extmod: Add VfsPosix filesystem component.

This VFS component allows to mount a host POSIX filesystem within the uPy
VFS sub-system.  All traditional POSIX file access then goes through the
VFS, allowing to sandbox a uPy process to a certain sub-dir of the host
system, as well as mount other filesystem types alongside the host
filesystem.

5 files changed, 666 insertions, 0 deletions

diff --git a/extmod/vfs_posix.c b/extmod/vfs_posix.c
new file mode 100644
index 000000000..0db45a0c1
--- /dev/null
+++ b/extmod/vfs_posix.c
@@ -0,0 +1,357 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2017-2018 Damien P. George
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "py/runtime.h"
+#include "py/mperrno.h"
+#include "extmod/vfs.h"
+#include "extmod/vfs_posix.h"
+
+#if MICROPY_VFS_POSIX
+
+#include <string.h>
+#include <sys/stat.h>
+#include <dirent.h>
+
+typedef struct _mp_obj_vfs_posix_t {
+    mp_obj_base_t base;
+    vstr_t root;
+    size_t root_len;
+    bool readonly;
+} mp_obj_vfs_posix_t;
+
+STATIC const char *vfs_posix_get_path_str(mp_obj_vfs_posix_t *self, mp_obj_t path) {
+    if (self->root_len == 0) {
+        return mp_obj_str_get_str(path);
+    } else {
+        self->root.len = self->root_len;
+        vstr_add_str(&self->root, mp_obj_str_get_str(path));
+        return vstr_null_terminated_str(&self->root);
+    }
+}
+
+STATIC mp_obj_t vfs_posix_get_path_obj(mp_obj_vfs_posix_t *self, mp_obj_t path) {
+    if (self->root_len == 0) {
+        return path;
+    } else {
+        self->root.len = self->root_len;
+        vstr_add_str(&self->root, mp_obj_str_get_str(path));
+        return mp_obj_new_str(self->root.buf, self->root.len);
+    }
+}
+
+STATIC mp_obj_t vfs_posix_fun1_helper(mp_obj_t self_in, mp_obj_t path_in, int (*f)(const char*)) {
+    mp_obj_vfs_posix_t *self = MP_OBJ_TO_PTR(self_in);
+    int ret = f(vfs_posix_get_path_str(self, path_in));
+    if (ret != 0) {
+        mp_raise_OSError(errno);
+    }
+    return mp_const_none;
+}
+
+mp_import_stat_t mp_vfs_posix_import_stat(mp_obj_vfs_posix_t *self, const char *path) {
+    if (self->root_len != 0) {
+        self->root.len = self->root_len;
+        vstr_add_str(&self->root, path);
+        path = vstr_null_terminated_str(&self->root);
+    }
+    struct stat st;
+    if (stat(path, &st) == 0) {
+        if (S_ISDIR(st.st_mode)) {
+            return MP_IMPORT_STAT_DIR;
+        } else if (S_ISREG(st.st_mode)) {
+            return MP_IMPORT_STAT_FILE;
+        }
+    }
+    return MP_IMPORT_STAT_NO_EXIST;
+}
+
+STATIC mp_obj_t vfs_posix_make_new(const mp_obj_type_t *type, size_t n_args, size_t n_kw, const mp_obj_t *args) {
+    mp_arg_check_num(n_args, n_kw, 0, 1, false);
+
+    mp_obj_vfs_posix_t *vfs = m_new_obj(mp_obj_vfs_posix_t);
+    vfs->base.type = type;
+    vstr_init(&vfs->root, 0);
+    if (n_args == 1) {
