xref: /xen/xen/common/hypfs.c

/******************************************************************************
 *
 * hypfs.c
 *
 * Simple sysfs-like file system for the hypervisor.
 */

#include <xen/err.h>
#include <xen/guest_access.h>
#include <xen/hypercall.h>
#include <xen/hypfs.h>
#include <xen/lib.h>
#include <xen/param.h>
#include <xen/rwlock.h>
#include <public/hypfs.h>

#ifdef CONFIG_COMPAT
#include <compat/hypfs.h>
CHECK_hypfs_dirlistentry;
#endif

#define DIRENTRY_NAME_OFF offsetof(struct xen_hypfs_dirlistentry, name)
#define DIRENTRY_SIZE(name_len) \
    (DIRENTRY_NAME_OFF +        \
     ROUNDUP((name_len) + 1, alignof(struct xen_hypfs_direntry)))

const struct hypfs_funcs hypfs_dir_funcs = {
    .enter = hypfs_node_enter,
    .exit = hypfs_node_exit,
    .read = hypfs_read_dir,
    .write = hypfs_write_deny,
    .getsize = hypfs_getsize,
    .findentry = hypfs_dir_findentry,
};
const struct hypfs_funcs hypfs_leaf_ro_funcs = {
    .enter = hypfs_node_enter,
    .exit = hypfs_node_exit,
    .read = hypfs_read_leaf,
    .write = hypfs_write_deny,
    .getsize = hypfs_getsize,
    .findentry = hypfs_leaf_findentry,
};
const struct hypfs_funcs hypfs_leaf_wr_funcs = {
    .enter = hypfs_node_enter,
    .exit = hypfs_node_exit,
    .read = hypfs_read_leaf,
    .write = hypfs_write_leaf,
    .getsize = hypfs_getsize,
    .findentry = hypfs_leaf_findentry,
};
const struct hypfs_funcs hypfs_bool_wr_funcs = {
    .enter = hypfs_node_enter,
    .exit = hypfs_node_exit,
    .read = hypfs_read_leaf,
    .write = hypfs_write_bool,
    .getsize = hypfs_getsize,
    .findentry = hypfs_leaf_findentry,
};
const struct hypfs_funcs hypfs_custom_wr_funcs = {
    .enter = hypfs_node_enter,
    .exit = hypfs_node_exit,
    .read = hypfs_read_leaf,
    .write = hypfs_write_custom,
    .getsize = hypfs_getsize,
    .findentry = hypfs_leaf_findentry,
};

static DEFINE_RWLOCK(hypfs_lock);
enum hypfs_lock_state {
    hypfs_unlocked,
    hypfs_read_locked,
    hypfs_write_locked
};
static DEFINE_PER_CPU(enum hypfs_lock_state, hypfs_locked);
static DEFINE_PER_CPU(void *, hypfs_dyndata);

static DEFINE_PER_CPU(const struct hypfs_entry *, hypfs_last_node_entered);

HYPFS_DIR_INIT(hypfs_root, "");

static void hypfs_read_lock(void)
{
    ASSERT(this_cpu(hypfs_locked) != hypfs_write_locked);

    read_lock(&hypfs_lock);
    this_cpu(hypfs_locked) = hypfs_read_locked;
}

static void hypfs_write_lock(void)
{
    ASSERT(this_cpu(hypfs_locked) == hypfs_unlocked);

    write_lock(&hypfs_lock);
    this_cpu(hypfs_locked) = hypfs_write_locked;
}

static void hypfs_unlock(void)
{
    enum hypfs_lock_state locked = this_cpu(hypfs_locked);

    this_cpu(hypfs_locked) = hypfs_unlocked;

    switch ( locked )
    {
    case hypfs_read_locked:
        read_unlock(&hypfs_lock);
        break;
    case hypfs_write_locked:
        write_unlock(&hypfs_lock);
        break;
    default:
        BUG();
    }
}

const struct hypfs_entry *cf_check hypfs_node_enter(
    const struct hypfs_entry *entry)
{
    return entry;
}

void cf_check hypfs_node_exit(const struct hypfs_entry *entry)
{
}

static int node_enter(const struct hypfs_entry *entry)
{
    const struct hypfs_entry **last = &this_cpu(hypfs_last_node_entered);

    entry = entry->funcs->enter(entry);
    if ( IS_ERR(entry) )
        return PTR_ERR(entry);

    ASSERT(entry);
    ASSERT(!*last || *last == entry->parent);

