garrity@garrity.applicon.UUCP (05/19/87)
Could somebody please point me at a good reference for mmap? Bach doesn't
discuss it. I presume that is because of Bach's SysV leanings. Is mmap
intended as a Berkeley shmat? Thanks in advance.
-- -MPG-
-- Mike Garrity
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-- {amd|bbncca|cbosgd|wjh12|ihnp4|yale}!ima!applicon!garrityguy%gorodish@Sun.COM (Guy Harris) (05/22/87)
> Could somebody please point me at a good reference for mmap? Bach doesn't > discuss it. I presume that is because of Bach's SysV leanings. No, it's probably because Berkeley didn't implement it. SunOS currently implements it only for devices; it's used for mapping things such as frame buffers into your address space. > Is mmap intended as a Berkeley shmat? That's what it would have been, sort of, had it been implemented. It takes a file descriptor and maps whatever that descriptor refers to into your address space. If this is a file, the file is mapped into your address space, so that page faults on addresses in the range mapped by "mmap" cause the page to be read from the file, and if the file is mapped in the appropriate fashion page pushes of those pages cause the data to be written to the file. If this is a device, something related to that device is mapped into your address space; precisely what that is depends on the device. The S5 shared memory IPC calls act on objects that don't exist in the file system and aren't referred to by file descriptors. Guy Harris {ihnp4, decvax, seismo, decwrl, ...}!sun!guy guy@sun.com