unix: Support MICROPY_VFS_POSIX and enable it in coverage build.

The unix coverage build is now switched fully to the VFS implementation, ie
the uos module is the uos_vfs module.  For example, one can now sandbox uPy
to their home directory via:

    $ ./micropython_coverage

    >>> import uos
    >>> uos.umount('/') # unmount existing root VFS
    >>> vfs = uos.VfsPosix('/home/user') # create new POSIX VFS
    >>> uos.mount(vfs, '/') # mount new POSIX VFS at root

Some filesystem/OS features may no longer work with the coverage build due
to this change, and these need to be gradually fixed.

The standard unix port remains unchanged, it still uses the traditional uos
module which directly accesses the underlying host filesystem.

ports/unix/file.c

@@ -37,7 +37,7 @@
 #include "py/mphal.h"
 #include "fdfile.h"
 
-#if MICROPY_PY_IO
+#if MICROPY_PY_IO && !MICROPY_VFS
 
 #ifdef _WIN32
 #define fsync _commit
@@ -277,4 +277,4 @@ const mp_obj_fdfile_t mp_sys_stdin_obj  = { .base = {&mp_type_textio}, .fd = STD
 const mp_obj_fdfile_t mp_sys_stdout_obj = { .base = {&mp_type_textio}, .fd = STDOUT_FILENO };
 const mp_obj_fdfile_t mp_sys_stderr_obj = { .base = {&mp_type_textio}, .fd = STDERR_FILENO };
 
-#endif // MICROPY_PY_IO
+#endif // MICROPY_PY_IO && !MICROPY_VFS

ports/unix/main.c

@@ -46,6 +46,8 @@
 #include "py/mphal.h"
 #include "py/mpthread.h"
 #include "extmod/misc.h"
+#include "extmod/vfs.h"
+#include "extmod/vfs_posix.h"
 #include "genhdr/mpversion.h"
 #include "input.h"
 
@@ -447,6 +449,18 @@ MP_NOINLINE int main_(int argc, char **argv) {
 
     mp_init();
 
+    #if MICROPY_VFS_POSIX
+    {
+        // Mount the host FS at the root of our internal VFS
+        mp_obj_t args[2] = {
+            mp_type_vfs_posix.make_new(&mp_type_vfs_posix, 0, 0, NULL),
+            MP_OBJ_NEW_QSTR(MP_QSTR__slash_),
+        };
+        mp_vfs_mount(2, args, (mp_map_t*)&mp_const_empty_map);
+        MP_STATE_VM(vfs_cur) = MP_STATE_VM(vfs_mount_table);
+    }
+    #endif
+
     char *home = getenv("HOME");
     char *path = getenv("MICROPYPATH");
     if (path == NULL) {
@@ -645,6 +659,7 @@ MP_NOINLINE int main_(int argc, char **argv) {
     return ret & 0xff;
 }
 
+#if !MICROPY_VFS
 uint mp_import_stat(const char *path) {
     struct stat st;
     if (stat(path, &st) == 0) {
@@ -656,6 +671,7 @@ uint mp_import_stat(const char *path) {
     }
     return MP_IMPORT_STAT_NO_EXIST;
 }
+#endif
 
 void nlr_jump_fail(void *val) {
     printf("FATAL: uncaught NLR %p\n", val);

ports/unix/moduos_vfs.c

@@ -28,6 +28,7 @@
 #include <string.h>
 
 #include "extmod/vfs.h"
+#include "extmod/vfs_posix.h"
 #include "extmod/vfs_fat.h"
 
 #if MICROPY_VFS
@@ -52,6 +53,9 @@ STATIC const mp_rom_map_elem_t uos_vfs_module_globals_table[] = {
     { MP_ROM_QSTR(MP_QSTR_statvfs), MP_ROM_PTR(&mp_vfs_statvfs_obj) },
     { MP_ROM_QSTR(MP_QSTR_unlink), MP_ROM_PTR(&mp_vfs_remove_obj) }, // unlink aliases to remove
 
+    #if MICROPY_VFS_POSIX
+    { MP_ROM_QSTR(MP_QSTR_VfsPosix), MP_ROM_PTR(&mp_type_vfs_posix) },
+    #endif
     #if MICROPY_VFS_FAT
     { MP_ROM_QSTR(MP_QSTR_VfsFat), MP_ROM_PTR(&mp_fat_vfs_type) },
     #endif

ports/unix/mpconfigport.h

@@ -180,9 +180,9 @@ extern const struct _mp_obj_module_t mp_module_ffi;
 extern const struct _mp_obj_module_t mp_module_jni;
 
 #if MICROPY_PY_UOS_VFS
-#define MICROPY_PY_UOS_VFS_DEF { MP_ROM_QSTR(MP_QSTR_uos_vfs), MP_ROM_PTR(&mp_module_uos_vfs) },
+#define MICROPY_PY_UOS_DEF { MP_ROM_QSTR(MP_QSTR_uos), MP_ROM_PTR(&mp_module_uos_vfs) },
 #else
-#define MICROPY_PY_UOS_VFS_DEF
+#define MICROPY_PY_UOS_DEF { MP_ROM_QSTR(MP_QSTR_uos), MP_ROM_PTR(&mp_module_os) },
 #endif
 #if MICROPY_PY_FFI
 #define MICROPY_PY_FFI_DEF { MP_ROM_QSTR(MP_QSTR_ffi), MP_ROM_PTR(&mp_module_ffi) },
@@ -221,8 +221,7 @@ extern const struct _mp_obj_module_t mp_module_jni;
     MICROPY_PY_UTIME_DEF \
     MICROPY_PY_SOCKET_DEF \
     { MP_ROM_QSTR(MP_QSTR_umachine), MP_ROM_PTR(&mp_module_machine) }, \
-    { MP_ROM_QSTR(MP_QSTR_uos), MP_ROM_PTR(&mp_module_os) }, \
-    MICROPY_PY_UOS_VFS_DEF \
+    MICROPY_PY_UOS_DEF \
     MICROPY_PY_USELECT_DEF \
     MICROPY_PY_TERMIOS_DEF \
 

ports/unix/mpconfigport_coverage.h

@@ -34,6 +34,7 @@
 
 #define MICROPY_FLOAT_HIGH_QUALITY_HASH (1)
 #define MICROPY_ENABLE_SCHEDULER       (1)
+#define MICROPY_READER_VFS             (1)
 #define MICROPY_PY_DELATTR_SETATTR     (1)
 #define MICROPY_PY_REVERSE_SPECIAL_METHODS (1)
 #define MICROPY_PY_BUILTINS_RANGE_BINOP (1)
@@ -43,7 +44,17 @@
 #define MICROPY_PY_URANDOM_EXTRA_FUNCS (1)
 #define MICROPY_PY_IO_BUFFEREDWRITER (1)
 #define MICROPY_PY_IO_RESOURCE_STREAM (1)
+#define MICROPY_VFS_POSIX              (1)
 #undef MICROPY_VFS_FAT
 #define MICROPY_VFS_FAT                (1)
 #define MICROPY_PY_FRAMEBUF            (1)
 #define MICROPY_PY_COLLECTIONS_NAMEDTUPLE__ASDICT (1)
+
+// TODO these should be generic, not bound to fatfs
+#define mp_type_fileio mp_type_vfs_posix_fileio
+#define mp_type_textio mp_type_vfs_posix_textio
+
+// use vfs's functions for import stat and builtin open
+#define mp_import_stat mp_vfs_import_stat
+#define mp_builtin_open mp_vfs_open
+#define mp_builtin_open_obj mp_vfs_open_obj