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NAMEmremap - re-map a virtual memory address
DESCRIPTIONfBmremapfR expands (or shrinks) an existing memory mapping, potentially moving it at the same time (controlled by the fIflagsfR argument and the available virtual address space).
fIold_addressfR is the old address of the virtual memory block that you want to expand (or shrink). Note that fIold_addressfR has to be page aligned. fIold_sizefR is the old size of the virtual memory block. fInew_sizefR is the requested size of the virtual memory block after the resize.
The fIflagsfR argument is a bitmap of flags.
In Linux the memory is divided into pages. A user process has (one or) several linear virtual memory segments. Each virtual memory segment has one or more mappings to real memory pages (in the page table). Each virtual memory segment has its own protection (access rights), which may cause a segmentation violation if the memory is accessed incorrectly (e.g., writing to a read-only segment). Accessing virtual memory outside of the segments will also cause a segmentation violation.
fBmremapfR uses the Linux page table scheme. fBmremapfR changes the mapping between virtual addresses and memory pages. This can be used to implement a very efficient fBreallocfR.
RETURN VALUEOn success fBmremapfR returns a pointer to the new virtual memory area. On error, the value MAP_FAILED (that is, (void *) -1) is returned, and fIerrnofR is set appropriately.
NOTESWith current glibc includes, in order to get the definition of MREMAP_MAYMOVE, you need to define _GNU_SOURCE before including <sys/mman.h>.
CONFORMING TOThis call is Linux-specific, and should not be used in programs intended to be portable. 4.2BSD had a (never actually implemented) mremap(2) call with completely different semantics.
SEE ALSOgetpagesize(2), realloc(3), malloc(3), brk(2), sbrk(2), mmap(2) Your favorite OS text book for more information on paged memory. (fIModern Operating SystemsfR by Andrew S. Tannenbaum, fIInside LinuxfR by Randolf Bentson, fIThe Design of the UNIX Operating SystemfR by Maurice J. Bach.)