+        vstr_add_str(&vfs->root, mp_obj_str_get_str(args[0]));
+        vstr_add_char(&vfs->root, '/');
+    }
+    vfs->root_len = vfs->root.len;
+    vfs->readonly = false;
+
+    return MP_OBJ_FROM_PTR(vfs);
+}
+
+STATIC mp_obj_t vfs_posix_mount(mp_obj_t self_in, mp_obj_t readonly, mp_obj_t mkfs) {
+    mp_obj_vfs_posix_t *self = MP_OBJ_TO_PTR(self_in);
+    if (mp_obj_is_true(readonly)) {
+        self->readonly = true;
+    }
+    if (mp_obj_is_true(mkfs)) {
+        mp_raise_OSError(MP_EPERM);
+    }
+    return mp_const_none;
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_3(vfs_posix_mount_obj, vfs_posix_mount);
+
+STATIC mp_obj_t vfs_posix_umount(mp_obj_t self_in) {
+    (void)self_in;
+    return mp_const_none;
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_1(vfs_posix_umount_obj, vfs_posix_umount);
+
+STATIC mp_obj_t vfs_posix_open(mp_obj_t self_in, mp_obj_t path_in, mp_obj_t mode_in) {
+    mp_obj_vfs_posix_t *self = MP_OBJ_TO_PTR(self_in);
+    const char *mode = mp_obj_str_get_str(mode_in);
+    if (self->readonly
+        && (strchr(mode, 'w') != NULL || strchr(mode, 'a') != NULL || strchr(mode, '+') != NULL)) {
+        mp_raise_OSError(MP_EROFS);
+    }
+    if (!MP_OBJ_IS_SMALL_INT(path_in)) {
+        path_in = vfs_posix_get_path_obj(self, path_in);
+    }
+    return mp_vfs_posix_file_open(&mp_type_textio, path_in, mode_in);
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_3(vfs_posix_open_obj, vfs_posix_open);
+
+STATIC mp_obj_t vfs_posix_chdir(mp_obj_t self_in, mp_obj_t path_in) {
+    return vfs_posix_fun1_helper(self_in, path_in, chdir);
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_2(vfs_posix_chdir_obj, vfs_posix_chdir);
+
+STATIC mp_obj_t vfs_posix_getcwd(mp_obj_t self_in) {
+    mp_obj_vfs_posix_t *self = MP_OBJ_TO_PTR(self_in);
+    char buf[MICROPY_ALLOC_PATH_MAX + 1];
+    const char *ret = getcwd(buf, sizeof(buf));
+    if (ret == NULL) {
+        mp_raise_OSError(errno);
+    }
+    ret += self->root_len;
+    return mp_obj_new_str(ret, strlen(ret));
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_1(vfs_posix_getcwd_obj, vfs_posix_getcwd);
+
+typedef struct _vfs_posix_ilistdir_it_t {
+    mp_obj_base_t base;
+    mp_fun_1_t iternext;
+    bool is_str;
+    DIR *dir;
+} vfs_posix_ilistdir_it_t;
+
+STATIC mp_obj_t vfs_posix_ilistdir_it_iternext(mp_obj_t self_in) {
+    vfs_posix_ilistdir_it_t *self = MP_OBJ_TO_PTR(self_in);
+
+    if (self->dir == NULL) {
+        return MP_OBJ_STOP_ITERATION;
+    }
+
+    for (;;) {
+        struct dirent *dirent = readdir(self->dir);
+        if (dirent == NULL) {
+            closedir(self->dir);
+            self->dir = NULL;
+            return MP_OBJ_STOP_ITERATION;
+        }
+        const char *fn = dirent->d_name;
+
+        if (fn[0] == '.' && (fn[1] == 0 || fn[1] == '.')) {
+            // skip . and ..
