VFS Implementation

VFS Nodes

Module	Name	Comment
SceSdstor	sdstor_dev_fs
SceExfatfs	exfat
SceIofilemgr	dummy_ttyp_dev_fs
ScePfsMgr	PFS_REDIRECT_INF	Redirect Pseudo Drive.
ScePfsMgr	PFS_GDSD_INF	Gamedata/Savedata Pseudo Drive.
ScePfsMgr	PFS_AC_INF	AC Pseudo Drive.

VFS Operations

• implemented operation is marked as implemented
• not implemented is marked as
• return 0 placeholder is marked as 0
• return error is marked with corresponding error name

Function	sdstor_dev_fs	exfat	dummy_ttyp_dev_fs	PFS_REDIRECT_INF	PFS_GDSD_INF	PFS_AC_INF
1	implemented	implemented	implemented	implemented	implemented	implemented
2	SCE_ERROR_ERRNO_EBUSY	implemented	0	implemented	implemented	implemented
3	implemented	implemented	implemented	implemented	implemented	implemented
4		implemented
5
6
7		implemented		0	implemented	implemented
8
9	0	0	0	0	0	0
10		0	0	0	0	0
11
12	implemented	implemented		implemented	implemented	implemented
13	implemented	implemented		implemented	implemented	implemented

VFS Node Operations

• implemented operation is marked as implemented
• not implemented is marked as
• return 0 placeholder is marked as 0
• return error is marked with corresponding error name

Function	sdstor_dev_fs	exfat	dummy_ttyp_dev_fs	PFS_REDIRECT_INF	PFS_GDSD_INF	PFS_AC_INF
1	implemented	implemented	0	implemented	implemented	implemented
2		implemented		implemented	implemented	implemented
3	implemented	implemented	0	implemented	implemented	implemented
4	implemented	implemented	implemented	implemented	implemented	implemented
5	implemented	implemented	0	implemented	implemented	implemented
6	implemented	implemented	implemented	implemented	implemented	implemented
7	implemented	implemented	0	implemented	implemented	implemented
8		SCE_ERROR_ERRNO_EUNSUP	0	implemented	implemented	implemented
9	implemented	implemented		implemented	implemented	implemented
10		implemented		implemented	implemented	implemented
11		implemented		implemented	implemented	implemented
12		implemented		implemented	implemented	implemented
13		implemented		implemented	implemented	implemented
14		implemented		implemented	implemented	implemented
15		implemented		implemented	implemented	implemented
16		implemented		implemented	implemented	implemented
17		implemented		implemented	implemented	implemented
18
19	implemented	implemented		implemented	implemented	implemented
20	implemented	implemented		implemented	implemented	implemented
21	0	implemented	0	implemented	implemented	implemented
22		implemented
23		implemented
24	0	implemented		implemented	implemented	implemented
25		implemented		implemented	implemented	implemented
26		implemented		implemented	implemented	implemented
27		implemented		implemented	implemented	implemented
28		implemented		implemented	implemented	implemented
29

Typical i/o operation execution

This is a very brief desctiption for overall understanding of io vfs_node operations. Implementation of SceIofilemgr is quite solid and most of the functions are implemented in the same manner however there could be exceptions. When io operation like sceIoLseek is called here is what happens:

• all user space arguments are copied to kernel space, usually onto the kernel stack. all user space uids are converted to kernel space uids
• optionally control may be passed to wrapper function that also does conversion
• then control is passed to kernel level function like sceIoLseekForDriver
• kernel level function checks 0x2198 (IoSchedulerDispatcher initialized) flag

if dispatcher is not initialized:

• kernel level function updates 0x1964 (i/o dirty) and 0x1980 (i/o counter) flags
• kernel level function spawns separate thread and passes all arguments in single structure
• separate thread then unpacks all arguments, finds vfs_node and calls exported function like vfs_node_func7
• exported function packs all arguments into single stucture and calls real callback since it has vfs_node with node operation table
• callback routine should be located in generic device driver, like SceSdstor, SceExfatfs or ScePfsMgr. It unpacks the arguments and then does something. For example SceSdstor dispatches the call further to SceSdif, SceWlanBt, SceMsif and SceUsbMass.
• kernel level function updates 0x1980 (i/o counter) flag

if dispatcher is initialized:

• kernel level function passes arguments to wrapper
• wrapper initializes io_contex and assigns i/o operation index
• wrapper updates 0x1964 (i/o dirty) and 0x1980 (i/o counter) flags
• wrapper runs dispatcher function (offset 0x17C00) in separate thread. this function selects proper vfs_node function based on i/o operation index.
• wrapper updates 0x1980 (i/o counter) flag