    *last = entry;

    return 0;
}

static void node_exit(const struct hypfs_entry *entry)
{
    const struct hypfs_entry **last = &this_cpu(hypfs_last_node_entered);

    ASSERT(*last == entry);
    *last = entry->parent;

    entry->funcs->exit(entry);
}

static void node_exit_all(void)
{
    const struct hypfs_entry **last = &this_cpu(hypfs_last_node_entered);

    while ( *last )
        node_exit(*last);
}

#undef hypfs_alloc_dyndata
void *hypfs_alloc_dyndata(unsigned long size)
{
    unsigned int cpu = smp_processor_id();
    void **dyndata = &per_cpu(hypfs_dyndata, cpu);

    ASSERT(per_cpu(hypfs_locked, cpu) != hypfs_unlocked);
    ASSERT(*dyndata == NULL);

    *dyndata = xzalloc_array(unsigned char, size);

    return *dyndata;
}

void *hypfs_get_dyndata(void)
{
    void *dyndata = this_cpu(hypfs_dyndata);

    ASSERT(dyndata);

    return dyndata;
}

void hypfs_free_dyndata(void)
{
    void **dyndata = &this_cpu(hypfs_dyndata);

    XFREE(*dyndata);
}

static int add_entry(struct hypfs_entry_dir *parent, struct hypfs_entry *new)
{
    int ret = -ENOENT;
    struct hypfs_entry *e;

    ASSERT(new->funcs->enter);
    ASSERT(new->funcs->exit);
    ASSERT(new->funcs->read);
    ASSERT(new->funcs->write);
    ASSERT(new->funcs->getsize);
    ASSERT(new->funcs->findentry);

    hypfs_write_lock();

    list_for_each_entry ( e, &parent->dirlist, list )
    {
        int cmp = strcmp(e->name, new->name);

        if ( cmp > 0 )
        {
            ret = 0;
            list_add_tail(&new->list, &e->list);
            break;
        }
        if ( cmp == 0 )
        {
            ret = -EEXIST;
            break;
        }
    }

    if ( ret == -ENOENT )
    {
        ret = 0;
        list_add_tail(&new->list, &parent->dirlist);
    }

    if ( !ret )
    {
        unsigned int sz = strlen(new->name);

        parent->e.size += DIRENTRY_SIZE(sz);
        new->parent = &parent->e;
    }

    hypfs_unlock();

    return ret;
}

int hypfs_add_dir(struct hypfs_entry_dir *parent,
                  struct hypfs_entry_dir *dir, bool nofault)
{
    int ret;

    ret = add_entry(parent, &dir->e);
    BUG_ON(nofault && ret);

    return ret;
}

void hypfs_add_dyndir(struct hypfs_entry_dir *parent,
                      struct hypfs_entry_dir *template)
{
    /*
     * As the template is only a placeholder for possibly multiple dynamically
     * generated directories, the link up to its parent can be static, while
     * the "real" children of the parent are to be found via the parent's
     * findentry function only.
     */
    template->e.parent = &parent->e;
}

int hypfs_add_leaf(struct hypfs_entry_dir *parent,
                   struct hypfs_entry_leaf *leaf, bool nofault)
{
    int ret;

    if ( !leaf->u.content )
        ret = -EINVAL;
    else
        ret = add_entry(parent, &leaf->e);
    BUG_ON(nofault && ret);

    return ret;
}

static int hypfs_get_path_user(char *buf,
                               XEN_GUEST_HANDLE_PARAM(const_char) uaddr,
                               unsigned long ulen)
{
    if ( ulen > XEN_HYPFS_MAX_PATHLEN )
        return -EINVAL;

    if ( copy_from_guest(buf, uaddr, ulen) )
        return -EFAULT;

    if ( memchr(buf, 0, ulen) != buf + ulen - 1 )
        return -EINVAL;

    return 0;
}

struct hypfs_entry *cf_check hypfs_leaf_findentry(
    const struct hypfs_entry_dir *dir, const char *name, unsigned int name_len)
{
    return ERR_PTR(-ENOTDIR);
}

struct hypfs_entry *cf_check hypfs_dir_findentry(
    const struct hypfs_entry_dir *dir, const char *name, unsigned int name_len)
{
    struct hypfs_entry *entry;

    list_for_each_entry ( entry, &dir->dirlist, list )
    {
        int cmp = strncmp(name, entry->name, name_len);

        if ( cmp < 0 )
            return ERR_PTR(-ENOENT);