+            continue;
+        }
+
+        // make 3-tuple with info about this entry
+        mp_obj_tuple_t *t = MP_OBJ_TO_PTR(mp_obj_new_tuple(3, NULL));
+
+        if (self->is_str) {
+            t->items[0] = mp_obj_new_str(fn, strlen(fn));
+        } else {
+            t->items[0] = mp_obj_new_bytes((const byte*)fn, strlen(fn));
+        }
+
+        #ifdef _DIRENT_HAVE_D_TYPE
+        if (dirent->d_type == DT_DIR) {
+            t->items[1] = MP_OBJ_NEW_SMALL_INT(MP_S_IFDIR);
+        } else if (dirent->d_type == DT_REG) {
+            t->items[1] = MP_OBJ_NEW_SMALL_INT(MP_S_IFREG);
+        } else {
+            t->items[1] = MP_OBJ_NEW_SMALL_INT(dirent->d_type);
+        }
+        #else
+        // DT_UNKNOWN should have 0 value on any reasonable system
+        t->items[1] = MP_OBJ_NEW_SMALL_INT(0);
+        #endif
+        #ifdef _DIRENT_HAVE_D_INO
+        t->items[2] = MP_OBJ_NEW_SMALL_INT(dirent->d_ino);
+        #else
+        t->items[2] = MP_OBJ_NEW_SMALL_INT(0);
+        #endif
+
+        return MP_OBJ_FROM_PTR(t);
+    }
+}
+
+STATIC mp_obj_t vfs_posix_ilistdir(mp_obj_t self_in, mp_obj_t path_in) {
+    mp_obj_vfs_posix_t *self = MP_OBJ_TO_PTR(self_in);
+    vfs_posix_ilistdir_it_t *iter = m_new_obj(vfs_posix_ilistdir_it_t);
+    iter->base.type = &mp_type_polymorph_iter;
+    iter->iternext = vfs_posix_ilistdir_it_iternext;
+    iter->is_str = mp_obj_get_type(path_in) == &mp_type_str;
+    const char *path = vfs_posix_get_path_str(self, path_in);
+    iter->dir = opendir(path);
+    if (iter->dir == NULL) {
+        mp_raise_OSError(errno);
+    }
+    return MP_OBJ_FROM_PTR(iter);
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_2(vfs_posix_ilistdir_obj, vfs_posix_ilistdir);
+
+typedef struct _mp_obj_listdir_t {
+    mp_obj_base_t base;
+    mp_fun_1_t iternext;
+    DIR *dir;
+} mp_obj_listdir_t;
+
+STATIC mp_obj_t vfs_posix_mkdir(mp_obj_t self_in, mp_obj_t path_in) {
+    mp_obj_vfs_posix_t *self = MP_OBJ_TO_PTR(self_in);
+    int ret = mkdir(vfs_posix_get_path_str(self, path_in), 0777);
+    if (ret != 0) {
+        mp_raise_OSError(errno);
+    }
+    return mp_const_none;
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_2(vfs_posix_mkdir_obj, vfs_posix_mkdir);
+
+STATIC mp_obj_t vfs_posix_remove(mp_obj_t self_in, mp_obj_t path_in) {
+    return vfs_posix_fun1_helper(self_in, path_in, unlink);
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_2(vfs_posix_remove_obj, vfs_posix_remove);
+
+STATIC mp_obj_t vfs_posix_rename(mp_obj_t self_in, mp_obj_t old_path_in, mp_obj_t new_path_in) {
+    mp_obj_vfs_posix_t *self = MP_OBJ_TO_PTR(self_in);
+    const char *old_path = vfs_posix_get_path_str(self, old_path_in);
+    const char *new_path = vfs_posix_get_path_str(self, new_path_in);
+    int ret = rename(old_path, new_path);
+    if (ret != 0) {
