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,
vm_paddr_t boundary);
void
contigfree(
void
*addr,
unsigned long size,
struct malloc_type *type);
DESCRIPTION¶
The
contigmalloc() function allocates
size bytes of contiguous 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.
M_NOWAIT- Causes
contigmalloc() to return
NULL if the request cannot be
immediately fulfilled due to resource shortage.
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 memory resources to be freed up, but instead actively reclaims
pages before giving up. However, unless
M_NOWAIT is specified, it may select a page
for reclamation that must first be written to backing storage, causing it to
sleep.
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)
