Physical Memory #

ARM11 #

Old 3DS	Address	Size	Description
Yes	0x00000000	0x00010000	Bootrom (super secret code/data @ 0x8000)
Yes	0x00010000	0x00010000	Bootrom mirror
Yes	0x10000000	?	IO memory
Yes	0x17E00000	0x00002000	MPCore private memory region
No	0x17E10000	0x00001000	L2C-310 r3p3 Level 2 Cache Controller (2MB)
Yes	0x18000000	0x00600000	VRAM (divided in two areas VRAM A and B, four banks in total)
No	0x1F000000	0x00400000	New_3DS additional memory
Yes	0x1FF00000	0x00080000	DSP memory
Yes	0x1FF80000	0x00080000	AXI WRAM
Yes	0x20000000	0x08000000	FCRAM
No	0x28000000	0x08000000	New_3DS FCRAM extension
Yes	0xFFFF0000	0x00010000	Bootrom mirror

0x17E10000 #

The 32-bit register at 0x17E10000+0x100 only has bit 0 set when, on New 3DS, PTMSYSM:ConfigureNew3DSCPU was used with bit 1 set for the input value (the L2 cache flag). All other bits in this register are normally all-zero. Therefore, bit 0 set = new cache hardware enabled, bit 0 clear = new cache hardware disabled. This bit is how the ARM11 kernel checks whether the additional cache hardware is enabled).

To enable the additional cache hardware, the following is used by the ARM11 kernel:

Sets bit 0 in 32-bit register 0x17E10000+0x100.

To disable the additional cache hardware, the following is used by the ARM11 kernel:

Writes value 0xFFFF to 32-bit register 0x17E10000+0x77C.
Waits for bit 0 in 32-bit register 0x17E10000+0x730 to become clear.
Writes value 0x0 to 32-bit register 0x17E10000+0x0.
Clears bit 0 in 32-bit register 0x17E10000+0x100.

`0x1F000000` ( New 3DS only) #

This area is used by QTM Services and Kernel11,starting at offset 0x200000, size 0x180000. This area is not accessible to the GPU on the old 3DS. The old 3DS and New 3DS GSP module has vaddr->physaddr conversion code for this entire region. On the New 3DS, only the first 0x200000 bytes (half of this memory) are accessible to the GPU.

ARM9 #

Old 3DS	Address	Size	Description
Yes	0x00000000	0x08000000	Instruction TCM, repeating each 0x8000 bytes.
Yes	0x01FF8000	0x00008000	Instruction TCM (Accessed by the kernel and process by this address)
Yes	0x07FF8000	0x00008000	Instruction TCM (Accessed by bootrom by this address)
Yes	0x08000000	0x00100000	ARM9-only internal memory (ARM7’s internal regions are mapped here as well)
No	0x08100000	0x00080000	New_3DS ARM9-only extension, only enabled when a certain CONFIG register is set.
Yes	0x10000000	0x08000000	IO memory
Yes	0x18000000	0x00600000	VRAM (divided in two banks, VRAM and VRAMB)
Yes	0x1FF00000	0x00080000	DSP memory
Yes	0x1FF80000	0x00080000	AXI WRAM
Yes	0x20000000	0x08000000	FCRAM
No	0x28000000	0x08000000	New_3DS FCRAM extension
Yes	0xFFF00000	0x00004000	Data TCM (Mapped during bootrom). Enabled at the time Boot9 jumps to FIRM, however Kernel9+arm9loader disables it.
Yes	0xFFFF0000	0x00010000	Bootrom, the main region is at +0x8000, which is disabled during system boot.

ARM9 MPU Regions #

For the below instruction permissions: RO = memory is executable, while None = not-executable.

NATIVE_FIRM/SAFE_MODE_FIRM ARM9 kernel #

Region	Address	Size	Privileged-mode data permissions	User-mode data permissions	Privileged-mode instruction permissions	User-mode instruction permissions
0	0xFFFF0000	32KB/0x8000	RO	None	RO	None
1	0x01FF8000	32KB/0x8000	RW	RW	RO	RO
2	0x08000000	1MB/0x100000. >= 8.0.0-X: 2MB/0x200000.	RW	RW	RO	RO
3	0x10000000	128KB/0x20000	RW	RW	None	None
4	0x10100000	512KB/0x80000	RW	RW	None	None
5	0x20000000	128MB/0x8000000. >= 8.0.0-X: 256MB/0x10000000.	RW	RW	None	None
6	0x08000000	128KB/0x20000	RW	None	RO	None
7	0x08020000	< 3.0.0-5: 64KB/0x10000. >= 3.0.0-5: 32KB/0x8000.	RW	None	RO	None

The above is the MPU region settings setup by the ARM9-kernel in the crt0.