        if ( !cmp && strlen(entry->name) == name_len )
            return entry;
    }

    return ERR_PTR(-ENOENT);
}

static struct hypfs_entry *hypfs_get_entry_rel(struct hypfs_entry_dir *dir,
                                               const char *path)
{
    const char *end;
    struct hypfs_entry *entry;
    unsigned int name_len;
    int ret;

    for ( ; ; )
    {
        if ( dir->e.type != XEN_HYPFS_TYPE_DIR )
            return ERR_PTR(-ENOENT);

        if ( !*path )
            return &dir->e;

        end = strchr(path, '/');
        if ( !end )
            end = strchr(path, '\0');
        name_len = end - path;

        ret = node_enter(&dir->e);
        if ( ret )
            return ERR_PTR(ret);

        entry = dir->e.funcs->findentry(dir, path, name_len);
        if ( IS_ERR(entry) || !*end )
            return entry;

        path = end + 1;
        dir = container_of(entry, struct hypfs_entry_dir, e);
    }

    return ERR_PTR(-ENOENT);
}

static struct hypfs_entry *hypfs_get_entry(const char *path)
{
    if ( path[0] != '/' )
        return ERR_PTR(-EINVAL);

    return hypfs_get_entry_rel(&hypfs_root, path + 1);
}

unsigned int cf_check hypfs_getsize(const struct hypfs_entry *entry)
{
    return entry->size;
}

/*
 * Fill the direntry for a dynamically generated entry. Especially the
 * generated name needs to be kept in sync with hypfs_gen_dyndir_id_entry().
 */
int hypfs_read_dyndir_id_entry(const struct hypfs_entry_dir *template,
                               unsigned int id, bool is_last,
                               XEN_GUEST_HANDLE_PARAM(void) *uaddr)
{
    struct xen_hypfs_dirlistentry direntry;
    char name[HYPFS_DYNDIR_ID_NAMELEN];
    unsigned int e_namelen, e_len;

    e_namelen = snprintf(name, sizeof(name), template->e.name, id);
    if ( e_namelen >= sizeof(name) )
    {
        ASSERT_UNREACHABLE();
        return -ENOBUFS;
    }
    e_len = DIRENTRY_SIZE(e_namelen);
    direntry.e.pad = 0;
    direntry.e.type = template->e.type;
    direntry.e.encoding = template->e.encoding;
    direntry.e.content_len = template->e.funcs->getsize(&template->e);
    direntry.e.max_write_len = template->e.max_size;
    direntry.off_next = is_last ? 0 : e_len;
    if ( copy_to_guest(*uaddr, &direntry, 1) )
        return -EFAULT;
    if ( copy_to_guest_offset(*uaddr, DIRENTRY_NAME_OFF, name,
                              e_namelen + 1) )
        return -EFAULT;

    guest_handle_add_offset(*uaddr, e_len);

    return 0;
}

static const struct hypfs_entry *cf_check hypfs_dyndir_enter(
    const struct hypfs_entry *entry)
{
    const struct hypfs_dyndir_id *data;

    data = hypfs_get_dyndata();

    /* Use template with original enter function. */
    return data->template->e.funcs->enter(&data->template->e);
}

static struct hypfs_entry *cf_check hypfs_dyndir_findentry(
    const struct hypfs_entry_dir *dir, const char *name, unsigned int name_len)
{
    const struct hypfs_dyndir_id *data;

    data = hypfs_get_dyndata();

    /* Use template with original findentry function. */
    return data->template->e.funcs->findentry(data->template, name, name_len);
}

static int cf_check hypfs_read_dyndir(
    const struct hypfs_entry *entry, XEN_GUEST_HANDLE_PARAM(void) uaddr)
{
    const struct hypfs_dyndir_id *data;

    data = hypfs_get_dyndata();

    /* Use template with original read function. */
    return data->template->e.funcs->read(&data->template->e, uaddr);
}

