vm_map_find9
Find a free region within a map, and optionally map a vm_object
Usage
#include <sys/param.h>
#include <vm/vm.h>
#include <vm/vm_map.h>
int
vm_map_find(vm_map_t map, vm_object_t object, vm_ooffset_t offset, vm_offset_t *addr, vm_size_t length, vm_offset_t max_addr, int find_space, vm_prot_t prot, vm_prot_t max, int cow);
Overview
The vm_map_find() function attempts to find a free region in the target map, with the given length. If a free region is found, vm_map_find() creates a mapping of object via a call to vm_map_insert(9).
The arguments offset, prot, max, and cow are passed unchanged to vm_map_insert(9) when creating the mapping, if and only if a free region is found.
If object is non-NULL, the reference count on the object must be incremented by the caller before calling this function to account for the new entry.
If max_addr is non-zero, it specifies an upper bound on the mapping. The mapping will only succeed if a free region can be found that resides entirely below max_addr.
The find_space argument specifies the strategy to use when searching for a free region of the requested length. For all values other than VMFS_NO_SPACE, vm_map_findspace(9) is called to locate a free region of the requested length with a starting address at or above *addr. The following strategies are supported:
- VMFS_NO_SPACE
-
The mapping will only succeed if there is a free region of the requested length at the given address *addr.
- VMFS_ANY_SPACE
-
The mapping will succeed as long as there is a free region.
- VMFS_SUPER_SPACE
-
The mapping will succeed as long as there is a free region that begins on a superpage boundary. If object is non-NULL and is already backed by superpages, then the mapping will require a free region that aligns relative to the existing superpages rather than one beginning on a superpage boundary.
- VMFS_OPTIMAL_SPACE
-
The mapping will succeed as long as there is a free region. However, if object is non-NULL and is already backed by superpages, this strategy will attempt to find a free region aligned relative to the existing superpages.
- VMFS_ALIGNED_SPACE(n)
-
The mapping will succeed as long as there is a free region that aligns on a 2^n boundary.
Implementation notes
This function acquires a lock on map by calling vm_map_lock(9), and holds it until the function returns.
The search for a free region is defined to be first-fit, from the address addr onwards.
Return values
The vm_map_find() function returns KERN_SUCCESS if the mapping was successfully created. If space could not be found or find_space was VMFS_NO_SPACE and the given address, addr, was already mapped, KERN_NO_SPACE will be returned. If the discovered range turned out to be bogus, KERN_INVALID_ADDRESS will be returned.
Releases
54 releases since FreeBSD 5.2-RELEASE; the text changed 34 times.