+        mp_raise_OSError(errno);
+    }
+    return mp_const_none;
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_3(vfs_posix_rename_obj, vfs_posix_rename);
+
+STATIC mp_obj_t vfs_posix_rmdir(mp_obj_t self_in, mp_obj_t path_in) {
+    return vfs_posix_fun1_helper(self_in, path_in, rmdir);
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_2(vfs_posix_rmdir_obj, vfs_posix_rmdir);
+
+STATIC mp_obj_t vfs_posix_stat(mp_obj_t self_in, mp_obj_t path_in) {
+    mp_obj_vfs_posix_t *self = MP_OBJ_TO_PTR(self_in);
+    struct stat sb;
+    int ret = stat(vfs_posix_get_path_str(self, path_in), &sb);
+    if (ret != 0) {
+        mp_raise_OSError(errno);
+    }
+    mp_obj_tuple_t *t = MP_OBJ_TO_PTR(mp_obj_new_tuple(10, NULL));
+    t->items[0] = MP_OBJ_NEW_SMALL_INT(sb.st_mode);
+    t->items[1] = MP_OBJ_NEW_SMALL_INT(sb.st_ino);
+    t->items[2] = MP_OBJ_NEW_SMALL_INT(sb.st_dev);
+    t->items[3] = MP_OBJ_NEW_SMALL_INT(sb.st_nlink);
+    t->items[4] = MP_OBJ_NEW_SMALL_INT(sb.st_uid);
+    t->items[5] = MP_OBJ_NEW_SMALL_INT(sb.st_gid);
+    t->items[6] = MP_OBJ_NEW_SMALL_INT(sb.st_size);
+    t->items[7] = MP_OBJ_NEW_SMALL_INT(sb.st_atime);
+    t->items[8] = MP_OBJ_NEW_SMALL_INT(sb.st_mtime);
+    t->items[9] = MP_OBJ_NEW_SMALL_INT(sb.st_ctime);
+    return MP_OBJ_FROM_PTR(t);
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_2(vfs_posix_stat_obj, vfs_posix_stat);
+
+#ifdef __ANDROID__
+#define USE_STATFS 1
+#endif
+
+#if USE_STATFS
+#include <sys/vfs.h>
+#define STRUCT_STATVFS struct statfs
+#define STATVFS statfs
+#define F_FAVAIL sb.f_ffree
+#define F_NAMEMAX sb.f_namelen
+#define F_FLAG sb.f_flags
+#else
+#include <sys/statvfs.h>
+#define STRUCT_STATVFS struct statvfs
+#define STATVFS statvfs
+#define F_FAVAIL sb.f_favail
+#define F_NAMEMAX sb.f_namemax
+#define F_FLAG sb.f_flag
+#endif
+
+STATIC mp_obj_t vfs_posix_statvfs(mp_obj_t self_in, mp_obj_t path_in) {
+    mp_obj_vfs_posix_t *self = MP_OBJ_TO_PTR(self_in);
+    STRUCT_STATVFS sb;
+    const char *path = vfs_posix_get_path_str(self, path_in);
+    int ret = STATVFS(path, &sb);
+    if (ret != 0) {
+        mp_raise_OSError(errno);
+    }
+    mp_obj_tuple_t *t = MP_OBJ_TO_PTR(mp_obj_new_tuple(10, NULL));
+    t->items[0] = MP_OBJ_NEW_SMALL_INT(sb.f_bsize);
+    t->items[1] = MP_OBJ_NEW_SMALL_INT(sb.f_frsize);
+    t->items[2] = MP_OBJ_NEW_SMALL_INT(sb.f_blocks);
+    t->items[3] = MP_OBJ_NEW_SMALL_INT(sb.f_bfree);
+    t->items[4] = MP_OBJ_NEW_SMALL_INT(sb.f_bavail);
+    t->items[5] = MP_OBJ_NEW_SMALL_INT(sb.f_files);
+    t->items[6] = MP_OBJ_NEW_SMALL_INT(sb.f_ffree);
+    t->items[7] = MP_OBJ_NEW_SMALL_INT(F_FAVAIL);
+    t->items[8] = MP_OBJ_NEW_SMALL_INT(F_FLAG);
+    t->items[9] = MP_OBJ_NEW_SMALL_INT(F_NAMEMAX);
+    return MP_OBJ_FROM_PTR(t);
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_2(vfs_posix_statvfs_obj, vfs_posix_statvfs);