The New3DS ARM9-kernel MPU region settings are the same as the Old3DS MPU region settings for >= 8.0.0-X.

At the start of the Process9 function executed in kernel-mode via svc7b during firm-launching, it changes some MPU region settings. At the end of that function, before it uses the ARM9/ARM11 entrypoint fields, it disables MPU.

New3DS ARM9-loader #

Region	Address	Size	Privileged-mode data permissions	User-mode data permissions	Privileged-mode instruction permissions	User-mode instruction permissions
0	0xFFFF0000	32KB/0x8000	RO	None	RO	None
1	0x01FF8000	32KB/0x8000	RW	None	RO	None
2	0x08000000	2MB/0x200000	RW	None	RO	None
3	0x10000000	128KB/0x20000	RW	None	None	None

MPU regions 4-7 are disabled. Note that the entire ARM9-loader runs in SVC-mode.

TWL_FIRM/AGB_FIRM ARM9 kernel #

Region	Address	Size	Privileged-mode data permissions	User-mode data permissions	Privileged-mode instruction permissions	User-mode instruction permissions
0	0xFFFF0000	32KB/0x8000	RO	None	RO	None
1	0x01FF8000	32KB/0x8000	RW	RW	RO	RO
2	0x08000000	1MB/0x100000. New3DS: 2MB/0x200000.	RW	RW	RO	RO
3	0x10000000	2MB/0x200000.	RW	RW	None	None
4	0x1FF00000	512KB/0x80000	RW	RW	None	None
5	0x20000000	128MB/0x8000000. New3DS: 256MB/0x10000000.	RW	RW	None	None
6	0x08000000	< 3.0.0-X: 256KB/0x40000. >= 3.0.0-X: 128KB/0x20000	RW	None	RO	None
7	0x08080000	128KB/0x20000	RW	RW	RO	RO

Boot9 #

Region	Address	Size	Privileged-mode data permissions	User-mode data permissions	Privileged-mode instruction permissions	User-mode instruction permissions
0	0x20000000	0x08000000	None	None	None	None
1	0x10000000	0x10000000	RW	RW	None	None
2	0x08000000	0x00100000	RW	RW	None	None
3	0x08000000	0x00000400	RW	RW	RO	RO
4	0xFFF00000	0x00004000	RW	RW	None	None
5	0x07FF8000	0x00008000	RW	RW	RO	RO
6	0xFFFF0000	0x00010000	RO	RO	RO	RO
7	0x1FFFE000	0x00000800	RW	RW	None	None

Instruction cachable bits = 0x40(only enabled for region6).
Data cachable bits = 0x44(only enabled for region2 and region6).
Data bufferable bits = 0x44(only enabled for region2 and region6).

These are the same for both Old3DS/New3DS.

