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Man Pages


Manual Reference Pages  -  VM_MAP_FIND (9)

NAME

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

CONTENTS

Synopsis
Description
Implementation Notes
Return Values
See Also
Authors

SYNOPSIS


.In sys/param.h
.In vm/vm.h
.In vm/vm_map.h int
.Fo 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
.Fc

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.

SEE ALSO

vm_map(9), vm_map_findspace(9), vm_map_insert(9), vm_map_lock(9)

AUTHORS

This manual page was written by
.An Bruce M Simpson Aq bms@spc.org .
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