Memory Map
Detailed memory layout of the NØNOS kernel.
Physical Memory Layout
The kernel is loaded at the standard x86 kernel location:
┌────────────────────────────────────────────────────────────────┐
│ PHYSICAL MEMORY MAP │
├────────────────────────────────────────────────────────────────┤
│ │
│ 0x00000000 ─┬─ Real Mode IVT / BIOS Data │
│ │ │
│ 0x00100000 ─┼─ KERNEL LOAD ADDRESS (1 MB) │
│ │ │
│ ├─ .multiboot Bootloader handoff structure │
│ │ │
│ 0x00101000 ─├─ .text Executable code (R-X) │
│ │ │
│ 0x00102000 ─├─ .rodata Read-only data (R--) │
│ │ │
│ 0x00103000 ─├─ .data Initialized data (RW-) │
│ │ │
│ 0x00104000 ─├─ .bss Zero-initialized data (RW-) │
│ │ __bss_start │
│ │ __bss_end │
│ │ │
│ 0x00105000 ─├─ .nonos.manifest Kernel manifest (R--) │
│ │ __nonos_manifest_start │
│ │ __nonos_manifest_end │
│ │ │
│ ├─ .nonos.sig Ed25519 signature (R--) │
│ │ __nonos_signature_start │
│ │ __nonos_signature_end │
│ │ (aligned to 8 bytes) │
│ │ │
│ 0x001FF000 ─├─ __stack_bottom │
│ │ │
│ │ ┌────────────────────────┐ │
│ │ │ KERNEL STACK │ │
│ │ │ 64 KB │ │
│ │ │ (grows downward) │ │
│ │ └────────────────────────┘ │
│ │ │
│ 0x0020F000 ─├─ __stack_top │
│ │ │
│ │ ... Heap / Dynamic Memory ... │
│ │ │
└────────────────────────────────────────────────────────────────┘Linker Script Symbols
The linker exports these symbols for runtime use:
__bss_start
Start of BSS section
__bss_end
End of BSS section
__nonos_manifest_start
Start of manifest section
__nonos_manifest_end
End of manifest section
__nonos_signature_start
Start of signature (64 bytes)
__nonos_signature_end
End of signature
__stack_bottom
Bottom of kernel stack
__stack_top
Top of kernel stack
Virtual Address Space
NØNOS uses higher-half kernel mapping:
Page Table Structure
NØNOS uses 4-level x86_64 paging:
Page Sizes
4 KB
PML4 → PDPT → PD → PT
12
2 MB
PML4 → PDPT → PD (huge)
21
1 GB
PML4 → PDPT (huge)
30
Page Flags
Present
0
Page is mapped
Writable
1
Write access allowed
User
2
User-mode accessible
Write-Through
3
Write-through caching
Cache Disable
4
Disable caching
Accessed
5
Page was accessed
Dirty
6
Page was written
Huge
7
2MB or 1GB page
Global
8
Don't flush from TLB
No-Execute
63
Disable code execution
W^X Enforcement
NØNOS enforces Write XOR Execute (W^X):
.text
No
Yes
.rodata
No
No
.data
Yes
No
.bss
Yes
No
Heap
Yes
No
Stack
Yes
No
No page is ever both writable AND executable.
Stack Layout
Each task has its own stack with guard pages:
Heap Allocator
NØNOS uses a linked-list allocator:
Allocator Type
Linked-list
Thread Safety
Spinlock
Minimum Allocation
8 bytes
Page Allocation
≥4 KB direct
Growth
On demand
KASLR
Kernel Address Space Layout Randomization:
Kernel base randomized at boot
Stack locations randomized
Entropy source: RDRAND/RDSEED
Memory Regions from UEFI
The bootloader passes memory map from UEFI:
Conventional
Available RAM
Allocation
Reserved
Hardware reserved
Avoid
ACPI Reclaim
ACPI tables (reclaimable)
Parse then free
ACPI NVS
ACPI non-volatile
Preserve
Unusable
Defective memory
Avoid
Framebuffer
GPU memory
Display only
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