contigmalloc(9)

NAME

contigmalloc, contigfree - manage contiguous kernel physical

memory

SYNOPSIS

#include <sys/types.h>
#include <sys/malloc.h>
void *
contigmalloc(unsigned  long  size, struct malloc_type *type,
int flags,
        vm_paddr_t  low,  vm_paddr_t  high,  unsigned   long
alignment,
        unsigned long boundary);
void
contigfree(void    *addr,   unsigned   long   size,   struct
malloc_type *type);

DESCRIPTION

The contigmalloc() function allocates size bytes of contigu

ous physical
memory that is aligned to alignment bytes, and which does

not cross a
boundary of boundary bytes. If successful, the allocation

will reside
between physical addresses low and high. The returned

pointer points to
a wired kernel virtual address range of size bytes allocated

from the
kernel virtual address (KVA) map.

The flags parameter modifies contigmalloc()'s behaviour as

follows:

M_ZERO Causes the allocated physical memory to be zero

filled.
Other flags (if present) are ignored.

The contigfree() function deallocates memory allocated by a

previous call
to contigmalloc().

IMPLEMENTATION NOTES

The contigmalloc() function does not sleep waiting for memo

ry resources
to be freed up, but instead scans available physical memory

a small number of times for a suitably sized free address range before

giving up.
Memory allocation is done on a first-fit basis, starting

from the top of
the provided address range.

RETURN VALUES

The contigmalloc() function returns a kernel virtual address

if allocation succeeds, or NULL otherwise.

EXAMPLES

void *p;
p = contigmalloc(8192, M_DEVBUF, M_ZERO, 0, (1L << 22),

32 * 1024, 1024 * 1024);

Ask for 8192 bytes of zero-filled memory residing between

physical
address 0 and 4194303 inclusive, aligned to a 32K boundary

and not crossing a 1M address boundary.

DIAGNOSTICS

The contigmalloc() function will panic if size is zero, or

if alignment
or boundary is not a power of two.

SEE ALSO

malloc(9), memguard(9)

BSD August 10, 2004

BSD