused)
{
    size_t ret;
    char *str;
    u32 nr, i;
    struct strbuf sb;

    ret = read(fd, &nr, sizeof(nr));
    if (ret != sizeof(nr))
        return -1;

    if (ph->needs_swap)
        nr = bswap_32(nr);

    ph->env.nr_cmdline = nr;
    strbuf_init(&sb, 128);

    for (i = 0; i < nr; i++) {
        str = do_read_string(fd, ph);
        if (!str)
            goto error;

        /* include a NULL character at the end */
        strbuf_add(&sb, str, strlen(str) + 1);
        free(str);
    }
    ph->env.cmdline = strbuf_detach(&sb, NULL);
    return 0;

error:
    strbuf_release(&sb);
    return -1;
}

static int process_cpu_topology(struct perf_file_section *section __maybe_unused,
                struct perf_header *ph, int fd,
                void *data __maybe_unused)
{
    size_t ret;
    u32 nr, i;
    char *str;
    struct strbuf sb;

    ret = read(fd, &nr, sizeof(nr));
    if (ret != sizeof(nr))
        return -1;

    if (ph->needs_swap)
        nr = bswap_32(nr);

    ph->env.nr_sibling_cores = nr;
    strbuf_init(&sb, 128);

    for (i = 0; i < nr; i++) {
        str = do_read_string(fd, ph);
        if (!str)
            goto error;

        /* include a NULL character at the end */
        strbuf_add(&sb, str, strlen(str) + 1);
        free(str);
    }
    ph->env.sibling_cores = strbuf_detach(&sb, NULL);

    ret = read(fd, &nr, sizeof(nr));
    if (ret != sizeof(nr))
        return -1;

    if (ph->needs_swap)
        nr = bswap_32(nr);

    ph->env.nr_sibling_threads = nr;

    for (i = 0; i < nr; i++) {
        str = do_read_string(fd, ph);
        if (!str)
            goto error;

        /* include a NULL character at the end */
        strbuf_add(&sb, str, strlen(str) + 1);
        free(str);
    }
    ph->env.sibling_threads = strbuf_detach(&sb, NULL);
    return 0;

error:
    strbuf_release(&sb);
    return -1;
}

static int process_numa_topology(struct perf_file_section *section __maybe_unused,
                 struct perf_header *ph, int fd,
                 void *data __maybe_unused)
{
    size_t ret;
    u32 nr, node, i;
    char *str;
    uint64_t mem_total, mem_free;
    struct strbuf sb;

    /* nr nodes */
    ret = read(fd, &nr, sizeof(nr));
    if (ret != sizeof(nr))
        goto error;

    if (ph->needs_swap)
        nr = bswap_32(nr);

    ph->env.nr_numa_nodes = nr;
    strbuf_init(&sb, 256);

    for (i = 0; i < nr; i++) {
        /* node number */
        ret = read(fd, &node, sizeof(node));
        if (ret != sizeof(node))
            goto error;

        ret = read(fd, &mem_total, sizeof(u64));
        if (ret != sizeof(u64))
            goto error;

        ret = read(fd, &mem_free, sizeof(u64));
        if (ret != sizeof(u64))
            goto error;

        if (ph->needs_swap) {
            node = bswap_32(node);
            mem_total = bswap_64(mem_total);
            mem_free = bswap_64(mem_free);
        }

        strbuf_addf(&sb, "%u:%"PRIu64":%"PRIu64":",
                node, mem_total, mem_free);

        str = do_read_string(fd, ph);
        if (!str)
            goto error;

        /* include a NULL character at the end */
        strbuf_add(&sb, str, strlen(str) + 1);
        free(str);
    }
    ph->env.numa_nodes = strbuf_detach(&sb, NULL);
    return 0;

error:
    strbuf_release(&sb);
    return -1;
}

static int process_pmu_mappings(struct perf_file_section *section __maybe_unused,
                struct perf_header *ph, int fd,
                void *data __maybe_unused)
{
    size_t ret;
    char *name;
    u32 pmu_num;
    u32 type;
    struct strbuf sb;

    ret = read(fd, &pmu_num, sizeof(pmu_num));
    if (ret != sizeof(pmu_num))
        return -1;

    if (ph->needs_swap)
        pmu_num = bswap_32(pmu_num);

    if (!pmu_num) {
        pr_debug("pmu mappings not available\n");
        return 0;
    }

