posix_mem_offset(3p) — Linux manual page

POSIX_MEM_OFFSET(3P)    POSIX Programmer's Manual   POSIX_MEM_OFFSET(3P)

PROLOG

       This manual page is part of the POSIX Programmer's Manual.  The
       Linux implementation of this interface may differ (consult the
       corresponding Linux manual page for details of Linux behavior),
       or the interface may not be implemented on Linux.

NAME

       posix_mem_offset — find offset and length of a mapped typed
       memory block (ADVANCED REALTIME)

SYNOPSIS

       #include <sys/mman.h>

       int posix_mem_offset(const void *restrict addr, size_t len,
           off_t *restrict off, size_t *restrict contig_len,
           int *restrict fildes);

DESCRIPTION

       The posix_mem_offset() function shall return in the variable
       pointed to by off a value that identifies the offset (or
       location), within a memory object, of the memory block currently
       mapped at addr.  The function shall return in the variable
       pointed to by fildes, the descriptor used (via mmap()) to
       establish the mapping which contains addr.  If that descriptor
       was closed since the mapping was established, the returned value
       of fildes shall be -1. The len argument specifies the length of
       the block of the memory object the user wishes the offset for;
       upon return, the value pointed to by contig_len shall equal
       either len, or the length of the largest contiguous block of the
       memory object that is currently mapped to the calling process
       starting at addr, whichever is smaller.

       If the memory object mapped at addr is a typed memory object,
       then if the off and contig_len values obtained by calling
       posix_mem_offset() are used in a call to mmap() with a file
       descriptor that refers to the same memory pool as fildes (either
       through the same port or through a different port), and that was
       opened with neither the POSIX_TYPED_MEM_ALLOCATE nor the
       POSIX_TYPED_MEM_ALLOCATE_CONTIG flag, the typed memory area that
       is mapped shall be exactly the same area that was mapped at addr
       in the address space of the process that called
       posix_mem_offset().

       If the memory object specified by fildes is not a typed memory
       object, then the behavior of this function is implementation-
       defined.

RETURN VALUE

       Upon successful completion, the posix_mem_offset() function shall
       return zero; otherwise, the corresponding error status value
       shall be returned.

ERRORS

       The posix_mem_offset() function shall fail if:

       EACCES The process has not mapped a memory object supported by
              this function at the given address addr.

       This function shall not return an error code of [EINTR].

       The following sections are informative.

EXAMPLES

       None.

APPLICATION USAGE

       None.

RATIONALE

       None.

FUTURE DIRECTIONS

       None.

SEE ALSO

       mmap(3p), posix_typed_mem_open(3p)

       The Base Definitions volume of POSIX.1‐2017, sys_mman.h(0p)

COPYRIGHT

       Portions of this text are reprinted and reproduced in electronic
       form from IEEE Std 1003.1-2017, Standard for Information
       Technology -- Portable Operating System Interface (POSIX), The
       Open Group Base Specifications Issue 7, 2018 Edition, Copyright
       (C) 2018 by the Institute of Electrical and Electronics
       Engineers, Inc and The Open Group.  In the event of any
       discrepancy between this version and the original IEEE and The
       Open Group Standard, the original IEEE and The Open Group
       Standard is the referee document. The original Standard can be
       obtained online at http://www.opengroup.org/unix/online.html .

       Any typographical or formatting errors that appear in this page
       are most likely to have been introduced during the conversion of
       the source files to man page format. To report such errors, see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group               2017              POSIX_MEM_OFFSET(3P)

Pages that refer to this page: sys_mman.h(0p), posix_typed_mem_open(3p)

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