ARM9 ITCM #

ITCM mirror address	ITCM bootrom mirror address	Offset	Size	Description
0x01FF8000		0x0	0x3700	Uninitialized memory.
0x01FFB700	0x07FFB700	0x3700	0x100	The unprotected ARM9-bootrom code copies code from unprotected bootrom to 0x07FFB700(ITCM mirror) size 0x100, then calls the code at 0x07FFB700. The code located here is the code used for disabling access to the bootroms.
0x01FFB800		0x3800	0x100	This is the first 0x90 bytes of plaintext OTP when OTP hash verification is successful. The remaining 0x70 bytes are cleared.
0x01FFB880		0x3890	0x70	This is all zeros; boot ROM does not reveal the console-specific keys or the OTP hash in ITCM.
0x01FFB900		0x3900	0x200	This is the 0x200-bytes from NAND sector0.
0x01FFBB00		0x3B00	0x200	This is the 0x200-bytes from the plaintext FIRM header for the FIRM which was loaded by Boot9. This is the only location Boot9 uses for storing the loaded FIRM headers internally, it's not stored anywhere else.
0x01FFBD00		0x3D00	0x100	This is the RSA-2048 modulus for RSA-engine slot0 set by bootrom.
0x01FFBE00		0x3E00	0x100	This is the RSA-2048 modulus for RSA-engine slot1 set by bootrom.
0x01FFBF00		0x3F00	0x100	This is the RSA-2048 modulus for RSA-engine slot2.
0x01FFC000		0x4000	0x100	This is the RSA-2048 modulus for RSA-engine slot3.
0x01FFC100		0x4100	0x800	These are RSA-2048 keys: 4 slots, each slot is 0x200-bytes. Slot+0 is the modulus, slot+0x100 is the private exponent. This can be confirmed by RSA-decrypting a message into a signature, then RSA-encrypting the signature back into a message, and comparing the original message with the output from the last operation. FIRM doesn't seem to ever use these. None of these are related to RSA-keyslot0 used for v6.0/v7.0 key generation. These moduli are separate from all other moduli used elsewhere.
0x01FFC900	0x07FFC900	0x4900	0x400	The unprotected ARM9-bootrom copies data to 0x07FFC900(mirror of 0x01FFC900) size 0x400. This data is copied from AXI WRAM, initialized by ARM11-bootrom(the addr used for the src is determined by REG_UNITINFO). These are RSA moduli: retailsrcptr = 0x1FFFD000, devsrvptr = 0x1FFFD400. The first 0x100-bytes here is the RSA-2048 modulus for the CFA NCCH header, and for the gamecard NCSD header. 0x01FFCA00 is the RSA-2048 modulus for the CXI accessdesc signature, written to rsaengine keyslot1 by NATIVE_FIRM. 0x01FFCB00 size 0x200 is unknown, probably RSA related, these aren't used by FIRM(these are not console-unique).
0x01FFCD00		0x4D00	0x80	Unknown, not used by FIRM. This isn't console-unique. The first 0x10-bytes are checked by the v6.0/v7.0 NATIVE_FIRM keyinit function, when non-zero it clears this block and continues to do the key generation. Otherwise when this block was already all-zero, it immediately returns. This memclear was probably an attempt at destroying the RSA slot0 modulus, that missed (exactly 0x1000-bytes away). Even though they "failed" here, one would still need to derive the private exponent, which would require obtaining a ciphertext and plaintext.
0x01FFCD80		0x4D80	0x64	0x01FFCD84 size 0x10-bytes is the NAND CID(the 0x64-byte region at 0x01FFCD80 is initialized by Process9 + ARM9-bootrom). The u32 at 0x01FFCDC4 is the total number of NAND sectors, read from a MMC command.
0x01FFCDE4		0x4DE4	0x21C	Uninitialized memory.
0x01FFD000	0x07FFD000	0x5000	0x2470	The unprotected ARM9-bootrom copies 0x1FFFA000(AXIWRAM mem initialized by ARM11-bootrom) size 0x2470 to 0x07FFD000(mirror of 0x01FFD000). This block contains DSi keys. 0x01FFD000 is the RSA-1024 modulus for the retail System Menu 0x01FFD080 is the RSA-1024 modulus for DSi Wifi firmware and DSi Sound 0x01FFD100 is the RSA-1024 modulus for base DSi apps (Settings, Shop, etc.) 0x01FFD180 is the RSA-1024 modulus for DSiWare and RSA-signed cartridge headers 0x01FFD210 is the keyY for per-console-encrypted ES blocks 0x01FFD220 is the keyY for fixed-keyX ES blocks 0x01FFD300 is the DSi common (normal)key 0x01FFD350 is a normalkey set on keyslot 0x02, and is likely only used during boot 0x01FFD380 is the keyslot 0x00 keyX and the first half of the retail keyX for modcrypt crypto "Nintendo" 0x01FFD398 is the keyX used for 'Tad' crypto, usually in keyslot 0x02 "Nintendo DS", .. 0x01FFD3A8 is set as the middle two words of keyslot 0x03's keyX, before being overwritten "NINTENDO" 0x01FFD3BC is the keyY for keyslot 0x01, see below 0x01FFD3C8 is the fixed keyY used for eMMC partition crypto on retail DSi, see below (keyslot 0x03) 0x01FFD3E0 is the 0x1048-byte Blowfish data for DSi cart crypto 0x01FFE428 is the 0x1048-byte Blowfish data for DS cart crypto On the 3DS, keyslots 0x01 and 0x03 have the last word set as 0xE1A00005 instead of the next word in ITCM. This is consistent with retail DSis.
0x01FFF470		0x7470	0xB90	Uninitialized memory.
0x01FFFC00		0x7C00	0x100	Starting with 9.5.0-X is the FIRM header used during FIRM-launching.

