| MQUERY(2) | System Calls Manual | MQUERY(2) |
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:
The mquery() function should not be used
in portable applications.
The mquery() function first appeared in
OpenBSD 3.4.
| July 2, 2014 | OpenBSD-current |