diff --git a/cio.c b/cio.c
deleted file mode 100644
index 13758e9..0000000
--- a/cio.c
+++ /dev/null
@@ -1,42 +0,0 @@
-#include <stdio.h>
-#include <stdlib.h>
-#include <string.h>
-#include <inttypes.h>
-#include "kolibri.h"
-
-typedef struct {
-    FILE *file;
-    uint64_t sect_cnt;
-    uint32_t sect_size;
-} vdisk_t;
-
-void *cio_disk_init(const char *fname) {
-    FILE *f = fopen(fname, "r+");
-    fseeko(f, 0, SEEK_END);
-    off_t fsize = ftello(f);
-    fseeko(f, 0, SEEK_SET);
-    size_t sect_size = 512;
-    if (strstr(fname, "s4096") != NULL || strstr(fname, "s4k") != NULL) {
-        sect_size = 4096;
-    }
-    vdisk_t *vdisk = (vdisk_t*)malloc(sizeof(vdisk_t));
-    *vdisk = (vdisk_t){f, (uint64_t)fsize / sect_size, sect_size};
-    return vdisk;
-}
-
-void cio_disk_free(vdisk_t *vdisk) {
-    fclose(vdisk->file);
-    free(vdisk);
-}
-
-f70status_t cio_disk_read(vdisk_t *vdisk, uint8_t *buffer, off_t startsector, uint32_t *numsectors) {
-    fseeko(vdisk->file, startsector * vdisk->sect_size, SEEK_SET);
-    fread(buffer, *numsectors * vdisk->sect_size, 1, vdisk->file);
-    return ERROR_SUCCESS;
-}
-
-f70status_t cio_disk_write(vdisk_t *vdisk, uint8_t *buffer, off_t startsector, uint32_t *numsectors) {
-    fseeko(vdisk->file, startsector * vdisk->sect_size, SEEK_SET);
-    fwrite(buffer, *numsectors * vdisk->sect_size, 1, vdisk->file);
-    return ERROR_SUCCESS;
-}
diff --git a/kolibri.h b/kolibri.h
index daa0d6c..17e6d7c 100644
--- a/kolibri.h
+++ b/kolibri.h
@@ -1,6 +1,7 @@
 #ifndef KOLIBRI_H_INCLUDED
 #define KOLIBRI_H_INCLUDED
 
+#include <stdio.h>
 #include <stdint.h>
 #include <stddef.h>
 
@@ -66,6 +67,23 @@ typedef enum {
     ERROR_OUT_OF_MEMORY,
 } f70status_t;
 
+typedef struct {
+    uint32_t flags;
+    uint32_t sector_size;
+    uint64_t capacity;  // in sectors
+} diskmediainfo_t;
+
+typedef struct {
+    uint32_t  strucsize;
+    void (*close)(void *userdata) __attribute__((__stdcall__));
+    void (*closemedia)(void *userdata) __attribute__((__stdcall__));
+    int (*querymedia)(void *userdata, diskmediainfo_t *info) __attribute__((__stdcall__));
+    int (*read)(void *userdata, void *buffer, off_t startsector, size_t *numsectors) __attribute__((__stdcall__));
+    int (*write)(void *userdata, void *buffer, off_t startsector, size_t *numsectors) __attribute__((__stdcall__));
+    int (*flush)(void* userdata) __attribute__((__stdcall__));
+    unsigned int (*adjust_cache_size)(uint32_t suggested_size) __attribute__((__stdcall__));
+} diskfunc_t;
+
 typedef struct {
     uint32_t attr;
     uint32_t enc;
diff --git a/makefile b/makefile
index 859a784..4e2e9df 100644
--- a/makefile
+++ b/makefile
@@ -11,10 +11,10 @@ all: umka_shell umka_fuse umka.sym umka.prp umka.lst tags tools/mkdirrange tools
 covpreproc: covpreproc.c
 	$(CC) $(CFLAGS) $(LDFLAGS) $^ -o $@
 
-umka_shell: umka_shell.o umka.o trace.o trace_lbr.o cio.o lodepng.o
+umka_shell: umka_shell.o umka.o trace.o trace_lbr.o vdisk.o lodepng.o
 	$(CC) $(LDFLAGS) $(LDFLAGS_32) $^ -o $@ -static
 
