Linking a L4 library with a L4Linux app?
fm3 at os.inf.tu-dresden.de
Thu Feb 24 16:32:21 CET 2005
On Thursday 24 February 2005 15:26, Leon Brits wrote:
> Thanks - It works!!!
> > But be aware that, as
> > Adam said, the Linux server is not aware of memory from external data-
> > spaces. So read/write syscalls don't work with this memory. To use these
> So as long as only my Linux app/kernel module accesses the data all is
> fine but to make it available to another Linux app I need to copy it to
> Linux allocated memory. Is this correct?
No. As long as your Linux application accesses the data, all is fine.
> > you had to use double buffering.
> What is double buffering? [The last time I heard this term was with
> graphics device drivers]
Do NOT try to this:
- create a dataspace
- attach it with l4rm_attach from emul_l4rm.c, you get address ADDR
- read(..., ADDR, ...)
because the Linux kernel is located in a separate address space and
it does not _see_ that memory. If you try this you will only get
Double buffering is this:
static char buf[...];
len = read(..., buf, ...);
/* make sure that len <= sizeof(buf)
memcpy(ADDR, buf, len);
## Dept. of Computer Science, Dresden University of Technology, Germany ##
## http://os.inf.tu-dresden.de/~fm3 ##
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