+
+STATIC const mp_rom_map_elem_t vfs_posix_locals_dict_table[] = {
+    { MP_ROM_QSTR(MP_QSTR_mount), MP_ROM_PTR(&vfs_posix_mount_obj) },
+    { MP_ROM_QSTR(MP_QSTR_umount), MP_ROM_PTR(&vfs_posix_umount_obj) },
+    { MP_ROM_QSTR(MP_QSTR_open), MP_ROM_PTR(&vfs_posix_open_obj) },
+
+    { MP_ROM_QSTR(MP_QSTR_chdir), MP_ROM_PTR(&vfs_posix_chdir_obj) },
+    { MP_ROM_QSTR(MP_QSTR_getcwd), MP_ROM_PTR(&vfs_posix_getcwd_obj) },
+    { MP_ROM_QSTR(MP_QSTR_ilistdir), MP_ROM_PTR(&vfs_posix_ilistdir_obj) },
+    { MP_ROM_QSTR(MP_QSTR_mkdir), MP_ROM_PTR(&vfs_posix_mkdir_obj) },
+    { MP_ROM_QSTR(MP_QSTR_remove), MP_ROM_PTR(&vfs_posix_remove_obj) },
+    { MP_ROM_QSTR(MP_QSTR_rename), MP_ROM_PTR(&vfs_posix_rename_obj) },
+    { MP_ROM_QSTR(MP_QSTR_rmdir), MP_ROM_PTR(&vfs_posix_rmdir_obj) },
+    { MP_ROM_QSTR(MP_QSTR_stat), MP_ROM_PTR(&vfs_posix_stat_obj) },
+    { MP_ROM_QSTR(MP_QSTR_statvfs), MP_ROM_PTR(&vfs_posix_statvfs_obj) },
+};
+STATIC MP_DEFINE_CONST_DICT(vfs_posix_locals_dict, vfs_posix_locals_dict_table);
+
+const mp_obj_type_t mp_type_vfs_posix = {
+    { &mp_type_type },
+    .name = MP_QSTR_VfsPosix,
+    .make_new = vfs_posix_make_new,
+    .locals_dict = (mp_obj_dict_t*)&vfs_posix_locals_dict,
+};
+
+#endif // MICROPY_VFS_POSIX
diff --git a/extmod/vfs_posix.h b/extmod/vfs_posix.h
new file mode 100644
index 000000000..35a255ff6
--- /dev/null
+++ b/extmod/vfs_posix.h
@@ -0,0 +1,41 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2018 Damien P. George
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+#ifndef MICROPY_INCLUDED_EXTMOD_VFS_POSIX_H
+#define MICROPY_INCLUDED_EXTMOD_VFS_POSIX_H
+
+#include "py/lexer.h"
+#include "py/obj.h"
+
+struct _mp_obj_vfs_posix_t;
+
+extern const mp_obj_type_t mp_type_vfs_posix;
+extern const mp_obj_type_t mp_type_vfs_posix_fileio;
+extern const mp_obj_type_t mp_type_vfs_posix_textio;
+
+mp_import_stat_t mp_vfs_posix_import_stat(struct _mp_obj_vfs_posix_t *self, const char *path_in);
+mp_obj_t mp_vfs_posix_file_open(const mp_obj_type_t *type, mp_obj_t file_in, mp_obj_t mode_in);
+
+#endif // MICROPY_INCLUDED_EXTMOD_VFS_POSIX_H
diff --git a/extmod/vfs_posix_file.c b/extmod/vfs_posix_file.c
new file mode 100644
index 000000000..435ac65cd
--- /dev/null
+++ b/extmod/vfs_posix_file.c
@@ -0,0 +1,261 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2013-2018 Damien P. George
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "py/runtime.h"
+#include "py/stream.h"
+#include "extmod/vfs_posix.h"
+
+#if MICROPY_VFS_POSIX
+
+#include <fcntl.h>
+
+#ifdef _WIN32
+#define fsync _commit
+#endif
+
+typedef struct _mp_obj_vfs_posix_file_t {
+    mp_obj_base_t base;
+    int fd;
+} mp_obj_vfs_posix_file_t;
+
+#ifdef MICROPY_CPYTHON_COMPAT
+STATIC void check_fd_is_open(const mp_obj_vfs_posix_file_t *o) {
+    if (o->fd < 0) {
