KMEM(9)                386BSD Kernel Programmer's Manual               KMEM(9)

NAME
     kmem - primary kernel memory / address space management functions

SYNOPSIS
     #include "vm.h"
     #include "kmem.h"
     #include "malloc.h"

     vm_offset_t
     kmemalloc(vm_map_t map, vm_size_t size, int flags)

     void
     kmemfree(vm_map_t map, vm_offset_t addr),vm_size_t size

     vm_map_t
     kmemsuballoc(vm_size_t size, boolean_t pageable)

     vm_offset_t
     kmemmmap(vm_map_t map, vm_offset_t addr, vm_size_t size)

     vm_offset_t
     kmemphys(vm_offset_t kva)

DESCRIPTION
     Kernel program memory in the 386BSD kernel is managed by the "kmem"
     facility, which allows for shared used by kernel threads of portions of
     kernel memory (or address space).  It is an interface to the virtual
     memory system as a way to allocate its resources for application in the
     kernel.

     The kmemalloc() function allocates page-granularity uninitialized space
     for an object whose size is specified by size from the address space or
     subspace specified by map. Either memory or just address space
     reservation can be allocated.  If no resource is available, kmemalloc()
     can optionally wait indefinitely for the resource to become available
     with the M_WAITOK option passed via the flags (note that this allocator
     can be also used from interrupt level without the blocking flag).  Since
     this function is used by the kernel malloc(9) allocator, both share the
     same option flags.

     kmemfree() is called to return the resource to the free pool. Since
     static array elements are consumed with certain maps (kmem_map),
     indefinite allocation is not always possible.

     The kmemsuballoc() function is used to create a subspace map within the
     kernel for independant management. It reserves a portion of the kernel
     address space for sole use by requestors using the allocated subspace map
     as an argument.

     The kmemmmap() function is used to remap a region of the current process
     into the kernel memory (not unlike the mmap(2) system call), allowing
     access to the processes memory region globally. The user address space
     mapped at addr and for length size is mapped into the kernel within the
     address space (or subspace) map.

     The kmemphys() function returns the physical address associated with the
     kva address in the kernel.

RETURN VALUES
     The kmemmalloc() function returns a address of the allocated resource if
     successful; otherwise a null address is returned.  The kmemsuballoc()
     function returns a new map instance as a handle to be used in memory
     allocation from that subspace, otherwise it returns a null value. The
     kmemmmap() function returns an address of where the requested contents
     of a process may be located in the kernel program's address space. The
     kmemphys() function returns the physical address or the null address if
     ther is no page.

SEE ALSO
     malloc(9),  free(9),  mmap(2),  pageout(9)

386BSD Release 1.0              August 29, 1994                              2