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