Filesystem services

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Cmd Name Arguments Notes
0 MountCode u64 TID + X descriptor #ContentPath Returns an #IFileSystem.
1 IsCodeMounted u64 PID Returns a bool (1 if code is mounted).


Cmd Name Arguments Notes
0 SetFsPermissions u8 storageID, u32 PID, u64 TID, ACI0_buf_size, ACID_buf_size + two A descriptors (the 0x1C FS-access control from ACI0 + the 0x2C FS-access control from ACID). Actual FS permissions are set to (ACI0_perms & ACID_perms). Will panic(svcBreak) when buffer sizes from ipc-rawdata are invalid.
1 ClearFsPermissions u32 PID to clear
256 SetEnabledProgramVerification bool enabled


Seems to sets a global flag to inputval & 1.

When the flag is zero, it will set ret=0 instead of ret={error} when verifying a RSA signature fails. This RSA signature seems to be the signature in the NPDM ACID. It then skips verifying what seems to be the second signature in the NCA header. Note that if verifying the NPDM(?) signature is successful, and verifying that second signature fails, it will throw an error and abort.


Cmd Name Required permissions-type and func
1 #Initialize
2 OpenDataFileSystemByCurrentProcess
7 #MountContent7
8 #MountContent Depends on input.
9 OpenDataFileSystemByApplicationId [3.0.0+]
11 #MountBis
12 #OpenBisPartition
13 InvalidateBisCache
17 OpenHostFileSystemImpl
18 MountSdCard
19 FormatSdCard
21 #DeleteSaveData
22 #CreateSaveData
23 #CreateSystemSaveData
24 RegisterSaveDataAtomicDeletion
25 DeleteSaveDataWithSpaceId
26 FormatSdCardDryRun
27 IsExFatSupported
30 #OpenGameCardPartition
31 #MountGameCardPartition
32 ExtendSaveData [3.0.0+]
51 #MountSaveData
52 #MountSystemSaveData
53 MountSaveDataReadOnly
57 ReadSaveDataFileSystemExtraDataWithSpaceId [3.0.0+]
58 ReadSaveDataFileSystemExtraData
59 WriteSaveDataFileSystemExtraData
60 OpenSaveDataInfoReader
61 OpenSaveDataIterator
80 OpenSaveDataThumbnailFile
100 MountImageDirectory
110 #MountContentStorage
200 OpenDataStorageByCurrentProcess
201 OpenDataStorageByApplicationId [3.0.0+]
202 #OpenDataStorageByDataId
203 Returns an #IStorage.
400 #OpenDeviceOperator
500 #OpenSdCardDetectionEventNotifier
501 #OpenGameCardDetectionEventNotifier
600 SetCurrentPosixTime 0x18, 1
601 QuerySaveDataTotalSize
602 #VerifySaveData
603 CorruptSaveDataForDebug
604 CreatePaddingFile
605 DeleteAllPaddingFiles
606 GetRightsId
607 RegisterExternalKey 0x18, 1
608 UnregisterExternalKey
609 GetRightsIdByPath
610 GetRightsIdByPath2 (returns extra byte) [3.0.0+]
620 #SetSdCardEncryptionSeed 0x19, 1
800 GetAndClearFileSystemProxyErrorInfo
1000 SetBisRootForHost
1001 SetSaveDataSize
1002 SetSaveDataRootPath
1003 DisableAutoSaveDataCreation
1004 #SetGlobalAccessLogMode 0x10, 1
1005 #GetGlobalAccessLogMode None
1006 #OutputAccessLogToSdCard None


Each time permissions are checked, the process-obj is loaded using the session PID, then a func is called with the permissions-type. The func retval is checked, then the permissions error is thrown if needed.

Internally in that process-obj load func, it will load the obj as normal when the PID is >6, otherwise it will use a fixed obj. If not done already, that fixed obj will be initialized using fixed input data, via the same code used internally by #fsp-pr.

In general this func uses the input permissions-type to determine what mask value to use. That value is masked with the permissions from the above process-obj. When the result is 0, 0 is returned, otherwise non-zero is returned. The default non-zero retval is basically 0x3.

Panic is triggered when the input type is >{max value} / invalid.