    ph->env.nr_pmu_mappings = pmu_num;
    strbuf_init(&sb, 128);

    while (pmu_num) {
        if (read(fd, &type, sizeof(type)) != sizeof(type))
            goto error;
        if (ph->needs_swap)
            type = bswap_32(type);

        name = do_read_string(fd, ph);
        if (!name)
            goto error;

        strbuf_addf(&sb, "%u:%s", type, name);
        /* include a NULL character at the end */
        strbuf_add(&sb, "", 1);

        free(name);
        pmu_num--;
    }
    ph->env.pmu_mappings = strbuf_detach(&sb, NULL);
    return 0;

error:
    strbuf_release(&sb);
    return -1;
}

struct feature_ops {
    int (*write)(int fd, struct perf_header *h, struct perf_evlist *evlist);
    void (*print)(struct perf_header *h, int fd, FILE *fp);
    int (*process)(struct perf_file_section *section,
               struct perf_header *h, int fd, void *data);
    const char *name;
    bool full_only;
};

#define FEAT_OPA(n, func) \
    [n] = { .name = #n, .write = write_##func, .print = print_##func }
#define FEAT_OPP(n, func) \
    [n] = { .name = #n, .write = write_##func, .print = print_##func, \
        .process = process_##func }
#define FEAT_OPF(n, func) \
    [n] = { .name = #n, .write = write_##func, .print = print_##func, \
        .process = process_##func, .full_only = true }

/* feature_ops not implemented: */
#define print_tracing_data  NULL
#define print_build_id      NULL

static const struct feature_ops feat_ops[HEADER_LAST_FEATURE] = {
    FEAT_OPP(HEADER_TRACING_DATA,   tracing_data),
    FEAT_OPP(HEADER_BUILD_ID,   build_id),
    FEAT_OPP(HEADER_HOSTNAME,   hostname),
    FEAT_OPP(HEADER_OSRELEASE,  osrelease),
    FEAT_OPP(HEADER_VERSION,    version),
    FEAT_OPP(HEADER_ARCH,       arch),
    FEAT_OPP(HEADER_NRCPUS,     nrcpus),
    FEAT_OPP(HEADER_CPUDESC,    cpudesc),
    FEAT_OPP(HEADER_CPUID,      cpuid),
    FEAT_OPP(HEADER_TOTAL_MEM,  total_mem),
    FEAT_OPP(HEADER_EVENT_DESC, event_desc),
    FEAT_OPP(HEADER_CMDLINE,    cmdline),
    FEAT_OPF(HEADER_CPU_TOPOLOGY,   cpu_topology),
    FEAT_OPF(HEADER_NUMA_TOPOLOGY,  numa_topology),
    FEAT_OPA(HEADER_BRANCH_STACK,   branch_stack),
    FEAT_OPP(HEADER_PMU_MAPPINGS,   pmu_mappings),
};

struct header_print_data {
    FILE *fp;
    bool full; /* extended list of headers */
};

static int perf_file_section__fprintf_info(struct perf_file_section *section,
                       struct perf_header *ph,
                       int feat, int fd, void *data)
{
    struct header_print_data *hd = data;

    if (lseek(fd, section->offset, SEEK_SET) == (off_t)-1) {
        pr_debug("Failed to lseek to %" PRIu64 " offset for feature "
                "%d, continuing...\n", section->offset, feat);
        return 0;
    }
    if (feat >= HEADER_LAST_FEATURE) {
        pr_warning("unknown feature %d\n", feat);
        return 0;
    }
    if (!feat_ops[feat].print)
        return 0;

    if (!feat_ops[feat].full_only || hd->full)
        feat_ops[feat].print(ph, fd, hd->fp);
    else
        fprintf(hd->fp, "# %s info available, use -I to display\n",
            feat_ops[feat].name);

    return 0;
}

int perf_header__fprintf_info(struct perf_session *session, FILE *fp, bool full)
{
    struct header_print_data hd;
    struct perf_header *header = &session->header;
    int fd = session->fd;
    hd.fp = fp;
    hd.full = full;

    perf_header__process_sections(header, fd, &hd,
                      perf_file_section__fprintf_info);
    return 0;
}

static int do_write_feat(int fd, struct perf_header *h, int type,
             struct perf_file_section **p,
             struct perf_evlist *evlist)
{
    int err;
    int ret = 0;

    if (perf_header__has_feat(h, type)) {
        if (!feat_ops[type].write)
            return -1;

