NPDM

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This is the Switch equivalent of 3DS exheader. This is the file with extension ".npdm" in {Switch ExeFS}. The size of this file varies.

Offset Size Description
0x0 0x80 META
0x80 <Varies> ACID
<See META> <See META> ACI0

META

Offset Size Description
0x0 0x4 Magic "META".
0x4 0x8 Reserved (Padding / Unused)
0xC 0x1 MmuFlags, bit0: 64-bit instructions, bits1-3: address space width (1=64-bit, 2=32-bit). Needs to be <= 0xF
0xD 0x1 Reserved (Padding / Unused)
0xE 0x1 Main thread priority (0-63)
0xF 0x1 DefaultCpuId
0x10 0x4 Reserved
0x14 0x4 System resource size (max size as of 5.x: 534773760). Unknown usage.
0x18 0x4 ProcessCategory (0: regular title, 1: kernel built-in). Should be 0 here.
0x1C 0x4 Main entrypoint stack size (Should(?) be page-aligned. In non-nspwn scenarios, values of 0 can also rarely break in Horizon. This might be something auto-adapting or a security feature of some sort?)
0x20 0x10 Title name
0x30 0x10 Product code
0x40 0x30 Reserved (Padding / Unused)
0x70 0x4 #ACI0 offset
0x74 0x4 #ACI0 size
0x78 0x4 #ACID offset
0x7C 0x4 #ACID size

ACID

Offset Size Description
0x0 0x100 RSA-2048 signature, seems to verify the data starting at 0x100 with the size field from 0x204.
0x100 0x100 RSA-2048 public key, seems to be used for the second NCA signature.
0x200 0x4 Magic "ACID".
0x204 0x4 s32 Size field used with the above signature(?).
0x208 0x4 Zeroes
0x20C 0x4 Flags. Bit0 must be 1 on retail, on devunit 0 is also allowed. Bit1 is unknown, set to 1 for ARMS? [5.0.0+] Bit3-2: PoolPartition? For applets set to 0b01, for sysmodules set to 0b10. Exceptions: "starter" is set to 0, "nvservices" is set to 3.
0x210 0x8 TitleIdRange_Min
0x218 0x8 TitleIdRange_Max
0x220 0x4 #FS Access Control offset
0x224 0x4 #FS Access Control size
0x228 0x4 #Service Access Control offset
0x22C 0x4 #Service Access Control size
0x230 0x4 #Kernel Access Control offset
0x234 0x4 #Kernel Access Control size
0x238 0x8 Padding

ACI0

Offset Size Description
0x0 0x4 Magic "ACI0".
0x4 0xC Zeroes
0x10 0x8 Title id
0x18 0x8 Reserved (Not currently used, potentially to be used for lowest title ID in future.)
0x20 0x4 #FS Access Header offset
0x24 0x4 #FS Access Header size
0x28 0x4 #Service Access Control offset
0x2C 0x4 #Service Access Control size
0x30 0x4 #Kernel Access Control offset
0x34 0x4 #Kernel Access Control size
0x38 0x8 Padding

FS Access Header

Offset Size Description
0x0 0x1 Version? Always 1. Must be non-zero.
0x1 0x3 Padding
0x4 0x8 Permissions bitmask
0xC 0x4 Data Size (Always 0x1C)
0x10 0x4 Size of Content Owner ID section.
0x14 0x4 Data size (0x1C) plus Content Owner size
0x18 0x4 Size of Save Data owners section (for applications that wish to share save data?)
0x1C 0x4 (OPTIONAL) Amount of content owner id's
0x1C 0x8 * Content Owner ID's Content owner ID's as uint64's.
VARIABLE 0x4 Amount of save owner id's
VARIABLE 0x1 * Save data owner accessibilities (?) Sets flags for what save data owners can do with other applications save data (?)
VARIABLE (Pad to nearest 4 bytes) 0x8 * Amount of save owner ID's Save data owner ID's

FS Access Control

Offset Size Description
0x0 0x1 Version? Always 1. Must be non-zero.
0x1 0x3 Padding
0x4 0x8 Permissions bitmask
0xC 0x20 Usually all zeroes for applications

Permissions bitmask:

Bit Description
0 MountContent* is accessible when set.
34 Enables access to Bis partitionID 27 and 28?
63 Enables access to everything: all permission-types which check a bitmask have this bit set.