+        nlr_raise(mp_obj_new_exception_msg(&mp_type_ValueError, "I/O operation on closed file"));
+    }
+}
+#else
+#define check_fd_is_open(o)
+#endif
+
+STATIC void vfs_posix_file_print(const mp_print_t *print, mp_obj_t self_in, mp_print_kind_t kind) {
+    (void)kind;
+    mp_obj_vfs_posix_file_t *self = MP_OBJ_TO_PTR(self_in);
+    mp_printf(print, "<io.%s %d>", mp_obj_get_type_str(self_in), self->fd);
+}
+
+mp_obj_t mp_vfs_posix_file_open(const mp_obj_type_t *type, mp_obj_t file_in, mp_obj_t mode_in) {
+    mp_obj_vfs_posix_file_t *o = m_new_obj(mp_obj_vfs_posix_file_t);
+    const char *mode_s = mp_obj_str_get_str(mode_in);
+
+    int mode_rw = 0, mode_x = 0;
+    while (*mode_s) {
+        switch (*mode_s++) {
+            case 'r':
+                mode_rw = O_RDONLY;
+                break;
+            case 'w':
+                mode_rw = O_WRONLY;
+                mode_x = O_CREAT | O_TRUNC;
+                break;
+            case 'a':
+                mode_rw = O_WRONLY;
+                mode_x = O_CREAT | O_APPEND;
+                break;
+            case '+':
+                mode_rw = O_RDWR;
+                break;
+            #if MICROPY_PY_IO_FILEIO
+            // If we don't have io.FileIO, then files are in text mode implicitly
+            case 'b':
+                type = &mp_type_vfs_posix_fileio;
+                break;
+            case 't':
+                type = &mp_type_vfs_posix_textio;
+                break;
+            #endif
+        }
+    }
+
+    o->base.type = type;
+
+    mp_obj_t fid = file_in;
+
+    if (MP_OBJ_IS_SMALL_INT(fid)) {
+        o->fd = MP_OBJ_SMALL_INT_VALUE(fid);
+        return MP_OBJ_FROM_PTR(o);
+    }
+
+    const char *fname = mp_obj_str_get_str(fid);
+    int fd = open(fname, mode_x | mode_rw, 0644);
+    if (fd == -1) {
+        mp_raise_OSError(errno);
+    }
+    o->fd = fd;
+    return MP_OBJ_FROM_PTR(o);
+}
+
+STATIC mp_obj_t vfs_posix_file_make_new(const mp_obj_type_t *type, size_t n_args, size_t n_kw, const mp_obj_t *args) {
+    static const mp_arg_t allowed_args[] = {
+        { MP_QSTR_file, MP_ARG_OBJ | MP_ARG_REQUIRED, {.u_rom_obj = MP_ROM_PTR(&mp_const_none_obj)} },
+        { MP_QSTR_mode, MP_ARG_OBJ, {.u_rom_obj = MP_ROM_QSTR(MP_QSTR_r)} },
+    };
+
+    mp_arg_val_t arg_vals[MP_ARRAY_SIZE(allowed_args)];
+    mp_arg_parse_all_kw_array(n_args, n_kw, args, MP_ARRAY_SIZE(allowed_args), allowed_args, arg_vals);
+    return mp_vfs_posix_file_open(type, arg_vals[0].u_obj, arg_vals[1].u_obj);
+}
+
+STATIC mp_obj_t vfs_posix_file_fileno(mp_obj_t self_in) {
+    mp_obj_vfs_posix_file_t *self = MP_OBJ_TO_PTR(self_in);
+    check_fd_is_open(self);
+    return MP_OBJ_NEW_SMALL_INT(self->fd);
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_1(vfs_posix_file_fileno_obj, vfs_posix_file_fileno);
+