        (*p)->offset = lseek(fd, 0, SEEK_CUR);

        err = feat_ops[type].write(fd, h, evlist);
        if (err < 0) {
            pr_debug("failed to write feature %d\n", type);

            /* undo anything written */
            lseek(fd, (*p)->offset, SEEK_SET);

            return -1;
        }
        (*p)->size = lseek(fd, 0, SEEK_CUR) - (*p)->offset;
        (*p)++;
    }
    return ret;
}

static int perf_header__adds_write(struct perf_header *header,
                   struct perf_evlist *evlist, int fd)
{
    int nr_sections;
    struct perf_file_section *feat_sec, *p;
    int sec_size;
    u64 sec_start;
    int feat;
    int err;

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

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

    sec_size = sizeof(*feat_sec) * nr_sections;

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

    for_each_set_bit(feat, header->adds_features, HEADER_FEAT_BITS) {
        if (do_write_feat(fd, header, feat, &p, evlist))
            perf_header__clear_feat(header, feat);
    }

    lseek(fd, sec_start, SEEK_SET);
    /*
     * may write more than needed due to dropped feature, but
     * this is okay, reader will skip the mising entries
     */
    err = do_write(fd, feat_sec, sec_size);
    if (err < 0)
        pr_debug("failed to write feature section\n");
    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_session__write_header(struct perf_session *session,
                   struct perf_evlist *evlist,
                   int fd, bool at_exit)
{
    struct perf_file_header f_header;
    struct perf_file_attr   f_attr;
    struct perf_header *header = &session->header;
    struct perf_evsel *evsel, *pair = NULL;
    int err;

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

    if (session->evlist != evlist)
        pair = perf_evlist__first(session->evlist);

    list_for_each_entry(evsel, &evlist->entries, node) {
        evsel->id_offset = lseek(fd, 0, SEEK_CUR);
        err = do_write(fd, evsel->id, evsel->ids * sizeof(u64));
        if (err < 0) {
out_err_write:
            pr_debug("failed to write perf header\n");
            return err;
        }
        if (session->evlist != evlist) {
            err = do_write(fd, pair->id, pair->ids * sizeof(u64));
            if (err < 0)
                goto out_err_write;
            evsel->ids += pair->ids;
            pair = perf_evsel__next(pair);
        }
    }

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

    list_for_each_entry(evsel, &evlist->entries, node) {
        f_attr = (struct perf_file_attr){
            .attr = evsel->attr,
            .ids  = {
                .offset = evsel->id_offset,
                .size   = evsel->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;
        }
    }

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

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

    if (at_exit) {
        err = perf_header__adds_write(header, evlist, 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 = header->attr_offset,
            .size   = evlist->nr_entries * sizeof(f_attr),
        },
        .data = {
            .offset = header->data_offset,
            .size   = header->data_size,
        },
        .event_types = {
            .offset = header->event_offset,
            .size   = header->event_size,
        },
    };

    memcpy(&f_header.adds_features, &header->adds_features, sizeof(header->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, header->data_offset + header->data_size, SEEK_SET);

    header->frozen = 1;
    return 0;
}

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

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

    return 0;
}

int perf_header__process_sections(struct perf_header *header, int fd,
                  void *data,
                  int (*process)(struct perf_file_section *section,
                         struct perf_header *ph,
                         int feat, int fd, void *data))
{
    struct perf_file_section *feat_sec, *sec;
    int nr_sections;
    int sec_size;
    int feat;
    int err;

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

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

    sec_size = sizeof(*feat_sec) * nr_sections;

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

    err = perf_header__getbuffer64(header, fd, feat_sec, sec_size);
    if (err < 0)
        goto out_free;

    for_each_set_bit(feat, header->adds_features, HEADER_LAST_FEATURE) {
        err = process(sec++, header, feat, fd, data);
        if (err < 0)
            goto out_free;
    }
    err = 0;
out_free:
    free(feat_sec);
    return err;
}

static const int attr_file_abi_sizes[] = {
    [0] = PERF_ATTR_SIZE_VER0,
    [1] = PERF_ATTR_SIZE_VER1,
    [2] = PERF_ATTR_SIZE_VER2,
    [3] = PERF_ATTR_SIZE_VER3,
    0,
};

