x86/modules: Add call patching

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As for the builtins create call thunks and patch the call sites to call the
thunk on Intel SKL CPUs for retbleed mitigation.

Note, that module init functions are ignored for sake of simplicity because
loading modules is not something which is done in high frequent loops and
the attacker has not really a handle on when this happens in order to
launch a matching attack. The depth tracking will still work for calls into
the builtins and because the call is not accounted it will underflow faster
and overstuff, but that's mitigated by the saturating counter and the side
effect is only temporary.

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20220915111147.575673066@infradead.org

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Thomas Gleixner 2022-09-15 13:11:24 +02:00 • committed by Peter Zijlstra

parent e81dc127ef

commit eaf44c816e

3 changed files with 43 additions and 1 deletions

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5

arch/x86/include/asm/alternative.h

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19

arch/x86/kernel/callthunks.c

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20

arch/x86/kernel/module.c

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