Memory map by firmware #

Virtual address mapping FW0B
Virtual address mapping FW1F
Virtual address mapping FW25
Virtual address mapping FW2E
Virtual address mapping FW37
Virtual address mapping FW38
Virtual address mapping FW3F
FW49( 9.6.0-X) and 10.0.0-X ARM11-kernel vmem mapping is identical to FW40( 9.5.0-X).

Virtual address mapping TWLFIRM04

ARM11 Detailed physical memory map #

18000000 - 18600000: VRAM

1FF80000 - 1FFAB000: Kernel code
1FFAB000 - 1FFF0000: SlabHeap [temporarily contains boot processes]
1FFF0000 - 1FFF1000: ?
1FFF1000 - 1FFF2000: ?
1FFF2000 - 1FFF3000: ?
1FFF3000 - 1FFF4000: ?
1FFF4000 - 1FFF5000: Exception vectors
1FFF5000 - 1FFF5800: Unused?
1FFF5800 - 1FFF5C00: 256-entry L2 MMU table for VA FF4xx000
1FFF5C00 - 1FFF6000: 256-entry L2 MMU table for VA FF5xx000
1FFF6000 - 1FFF6400: 256-entry L2 MMU table for VA FF6xx000
1FFF6400 - 1FFF6800: 256-entry L2 MMU table for VA FF7xx000
1FFF6800 - 1FFF6C00: 256-entry L2 MMU table for VA FF8xx000
1FFF6C00 - 1FFF7000: 256-entry L2 MMU table for VA FF9xx000
1FFF7000 - 1FFF7400: 256-entry L2 MMU table for VA FFAxx000
1FFF7400 - 1FFF7800: 256-entry L2 MMU table for VA FFBxx000
1FFF7800 - 1FFF7C00: MMU table but unused?
1FFF7C00 - 1FFF8000: 256-entry L2 MMU table for VA FFFxx000 
1FFF8000 - 1FFFC000: 4096-entry L1 MMU table for VA xxx00000 (CPU 0)
1FFFC000 - 20000000: 4096-entry L1 MMU table for VA xxx00000 (CPU 1)
20000000 - 28000000: Main memory

The entire FCRAM is cleared during NATIVE_FIRM boot. This is done by the ARM11 kernel in order by region as it initializes after loading FIRM launch parameters from FCRAM.

FCRAM memory-regions layout #

FCRAM is partitioned into three regions of memory (APPLICATION, SYSTEM, and BASE). Most applications can only allocate memory from one of these regions (which is encoded in the process kernel flags). There is a fixed set of possible size of each memory region, determined by the APPMEMTYPE value in configuration memory (which in turn is set up according to the firmware launch parameters).

Support for APPMEMTYPEs 6 and 7 (and 8?) was implemented in NS with 8.0.0-18. These configurations are only supported in the New_3DS ARM11-kernel, and are in fact the only ones supported there at all. Applications only get access to the larger memory regions when this is specified in their extended header.

APPMEMTYPE	APPLICATION starting address (relative to FCRAM)	APPLICATION region size	SYSTEM starting address (relative to FCRAM)	SYSTEM region size	BASE starting address (relative to FCRAM)	BASE region size
0 (default with regular 3DS kernel, used when the type is not 2-5)	0x0	0x04000000(64MB)	0x04000000	0x02C00000	0x06C00000	0x01400000
2	0x0	0x06000000(96MB)	0x06000000	0x00C00000	0x06C00000	0x01400000
3	0x0	0x05000000(80MB)	0x05000000	0x01C00000	0x06C00000	0x01400000
4	0x0	0x04800000(72MB)	0x04800000	0x02400000	0x06C00000	0x01400000
5	0x0	0x02000000(32MB)	0x02000000	0x04C00000	0x06C00000	0x01400000
6 and 8 (6 is the default on New3DS. With New_3DS kernel this is the type used when the value is neither 7 nor 8)	0x0	0x07C00000(124MB)	0x07C00000	0x06400000	0x0E000000	0x02000000
7	0x0	0x0B200000(178MB)	0x0B200000	0x02E00000	0x0E000000	0x02000000

The SYSTEM mem-region size is calculated with: size = FCRAMTOTALSIZE - (APPLICATION_MEMREGIONSIZE + BASE_MEMREGIONSIZE).