/*
 * Fill dyndata with a dynamically generated entry based on a template
 * and a numerical id.
 * Needs to be kept in sync with hypfs_read_dyndir_id_entry() regarding the
 * name generated.
 */
struct hypfs_entry *hypfs_gen_dyndir_id_entry(
    const struct hypfs_entry_dir *template, unsigned int id, void *data)
{
    struct hypfs_dyndir_id *dyndata;

    dyndata = hypfs_get_dyndata();

    dyndata->template = template;
    dyndata->id = id;
    dyndata->data = data;
    snprintf(dyndata->name, sizeof(dyndata->name), template->e.name, id);
    dyndata->dir = *template;
    dyndata->dir.e.name = dyndata->name;
    dyndata->dir.e.funcs = &dyndata->funcs;
    dyndata->funcs = *template->e.funcs;
    dyndata->funcs.enter = hypfs_dyndir_enter;
    dyndata->funcs.findentry = hypfs_dyndir_findentry;
    dyndata->funcs.read = hypfs_read_dyndir;

    return &dyndata->dir.e;
}

unsigned int hypfs_dynid_entry_size(const struct hypfs_entry *template,
                                    unsigned int id)
{
    return DIRENTRY_SIZE(snprintf(NULL, 0, template->name, id));
}

int cf_check hypfs_read_dir(const struct hypfs_entry *entry,
                            XEN_GUEST_HANDLE_PARAM(void) uaddr)
{
    const struct hypfs_entry_dir *d;
    const struct hypfs_entry *e;
    unsigned int size = entry->funcs->getsize(entry);
    int ret;

    ASSERT(this_cpu(hypfs_locked) != hypfs_unlocked);

    d = container_of(entry, const struct hypfs_entry_dir, e);

    list_for_each_entry ( e, &d->dirlist, list )
    {
        struct xen_hypfs_dirlistentry direntry;
        unsigned int e_namelen = strlen(e->name);
        unsigned int e_len = DIRENTRY_SIZE(e_namelen);

        ret = node_enter(e);
        if ( ret )
            return ret;

        direntry.e.pad = 0;
        direntry.e.type = e->type;
        direntry.e.encoding = e->encoding;
        direntry.e.content_len = e->funcs->getsize(e);
        direntry.e.max_write_len = e->max_size;
        direntry.off_next = list_is_last(&e->list, &d->dirlist) ? 0 : e_len;

        node_exit(e);

        if ( copy_to_guest(uaddr, &direntry, 1) )
            return -EFAULT;

        if ( copy_to_guest_offset(uaddr, DIRENTRY_NAME_OFF,
                                  e->name, e_namelen + 1) )
            return -EFAULT;

        guest_handle_add_offset(uaddr, e_len);

        ASSERT(e_len <= size);
        size -= e_len;
    }

    return 0;
}

int cf_check hypfs_read_leaf(
    const struct hypfs_entry *entry, XEN_GUEST_HANDLE_PARAM(void) uaddr)
{
    const struct hypfs_entry_leaf *l;
    unsigned int size = entry->funcs->getsize(entry);

    ASSERT(this_cpu(hypfs_locked) != hypfs_unlocked);

    l = container_of(entry, const struct hypfs_entry_leaf, e);

    return copy_to_guest(uaddr, l->u.content, size) ?  -EFAULT : 0;
}

static int hypfs_read(const struct hypfs_entry *entry,
                      XEN_GUEST_HANDLE_PARAM(void) uaddr, unsigned long ulen)
{
    struct xen_hypfs_direntry e;
    unsigned int size = entry->funcs->getsize(entry);
    long ret = -EINVAL;

    if ( ulen < sizeof(e) )
        goto out;

    e.pad = 0;
    e.type = entry->type;
    e.encoding = entry->encoding;
    e.content_len = size;
    e.max_write_len = entry->max_size;

    ret = -EFAULT;
    if ( copy_to_guest(uaddr, &e, 1) )
        goto out;

    ret = -ENOBUFS;
    if ( ulen < size + sizeof(e) )
        goto out;

    guest_handle_add_offset(uaddr, sizeof(e));

    ret = entry->funcs->read(entry, uaddr);

 out:
    return ret;
}

int cf_check hypfs_write_leaf(
    struct hypfs_entry_leaf *leaf, XEN_GUEST_HANDLE_PARAM(const_void) uaddr,
    unsigned int ulen)
{
    char *buf;
    int ret;
    struct hypfs_entry *e = &leaf->e;

