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MQUERY(2)		  FreeBSD System Calls Manual		     MQUERY(2)

NAME
     mquery -- provide mapping hints to	applications

SYNOPSIS
     #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(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 re-
     turn 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 MAP_FAILED 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_FIXED was specified	and the	requested memory area
			is unavailable.

     [ENOMEM]		There was not enough memory left after the hint	speci-
			fied.

     [EBADF]		fd is not a valid open file descriptor.

SEE ALSO
     mmap(2)

STANDARDS
     The mquery() function should not be used in portable applications.

HISTORY
     The mquery() function first appeared in OpenBSD 3.4.

FreeBSD	13.0		       January 20, 2021			  FreeBSD 13.0

NAME | SYNOPSIS | DESCRIPTION | RETURN VALUES | ERRORS | SEE ALSO | STANDARDS | HISTORY

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