/*
 * In the legacy file format, the magic number is not used to encode endianness.
 * hdr_sz was used to encode endianness. But given that hdr_sz can vary based
 * on ABI revisions, we need to try all combinations for all endianness to
 * detect the endianness.
 */
static int try_all_file_abis(uint64_t hdr_sz, struct perf_header *ph)
{
    uint64_t ref_size, attr_size;
    int i;

    for (i = 0 ; attr_file_abi_sizes[i]; i++) {
        ref_size = attr_file_abi_sizes[i]
             + sizeof(struct perf_file_section);
        if (hdr_sz != ref_size) {
            attr_size = bswap_64(hdr_sz);
            if (attr_size != ref_size)
                continue;

            ph->needs_swap = true;
        }
        pr_debug("ABI%d perf.data file detected, need_swap=%d\n",
             i,
             ph->needs_swap);
        return 0;
    }
    /* could not determine endianness */
    return -1;
}

#define PERF_PIPE_HDR_VER0  16

static const size_t attr_pipe_abi_sizes[] = {
    [0] = PERF_PIPE_HDR_VER0,
    0,
};

/*
 * In the legacy pipe format, there is an implicit assumption that endiannesss
 * between host recording the samples, and host parsing the samples is the
 * same. This is not always the case given that the pipe output may always be
 * redirected into a file and analyzed on a different machine with possibly a
 * different endianness and perf_event ABI revsions in the perf tool itself.
 */
static int try_all_pipe_abis(uint64_t hdr_sz, struct perf_header *ph)
{
    u64 attr_size;
    int i;

    for (i = 0 ; attr_pipe_abi_sizes[i]; i++) {
        if (hdr_sz != attr_pipe_abi_sizes[i]) {
            attr_size = bswap_64(hdr_sz);
            if (attr_size != hdr_sz)
                continue;

            ph->needs_swap = true;
        }
        pr_debug("Pipe ABI%d perf.data file detected\n", i);
        return 0;
    }
    return -1;
}

static int check_magic_endian(u64 magic, uint64_t hdr_sz,
                  bool is_pipe, struct perf_header *ph)
{
    int ret;

    /* check for legacy format */
    ret = memcmp(&magic, __perf_magic1, sizeof(magic));
    if (ret == 0) {
        pr_debug("legacy perf.data format\n");
        if (is_pipe)
            return try_all_pipe_abis(hdr_sz, ph);

        return try_all_file_abis(hdr_sz, ph);
    }
    /*
     * the new magic number serves two purposes:
     * - unique number to identify actual perf.data files
     * - encode endianness of file
     */

    /* check magic number with one endianness */
    if (magic == __perf_magic2)
        return 0;

    /* check magic number with opposite endianness */
    if (magic != __perf_magic2_sw)
        return -1;

    ph->needs_swap = true;

    return 0;
}

int perf_file_header__read(struct perf_file_header *header,
               struct perf_header *ph, int fd)
{
    int ret;

    lseek(fd, 0, SEEK_SET);

    ret = readn(fd, header, sizeof(*header));
    if (ret <= 0)
        return -1;

    if (check_magic_endian(header->magic,
                   header->attr_size, false, ph) < 0) {
        pr_debug("magic/endian check failed\n");
        return -1;
    }

    if (ph->needs_swap) {
        mem_bswap_64(header, offsetof(struct perf_file_header,
                 adds_features));
    }

    if (header->size != sizeof(*header)) {
        /* Support the previous format */
        if (header->size == offsetof(typeof(*header), adds_features))
            bitmap_zero(header->adds_features, HEADER_FEAT_BITS);
        else
            return -1;
    } else if (ph->needs_swap) {
        /*
         * feature bitmap is declared as an array of unsigned longs --
         * not good since its size can differ between the host that
         * generated the data file and the host analyzing the file.
         *
         * We need to handle endianness, but we don't know the size of
         * the unsigned long where the file was generated. Take a best
         * guess at determining it: try 64-bit swap first (ie., file
         * created on a 64-bit host), and check if the hostname feature
         * bit is set (this feature bit is forced on as of fbe96f2).
         * If the bit is not, undo the 64-bit swap and try a 32-bit
         * swap. If the hostname bit is still not set (e.g., older data
         * file), punt and fallback to the original behavior --
         * clearing all feature bits and setting buildid.
         */
        mem_bswap_64(&header->adds_features,
                BITS_TO_U64(HEADER_FEAT_BITS));

        if (!test_bit(HEADER_HOSTNAME, header->adds_features)) {
            /* unswap as u64 */
            mem_bswap_64(&header->adds_features,
                    BITS_TO_U64(HEADER_FEAT_BITS));