-umka_fuse: umka_fuse.o umka.o cio.o
+umka_fuse: umka_fuse.o umka.o vdisk.o
 	$(CC) $(LDFLAGS) $(LDFLAGS_32) $^ -o $@ `pkg-config fuse3 --libs`
 
 umka.o umka.fas: umka.asm skin.skn
@@ -44,7 +44,7 @@ trace.o: trace.c trace.h trace_lbr.h
 trace_lbr.o: trace_lbr.c trace_lbr.h kolibri.h
 	$(CC) $(CFLAGS) $(CFLAGS_32) -c $<
 
-cio.o: cio.c
+vdisk.o: vdisk.c
 	$(CC) $(CFLAGS) $(CFLAGS_32) -c $<
 
 umka_shell.o: umka_shell.c kolibri.h trace.h syscalls.h
diff --git a/umka.asm b/umka.asm
index 70378a8..2b7842a 100644
--- a/umka.asm
+++ b/umka.asm
@@ -5,6 +5,7 @@ __DEBUG_LEVEL__ = 1
 
 extrn 'malloc' as libc_malloc
 extrn 'free' as libc_free
+extrn vdisk_functions
 
 cli equ nop
 iretd equ retd
@@ -113,7 +114,7 @@ include 'gui/mouse.inc'
 include 'hid/keyboard.inc'
 include 'hid/mousedrv.inc'
 include 'network/stack.inc'
- 
+
 include 'sha3.asm'
 
 struct VDISK
@@ -256,8 +257,8 @@ endp
 
 public kos_disk_add
 proc kos_disk_add c uses ebx esi edi ebp, _file_name, _disk_name
-        extrn cio_disk_init
-        ccall   cio_disk_init, [_file_name]
+        extrn vdisk_init
+        ccall   vdisk_init, [_file_name]
         stdcall disk_add, vdisk_functions, [_disk_name], eax, DISK_NO_INSERT_NOTIFICATION
         push    eax
         stdcall disk_media_changed, eax, 1
@@ -327,45 +328,6 @@ proc kos_disk_del c uses ebx esi edi ebp, _name
         ret
 endp
 
-
-proc vdisk_close stdcall uses ebx esi edi ebp, _userdata
-        extrn cio_disk_free
-        ccall   cio_disk_free, [_userdata]
-        ret
-endp
-
-
-proc vdisk_read stdcall uses ebx esi edi ebp, _userdata, _buffer, _startsector:qword, _numsectors
-        extrn cio_disk_read
-        ccall   cio_disk_read, [_userdata], [_buffer], dword[_startsector+0], dword[_startsector+4], [_numsectors]
-        movi    eax, DISK_STATUS_OK
-        ret
-endp
-
-
-proc vdisk_write stdcall uses ebx esi edi ebp, userdata, buffer, startsector:qword, numsectors
-        extrn cio_disk_write
-        ccall   cio_disk_write, [userdata], [buffer], dword[startsector+0], dword[startsector+4], [numsectors]
-        movi    eax, DISK_STATUS_OK
-        ret
-endp
-
-
-proc vdisk_querymedia stdcall uses ebx esi edi ebp, vdisk, mediainfo
-        mov     ecx, [mediainfo]
-        mov     edx, [vdisk]
-        mov     [ecx + DISKMEDIAINFO.Flags], 0
-        mov     eax, [edx + VDISK.SectSize]
-        mov     [ecx + DISKMEDIAINFO.SectorSize], eax
-        mov     eax, [edx + VDISK.SectCnt.lo]
-        mov     dword [ecx + DISKMEDIAINFO.Capacity + 0], eax
-        mov     eax, [edx + VDISK.SectCnt.hi]
-        mov     dword [ecx + DISKMEDIAINFO.Capacity + 4], eax
-        
-        movi    eax, DISK_STATUS_OK
-        ret
-endp
-
 proc alloc_page
         ret
         push    ecx edx
@@ -540,16 +502,6 @@ public coverage_end
 
