fd_table.c

#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>

#ifndef _WIN32
# include <sys/types.h>
#endif /* _WIN32 */

#include "uv.h"
#include "fd_table.h"
#include "path_resolver.h"
#include "wasi_types.h"
#include "wasi_rights.h"
#include "uv_mapping.h"
#include "uvwasi_alloc.h"


static uvwasi_errno_t uvwasi__insert_stdio(uvwasi_t* uvwasi,
                                           struct uvwasi_fd_table_t* table,
                                           const uvwasi_fd_t fd,
                                           const uvwasi_fd_t expected,
                                           const char* name) {
  struct uvwasi_fd_wrap_t* wrap;
  uvwasi_filetype_t type;
  uvwasi_rights_t base;
  uvwasi_rights_t inheriting;
  uvwasi_errno_t err;

  err = uvwasi__get_filetype_by_fd(fd, &type);
  if (err != UVWASI_ESUCCESS)
    return err;

  err = uvwasi__get_rights(fd, UV_FS_O_RDWR, type, &base, &inheriting);
  if (err != UVWASI_ESUCCESS)
    return err;

  err = uvwasi_fd_table_insert(uvwasi,
                               table,
                               fd,
                               name,
                               name,
                               type,
                               base,
                               inheriting,
                               0,
                               &wrap);
  if (err != UVWASI_ESUCCESS)
    return err;

  if (wrap->id != expected)
    err = UVWASI_EBADF;

  uv_mutex_unlock(&wrap->mutex);
  return err;
}


uvwasi_errno_t uvwasi_fd_table_insert(uvwasi_t* uvwasi,
                                      struct uvwasi_fd_table_t* table,
                                      uv_file fd,
                                      const char* mapped_path,
                                      const char* real_path,
                                      uvwasi_filetype_t type,
                                      uvwasi_rights_t rights_base,
                                      uvwasi_rights_t rights_inheriting,
                                      int preopen,
                                      struct uvwasi_fd_wrap_t** wrap) {
  struct uvwasi_fd_wrap_t* entry;
  struct uvwasi_fd_wrap_t** new_fds;
  uvwasi_errno_t err;
  uint32_t new_size;
  uint32_t index;
  uint32_t i;
  int r;
  size_t mp_len;
  char* mp_copy;
  size_t rp_len;
  char* rp_copy;
  char* np_copy;

  mp_len = strlen(mapped_path);
  rp_len = strlen(real_path);
  /* Reserve room for the mapped path, real path, and normalized mapped path. */
  entry = (struct uvwasi_fd_wrap_t*)
    uvwasi__malloc(uvwasi, sizeof(*entry) + mp_len + mp_len + rp_len + 3);
  if (entry == NULL)
    return UVWASI_ENOMEM;

  mp_copy = (char*)(entry + 1);
  rp_copy = mp_copy + mp_len + 1;
  np_copy = rp_copy + rp_len + 1;
  memcpy(mp_copy, mapped_path, mp_len);
  mp_copy[mp_len] = '\0';
  memcpy(rp_copy, real_path, rp_len);
  rp_copy[rp_len] = '\0';

  /* Calculate the normalized version of the mapped path, as it will be used for
     any path calculations on this fd. Use the length of the mapped path as an
     upper bound for the normalized path length. */
  err = uvwasi__normalize_path(mp_copy, mp_len, np_copy, mp_len);
  if (err) {
    uvwasi__free(uvwasi, entry);
    goto exit;
  }

  uv_rwlock_wrlock(&table->rwlock);

  /* Check that there is room for a new item. If there isn't, grow the table. */
  if (table->used >= table->size) {
    new_size = table->size * 2;
    new_fds = uvwasi__realloc(uvwasi, table->fds, new_size * sizeof(*new_fds));
    if (new_fds == NULL) {
      uvwasi__free(uvwasi, entry);
      err = UVWASI_ENOMEM;
      goto exit;
    }

    for (i = table->size; i < new_size; ++i)
      new_fds[i] = NULL;

    index = table->size;
    table->fds = new_fds;
    table->size = new_size;
  } else {
    /* The table is big enough, so find an empty slot for the new data. */
    int valid_slot = 0;
    for (i = 0; i < table->size; ++i) {
      if (table->fds[i] == NULL) {
        valid_slot = 1;
        index = i;
        break;
      }
    }