+STATIC mp_obj_t vfs_posix_file___exit__(size_t n_args, const mp_obj_t *args) {
+    (void)n_args;
+    return mp_stream_close(args[0]);
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_VAR_BETWEEN(vfs_posix_file___exit___obj, 4, 4, vfs_posix_file___exit__);
+
+STATIC mp_uint_t vfs_posix_file_read(mp_obj_t o_in, void *buf, mp_uint_t size, int *errcode) {
+    mp_obj_vfs_posix_file_t *o = MP_OBJ_TO_PTR(o_in);
+    check_fd_is_open(o);
+    mp_int_t r = read(o->fd, buf, size);
+    if (r == -1) {
+        *errcode = errno;
+        return MP_STREAM_ERROR;
+    }
+    return r;
+}
+
+STATIC mp_uint_t vfs_posix_file_write(mp_obj_t o_in, const void *buf, mp_uint_t size, int *errcode) {
+    mp_obj_vfs_posix_file_t *o = MP_OBJ_TO_PTR(o_in);
+    check_fd_is_open(o);
+    #if MICROPY_PY_OS_DUPTERM
+    if (o->fd <= STDERR_FILENO) {
+        mp_hal_stdout_tx_strn(buf, size);
+        return size;
+    }
+    #endif
+    mp_int_t r = write(o->fd, buf, size);
+    while (r == -1 && errno == EINTR) {
+        if (MP_STATE_VM(mp_pending_exception) != MP_OBJ_NULL) {
+            mp_obj_t obj = MP_STATE_VM(mp_pending_exception);
+            MP_STATE_VM(mp_pending_exception) = MP_OBJ_NULL;
+            nlr_raise(obj);
+        }
+        r = write(o->fd, buf, size);
+    }
+    if (r == -1) {
+        *errcode = errno;
+        return MP_STREAM_ERROR;
+    }
+    return r;
+}
+
+STATIC mp_uint_t vfs_posix_file_ioctl(mp_obj_t o_in, mp_uint_t request, uintptr_t arg, int *errcode) {
+    mp_obj_vfs_posix_file_t *o = MP_OBJ_TO_PTR(o_in);
+    check_fd_is_open(o);
+    switch (request) {
+        case MP_STREAM_FLUSH:
+            if (fsync(o->fd) < 0) {
+                *errcode = errno;
+                return MP_STREAM_ERROR;
+            }
+            return 0;
+        case MP_STREAM_SEEK: {
+            struct mp_stream_seek_t *s = (struct mp_stream_seek_t*)arg;
+            off_t off = lseek(o->fd, s->offset, s->whence);
+            if (off == (off_t)-1) {
+                *errcode = errno;
+                return MP_STREAM_ERROR;
+            }
+            s->offset = off;
+            return 0;
+        }
+        case MP_STREAM_CLOSE:
+            close(o->fd);
+            #ifdef MICROPY_CPYTHON_COMPAT
+            o->fd = -1;
+            #endif
+            return 0;
+        default:
+            *errcode = EINVAL;
+            return MP_STREAM_ERROR;
+    }
+}
+
+STATIC const mp_rom_map_elem_t rawfile_locals_dict_table[] = {
+    { MP_ROM_QSTR(MP_QSTR_fileno), MP_ROM_PTR(&vfs_posix_file_fileno_obj) },
+    { MP_ROM_QSTR(MP_QSTR_read), MP_ROM_PTR(&mp_stream_read_obj) },
+    { MP_ROM_QSTR(MP_QSTR_readinto), MP_ROM_PTR(&mp_stream_readinto_obj) },
+    { MP_ROM_QSTR(MP_QSTR_readline), MP_ROM_PTR(&mp_stream_unbuffered_readline_obj) },
+    { MP_ROM_QSTR(MP_QSTR_readlines), MP_ROM_PTR(&mp_stream_unbuffered_readlines_obj) },
