NAME
uvm_km —
raw kernel memory or address space
allocator
SYNOPSIS
#include
<sys/param.h>
#include <uvm/uvm.h>
vaddr_t
uvm_km_alloc(struct
vm_map *map, vsize_t
size, vsize_t
align, uvm_flag_t
flags);
void
uvm_km_free(struct
vm_map *map, vaddr_t
addr, vsize_t size,
uvm_flag_t flags);
struct vm_map *
uvm_km_suballoc(struct
vm_map *map, vaddr_t
*min, vaddr_t *max,
vsize_t size,
int flags,
bool fixed,
struct vm_map
*submap);
DESCRIPTION
The UVM facility for allocation of kernel memory or address space in pages. Both wired and pageable memory can be allocated by this facility, as well as kernel address space. Note that this is a raw allocator. For general purpose memory allocation, kmem(9) interface should be used.FUNCTIONS
uvm_km_alloc()
allocates a contiguous range of size bytes of kernel
memory in map map and returns the virtual address of
the range, or returns zero on failure. The first address of the allocated
memory range will be aligned according to the align
argument (specify 0 if no alignment is necessary). The alignment must be a
multiple of page size. The flags is a bitwise
inclusive OR of the allocation type and operation flags.
The allocation type should be one of:
- UVM_KMF_WIRED
- Wired memory.
- UVM_KMF_PAGEABLE
- Demand-paged zero-filled memory.
- UVM_KMF_VAONLY
- Virtual address only. No physical pages are mapped in the allocated region. If necessary, it is the caller's responsibility to enter page mappings. It is also the caller's responsibility to clean up the mappings before freeing the address range.
The following operation flags are available:
- UVM_KMF_CANFAIL
- Can fail even if
UVM_KMF_NOWAITis not specified andUVM_KMF_WAITVAis specified. - UVM_KMF_ZERO
- Request zero-filled memory. Only supported for
UVM_KMF_WIRED. Should not be used with other types. - UVM_KMF_EXEC
- Request memory with executable rights.
- UVM_KMF_TRYLOCK
- Fail if cannot lock the map without sleeping.
- UVM_KMF_NOWAIT
- Fail immediately if no memory is available.
- UVM_KMF_WAITVA
- Sleep to wait for the virtual address resources if needed.
If neither
UVM_KMF_NOWAIT nor
UVM_KMF_CANFAIL are specified and
UVM_KMF_WAITVA is specified,
uvm_km_alloc()
will never fail, but rather sleep indefinitely until the allocation
succeeds.
Pageability of the pages allocated with
UVM_KMF_PAGEABLE can be changed by
uvm_map_pageable().
In that case, the entire range must be changed atomically. Changing a part
of the range is not supported.
uvm_km_free()
frees the memory range allocated by uvm_km_alloc().
addr must be an address returned by
uvm_km_alloc(). map and
size must be the same as the ones used for the
corresponding uvm_km_alloc().
flags must be the allocation type used for the
corresponding uvm_km_alloc(). Note that
uvm_km_free() is the only way to free memory ranges
allocated by uvm_km_alloc().
uvm_unmap()
must not be used.
uvm_km_suballoc()
allocates submap from map, creating a new map if
submap is NULL. The addresses
of the submap can be specified explicitly by setting the
fixed argument to true, which causes the
min argument to specify the beginning of the address
in the submap. If fixed is false, any address of size
size will be allocated from map
and the start and end addresses returned in min and
max. The flags are used to
initialize the created submap. The following flags can be set:
- VM_MAP_PAGEABLE
- Entries in the map may be paged out.
- VM_MAP_INTRSAFE
- Map should be interrupt-safe.
- VM_MAP_TOPDOWN
- A top-down mapping should be arranged.
SEE ALSO
kmem(9), pmap(9), pool_cache(9), uvm(9), uvm_map(9), vmem(9)
HISTORY
UVM and uvm_km first appeared in
NetBSD 1.4.