    /* This should never happen. */
    if (valid_slot == 0) {
      uvwasi__free(uvwasi, entry);
      err = UVWASI_ENOSPC;
      goto exit;
    }
  }

  table->fds[index] = entry;

  r = uv_mutex_init(&entry->mutex);
  if (r != 0) {
    err = uvwasi__translate_uv_error(r);
    goto exit;
  }

  entry->id = index;
  entry->fd = fd;
  entry->path = mp_copy;
  entry->real_path = rp_copy;
  entry->normalized_path = np_copy;
  entry->type = type;
  entry->rights_base = rights_base;
  entry->rights_inheriting = rights_inheriting;
  entry->preopen = preopen;

  if (wrap != NULL) {
    uv_mutex_lock(&entry->mutex);
    *wrap = entry;
  }

  table->used++;
  err = UVWASI_ESUCCESS;
exit:
  uv_rwlock_wrunlock(&table->rwlock);
  return err;
}


uvwasi_errno_t uvwasi_fd_table_init(uvwasi_t* uvwasi,
                                    uvwasi_options_t* options) {
  struct uvwasi_fd_table_t* table;
  uvwasi_errno_t err;
  int r;

  /* Require an initial size of at least three to store the stdio FDs. */
  if (uvwasi == NULL || options == NULL || options->fd_table_size < 3)
    return UVWASI_EINVAL;

  table = &uvwasi->fds;
  table->fds = NULL;
  table->used = 0;
  table->size = options->fd_table_size;
  table->fds = uvwasi__calloc(uvwasi,
                              options->fd_table_size,
                              sizeof(struct uvwasi_fd_wrap_t*));

  if (table->fds == NULL)
    return UVWASI_ENOMEM;

  r = uv_rwlock_init(&table->rwlock);
  if (r != 0) {
    err = uvwasi__translate_uv_error(r);
    /* Free table->fds and set it to NULL here. This is done explicitly instead
       of jumping to error_exit because uvwasi_fd_table_free() relies on fds
       being NULL to know whether or not to destroy the rwlock.
    */
    uvwasi__free(uvwasi, table->fds);
    table->fds = NULL;
    return err;
  }

  /* Create the stdio FDs. */
  err = uvwasi__insert_stdio(uvwasi, table, options->in, 0, "<stdin>");
  if (err != UVWASI_ESUCCESS)
    goto error_exit;

  err = uvwasi__insert_stdio(uvwasi, table, options->out, 1, "<stdout>");
  if (err != UVWASI_ESUCCESS)
    goto error_exit;

  err = uvwasi__insert_stdio(uvwasi, table, options->err, 2, "<stderr>");
  if (err != UVWASI_ESUCCESS)
    goto error_exit;

  return UVWASI_ESUCCESS;
error_exit:
  uvwasi_fd_table_free(uvwasi, table);
  return err;
}


void uvwasi_fd_table_free(uvwasi_t* uvwasi, struct uvwasi_fd_table_t* table) {
  struct uvwasi_fd_wrap_t* entry;
  uint32_t i;

  if (table == NULL)
    return;

  for (i = 0; i < table->size; i++) {
    entry = table->fds[i];
    if (entry == NULL) continue;

    uv_mutex_destroy(&entry->mutex);
    uvwasi__free(uvwasi, entry);
  }

  if (table->fds != NULL) {
    uvwasi__free(uvwasi, table->fds);
    table->fds = NULL;
    table->size = 0;
    table->used = 0;
    uv_rwlock_destroy(&table->rwlock);
  }
}


uvwasi_errno_t uvwasi_fd_table_insert_preopen(uvwasi_t* uvwasi,
                                              struct uvwasi_fd_table_t* table,
                                              const uv_file fd,
                                              const char* path,
                                              const char* real_path) {
  uvwasi_filetype_t type;
  uvwasi_rights_t base;
  uvwasi_rights_t inheriting;
  uvwasi_errno_t err;

  if (table == NULL || path == NULL || real_path == NULL)
    return UVWASI_EINVAL;

  err = uvwasi__get_filetype_by_fd(fd, &type);
  if (err != UVWASI_ESUCCESS)
    return err;

  if (type != UVWASI_FILETYPE_DIRECTORY)
    return UVWASI_ENOTDIR;

  err = uvwasi__get_rights(fd, 0, type, &base, &inheriting);
  if (err != UVWASI_ESUCCESS)
    return err;

  return uvwasi_fd_table_insert(uvwasi,
                                table,
                                fd,
                                path,
                                real_path,
                                UVWASI_FILETYPE_DIRECTORY,
                                UVWASI__RIGHTS_DIRECTORY_BASE,
                                UVWASI__RIGHTS_DIRECTORY_INHERITING,
                                1,
                                NULL);
}


uvwasi_errno_t uvwasi_fd_table_get(struct uvwasi_fd_table_t* table,
                                   const uvwasi_fd_t id,
                                   struct uvwasi_fd_wrap_t** wrap,
                                   uvwasi_rights_t rights_base,
                                   uvwasi_rights_t rights_inheriting) {
  uvwasi_errno_t err;

  if (table == NULL)
    return UVWASI_EINVAL;

  uv_rwlock_wrlock(&table->rwlock);
  err = uvwasi_fd_table_get_nolock(table,
                                   id,
                                   wrap,
                                   rights_base,
                                   rights_inheriting);
  uv_rwlock_wrunlock(&table->rwlock);
  return err;
}


