Re: syscall __NR_mmap2

From: Richard B. Johnson (
Date: Tue Jul 08 2003 - 06:56:49 EST

On Mon, 7 Jul 2003, Ulrich Drepper wrote:

> Hash: SHA1
> Richard B. Johnson wrote:
> > write(1, "Addr = 000b8000\n", 16) = 16
> > open("/dev/mem", O_RDWR) = 3
> > mmap2(0xb8000, 8192, PROT_READ|PROT_WRITE, MAP_SHARED|MAP_FIXED, 3, 0xb8000) = 0xb8000
> mmap64() (and if you compile glibc with an adequate minimal kernel
> requirement mmap as well) is implemented using mmap2. It works nicely.
> Admittedly, I haven't used the stock 2.4 kernel. And I also haven't
> used /dev/mem. But at least for the first part I would expect to see
> problem reports since the code is used and glibc wouldn't work.
> In your code, assuming this is x86, do you really want to read the
> memory starting at address 0xb8000000? This is what your code does. I
> don't know enough about the kernel memory layout to say whether
> something is supposed to be there or not.

Yes. Thanks. There is no known documentation that states that
the address to the function is in PAGES. Certainly, this will
work once I use pages instead of bytes.

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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