George Kulakowski
1.9 KiB
Virtual Memory Object
NAME
vm_object - Virtual memory containers
SYNOPSIS
A Virtual Memory Object (VMO) represents a contiguous region of virtual memory that may be mapped into multiple address spaces.
DESCRIPTION
VMOs are used in by the kernel and userspace to represent both paged and physical memory. They are the standard method of sharing memory between processes, as well as between the kernel and userspace.
VMOs are created with vmo_create and basic I/O can be performed on them with vmo_read and vmo_write. A VMO's size may be set using vmo_set_size. Conversely, vmo_get_size will retrieve a VMO's current size.
Pages are committed (allocated) for VMOs on demand through vmo_read, vmo_write, or by mapping the VMO using vmar_map. Pages can be commited and decommited from a VMO manually by calling vmo_op_range with the MX_VMO_OP_COMMIT and MX_VMO_OP_DECOMMIT operations, but this should be considered a low level operation. vmo_op_range can also be used for cache and locking operations against pages a VMO holds.
SYSCALLS
- vmo_create - create a new vmo
- vmo_read - read from a vmo
- vmo_write - write to a vmo
- vmo_get_size - obtain the size of a vmo
- vmo_set_size - adjust the size of a vmo
- vmo_op_range - perform an operation on a range of a vmo
- vmar_map - map a VMO into a process
- vmar_unmap - unmap memory from a process