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NAMEvm_map_find - find a free region within a map, and optionally map a vm_object
SYNOPSISIn sys/param.h In vm/vm.h In vm/vm_map.h Ft int Fo vm_map_find Fa vm_map_t map vm_object_t object vm_ooffset_t offset Fa vm_offset_t *addr vm_size_t length vm_offset_t max_addr Fa int find_space vm_prot_t prot vm_prot_t max int cow Fc
DESCRIPTIONThe Fn vm_map_find function attempts to find a free region in the target Fa map , with the given Fa length. If a free region is found, Fn vm_map_find creates a mapping of Fa object via a call to vm_map_insert9.
The arguments Fa offset , Fa prot , Fa max , and Fa cow are passed unchanged to vm_map_insert9 when creating the mapping, if and only if a free region is found.
If Fa 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 Fa 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 Fa max_addr .
The Fa 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_findspace9 is called to locate a free region of the requested length with a starting address at or above Fa *addr . The following strategies are supported:
- The mapping will only succeed if there is a free region of the requested length at the given address Fa *addr .
- The mapping will succeed as long as there is a free region.
- The mapping will succeed as long as there is a free region that begins on a superpage boundary. If Fa 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.
- The mapping will succeed as long as there is a free region. However, if Fa 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 (Fa n )
- The mapping will succeed as long as there is a free region that aligns on a 2^ Fa n boundary.
IMPLEMENTATION NOTESThis function acquires a lock on Fa map by calling vm_map_lock9, and holds it until the function returns.
The search for a free region is defined to be first-fit, from the address Fa addr onwards.