Type(s) Mask Non-zero retval Notes
0xA 0xD 0x16 0x1F 0x20 0x21 0x22 0x8000000000000080 Default
0x15 0x17 0x18 0x19 0x1A 0x1B 0x1C 0x8000000000010080 Default
0x0 0x1 0x2 0x3 0x4 0x5 0x8000000000000801 0x1
0x9 0x1D 0x1E 0x8000000000000084 Default
0xB 0xC 0x8000000000008080 Default
0xE 0x23 0xC000000000200000 Default
0x12 0x13 0x8000000000000020 Default
0x6 In this case it appears the func returns retval & 0xff, where retval = {bit0=0, bit1..bit63=obj_permissions starting at bit0}?
0x7 0x8000000000000800 Default
0x8 0x8000000000001000 Default
0xF 0x8000000000000010 Default
0x10 0x8000000000040020 Default
0x11 0x8000000000000028 Default
0x14 0x8000000000010082 Default
0x24 0x8000000000000100 Default
0x25 0x8000000000100008 0x1
0x26 0xC000000000400000 Default

Func1(non-zero retval is always 0x1):

Type(s) Mask Notes
0x0 0x1 0x8000000000000080
0x2 0x3 0x8000000000000010
0x4 0x5 0x8000000000000200
0x7 0xB 0x8000000000000060
0xC 0x1A 0x8000000000004020
0x10 0x11 0x8000000000080000
0x6 0x8000000000002020
0x8 0x8000000000000028
0x9 0x8000000000000020
0xA 0x8000000000004028
0xD 0x8000000000020000
0xE 0x8000000000000400
0xF 0x8000000000004060
0x13 0xC000000000800000
0x14 0xC000000001000000
0x15 0xC000000002000000
0x16 0x8000000004000000
0x17 0x8000000008000000
0x18 0x8000000010000000
0x19 0x8000000000000800
0x12 Invalid


Word Value
0 0x00000004
1 0x8000000E
2 0x00000001
0-1 Pid
0 Always. 0x18000001
1 Always. 0
2 "SCFI"
3 0x00000001
4 Always 0.


Takes an input u32 (NCA-type) and an u64 title-id. Web-applet loads the u32 from u32_table[inparam]. Only type4 is usable with this?

Returns an #IFileSystem.

Note: web-applet strings refer to both this cmd and the below "MountContent" as "MountContent".


Takes a type-0x19 input buffer, an in32, and an input title-id.

The in32 must be 5 if the NCA type is 0 (control).

The in32 must be 2..7.

The input buffer is the output string path from nsam GetContentNcaPath.

Returns an #IFileSystem.

May return errors when attempting to access NCA-paths for an update-title with a gamecard, when the gamecard isn't inserted. May return error 0x7D402 in some cases with update-titles. Non-val2 in32 values with NCA-type1 are unusable, even for normal titles.

The official "MountApplicationPackage" func uses this with in64=0 and in32=7.

After the in32-specific permissions are checked, it then gets the func retval for permissions-type 0x25 and func0.

When in32=5, it uses in64=0xffffffffffffffff internally, otherwise it checks if in64 is set to 0xffffffffffffffff then throws an error if so.

in32 Required permissions-type and func
2 0x0, 0
3 0x2, 0
4 0x3, 0
5 0x1, 0
6 0x4, 0
7 0x5, 0


Takes a type-0x19 input buffer string and a u32 Bis partitionID(see below). Official user-process code sets instr[0] = 0 normally.

Returns an #IFileSystem.

Only partitionIDs for FAT partitions are usable with this, otherwise error 0x2EE202 is returned. Seems to be about the same as #OpenBisPartition except this mounts the partition filesystem instead of allowing direct access to the partition sectors.


Takes a u32 partition ID, returns 0x2EE202 for partitions which do not exist, 0x320002 for partitions which cannot be opened and a valid #IStorage handle otherwise.


Takes an input u64.


Takes a 0x40-byte Save-struct entry, a 0x40-byte SaveCreate-struct entry, and a 0x10-byte input struct.

