SRAM Fault Injection

[seldridge]

Following on from a discussion with @nandhinic, We need the ability to inject into SRAMs. There are two working examples of how this should work:

1. A shadow SRAM that stores a bit flip mask. On a read, you read one word from the normal SRAM and one word from the shadow SRAM and xor them together.
2. (1) augmented with a probability. This adds one configurable register that stores a bit flip probability. On an SRAM read, this determines the probability of a bit flip. Note: this overlays a uniform probability across the entire SRAM.

At this point, pre-bit IID probabilities are possibly desirable, but very expensive. This, like with the existing LFSR injector requires one word storing a probability for each bit flip. If the probabilities are stored as 32-bit integers, then this would mean a 32x increase in area.