vdso.c

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// SPDX-License-Identifier: GPL-2.0
#include <errno.h>
#include <unistd.h>
#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <stdlib.h>
#include <linux/kernel.h>

#include "vdso.h"
#include "util.h"
#include "symbol.h"
#include "machine.h"
#include "thread.h"
#include "linux/string.h"
#include "debug.h"

/*
 * Include definition of find_vdso_map() also used in perf-read-vdso.c for
 * building perf-read-vdso32 and perf-read-vdsox32.
 */
#include "find-vdso-map.c"

#define VDSO__TEMP_FILE_NAME "/tmp/perf-vdso.so-XXXXXX"

struct vdso_file {
    bool found;
    bool error;
    char temp_file_name[sizeof(VDSO__TEMP_FILE_NAME)];
    const char *dso_name;
    const char *read_prog;
};

struct vdso_info {
    struct vdso_file vdso;
#if BITS_PER_LONG == 64
    struct vdso_file vdso32;
    struct vdso_file vdsox32;
#endif
};

static struct vdso_info *vdso_info__new(void)
{
    static const struct vdso_info vdso_info_init = {
        .vdso    = {
            .temp_file_name = VDSO__TEMP_FILE_NAME,
            .dso_name = DSO__NAME_VDSO,
        },
#if BITS_PER_LONG == 64
        .vdso32  = {
            .temp_file_name = VDSO__TEMP_FILE_NAME,
            .dso_name = DSO__NAME_VDSO32,
            .read_prog = "perf-read-vdso32",
        },
        .vdsox32  = {
            .temp_file_name = VDSO__TEMP_FILE_NAME,
            .dso_name = DSO__NAME_VDSOX32,
            .read_prog = "perf-read-vdsox32",
        },
#endif
    };

    return memdup(&vdso_info_init, sizeof(vdso_info_init));
}

static char *get_file(struct vdso_file *vdso_file)
{
    char *vdso = NULL;
    char *buf = NULL;
    void *start, *end;
    size_t size;
    int fd;

    if (vdso_file->found)
        return vdso_file->temp_file_name;

    if (vdso_file->error || find_vdso_map(&start, &end))
        return NULL;

    size = end - start;

    buf = memdup(start, size);
    if (!buf)
        return NULL;

    fd = mkstemp(vdso_file->temp_file_name);
    if (fd < 0)
        goto out;

    if (size == (size_t) write(fd, buf, size))
        vdso = vdso_file->temp_file_name;

    close(fd);

 out:
    free(buf);

    vdso_file->found = (vdso != NULL);
    vdso_file->error = !vdso_file->found;
    return vdso;
}

void machine__exit_vdso(struct machine *machine)
{
    struct vdso_info *vdso_info = machine->vdso_info;

    if (!vdso_info)
        return;

    if (vdso_info->vdso.found)
        unlink(vdso_info->vdso.temp_file_name);
#if BITS_PER_LONG == 64
    if (vdso_info->vdso32.found)
        unlink(vdso_info->vdso32.temp_file_name);
    if (vdso_info->vdsox32.found)
        unlink(vdso_info->vdsox32.temp_file_name);
#endif

    zfree(&machine->vdso_info);
}

static struct dso *__machine__addnew_vdso(struct machine *machine, const char *short_name,
                      const char *long_name)
{
    struct dso *dso;

    dso = dso__new(short_name);
    if (dso != NULL) {
        __dsos__add(&machine->dsos, dso);
        dso__set_long_name(dso, long_name, false);
    }

    return dso;
}

static enum dso_type machine__thread_dso_type(struct machine *machine,
                          struct thread *thread)
{
    enum dso_type dso_type = DSO__TYPE_UNKNOWN;
    struct map *map = map_groups__first(thread->mg);

    for (; map ; map = map_groups__next(map)) {
        struct dso *dso = map->dso;
        if (!dso || dso->long_name[0] != '/')
            continue;
        dso_type = dso__type(dso, machine);
        if (dso_type != DSO__TYPE_UNKNOWN)
            break;
    }

    return dso_type;
}

#if BITS_PER_LONG == 64

static int vdso__do_copy_compat(FILE *f, int fd)
{
    char buf[4096];
    size_t count;

    while (1) {
        count = fread(buf, 1, sizeof(buf), f);
        if (ferror(f))
            return -errno;
        if (feof(f))
            break;
        if (count && writen(fd, buf, count) != (ssize_t)count)
            return -errno;
    }

    return 0;
}

static int vdso__copy_compat(const char *prog, int fd)
{
    FILE *f;
    int err;

    f = popen(prog, "r");
    if (!f)
        return -errno;

    err = vdso__do_copy_compat(f, fd);

