Module kernel_config::memory

The basic virtual memory map that Theseus assumes.

Current P4 (top-level page table) mappings:

• 511: kernel text sections.
• 510: recursive mapping for accessing the current P4 root page table frame.
• 509: kernel heap.
• 508: recursive mapping for accessing the P4 root page table frame of an upcoming new page table.
• 507 down to 0: available for general usage.

Constants

ADDRESSABILITY_PER_P4_ENTRY

Value: 512 GiB.

BYTES_PER_ADDR

64-bit architecture results in 8 bytes per address.

ENTRIES_PER_PAGE_TABLE

Value: 512.

KERNEL_HEAP_INITIAL_SIZE

KERNEL_HEAP_MAX_SIZE

the kernel heap gets the whole 509th P4 entry.

KERNEL_HEAP_P4_INDEX

Value: 509. The 509th entry is used for the kernel heap

KERNEL_HEAP_START

The higher-half heap gets the 512GB address range starting at the 509th P4 entry, which is the slot right below the recursive P4 entry (510). Actual value: 0o177777_775_000_000_000_0000, or 0xFFFF_FE80_0000_0000

KERNEL_OFFSET

The virtual address where the initial kernel (the nano_core) is mapped to. Actual value: 0xFFFFFFFF80000000 on x86_64. i.e., the linear offset between physical memory and kernel memory. So, for example, the VGA buffer will be mapped from 0xb8000 to 0xFFFFFFFF800b8000 (on x86_64). This is -2GiB from the end of the 64-bit address space.

KERNEL_STACK_SIZE_IN_PAGES

KERNEL_TEXT_MAX_SIZE

The size in bytes, not in pages.

KERNEL_TEXT_P4_INDEX

Value: 511. The 511th entry is used for kernel text sections

KERNEL_TEXT_START

The kernel text region is where we load kernel modules. It starts at the 511th P4 entry and goes up until the KERNEL_OFFSET, which is where the nano_core itself starts. Actual value on x86_64: 0o177777_777_000_000_000_0000, or 0xFFFF_FF80_0000_0000

MAX_PAGE_NUMBER

MAX_VIRTUAL_ADDRESS

P1_INDEX_SHIFT

Value: 0. Shift the Page number (not the address!) by this to get the P1 index.

P2_INDEX_SHIFT

Value: 9. Shift the Page number (not the address!) by this to get the P2 index.

P3_INDEX_SHIFT

Value: 18. Shift the Page number (not the address!) by this to get the P3 index.

P4_INDEX_SHIFT

Value: 27. Shift the Page number (not the address!) by this to get the P4 index.

PAGE_SHIFT

The lower 12 bits of a virtual address correspond to the P1 page frame offset.

PAGE_SIZE

Page size is 4096 bytes, 4KiB pages.

RECURSIVE_P4_INDEX

Value: 510. The 510th entry is used to recursively map the current P4 root page table frame

TEMPORARY_PAGE_VIRT_ADDR

UPCOMING_PAGE_TABLE_RECURSIVE_MEMORY_START

The system (page allocator) must not use addresses at or above this address.

UPCOMING_PAGE_TABLE_RECURSIVE_P4_INDEX

Value: 508. The 508th entry is used to temporarily recursively map the P4 root page table frame