/* uvwasi_fd_table_get_nolock() retrieves a file descriptor and locks its mutex,
   but does not lock the file descriptor table like uvwasi_fd_table_get() does.
*/
uvwasi_errno_t uvwasi_fd_table_get_nolock(struct uvwasi_fd_table_t* table,
                                          const uvwasi_fd_t id,
                                          struct uvwasi_fd_wrap_t** wrap,
                                          uvwasi_rights_t rights_base,
                                          uvwasi_rights_t rights_inheriting) {
  struct uvwasi_fd_wrap_t* entry;

  if (table == NULL || wrap == NULL)
    return UVWASI_EINVAL;

  if (id >= table->size)
    return UVWASI_EBADF;

  entry = table->fds[id];

  if (entry == NULL || entry->id != id)
    return UVWASI_EBADF;

  /* Validate that the fd has the necessary rights. */
  if ((~entry->rights_base & rights_base) != 0 ||
      (~entry->rights_inheriting & rights_inheriting) != 0) {
    return UVWASI_ENOTCAPABLE;
  }

  uv_mutex_lock(&entry->mutex);
  *wrap = entry;
  return UVWASI_ESUCCESS;
}


uvwasi_errno_t uvwasi_fd_table_remove_nolock(uvwasi_t* uvwasi,
                                             struct uvwasi_fd_table_t* table,
                                             const uvwasi_fd_t id) {
  struct uvwasi_fd_wrap_t* entry;

  if (table == NULL)
    return UVWASI_EINVAL;

  if (id >= table->size)
    return UVWASI_EBADF;

  entry = table->fds[id];

  if (entry == NULL || entry->id != id)
    return UVWASI_EBADF;

  uv_mutex_destroy(&entry->mutex);
  uvwasi__free(uvwasi, entry);
  table->fds[id] = NULL;
  table->used--;
  return UVWASI_ESUCCESS;
}


uvwasi_errno_t uvwasi_fd_table_renumber(struct uvwasi_s* uvwasi,
                                        struct uvwasi_fd_table_t* table,
                                        const uvwasi_fd_t dst,
                                        const uvwasi_fd_t src) {
  struct uvwasi_fd_wrap_t* dst_entry;
  struct uvwasi_fd_wrap_t* src_entry;
  uv_fs_t req;
  uvwasi_errno_t err;
  int r;

  if (uvwasi == NULL || table == NULL)
    return UVWASI_EINVAL;

  if (dst == src)
    return UVWASI_ESUCCESS;

  uv_rwlock_wrlock(&table->rwlock);

  if (dst >= table->size || src >= table->size) {
    err = UVWASI_EBADF;
    goto exit;
  }

  dst_entry = table->fds[dst];
  src_entry = table->fds[src];

  if (dst_entry == NULL || dst_entry->id != dst ||
      src_entry == NULL || src_entry->id != src) {
    err = UVWASI_EBADF;
    goto exit;
  }

  uv_mutex_lock(&dst_entry->mutex);
  uv_mutex_lock(&src_entry->mutex);

  /* Close the existing destination descriptor. */
  r = uv_fs_close(NULL, &req, dst_entry->fd, NULL);
  uv_fs_req_cleanup(&req);
  if (r != 0) {
    uv_mutex_unlock(&src_entry->mutex);
    uv_mutex_unlock(&dst_entry->mutex);
    err = uvwasi__translate_uv_error(r);
    goto exit;
  }

  /* Move the source entry to the destination slot in the table. */
  table->fds[dst] = table->fds[src];
  table->fds[dst]->id = dst;
  uv_mutex_unlock(&table->fds[dst]->mutex);
  table->fds[src] = NULL;
  table->used--;

  /* Clean up what's left of the old destination entry. */
  uv_mutex_unlock(&dst_entry->mutex);
  uv_mutex_destroy(&dst_entry->mutex);
  uvwasi__free(uvwasi, dst_entry);

  err = UVWASI_ESUCCESS;
exit:
  uv_rwlock_wrunlock(&table->rwlock);
  return err;
}


uvwasi_errno_t uvwasi_fd_table_lock(struct uvwasi_fd_table_t* table) {
  if (table == NULL)
    return UVWASI_EINVAL;

  uv_rwlock_wrlock(&table->rwlock);
  return UVWASI_ESUCCESS;
}


uvwasi_errno_t uvwasi_fd_table_unlock(struct uvwasi_fd_table_t* table) {
  if (table == NULL)
    return UVWASI_EINVAL;

  uv_rwlock_wrunlock(&table->rwlock);
  return UVWASI_ESUCCESS;
}