All memory allocated by the kernel itself for kernel use is located under BASE. Most system-modules run under the BASE memregion too.

Free/used memory on 4.5.0-10 with Home Menu / Internet Browser, with the default APPMEMTYPE on retail:

Region	Base address relative to FCRAM+0	Region size	Used memory once Home Menu finishes loading for system boot, on 4.5.0-10	Used memory with Internet Browser running instead of Home Menu, on 4.5.0-10	Free memory once Home Menu finishes loading for system boot, on 4.5.0-10	Free memory with Internet Browser running instead of Home Menu, on 4.5.0-10
APPLICATION	0x0	0x04000000	0x0		0x04000000
SYSTEM	0x04000000	0x02C00000	0x01488000	0x02A50000	0x01778000	0x001B0000
BASE	0x06C00000	0x01400000	0x01202000	0x01236000	0x001FE000	0x001CA000

ARM11 Detailed virtual memory map #

(valid only for FW0B, see Memory map by firmware for subsequent versions)

E8000000 - E8600000: mapped VRAM (18000000 - 18600000)

EFF00000 - F0000000: mapped Internal memory (1FF00000 - 20000000)
F0000000 - F8000000: mapped Main memory

FF401000 - FF402000: mapped ? (27FC7000 - 27FC8000)

FF403000 - FF404000: mapped ? (27FC2000 - 27FC3000)

FF405000 - FF406000: mapped ? (27FBB000 - 27FBC000)

FF407000 - FF408000: mapped ? (27FB3000 - 27FB4000)

FF409000 - FF40A000: mapped ? (27F8E000 - 27F8F000)

FFF00000 - FFF45000: mapped SlabHeap

FFF60000 - FFF8B000: mapped Kernel code

FFFCC000 - FFFCD000: mapped IO `[`I2C`](I2C "wikilink")` second bus (10144000 - 10145000)

FFFCE000 - FFFCF000: mapped IO PDC(`[`LCD`](LCD "wikilink")`) (10400000 - 10401000)

FFFD0000 - FFFD1000: mapped IO PDN (10141000 - 10142000)

FFFD2000 - FFFD3000: mapped IO PXI (10163000 - 10164000)

FFFD4000 - FFFD5000: mapped IO PAD (10146000 - 10147000)

FFFD6000 - FFFD7000: mapped IO LCD (10202000 - 10203000)

FFFD8000 - FFFD9000: mapped IO DSP (10140000 - 10141000)

FFFDA000 - FFFDB000: mapped IO XDMA (10200000 - 10201000)

FFFDC000 - FFFE0000: mapped ? (1FFF8000 - 1FFFC000)

FFFE1000 - FFFE2000: mapped ? (1FFF0000 - 1FFF1000)

FFFE3000 - FFFE4000: mapped ? (1FFF2000 - 1FFF3000)

FFFE5000 - FFFE9000: mapped L1 MMU table for VA xxx00000

FFFEA000 - FFFEB000: mapped ? (1FFF1000 - 1FFF2000)

FFFEC000 - FFFED000: mapped ? (1FFF3000 - 1FFF4000)

FFFEE000 - FFFF0000: mapped IO IRQ (17E00000 - 17E02000)

FFFF0000 - FFFF1000: mapped Exception vectors

FFFF2000 - FFFF6000: mapped L1 MMU table for VA xxx00000

FFFF7000 - FFFF8000: mapped ? (1FFF1000 - 1FFF2000)

FFFF9000 - FFFFA000: mapped ? (1FFF3000 - 1FFF4000)

FFFFB000 - FFFFE000: mapped L2 MMU tables (1FFF5000 - 1FFF8000)

0xFF4XX000 #

Each thread is allocated a 0x1000-byte page in this region for the thread context: the first page at 0xFF401000 is for the first created thread, 0xFF403000 for the second thread. This region is used to store the SVC-mode stack for the thread, and thread context data used for context switching. When the IRQ handler, prefetch/data abort handlers, and undefined instruction handler are entered where the SPSR-mode=user, these handlers then store LR+SPSR for the current mode on the SVC-mode stack, then these handlers switch to SVC-mode.

This page does not contain a dedicated block for storing R0-PC(etc). For user-mode, the user-mode regs are instead saved on the SVC-mode stack when IRQs such as timers for context switching are triggered.