            /* unswap as u32 */
            mem_bswap_32(&header->adds_features,
                    BITS_TO_U32(HEADER_FEAT_BITS));
        }

        if (!test_bit(HEADER_HOSTNAME, header->adds_features)) {
            bitmap_zero(header->adds_features, HEADER_FEAT_BITS);
            set_bit(HEADER_BUILD_ID, header->adds_features);
        }
    }

    memcpy(&ph->adds_features, &header->adds_features,
           sizeof(ph->adds_features));

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

static int perf_file_section__process(struct perf_file_section *section,
                      struct perf_header *ph,
                      int feat, int fd, void *data)
{
    if (lseek(fd, section->offset, SEEK_SET) == (off_t)-1) {
        pr_debug("Failed to lseek to %" PRIu64 " offset for feature "
              "%d, continuing...\n", section->offset, feat);
        return 0;
    }

    if (feat >= HEADER_LAST_FEATURE) {
        pr_debug("unknown feature %d, continuing...\n", feat);
        return 0;
    }

    if (!feat_ops[feat].process)
        return 0;

    return feat_ops[feat].process(section, ph, fd, data);
}

static int perf_file_header__read_pipe(struct perf_pipe_file_header *header,
                       struct perf_header *ph, int fd,
                       bool repipe)
{
    int ret;

    ret = readn(fd, header, sizeof(*header));
    if (ret <= 0)
        return -1;

    if (check_magic_endian(header->magic, header->size, true, ph) < 0) {
        pr_debug("endian/magic failed\n");
        return -1;
    }

    if (ph->needs_swap)
        header->size = bswap_64(header->size);

    if (repipe && do_write(STDOUT_FILENO, header, sizeof(*header)) < 0)
        return -1;

    return 0;
}

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

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

    session->fd = fd;

    return 0;
}

static int read_attr(int fd, struct perf_header *ph,
             struct perf_file_attr *f_attr)
{
    struct perf_event_attr *attr = &f_attr->attr;
    size_t sz, left;
    size_t our_sz = sizeof(f_attr->attr);
    int ret;

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

    /* read minimal guaranteed structure */
    ret = readn(fd, attr, PERF_ATTR_SIZE_VER0);
    if (ret <= 0) {
        pr_debug("cannot read %d bytes of header attr\n",
             PERF_ATTR_SIZE_VER0);
        return -1;
    }

    /* on file perf_event_attr size */
    sz = attr->size;

    if (ph->needs_swap)
        sz = bswap_32(sz);

    if (sz == 0) {
        /* assume ABI0 */
        sz =  PERF_ATTR_SIZE_VER0;
    } else if (sz > our_sz) {
        pr_debug("file uses a more recent and unsupported ABI"
             " (%zu bytes extra)\n", sz - our_sz);
        return -1;
    }
    /* what we have not yet read and that we know about */
    left = sz - PERF_ATTR_SIZE_VER0;
    if (left) {
        void *ptr = attr;
        ptr += PERF_ATTR_SIZE_VER0;

        ret = readn(fd, ptr, left);
    }
    /* read perf_file_section, ids are read in caller */
    ret = readn(fd, &f_attr->ids, sizeof(f_attr->ids));

    return ret <= 0 ? -1 : 0;
}

static int perf_evsel__prepare_tracepoint_event(struct perf_evsel *evsel,
                        struct pevent *pevent)
{
    struct event_format *event;
    char bf[128];

    /* already prepared */
    if (evsel->tp_format)
        return 0;

    event = pevent_find_event(pevent, evsel->attr.config);
    if (event == NULL)
        return -1;

    if (!evsel->name) {
        snprintf(bf, sizeof(bf), "%s:%s", event->system, event->name);
        evsel->name = strdup(bf);
        if (evsel->name == NULL)
            return -1;
    }

    evsel->tp_format = event;
    return 0;
}

static int perf_evlist__prepare_tracepoint_events(struct perf_evlist *evlist,
                          struct pevent *pevent)
{
    struct perf_evsel *pos;

    list_for_each_entry(pos, &evlist->entries, node) {
        if (pos->attr.type == PERF_TYPE_TRACEPOINT &&
            perf_evsel__prepare_tracepoint_event(pos, pevent))
            return -1;
    }

    return 0;
}

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

    session->evlist = perf_evlist__new(NULL, NULL);
    if (session->evlist == NULL)
        return -ENOMEM;