Only the first 0x5-bytes in the 0x10-byte struct are initialized: all-zero when automatically creating savedata during savecommon mount by official user-processes. In the dedicated save-creation code in official user-processes: +0 u32 = 0x40060, +4 u8 = 1.

Creates regular savedata.


Takes a 0x40-byte Save-struct entry and a 0x40-byte SaveCreate-struct entry.

Creates savedata in the SYSTEM NAND partition.


Takes an input u32 (partition ID), and returns an #IStorage for the partition.


Takes two input u32s, with the second u32 located at +4 in rawdata after the first u32.

Returns an #IFileSystem.

Mounts a gamecard partition.


Takes an input u8 and a 0x40-byte Save-struct entry. Official user-process code is only known to use value 1 for the u8.

Returns an #IFileSystem.

Permissions aren't checked until the specified save is successfully found.

Only one process can mount a given savedata at any given time (this includes systemsavedata).


Takes an input u8 and a 0x40-byte Save-struct entry. Web-applet only uses value0 for the input u8.

Returns an #IFileSystem.

Mounts savedata in the SYSTEM NAND partition.


Takes a #ContentStorageId. Invalid values return 0x2EE202.

Returns an #IFileSystem with NCA files. The read data from these files is identical to the data read by Content_Manager_services#ReadEntryRaw.


Takes a #StorageId and a TitleID.

Returns a domain object ID implementing the #IStorage interface for data archives.


This command returns a session to a port implementing the #IDeviceOperator interface.


This command returns a session to a port implementing the #IEventNotifier interface.


This command returns a session to a port implementing the #IEventNotifier interface.


Takes an unknown input u64 and a type-0x6 output buffer.

The input u64 high-byte must be non-zero, otherwise an error is returned(0xE02).


Takes 0x10-bytes of input.

Appears to be used to load the seed into FS-module state, since FS-module itself doesn't seem to have file-reading code to handle this itself.

NS-module uses this with data read from a file.


Takes an input u32.


Returns an output u32.

GlobalAccessLogMode is normally 0.


Takes a type-0x5 input buffer.

The input buffer is the string to output to the log. User-processes normally include a newline at the end.

User-processes only use this when the value previously loaded from #GetGlobalAccessLogMode has bit1 set.

When bit1 in GlobalAccessLogMode is clear, FS-module will just return 0 for OutputAccessLogToSdCard. However even with that set the log doesn't show up SD, unknown why.

The input buffer is written to the "$FsAccessLog:/FsAccessLog.txt" file, where "$FsAccessLog" is the SD-card mount-name. It's written to the current end of the file(appended).


This is the interface for a raw device, usually a block device.

Cmd Name Arguments
0 Read Takes a type-0x46 buffer, an offset and length
1 Write Takes a type-0x45 buffer, an offset and length
2 Flush None
3 SetSize Takes a size
4 GetSize None


There are two main implementations of this interface:

  • RomFS: Filesystem implementation statically linked in the binary. Uses an #IStorage interface as underlying raw device.
  • IPC proxy: Used for all non-RomFS filesystems. In this case, actual filesystem implementation is in the FS process.
Cmd Name
0 CreateFile
1 DeleteFile
2 CreateDirectory
3 DeleteDirectory
4 DeleteDirectoryRecursively
5 RenameFile
6 RenameDirectory
7 GetEntryType
8 OpenFile
9 OpenDirectory
10 Commit
11 GetFreeSpaceSize
12 GetTotalSpaceSize


Like 3DS, this has to be used after writing to savedata for the changes to take affect.


Cmd Name
0 Read
1 GetEntryCount


Cmd Name
0 Read
1 Write
2 Flush
3 SetSize
4 GetSize



Cmd Name
0 IsSdCardInserted
1 GetSdCardSpeedMode
2 GetSdCardCid
3 GetSdCardUserAreaSize
4 GetSdCardProtectedAreaSize
5 GetAndClearSdCardErrorInfo
100 GetMmcCid
101 GetMmcSpeedMode
110 EraseMmc
111 GetMmcPartitionSize
112 GetMmcPatrolCount
113 GetAndClearMmcErrorInfo
114 GetMmcExtendedCsd
200 IsGameCardInserted
201 EraseGameCard
202 GetGameCardHandle
203 #GetGameCardUpdatePartitionInfo
204 FinalizeGameCardDriver
205 GetGameCardAttribute
206 GetGameCardDeviceCertificate
207 GetGameCardAsicInfo
208 GetGameCardIdSet
209 WriteToGameCard
210 SetVerifyWriteEnalbleFlag
211 GetGameCardImageHash
212 GetGameCardErrorInfo
214 GetGameCardCid
217 [2.1.0+] Returns 0x40-bytes of output data.
300 SetSpeedEmulationMode
301 GetSpeedEmulationMode


Returns a titleID and the title-version for it.