For NATIVE_FIRM the memory pages for this region are located in FCRAM, however for TWL_FIRM these are located in AXI WRAM. For TWL_FIRM v6704 the first thread’s page for this region is located at physical address 0x1FF93000, the next one at 0x1FF92000, etc.

IO Process virtual addressing equivalence #

It seems an IO register’s process virtual address can be calculated by adding 0xEB00000 to its physical address. However for kernel mappings there is no fixed address equivalence.

ARM11 User-land memory regions #

NATIVE_FIRM/SAFE_MODE_FIRM Userland Memory #

Virtual Address Base	Physical Address Base	Region Max Size	Address-range available for svcMapMemoryBlock	Description
0x00100000 / 0x14000000		0x03F00000	No	The ExeFS:/.code is loaded here, executables must be loaded to the 0x00100000 region when the exheader “special memory” flag is clear. The 0x03F00000-byte size restriction only applies when this flag is clear. Executables are usually loaded to 0x14000000 when the exheader “special memory” flag is set, however this address can be arbitrary.
0x04000000	?	?	No	Used for mapping buffers during IPC, see IPC Command Structure.
0x08000000	Main stack physaddr - <heap size for the allocated vaddr 0x08000000 memory>	0x08000000	Yes	Heap mapped by ControlMemory
0x10000000-StackSize	.bss physical address - total stack pages	StackSize from process exheader		Stack for the main-thread, initialized by the ARM11 kernel. The StackSize from the exheader is usually 0x4000, therefore the stack-bottom is usually 0x0FFFC000. The stack for the other threads is normally located in the process .data section however this can be arbitrary.
0x10000000		0x04000000	Yes	Shared memory
0x14000000	FCRAM+0	0x08000000	No	Can be mapped by ControlMemory, this is used for processes’ LINEAR/GSP heap.
0x1E800000	0x1F000000	0x00400000	No	New_3DS additional memory, access to this is specified by the exheader. Added with 8.0.0-18, see above section regarding this memory.
0x1EC00000	0x10100000	0x00400000	No	IO registers, the mapped IO pages which each process can access is specified in the exheader. (Applications normally don’t have access to registers in this range)
0x1F000000	0x18000000	0x00600000	No	VRAM, access to this is specified by the exheader.
0x1FF00000	0x1FF00000	0x00080000	No	DSP memory, access to this is specified by the exheader.
0x1FF80000	FCRAM memory page allocated by the ARM11 kernel.	0x1000	No	Configuration Memory, all processes have read-only access to this.
0x1FF81000	FCRAM memory page allocated by the ARM11 kernel.	0x1000	No	Shared page, all processes have read-access to this. Write access to this is specified by the exheader “Shared page writing” kernel flag.
0x1FF82000	Dynamically taken from the BASE region of FCRAM	Number of threads * 0x1000 / 8	No	Thread Local Storage
0x30000000	FCRAM+0	0x08000000(Old3DS) / 0x10000000( New_3DS)	No	This LINEAR memory mapping was added with 8.0.0-18, see here. This replaces the original 0x14000000 mapping, for system(memory-region=BASE)/newer titles. The Old3DS kernel uses size 0x08000000 for LINEAR-memory address range checks, while the New3DS kernel uses size 0x10000000 for those range checks. Old3DS/New3DS system-module code doing vaddr->phys-addr conversion uses size 0x10000000.
0x20000000 / 0x40000000				This is the end-address of userland memory, memory under this address is process-unique. Memory starting at this address is only accessible in privileged-mode. This address was changed from 0x20000000 to 0x40000000 with 8.0.0-18.

All executable pages are read-only, and data pages have the execute-never permission set. Normally .text from the loaded ExeFS:/.code is the only mapped executable memory. Executable CROs can be loaded into memory, once loaded the CRO .text section memory page permissions are changed via ControlProcessMemory from RW- to R-X. The address and size of each ExeFS:/.code section is stored in the exheader, the permissions for each section is: .text R-X, .rodata R–, .data RW-, and .bss RW-. The loaded .code is mapped to the addresses specified in the exheader by the ARM11 kernel. The stack permissions is initialized by the ARM11 kernel: RW-. The heap permissions is normally RW-.

All userland memory is mapped with RW permissions for privileged-mode. However, normally the ARM11 kernel only uses userland read/write instructions(or checks that the memory can be written from userland first) for accessing memory specified by SVCs.

