NAME
mquery —
provide mapping hints to
applications
SYNOPSIS
#include
<sys/types.h>
#include <sys/mman.h>
void *
mquery(void
*addr, size_t len,
int prot,
int flags,
int fd,
off_t offset);
DESCRIPTION
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()
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().
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.
RETURN VALUES
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.
ERRORS
mquery() will fail if:
- [
EINVAL] MAP_FIXEDwas 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.
SEE ALSO
STANDARDS
The mquery() function should not be used
in portable applications.
HISTORY
The mquery() function first appeared in
OpenBSD 3.4.