For bit62 in permissions, see here.

Web-applets permissions:

  • "LibAppletWeb" and "LibAppletOff" have same access control: bit0 and bit3 set, and bit62 set.
  • Rest of the web-applets: Same as above except bit0 isn't set.

Service Access Control

This is a list of service-name strings which the title has access to, with the following structure:

 +0: control_byte
 +1: {service-name without nul-terminator}

Bitmask 0x07 in control_byte is the {length of the service-name without nul-terminator} - 1.

Bitmask 0x80 in control_byte means service is allowed to be registered.

The service string can contain a wildcard * character.

Kernel Access Control

On Switch, descriptors are identified by pattern 01..11 in low bits.

Pattern of lower bits Lowest clear bitmask/bit Type Fields
0bxxxxxxxxxxxx0111 Bit3 KernelFlags Bit31-24: Highest allowed cpu id, bit23-16: Lowest allowed cpu id, bit15-10: Highest allowed thread prio, bit9-4: Lowest allowed thread prio
0bxxxxxxxxxxx01111 Bit4 SyscallMask Bits 29-31: Syscall mask table index; Bits 5-28: Mask
0bxxxxxxxxx0111111 Bit6 MapIoOrNormalRange Bits 7-30: Alternating start page and number of pages, bit31: Alternating read-only flag then MemoryAttribute 0x2001/0x42002 selector flag
0bxxxxxxxx01111111 Bit7 MapNormalPage (RW) Bits 8-31: Page
0bxxxx011111111111 Bit11 InterruptPair Bits 12-21: Irq0, bits 20-31: Irq1, 0x3FF means empty.
0bxx01111111111111 Bit13 ApplicationType Bit16-14: ApplicationType (0=sysmodule, 1=application, 2=applet), bit16 ignored. Parsed by Process Manager services. Defaults to 0 if descriptor doesn't exist. Can only run 1 application at a time.
0bx011111111111111 Bit14 KernelReleaseVersion Bits 15-X: Version. The raw descriptor is compared with 0x80000, when less than an error is returned. This is equivalent to comparing the bits starting at bit15 with 0x10. This enforces a minimum required version, not a maximum.
0b0111111111111111 Bit15 HandleTableSize Bit25-16: Number of handles the table shall fit.
0b1111111111111111 Bit16 DebugFlags Bit17: can be debugged, bit18: can debug others
All ones Ignored

Mapping restrictions

The physaddr range 0x80060000-0x2000000000 is not allowed to be mapped as IO. The physaddr range 0x80000000-0x2000000000 is not allowed to be mapped as Normal.

[2.0.0-4.1.0] The range for IO was changed into 0x80060000-0x81D3FFFF.

[2.0.0-4.1.0] A blacklist was added for IO and Normal mappings:

  • 0x50040000-0x50060000 (ARM, Interrupt Controller)
  • 0x6000F000 (Exception Vectors)
  • 0x6001DC00-0x6001E000 (IPATCH)
  • 0x7000E000 (RTC/PMC)
  • 0x70019000 (MC)
  • 0x7001C000 (MC0)
  • 0x7001D000 (MC1)

[5.0.0+] For IO, this blacklist was abandoned and instead two range checks were added. For Normal mappings it is still applied

Kernel versions

Firmware Kernel Version Minimum Allowed
1.0.0 5.0.0 3.0.0
2.0.0 6.1.0 3.0.0
3.0.0 7.4.0 3.0.0
3.0.2 7.4.0 3.0.0
5.0.0 9.3.0 3.0.0

Bit31-19: Major version Bit18-15: Minor version Bit14-0: Zeroes