focal (9) vm_map_find.9freebsd.gz

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.

SEE ALSO

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

AUTHORS

     This manual page was written by Bruce M Simpson <bms@spc.org>.