Re: Interrupt handling

[Maciej Zenczykowski]

On Thu, 16 Oct 2003, Richard B. Johnson wrote:

> The memory-map idea has security problems, though.
> If the area ever gets unmapped (the user exits), a
> fatal error could occur in kernel mode within the
> ISR. In general, it's always best to allocate an
> interrupt-safe buffer within the driver (module),
> that is guaranteed to persist as long as the driver
> is installed. This ultimately means that a copy
> operation is necessary.
> 
> Memory-to-memory copy is real fast now days. The
> copy_to_user() is just memcpy() with a trap mechanism
> that can save the kernel from a user-induced seg-fault.
> The actual trap is hardware-induced in ix86 machines
> and therefore adds no overhead to the normal copy operation.

Is there any reason why we couldn't via kernel routine let user space 
access read-only certain pages of kernel memory?  I.e. having the 
userspace function call the driver to map into it's (user) address space a 
read-only mapping of the drivers (kernel) private r/w area?
If I'm not mistaken this is doable on x86 hardware isn't it?

Cheers,
MaZe.

-
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/