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diff --git a/instrumentation/README.ctx.md b/instrumentation/README.ctx.md deleted file mode 100644 index 335e9921..00000000 --- a/instrumentation/README.ctx.md +++ /dev/null @@ -1,38 +0,0 @@ -# AFL Context Sensitive Branch Coverage - -## What is this? - -This is an LLVM-based implementation of the context sensitive branch coverage. - -Basically every function gets its own ID and, every time when an edge is logged, -all the IDs in the callstack are hashed and combined with the edge transition -hash to augment the classic edge coverage with the information about the -calling context. - -So if both function A and function B call a function C, the coverage -collected in C will be different. - -In math the coverage is collected as follows: -`map[current_location_ID ^ previous_location_ID >> 1 ^ hash_callstack_IDs] += 1` - -The callstack hash is produced XOR-ing the function IDs to avoid explosion with -recursive functions. - -## Usage - -Set the `AFL_LLVM_INSTRUMENT=CTX` or `AFL_LLVM_CTX=1` environment variable. - -It is highly recommended to increase the MAP_SIZE_POW2 definition in -config.h to at least 18 and maybe up to 20 for this as otherwise too -many map collisions occur. - -## Caller Branch Coverage - -If the context sensitive coverage introduces too may collisions and becoming -detrimental, the user can choose to augment edge coverage with just the -called function ID, instead of the entire callstack hash. - -In math the coverage is collected as follows: -`map[current_location_ID ^ previous_location_ID >> 1 ^ previous_callee_ID] += 1` - -Set the `AFL_LLVM_INSTRUMENT=CALLER` or `AFL_LLVM_CALLER=1` environment variable. |