Messages in this thread | | | Date | Wed, 28 Aug 2002 12:11:30 +0000 | From | Pavel Machek <> | Subject | Re: [PATCH 1 / ...] i386 dynamic fixup/self modifying code |
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Hi!
> This patch implements a system that modifies the kernel code at runtime > depending on CPU features and SMPness.
Nice!
> This patch requires the is_smp() patch I posted earlier and also > requires the new CPU selection code and the code that actually uses > both. > This code already exists, but needs a few adjustments so it may not > arrive immediately. > > The code is invoked in the following ways: > * Undefined exception handler: this is used to replace > unsupported instructions with supported ones. Used for invlpg > -> flushall, prefetchnta -> prefetch -> nop, *fence -> lock > addl 0, (%esp), movntq -> movq > * Int3 handler: this is used when a 1 byte opcode is desired. > This is controlled by a config option so that debuggers and > kprobe won't break. Used for lock/nop and APIC write
Why not do *everything* using int3 handler? It should simplify your code.
Hooking on 'unknown instruction' should not be really neccessary if you replace all invlpgs (etc) with 0xcc... Pavel > Unfortunately with this patch executing invalid code will cause the > processor to enter an infinite exception loop rather than panic. Fixing > this is not trivial for SMP+preempt so it's not done at the moment.
Using 0xcc for everything should fix that, right?
-- Philips Velo 1: 1"x4"x8", 300gram, 60, 12MB, 40bogomips, linux, mutt, details at http://atrey.karlin.mff.cuni.cz/~pavel/velo/index.html.
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