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

    if (perf_file_header__read(&f_header, header, fd) < 0)
        return -EINVAL;

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

    for (i = 0; i < nr_attrs; i++) {
        struct perf_evsel *evsel;
        off_t tmp;

        if (read_attr(fd, header, &f_attr) < 0)
            goto out_errno;

        if (header->needs_swap)
            perf_event__attr_swap(&f_attr.attr);

        tmp = lseek(fd, 0, SEEK_CUR);
        evsel = perf_evsel__new(&f_attr.attr, i);

        if (evsel == NULL)
            goto out_delete_evlist;

        evsel->needs_swap = header->needs_swap;
        /*
         * Do it before so that if perf_evsel__alloc_id fails, this
         * entry gets purged too at perf_evlist__delete().
         */
        perf_evlist__add(session->evlist, evsel);

        nr_ids = f_attr.ids.size / sizeof(u64);
        /*
         * We don't have the cpu and thread maps on the header, so
         * for allocating the perf_sample_id table we fake 1 cpu and
         * hattr->ids threads.
         */
        if (perf_evsel__alloc_id(evsel, 1, nr_ids))
            goto out_delete_evlist;

        lseek(fd, f_attr.ids.offset, SEEK_SET);

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

            perf_evlist__id_add(session->evlist, evsel, 0, j, f_id);
        }

        lseek(fd, tmp, SEEK_SET);
    }

    symbol_conf.nr_events = nr_attrs;

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

    perf_header__process_sections(header, fd, &session->pevent,
                      perf_file_section__process);

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

    if (perf_evlist__prepare_tracepoint_events(session->evlist,
                           session->pevent))
        goto out_delete_evlist;

    header->frozen = 1;
    return 0;
out_errno:
    return -errno;

out_delete_evlist:
    perf_evlist__delete(session->evlist);
    session->evlist = NULL;
    return -ENOMEM;
}

int perf_event__synthesize_attr(struct perf_tool *tool,
                struct perf_event_attr *attr, u32 ids, u64 *id,
                perf_event__handler_t process)
{
    union perf_event *ev;
    size_t size;
    int err;

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

    ev = malloc(size);

    if (ev == NULL)
        return -ENOMEM;

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

    ev->attr.header.type = PERF_RECORD_HEADER_ATTR;
    ev->attr.header.size = (u16)size;

    if (ev->attr.header.size == size)
        err = process(tool, ev, NULL, NULL);
    else
        err = -E2BIG;

    free(ev);

    return err;
}

int perf_event__synthesize_attrs(struct perf_tool *tool,
                   struct perf_session *session,
                   perf_event__handler_t process)
{
    struct perf_evsel *evsel;
    int err = 0;

    list_for_each_entry(evsel, &session->evlist->entries, node) {
        err = perf_event__synthesize_attr(tool, &evsel->attr, evsel->ids,
                          evsel->id, process);
        if (err) {
            pr_debug("failed to create perf header attribute\n");
            return err;
        }
    }

    return err;
}

int perf_event__process_attr(union perf_event *event,
                 struct perf_evlist **pevlist)
{
    u32 i, ids, n_ids;
    struct perf_evsel *evsel;
    struct perf_evlist *evlist = *pevlist;

    if (evlist == NULL) {
        *pevlist = evlist = perf_evlist__new(NULL, NULL);
        if (evlist == NULL)
            return -ENOMEM;
    }

    evsel = perf_evsel__new(&event->attr.attr, evlist->nr_entries);
    if (evsel == NULL)
        return -ENOMEM;

    perf_evlist__add(evlist, evsel);

    ids = event->header.size;
    ids -= (void *)&event->attr.id - (void *)event;
    n_ids = ids / sizeof(u64);
    /*
     * We don't have the cpu and thread maps on the header, so
     * for allocating the perf_sample_id table we fake 1 cpu and
     * hattr->ids threads.
     */
    if (perf_evsel__alloc_id(evsel, 1, n_ids))
        return -ENOMEM;

    for (i = 0; i < n_ids; i++) {
        perf_evlist__id_add(evlist, evsel, 0, i, event->attr.id[i]);
    }

