--- name: "contigmalloc" section: "9" platform: "linux" package: "freebsd-manpages" version: "6.0-5" release: "Debian 4.0 (Etch)" platforms: ["linux", "freebsd"] url: "https://new.carta.tech/contigmalloc" --- # contigmalloc(9) manage contiguous kernel physical memory ## NAME **contigmalloc**, **contigfree** – manage contiguous kernel physical memory ## SYNOPSIS **#include \** **#include \** *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 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**(*Ns*, *'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 memory 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)](/malloc/9.md), [memguard(9)](/memguard/9.md)