Ubuntu Manpage: vm_map_find — find a free region within a map, and optionally map a vm

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NAME

     vm_map_find — find a free region within a map, and optionally map a vm_object

SYNOPSIS

     #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);

DESCRIPTION

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.

AUTHORS