Re: syscall __NR_mmap2

From: Richard B. Johnson (
Date: Tue Jul 08 2003 - 09:40:15 EST

On Tue, 8 Jul 2003, Jamie Lokier wrote:

> Richard B. Johnson wrote:
> > > The offset argument to mmap2 is divided by PAGE_SIZE.
> > > That is the whole point of mmap2 :)
> >
> > Okay. Do you know where that's documented? Nothing in linux/Documentation,
> > and nothing in any headers. Do you have to read the code to find out?
> >
> > So, the address is now the offset in PAGES, not bytes. Seems logical,
> > but there is no clue in any documentation.
> I found this great command which really helps. Only 1337 kernel
> gnurus know about it, now u can be 1 2 :)
> $ man mmap2
> [...]
> The function mmap2 operates in exactly the same way as mmap(2), except
> that the final argument specifies the offset into the file in units of
> the system page size (instead of bytes).
> -- Jamie

Yeah? So the Linux kernel now requires a specific vendor distribution?
Since when?

So, to get the proper documentation of the Linux Kernel, I now
need to purchase a vendor's distribution??? I think not. I think
the sys-calls need to be documented and I think that I have established
proof of that supposition.

Script started on Tue Jul 8 10:35:05 2003
# man mmap2
No manual entry for mmap2
# mmap
# man map

MMAP(2) Linux Programmer's Manual MMAP(2)

       mmap, munmap - map or unmap files or devices into memory

       #include <sys/types.h>
       #include <sys/mman.h>

       caddr_t mmap(caddr_t addr, size_t len, int prot , int
       flags, int fd, off_t offset );
       int munmap(caddr_t addr, size_t len);

       WARNING: This is a BSD man page. Linux 0.99.11 can't map
       files, and can't do other things documented here.

       The mmap function causes the pages starting at addr and
       continuing for at most len bytes to be mapped from the
       object described by fd, starting at byte offset offset.
       If offset or len is not a multiple of the pagesize, the
       mapped region may extend past the specified range.

line 1
# exit

Script done on Tue Jul 8 10:35:29 2003

Dick Johnson
Penguin : Linux version 2.4.20 on an i686 machine (797.90 BogoMips).
Why is the government concerned about the lunatic fringe? Think about it.

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This archive was generated by hypermail 2b29 : Tue Jul 15 2003 - 22:00:27 EST