Create a pager owned vmo.
#include <zircon/syscalls.h> zx_status_t zx_pager_create_vmo(zx_handle_t pager, uint32_t options, zx_handle_t port, uint64_t key, uint64_t size, zx_handle_t* out);
Creates a VMO owned by a pager object. size will be rounded up to the next page size boundary, and options must be zero or ZX_VMO_NON_RESIZABLE.
On success, the returned vmo has the same rights as a vmo created with zx_vmo_create(), as well as having the same behavior with respect to ZX_VMO_ZERO_CHILDREN. Syscalls which operate on VMOs require an explicit flag to allow blocking IPC to the userspace pager service; beyond this, whether or not a VMO is owned by a pager does not affect the semantics of syscalls.
TODO(stevend): Update differences after updates to cloning and decommit
Page requests will be delivered to port when certain conditions are met. Those packets will have type set to ZX_PKT_TYPE_PAGE_REQUEST and key set to the value provided to zx_pager_create_vmo(). The packet's union is of type zx_packet_page_request_t:
typedef struct zx_packet_page_request {
uint16_t command;
uint16_t flags;
uint32_t reserved0;
uint64_t offset;
uint64_t length;
uint64_t reserved1;
} zx_packet_page_request_t;
offset and length are always page-aligned. The value of any bits in flags for which flags are not defined is unspecified - currently no flags are defined. The trigger and meaning of the packet depends on command, which can take one of the following values:
ZX_PAGER_VMO_READ: Sent when an application accesses a non-resident page in a pager's VMO. The pager service should populate the range [offset, offset + length) in the registered vmo with zx_pager_supply_pages(). Supplying pages is an implicit positive acknowledgement of the request.
ZX_PAGER_VMO_COMPLETE: Sent when no more pager requests will be sent for the corresponding VMO, either because of zx_pager_detach_vmo() or because no references to the VMO remain.
If pager is closed, then no more packets will be delivered to port (including no ZX_PAGER_VMO_COMPLETE message). Furthermore, all future accesses will behave as if zx_pager_detach_vmo() had been called.
pager must be of type ZX_OBJ_TYPE_PAGER.
port must be of type ZX_OBJ_TYPE_PORT and have ZX_RIGHT_WRITE.
zx_pager_create_vmo() returns ZX_OK on success, or one of the following error codes on failure.
ZX_ERR_INVALID_ARGS out is an invalid pointer or NULL, or options is any value other than 0 or ZX_VMO_NON_RESIZABLE.
ZX_ERR_BAD_HANDLE pager or port is not a valid handle.
ZX_ERR_ACCESS_DENIED port does not have ZX_RIGHT_WRITE.
ZX_ERR_WRONG_TYPE pager is not a pager handle or port is not a port handle.
ZX_ERR_OUT_OF_RANGE The requested size is larger than the maximum vmo size.
ZX_ERR_NO_MEMORY Failure due to lack of memory.