mquery —
provide mapping hints to applications
#include
<sys/mman.h>
void *
mquery(
void
*addr,
size_t
len,
int
prot,
int
flags,
int
fd,
off_t
offset);
The
mquery() system call checks the existing
memory mappings of a process and returns hints to the caller about where to
put a memory mapping. This hint can be later used when performing memory
mappings with the
mmap(2) system
call with
MAP_FIXED in the flags. The
addr argument should be a memory location
that which the caller specifies the preferred address. The
size argument specifies the requested size of
the memory area the caller is looking for. The
fd and
off
arguments specify the file that will be mapped and the offset in it, this is
the same as the corresponding arguments to
mmap(2).
The behavior of the function depends on the
flags argument. If set to
MAP_FIXED the pointer
addr is used as a fixed hint and
mquery() will return
MAP_FAILED and set
errno to
ENOMEM if there is not
size bytes free after that address. Otherwise
it will return the hint addr. If no flags are set
mquery() will use
addr as a starting point in memory and will
search forward to find a memory area with
size bytes free and that will be suitable for
creating a mapping for the file and offset specified in the
fd and
off
arguments. When no such area can be found
mquery() will return and set
errno to indicate the error.
When a memory range satisfying the request is found
mquery() returns the available address.
Otherwise,
MAP_FAILED is returned and
errno is set to indicate the error.
mquery() will fail if:
-
-
- [
EINVAL]
MAP_FIXED
was specified and the requested memory area is unavailable.-
-
- [
ENOMEM]
- There was not enough memory left after the hint specified.
-
-
- [
EBADF]
- fd is not a valid open file
descriptor.
mmap(2)
The
mquery() function should not be used in
portable applications.
The
mquery() function first appeared in
OpenBSD 3.4.
![[OpenBSD]](/openbsd.gif){kind=small}