+    { MP_ROM_QSTR(MP_QSTR_write), MP_ROM_PTR(&mp_stream_write_obj) },
+    { MP_ROM_QSTR(MP_QSTR_seek), MP_ROM_PTR(&mp_stream_seek_obj) },
+    { MP_ROM_QSTR(MP_QSTR_tell), MP_ROM_PTR(&mp_stream_tell_obj) },
+    { MP_ROM_QSTR(MP_QSTR_flush), MP_ROM_PTR(&mp_stream_flush_obj) },
+    { MP_ROM_QSTR(MP_QSTR_close), MP_ROM_PTR(&mp_stream_close_obj) },
+    { MP_ROM_QSTR(MP_QSTR___enter__), MP_ROM_PTR(&mp_identity_obj) },
+    { MP_ROM_QSTR(MP_QSTR___exit__), MP_ROM_PTR(&vfs_posix_file___exit___obj) },
+};
+
+STATIC MP_DEFINE_CONST_DICT(rawfile_locals_dict, rawfile_locals_dict_table);
+
+#if MICROPY_PY_IO_FILEIO
+STATIC const mp_stream_p_t fileio_stream_p = {
+    .read = vfs_posix_file_read,
+    .write = vfs_posix_file_write,
+    .ioctl = vfs_posix_file_ioctl,
+};
+
+const mp_obj_type_t mp_type_vfs_posix_fileio = {
+    { &mp_type_type },
+    .name = MP_QSTR_FileIO,
+    .print = vfs_posix_file_print,
+    .make_new = vfs_posix_file_make_new,
+    .getiter = mp_identity_getiter,
+    .iternext = mp_stream_unbuffered_iter,
+    .protocol = &fileio_stream_p,
+    .locals_dict = (mp_obj_dict_t*)&rawfile_locals_dict,
+};
+#endif
+
+STATIC const mp_stream_p_t textio_stream_p = {
+    .read = vfs_posix_file_read,
+    .write = vfs_posix_file_write,
+    .ioctl = vfs_posix_file_ioctl,
+    .is_text = true,
+};
+
+const mp_obj_type_t mp_type_vfs_posix_textio = {
+    { &mp_type_type },
+    .name = MP_QSTR_TextIOWrapper,
+    .print = vfs_posix_file_print,
+    .make_new = vfs_posix_file_make_new,
+    .getiter = mp_identity_getiter,
+    .iternext = mp_stream_unbuffered_iter,
+    .protocol = &textio_stream_p,
+    .locals_dict = (mp_obj_dict_t*)&rawfile_locals_dict,
+};
+
+const mp_obj_vfs_posix_file_t mp_sys_stdin_obj  = {{&mp_type_textio}, STDIN_FILENO};
+const mp_obj_vfs_posix_file_t mp_sys_stdout_obj = {{&mp_type_textio}, STDOUT_FILENO};
+const mp_obj_vfs_posix_file_t mp_sys_stderr_obj = {{&mp_type_textio}, STDERR_FILENO};
+
+#endif // MICROPY_VFS_POSIX
diff --git a/py/mpconfig.h b/py/mpconfig.h
index 100e2a981..dc0fc5d40 100644
--- a/py/mpconfig.h
+++ b/py/mpconfig.h
@@ -681,6 +681,11 @@ typedef double mp_float_t;
 #define MICROPY_VFS (0)
 #endif
 
+// Support for VFS POSIX component, to mount a POSIX filesystem within VFS
+#ifndef MICROPY_VFS
+#define MICROPY_VFS_POSIX (0)
+#endif
+
 /*****************************************************************************/
 /* Fine control over Python builtins, classes, modules, etc                  */
 
diff --git a/py/py.mk b/py/py.mk
index a91813526..f4b62a88a 100644
--- a/py/py.mk
+++ b/py/py.mk
@@ -241,6 +241,8 @@ PY_EXTMOD_O_BASENAME = \
 	extmod/modframebuf.o \
 	extmod/vfs.o \
 	extmod/vfs_reader.o \
+	extmod/vfs_posix.o \
+	extmod/vfs_posix_file.o \
 	extmod/vfs_fat.o \
 	extmod/vfs_fat_diskio.o \
 	extmod/vfs_fat_file.o \