    if (pclose(f) == -1)
        return -errno;

    return err;
}

static int vdso__create_compat_file(const char *prog, char *temp_name)
{
    int fd, err;

    fd = mkstemp(temp_name);
    if (fd < 0)
        return -errno;

    err = vdso__copy_compat(prog, fd);

    if (close(fd) == -1)
        return -errno;

    return err;
}

static const char *vdso__get_compat_file(struct vdso_file *vdso_file)
{
    int err;

    if (vdso_file->found)
        return vdso_file->temp_file_name;

    if (vdso_file->error)
        return NULL;

    err = vdso__create_compat_file(vdso_file->read_prog,
                       vdso_file->temp_file_name);
    if (err) {
        pr_err("%s failed, error %d\n", vdso_file->read_prog, err);
        vdso_file->error = true;
        return NULL;
    }

    vdso_file->found = true;

    return vdso_file->temp_file_name;
}

static struct dso *__machine__findnew_compat(struct machine *machine,
                         struct vdso_file *vdso_file)
{
    const char *file_name;
    struct dso *dso;

    dso = __dsos__find(&machine->dsos, vdso_file->dso_name, true);
    if (dso)
        goto out;

    file_name = vdso__get_compat_file(vdso_file);
    if (!file_name)
        goto out;

    dso = __machine__addnew_vdso(machine, vdso_file->dso_name, file_name);
out:
    return dso;
}

static int __machine__findnew_vdso_compat(struct machine *machine,
                      struct thread *thread,
                      struct vdso_info *vdso_info,
                      struct dso **dso)
{
    enum dso_type dso_type;

    dso_type = machine__thread_dso_type(machine, thread);

#ifndef HAVE_PERF_READ_VDSO32
    if (dso_type == DSO__TYPE_32BIT)
        return 0;
#endif
#ifndef HAVE_PERF_READ_VDSOX32
    if (dso_type == DSO__TYPE_X32BIT)
        return 0;
#endif

    switch (dso_type) {
    case DSO__TYPE_32BIT:
        *dso = __machine__findnew_compat(machine, &vdso_info->vdso32);
        return 1;
    case DSO__TYPE_X32BIT:
        *dso = __machine__findnew_compat(machine, &vdso_info->vdsox32);
        return 1;
    case DSO__TYPE_UNKNOWN:
    case DSO__TYPE_64BIT:
    default:
        return 0;
    }
}

#endif

static struct dso *machine__find_vdso(struct machine *machine,
                      struct thread *thread)
{
    struct dso *dso = NULL;
    enum dso_type dso_type;

    dso_type = machine__thread_dso_type(machine, thread);
    switch (dso_type) {
    case DSO__TYPE_32BIT:
        dso = __dsos__find(&machine->dsos, DSO__NAME_VDSO32, true);
        if (!dso) {
            dso = __dsos__find(&machine->dsos, DSO__NAME_VDSO,
                       true);
            if (dso && dso_type != dso__type(dso, machine))
                dso = NULL;
        }
        break;
    case DSO__TYPE_X32BIT:
        dso = __dsos__find(&machine->dsos, DSO__NAME_VDSOX32, true);
        break;
    case DSO__TYPE_64BIT:
    case DSO__TYPE_UNKNOWN:
    default:
        dso = __dsos__find(&machine->dsos, DSO__NAME_VDSO, true);
        break;
    }

    return dso;
}

struct dso *machine__findnew_vdso(struct machine *machine,
                  struct thread *thread)
{
    struct vdso_info *vdso_info;
    struct dso *dso = NULL;

    down_write(&machine->dsos.lock);
    if (!machine->vdso_info)
        machine->vdso_info = vdso_info__new();

    vdso_info = machine->vdso_info;
    if (!vdso_info)
        goto out_unlock;

    dso = machine__find_vdso(machine, thread);
    if (dso)
        goto out_unlock;

#if BITS_PER_LONG == 64
    if (__machine__findnew_vdso_compat(machine, thread, vdso_info, &dso))
        goto out_unlock;
#endif

    dso = __dsos__find(&machine->dsos, DSO__NAME_VDSO, true);
    if (!dso) {
        char *file;

        file = get_file(&vdso_info->vdso);
        if (file)
            dso = __machine__addnew_vdso(machine, DSO__NAME_VDSO, file);
    }

out_unlock:
    dso__get(dso);
    up_write(&machine->dsos.lock);
    return dso;
}

bool dso__is_vdso(struct dso *dso)
{
    return !strcmp(dso->short_name, DSO__NAME_VDSO) ||
           !strcmp(dso->short_name, DSO__NAME_VDSO32) ||
           !strcmp(dso->short_name, DSO__NAME_VDSOX32);
}