 section '.data' writeable align 64
 ;include_debug_strings
-vdisk_functions:
-        dd vdisk_functions_end - vdisk_functions
-        dd 0;vdisk_close    ; close
-        dd 0    ; closemedia
-        dd vdisk_querymedia
-        dd vdisk_read
-        dd vdisk_write
-        dd 0    ; flush
-        dd 0    ; adjust_cache_size
-vdisk_functions_end:
 
 timer_ticks dd 0
 fpu_owner dd ?
diff --git a/umka_shell.c b/umka_shell.c
index f998433..701d4d8 100644
--- a/umka_shell.c
+++ b/umka_shell.c
@@ -214,7 +214,7 @@ void umka_disk_del(int argc, char **argv) {
     return;
 }
 
-void umka_pwd(int argc, char **argv) {
+void shell_pwd(int argc, char **argv) {
     (void)argc;
     (void)argv;
     bool quoted = false;
@@ -875,7 +875,7 @@ func_table_t funcs[] = {
                         { "stat80",             umka_stat80 },
                         { "read70",             umka_read70 },
                         { "read80",             umka_read80 },
-                        { "pwd",                umka_pwd },
+                        { "pwd",                shell_pwd },
                         { "cd",                 shell_cd },
                         { "set_cwd",            shell_cd },
                         { "draw_window",        umka_draw_window },
diff --git a/vdisk.c b/vdisk.c
new file mode 100644
index 0000000..5d990a3
--- /dev/null
+++ b/vdisk.c
@@ -0,0 +1,68 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <inttypes.h>
+#include "kolibri.h"
+
+typedef struct {
+    FILE *file;
+    uint64_t sect_cnt;
+    uint32_t sect_size;
+} vdisk_t;
+
+void *vdisk_init(const char *fname) {
+    FILE *f = fopen(fname, "r+");
+    fseeko(f, 0, SEEK_END);
+    off_t fsize = ftello(f);
+    fseeko(f, 0, SEEK_SET);
+    size_t sect_size = 512;
+    if (strstr(fname, "s4096") != NULL || strstr(fname, "s4k") != NULL) {
+        sect_size = 4096;
+    }
+    vdisk_t *vdisk = (vdisk_t*)malloc(sizeof(vdisk_t));
+    *vdisk = (vdisk_t){f, (uint64_t)fsize / sect_size, sect_size};
+    return vdisk;
+}
+
+__attribute__((__stdcall__))
+void vdisk_close(void *userdata) {
+    vdisk_t *vdisk = userdata;
+    fclose(vdisk->file);
+    free(vdisk);
+}
+
+__attribute__((__stdcall__))
+int vdisk_read(void *userdata, void *buffer, off_t startsector, size_t *numsectors) {
+    vdisk_t *vdisk = userdata;
+    fseeko(vdisk->file, startsector * vdisk->sect_size, SEEK_SET);
+    fread(buffer, *numsectors * vdisk->sect_size, 1, vdisk->file);
+    return ERROR_SUCCESS;
+}
+
+__attribute__((__stdcall__))
+int vdisk_write(void *userdata, void *buffer, off_t startsector, size_t *numsectors) {
+    vdisk_t *vdisk = userdata;
+    fseeko(vdisk->file, startsector * vdisk->sect_size, SEEK_SET);
+    fwrite(buffer, *numsectors * vdisk->sect_size, 1, vdisk->file);
+    return ERROR_SUCCESS;
+}
+
+__attribute__((__stdcall__))
+int vdisk_querymedia(void *userdata, diskmediainfo_t *minfo) {
+    vdisk_t *vdisk = userdata;
+    minfo->flags = 0u;
+    minfo->sector_size = vdisk->sect_size;
+    minfo->capacity = vdisk->sect_cnt;
+    return ERROR_SUCCESS;
+}
+
+diskfunc_t vdisk_functions = {
+                                 .strucsize = sizeof(diskfunc_t),
+                                 .close = vdisk_close,
+                                 .closemedia = NULL,
+                                 .querymedia = vdisk_querymedia,
+                                 .read = vdisk_read,
+                                 .write = vdisk_write,
+                                 .flush = NULL,
+                                 .adjust_cache_size = NULL,
+                                };