Difference between revisions of "VFS Implementation"
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| + | == Typical i/o operation execution == | ||
| + | |||
| + | This is a very brief desctiption for overall understanding of io <code>vfs_node</code> 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 <code>sceIoLseek</code> 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 <code>sceIoLseekForDriver</code> | ||
| + | *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 <code>vfs_node</code> and calls exported function like <code>vfs_node_func7</code> | ||
| + | *exported function packs all arguments into single stucture and calls real callback since it has <code>vfs_node</code> 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 <code>io_contex</code> 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 <code>vfs_node</code> function based on i/o operation index. | ||
| + | *wrapper updates 0x1980 (i/o counter) flag | ||
Revision as of 16:29, 1 October 2017
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_nodeand calls exported function likevfs_node_func7 - exported function packs all arguments into single stucture and calls real callback since it has
vfs_nodewith 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_contexand 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_nodefunction based on i/o operation index. - wrapper updates 0x1980 (i/o counter) flag