    return 0;
}

int perf_event__synthesize_event_type(struct perf_tool *tool,
                      u64 event_id, char *name,
                      perf_event__handler_t process,
                      struct machine *machine)
{
    union perf_event 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(ev.event_type.event_type.name);
    size = PERF_ALIGN(size, sizeof(u64));
    ev.event_type.header.size = sizeof(ev.event_type) -
        (sizeof(ev.event_type.event_type.name) - size);

    err = process(tool, &ev, NULL, machine);

    return err;
}

int perf_event__synthesize_event_types(struct perf_tool *tool,
                       perf_event__handler_t process,
                       struct machine *machine)
{
    struct perf_trace_event_type *type;
    int i, err = 0;

    for (i = 0; i < trace_event_count; i++) {
        type = &trace_events[i];

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

    return err;
}

int perf_event__process_event_type(struct perf_tool *tool __maybe_unused,
                   union perf_event *event)
{
    if (perf_header__push_event(event->event_type.event_type.event_id,
                    event->event_type.event_type.name) < 0)
        return -ENOMEM;

    return 0;
}

int perf_event__synthesize_tracing_data(struct perf_tool *tool, int fd,
                    struct perf_evlist *evlist,
                    perf_event__handler_t process)
{
    union perf_event ev;
    struct tracing_data *tdata;
    ssize_t size = 0, aligned_size = 0, padding;
    int err __maybe_unused = 0;

    /*
     * We are going to store the size of the data followed
     * by the data contents. Since the fd descriptor is a pipe,
     * we cannot seek back to store the size of the data once
     * we know it. Instead we:
     *
     * - write the tracing data to the temp file
     * - get/write the data size to pipe
     * - write the tracing data from the temp file
     *   to the pipe
     */
    tdata = tracing_data_get(&evlist->entries, fd, true);
    if (!tdata)
        return -1;

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

    ev.tracing_data.header.type = PERF_RECORD_HEADER_TRACING_DATA;
    size = tdata->size;
    aligned_size = PERF_ALIGN(size, sizeof(u64));
    padding = aligned_size - size;
    ev.tracing_data.header.size = sizeof(ev.tracing_data);
    ev.tracing_data.size = aligned_size;

    process(tool, &ev, NULL, NULL);

    /*
     * The put function will copy all the tracing data
     * stored in temp file to the pipe.
     */
    tracing_data_put(tdata);

    write_padded(fd, NULL, 0, padding);

    return aligned_size;
}

int perf_event__process_tracing_data(union perf_event *event,
                     struct perf_session *session)
{
    ssize_t size_read, padding, size = event->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, &session->pevent,
                 session->repipe);
    padding = PERF_ALIGN(size_read, sizeof(u64)) - size_read;

    if (read(session->fd, buf, padding) < 0)
        die("reading input file");
    if (session->repipe) {
        int retw = write(STDOUT_FILENO, buf, padding);
        if (retw <= 0 || retw != padding)
            die("repiping tracing data padding");
    }

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

    perf_evlist__prepare_tracepoint_events(session->evlist,
                           session->pevent);

    return size_read + padding;
}

int perf_event__synthesize_build_id(struct perf_tool *tool,
                    struct dso *pos, u16 misc,
                    perf_event__handler_t process,
                    struct machine *machine)
{
    union perf_event ev;
    size_t len;
    int err = 0;

    if (!pos->hit)
        return err;

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

    len = pos->long_name_len + 1;
    len = PERF_ALIGN(len, NAME_ALIGN);
    memcpy(&ev.build_id.build_id, pos->build_id, sizeof(pos->build_id));
    ev.build_id.header.type = PERF_RECORD_HEADER_BUILD_ID;
    ev.build_id.header.misc = misc;
    ev.build_id.pid = machine->pid;
    ev.build_id.header.size = sizeof(ev.build_id) + len;
    memcpy(&ev.build_id.filename, pos->long_name, pos->long_name_len);

    err = process(tool, &ev, NULL, machine);

    return err;
}

int perf_event__process_build_id(struct perf_tool *tool __maybe_unused,
                 union perf_event *event,
                 struct perf_session *session)
{
    __event_process_build_id(&event->build_id,
                 event->build_id.filename,
                 session);
    return 0;
}

void disable_buildid_cache(void)
{
    no_buildid_cache = true;
}