Re: [RFC][PATCH] new timeofday core subsystem (v. A3)

[Russell King]

On Thu, Mar 17, 2005 at 02:44:57PM -0500, Albert Cahalan wrote:
> Does the ARM kernel provide a special page of code for
> apps to execute? If not, then ARM is irrelevant.

No.  However, I was responding to your suggestion that supporting
self modifying code in the kernel is trivial.

> Doesn't ARM always have an MMU? If you have an MMU, then
> it is no problem to have one single page of non-XIP code
> for this purpose.

No.  You also have a big misconception about how we map system memory.
We have 1MB mappings, and replacing 1MB of code/data (which would
equate to half a kernel) would completely negate the whole point of
XIP.

> Supposing that you do support the vsyscall hack and you don't
> have an MMU, you can just place the tiny code fragment on the
> stack (or anywhere else) when an exec is performed.
> 
> So, as far as I can see, ARM is fully capable of supporting this.

<cough>

-- 
Russell King
 Linux kernel    2.6 ARM Linux   - http://www.arm.linux.org.uk/
 maintainer of:  2.6 Serial core
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