    ASSERT(this_cpu(hypfs_locked) == hypfs_write_locked);
    ASSERT(leaf->e.max_size);

    if ( ulen > e->max_size )
        return -ENOSPC;

    if ( e->type != XEN_HYPFS_TYPE_STRING &&
         e->type != XEN_HYPFS_TYPE_BLOB && ulen != e->funcs->getsize(e) )
        return -EDOM;

    buf = xmalloc_array(char, ulen);
    if ( !buf )
        return -ENOMEM;

    ret = -EFAULT;
    if ( copy_from_guest(buf, uaddr, ulen) )
        goto out;

    ret = -EINVAL;
    if ( e->type == XEN_HYPFS_TYPE_STRING &&
         e->encoding == XEN_HYPFS_ENC_PLAIN &&
         memchr(buf, 0, ulen) != (buf + ulen - 1) )
        goto out;

    ret = 0;
    memcpy(leaf->u.write_ptr, buf, ulen);
    e->size = ulen;

 out:
    xfree(buf);
    return ret;
}

int cf_check hypfs_write_bool(
    struct hypfs_entry_leaf *leaf, XEN_GUEST_HANDLE_PARAM(const_void) uaddr,
    unsigned int ulen)
{
    bool buf;

    ASSERT(this_cpu(hypfs_locked) == hypfs_write_locked);
    ASSERT(leaf->e.type == XEN_HYPFS_TYPE_BOOL &&
           leaf->e.funcs->getsize(&leaf->e) == sizeof(bool) &&
           leaf->e.max_size == sizeof(bool) );

    if ( ulen != leaf->e.max_size )
        return -EDOM;

    if ( copy_from_guest(&buf, uaddr, ulen) )
        return -EFAULT;

    *(bool *)leaf->u.write_ptr = buf;

    return 0;
}

int cf_check hypfs_write_custom(
    struct hypfs_entry_leaf *leaf, XEN_GUEST_HANDLE_PARAM(const_void) uaddr,
    unsigned int ulen)
{
    struct param_hypfs *p;
    char *buf;
    int ret;

    ASSERT(this_cpu(hypfs_locked) == hypfs_write_locked);
    ASSERT(leaf->e.max_size);

    /* Avoid oversized buffer allocation. */
    if ( ulen > MAX_PARAM_SIZE )
        return -ENOSPC;

    buf = xzalloc_array(char, ulen);
    if ( !buf )
        return -ENOMEM;

    ret = -EFAULT;
    if ( copy_from_guest(buf, uaddr, ulen) )
        goto out;

    ret = -EDOM;
    if ( memchr(buf, 0, ulen) != (buf + ulen - 1) )
        goto out;

    p = container_of(leaf, struct param_hypfs, hypfs);
    ret = p->func(buf);

 out:
    xfree(buf);
    return ret;
}

int cf_check hypfs_write_deny(
    struct hypfs_entry_leaf *leaf, XEN_GUEST_HANDLE_PARAM(const_void) uaddr,
    unsigned int ulen)
{
    return -EACCES;
}

static int hypfs_write(struct hypfs_entry *entry,
                       XEN_GUEST_HANDLE_PARAM(const_void) uaddr,
                       unsigned long ulen)
{
    struct hypfs_entry_leaf *l;

    l = container_of(entry, struct hypfs_entry_leaf, e);

    return entry->funcs->write(l, uaddr, ulen);
}

long do_hypfs_op(
    unsigned int cmd, XEN_GUEST_HANDLE_PARAM(const_char) arg1,
    unsigned long arg2, XEN_GUEST_HANDLE_PARAM(void) arg3, unsigned long arg4)
{
    int ret;
    struct hypfs_entry *entry;
    static char path[XEN_HYPFS_MAX_PATHLEN];

    if ( xsm_hypfs_op(XSM_PRIV) )
        return -EPERM;

    if ( cmd == XEN_HYPFS_OP_get_version )
    {
        if ( !guest_handle_is_null(arg1) || arg2 ||
             !guest_handle_is_null(arg3) || arg4 )
            return -EINVAL;

        return XEN_HYPFS_VERSION;
    }

    if ( cmd == XEN_HYPFS_OP_write_contents )
        hypfs_write_lock();
    else
        hypfs_read_lock();

    ret = hypfs_get_path_user(path, arg1, arg2);
    if ( ret )
        goto out;

    entry = hypfs_get_entry(path);
    if ( IS_ERR(entry) )
    {
        ret = PTR_ERR(entry);
        goto out;
    }

    ret = node_enter(entry);
    if ( ret )
        goto out;

    switch ( cmd )
    {
    case XEN_HYPFS_OP_read:
        ret = hypfs_read(entry, arg3, arg4);
        break;

    case XEN_HYPFS_OP_write_contents:
        ret = hypfs_write(entry, guest_handle_const_cast(arg3, void), arg4);
        break;

    default:
        ret = -EOPNOTSUPP;
        break;
    }

 out:
    node_exit_all();

    hypfs_unlock();

    return ret;
}