Module mm

Memory management.

This is an overview of Hermit’s memory layout:

• DeviceAlloc.device_offset is 0 if !cfg!(careful)
• User space virtual memory is only used if !cfg!(feature = "common-os")
• On x86-64, PCI BARs, I/O APICs, and local APICs may be in 0xc0000000..0xffffffff, which could be inside of MEM.

                              Virtual address
                                   space

                                ...┌───┬──► 00000000
          Physical address   ...   │   │
               space      ...      │   │ Identity map
                       ...         │   │
   00000000 ◄──┬───┐...         ...├───┼──► mem_size
               │   │   ...   ...   │   │
PHYS_FREE_LIST │MEM│      ...      │   │ Unused
               │   │   ...   ...   │   │
   mem_size ◄──┼───┤...         ...├───┼──► DeviceAlloc.phys_offset
               │   │   ...         │   │
               │   │      ...      │   │ DeviceAlloc
               │   │         ...   │   │
         Empty │   │            ...├───┼──► DeviceAlloc.phys_offset + mem_size
               │   │               │   │
               │   │               │   │
               │   │               │   │ Unused
    Unknown ◄──┼───┤               │   │
               │   │               │   │
           PCI │   │               ├───┼──► kernel_virt_start
               │   │               │   │
    Unknown ◄──┼───┤               │   │ KERNEL_FREE_LIST
               │   │               │   │
               │   │               ├───┼──► kernel_virt_end
               │   │               │   │
         Empty │   │               │   │
               │   │               │   │ User space
               │   │               │   │
               │   │               │   │

Structs

PhysAddr

A 64-bit physical memory address.

VirtAddr

A canonical 64-bit virtual memory address.

Functions

virtual_to_physical

Translate a virtual memory address to a physical one.