| 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 |