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Memory layout

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ARM11 Physical memory regions

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
? 0x17E10000 0x00001000 ?
Yes 0x18000000 0x00600000 VRAM
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

ARM9 Physical memory regions

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
No 0x08100000 0x00080000 New_3DS ARM9-only extension
Yes 0x10000000 0x08000000 IO memory
Yes 0x18000000 0x00600000 VRAM
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)
Yes 0xFFFF0000 0x00010000 Bootrom, the main region is at +0x8000, which is disabled during system boot.

New_3DS physical 0x1F000000 memory

This area is used by QTM Services(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.

Memory map by firmware

ARM11 Detailed physical memory map

18000000 - 18600000: VRAM

1FF80000 - 1FFAB000: Kernel code
1FFAB000 - 1FFF0000: SlabHeap [temporarily contains boot processes]
1FFF0000 - 1FFF1000:Ā ?
1FFF1000 - 1FFF2000:Ā ?
1FFF2000 - 1FFF3000:Ā ?
1FFF3000 - 1FFF4000:Ā ?
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 probably done by the ARM11 kernel(after loading FIRM launch parameters from FCRAM)?

FCRAM memory-regions layout

Configmem-APPMEMTYPE Value Base address relative to FCRAM+0, for APPLICATION mem-region Region size, for APPLICATION mem-region Base address relative to FCRAM+0, for SYSTEM mem-region Region size, for SYSTEM mem-region Base address relative to FCRAM+0, for BASE mem-region Region size, for BASE mem-region
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 (This is the default on New3DS. With New_3DS kernel this is the type used when the value is not 7) 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).

Support for type6/7 was implemented in NS with 8.0.0-18, these are only supported in the New_3DS ARM11-kernel not the regular 3DS kernel. These two types are the only ones supported by the New3DS kernel.

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: mappedĀ ? (27FC7000 - 27FC8000)

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

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

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

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

FFF00000 - FFF45000: mapped SlabHeap 

FFF60000 - FFF8B000: mapped Kernel code

FFFCC000 - FFFCD000: mapped IO I2C second bus (10144000 - 10145000)

FFFCE000 - FFFCF000: mapped IO PDC(LCD) (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: mappedĀ ? (1FFF8000 - 1FFFC000)

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

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

FFFE5000 - FFFE9000: mapped L1 MMU table for VA xxx00000

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

FFFEC000 - FFFED000: mappedĀ ? (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: mappedĀ ? (1FFF1000 - 1FFF2000)

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

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

0xFF4XX000

Each thread is allocated a 0x1000-byte page in this region: 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.

Structure of this page, relative to page_endaddr-0xC8:

Offset Size Description
0x0 SVC-mode stack-top
0x18 0x28 SVC-mode saved registers, stored/loaded during context switches: R4-R9, SL, FP, SP, LR. After loading these registers, the context switch code will jump to the loaded LR.
0xC0 4 fpexc from vmrs, used during context switches with the above saved registers.

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.

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 0x01000000 No IO registers, the mapped IO pages which each process can access is specified in the CXI 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 ? ? 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 modulo, or a seperate modulo: 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
0xFFFF9010 Pointer to the last KThread to encounter an exception

Handles

The handle 0xFFFF8001 is a reference to the current KProcess.
The handle 0xFFFF8000 is a reference to the current KThread.

IO Process/Kernel virtual addressing equivalence

It seems an IO register's process virtual address can be calculated by adding 0xEB00000 to its physical address.

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 left framebuffer 1(240x400x3)
  • 0x273000-0x2B9500 -- top screen 3D right framebuffer 0(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.

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