A manual page for contigmalloc(9).

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share/man/man9/contigmalloc.9

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+.\"
+.\" Copyright (c) 2004 Joseph Koshy
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+.\" THIS SOFTWARE IS PROVIDED BY JOSEPH KOSHY AND CONTRIBUTORS ``AS IS''
+.\" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
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+.\" $FreeBSD$
+.\"
+.Dd March 4, 2004
+.Dt CONTIGMALLOC 9
+.Os
+.Sh NAME
+.Nm contigmalloc , contigfree
+.Nd manage contiguous kernel physical memory
+.Sh SYNOPSIS
+.In sys/types.h
+.In sys/malloc.h
+.Ft "void *"
+.Fo contigmalloc
+.Fa "unsigned long size"
+.Fa "struct malloc_type *type"
+.Fa "int flags"
+.Fa "vm_paddr_t low"
+.Fa "vm_paddr_t high"
+.Fa "unsigned long alignment"
+.Fa "unsigned long boundary"
+.Fc
+.Ft void
+.Fo contigfree
+.Fa "void *addr"
+.Fa "unsigned long size"
+.Fa "struct malloc_type *type"
+.Fc
+.Sh DESCRIPTION
+The
+.Fn contigmalloc
+function allocates
+.Fa size
+bytes of contiguous physical memory that is aligned to
+.Fa alignment
+bytes, and which does not cross a boundary of
+.Fa boundary
+bytes.
+If successful, the allocation will reside between physical addresses
+.Fa low
+and
+.Fa high .
+The returned pointer points to a wired kernel virtual
+address range of
+.Fa size
+bytes allocated from the kernel virtual address (KVA) map.
+.Pp
+The
+.Fa flags
+parameter modifies
+.Fn contigmalloc Ns 's
+behaviour as follows:
+.Bl -tag -width indent
+.It Dv M_ZERO
+Causes the allocated physical memory to be zero filled.
+.El
+Other flags (if present) are ignored.
+.Pp
+The
+.Fn contigfree
+function deallocates memory allocated by a previous call to
+.Fn contigmalloc .
+.Sh IMPLEMENTATION NOTES
+The
+.Fn 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.
+.Sh RETURN VALUES
+The
+.Fn contigmalloc
+function returns a kernel virtual address if allocation succeeds,
+or
+.Dv NULL
+otherwise.
+.Sh EXAMPLES
+.Bd -literal
+void *p;
+p = contigmalloc(8192, M_DEVBUF, M_ZERO, 0, (1L << 22),
+    32 * 1024, 1024 * 1024);
+.Ed
+.Pp
+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.
+.Sh SEE ALSO
+.Xr malloc 9
+.Sh DIAGNOSTICS
+The
+.Fn contigmalloc
+function will panic if
+.Fa size
+is zero, or if
+.Fa alignment
+or
+.Fa boundary
+is not a power of two.
+.Sh BUGS
+The
+.Fa type
+argument to
+.Fn contigmalloc
+and
+.Fn contigfree
+is ignored.