  • Output u32 with ARMS-gamecard: title-version v131162. This is the title-version for 2.1.0, which is the sysupdate included with this gamecard. Launch-day gamecards return title-version v450.
  • Output u64 with ARMS-gamecard: titleID 0100000000000816.

NS appears to only use this with Content_Manager_services#GetTitleIdInfo and Content_Manager_services#GetUpdateTitleList with storageid=nandsys, for checking whether a sysupdate is required.


Cmd Name
0 BindEvent


Value Name
0 None
1 Host
2 GameCard
3 NandSystem
4 NandUser
5 SdCard


Value Name
0 NandSystem
1 NandUser
2 SdCard


These are the 0x300 paths to NCA files for the various filesystems FS can access, beginning with @. They're passed via X descriptors, and returned via various ncm/lr commands.

Path Notes
@GcApp Gamecard App partition (Partition 2)
@GcS00000001 Gamecard Contents.
@SdCardContent Installed SD card contents
@Sdcard Raw SD card partition
@SystemContent NandSystem partition.
@upp Gamecard update partition (Partition 0)
@UserContent NandUser partition.


  • 0: Raw NAND sectors access for MMC boot partition 0.
  • 10: Raw NAND sectors access for MMC boot partition 1.
  • Rest: see here.

Save Struct

Offset Size Description
0x0 0x8 0 for SystemSaveData. SaveData: 0 can be used for accessing the savedata associated with the current FS session titleID, otherwise when set this is the titleID associated with the savedata to access.
0x8 0x10 userID for user-specific savedata(saveuser) when set, otherwise when zero this indicates the common savedata(savecommon). This is loaded from Account_services.
0x18 0x8 u64 saveID. 0 for SaveData.
0x20 0x8 ContentStorageId? 0 for SystemSaveData. 1 for SaveData. 2 for DeviceSaveData(with official user-processes all other fields are 0 for DeviceSaveData).
0x28 0x8 0 for SystemSaveData/SaveData.
0x30 0x8 0 for SystemSaveData/SaveData.
0x38 0x8 0 for SystemSaveData/SaveData.

Total size is 0x40-bytes.

SaveCreate Struct

Offset Size Description
0x0 0x8 IVFC level4 size?
0x8 0x8 Same as offset 0x0 normally? Hard-coded to 0x80000 for BcatSaveData.
0x10 0x8 0x4000 for SystemSaveData/SaveData/DeviceSaveData/BcatSaveData. IVFC level4 block-size in bytes?
0x18 0x8 Official user-processes only uses 0 here for SystemSaveData/SaveData. For the dedicated save-creation code with SaveData/DeviceSaveData, this value comes from an input param with official user-processes. For BcatSaveData, this is the hard-coded titleID of the bcat-sysmodule.
0x20 0x4 Written using an input param for official user-processes. Hard-coded 0 for BcatSaveData.
0x24 0x1 Official user-processes only uses 0 here for SystemSaveData, 1 for SaveData/DeviceSaveData/BcatSaveData.
0x25 0x1 0 for SystemSaveData/SaveData.
0x26 0x1A Not initialized for SystemSaveData/SaveData.

Total size is 0x40-bytes.


This is accessed using the same commands for SaveData with the same input u8, the only difference compared to SaveData is the Save-struct.


This is accessed using the same commands for SaveData with the same input u8. The Save-struct is the same as DeviceSaveData, except that the titleID field is set to <input titleID>. See above regarding SaveCreate-struct.

The 0x10-byte struct passed to #CreateSaveData has the first 0x5-bytes set to all-zero.