NPDM

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
0xC	0x1	MmuFlags, bit0: 64-bit instructions, bits1-3: address space width (1=64-bit, 2=32-bit). Needs to be <= 0xF
0xE	0x1	MainThreadPrio
0xF	0x1	DefaultCpuId
0x10
0x18	0x4	ProcessCategory (0: regular title, 1: kernel built-in). Should be 0 here.
0x1C	0x4	MainStackSize
0x20	?	Title name
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? Bit2 is set for applets with [5.0.0+], bit3 is set for sysmodules with [5.0.0+].
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	Lowest allowed title id? Always 0?
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	Usually 0x1C
0x10	0x4	Usually 0x0
0x14	0x4	Usually 0x1C
0x18	0x4	Usually 0x0

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 0x0F 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

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