Processes can’t directly access memory for other processes. When service commands are used, the kernel maps memory in the destination process for input/output buffers, where the addresses in the command received by the process is replaced by this mapped memory. When this is an input buffer, the buffer data is copied to the mapped memory. When this is an output buffer, the data stored in the mapped memory is copied to the destination buffer specified in the command.

The physical address which memory for the application memory-type is mapped to begins at FCRAM+0, the total memory allocated for this memory-type is stored in Configuration_Memory. Applications' .text + .rodata + .data under the application memory-type is mapped at FCRAM + APPMEMALLOC - (aligned page-size for .text + .rodata + .data). The application .bss is mapped at CODEADDR - .bss size aligned down to the page size.

TWL_FIRM Userland Memory #

Virtual Address Base	Physical Address Base	Size	Description
0x00100000	0x1FFAB000 (with newer TWL_FIRM such as v6704 this is located at 0x1FFAC000)	0x00055000	Code + .(ro)data copied from the process 0x00300000 region is located here(.bss is located here as well).
0x00155000	0x18555000	0x000AB000
0x00200000	0x18500000	0x00100000
0x00300000	0x24000000	0x04000000	The beginning of the ARM11 process .text is located here.
0x08000000	0x20000000	0x07E00000
0x1EC00000	0x10100000	0x00400000	IO
0x1F000000	0x18000000	0x00600000	VRAM
0x1FF00000	0x1FF00000	0x00080000	This is mapped to the DSP memory.

The above regions are mapped by the ARM11 kernel. Later when the ARM11 process uses svcKernelSetState with type4, the kernel unmaps(?) the following regions: 0x00300000..0x04300000, 0x08000000..0x0FE00000, and 0x10000000..0xF8000000.

Detailed TWL_FIRM ARM11 Memory #

Process Virtual Address	Physical Address	Size	Description
0x08000000	0x20000000	0x01000000*4	DS(i) 0x02000000 RAM. Vaddr = (DSRAMOffset*4) + 0x08000000, where DSRAMOffset is DSRAMAddr-0x02000000.
0x0FC00000	0x27C00000		Loaded SRL binary, initially the dev DSi launcher SRL is located here(copied here by the ARM11 process).
0x0FD00000	0x27D00000		The data located here is copied to here by the ARM11 process. The data located here is a TWL NAND 🔗 bootloader image, using the same format+encryption/verification methods as the DSi NAND bootloader(stage2). The keyX for this bootloader keyslot is initially set to the retail DSi key-data, however when TWL_FIRM is launched this keyX key-data is replaced with a separate keyX. TWL_FIRM can use either the retail DSi bootloader RSA-1024 modulus, or a seperate modulus: normally only the latter is used(the former is only used when loading the image from FS instead of FCRAM). When using the image from FCRAM(default code-path), TWL_FIRM will not calculate+check the hashes for the bootloader code binaries(this is done when loading from FS however).
0x0FDF7000	0x27DF7000	0x1000	SRL header

System memory details #

0xFFFF9000 Pointer to the current KThread instance
0xFFFF9004 Pointer to the current KProcess instance
0xFFFF9008 Pointer to the current KScheduler instance
0xFFFF900C Pointer to the current KSchedulableInterruptEventLinkedList instance
0xFFFF9010 Pointer to the last KThread to encounter an exception

0x8000040 Pointer to the current KThread instance on the ARM9
0x8000044 Pointer to the current KProcess instance on the ARM9
0x8000048 Pointer to the current KScheduler instance on the ARM9

VRAM Map While Running System Applets #

0x1E6000-0x22C500 – top screen 3D left framebuffer 0(240x400x3) (The “3D right first-framebuf” addr stored in the LCD register is set to this, when the 3D is set to “off”)
0x22C800-0x272D00 – top screen 3D right framebuffer 0(240x400x3)
0x273000-0x2B9500 – top screen 3D left framebuffer 1(240x400x3)
0x2B9800-0x2FFD00 – top screen 3D right framebuffer 1(240x400x3)
0x48F000-0x4C7400 – bottom screen framebuffer 0(240x320x3)
0x4C7800-0x4FF800 – bottom screen framebuffer 1(240x320x3)

These LCD framebuffer addresses are not changed by the system when launching regular applications, the application itself handles that if needed. These VRAM framebuffers are cleared when launching regular applications.

Memory Layout