Requirements

GREASE features a memory model that is capable of detecting many types of common software-related issues, such as double-frees or uninitialized stack reads (see Undefined behavior for details). In addition to the checks that the memory model performs, GREASE users can opt into checking additional requirements that assert properties that are not covered by the memory model. The difference between a memory model check and a requirement is mostly a matter of performance considerations, as most properties require instrumenting GREASE's control flow to insert re-run simulation with extra assertions enabled.

To opt into checking a requirement, pass --req <NAME> one or more times at the command line, where <NAME> is one of the following:

• in-text: Assert that code is never executed from memory that has write permissions. In practice, this amounts to checking that the program counter only contains addresses from certain parts of the binary, such as the @.text@ section or PLT stub addresses.

• no-mprotect: The requirement that code is not self-modifying. In practice, this amounts to checking that a PLT stub named mprotect is never called. A limitation of this approach is that it can only detect calls to mprotect from an external library such as libc. If mprotect is statically linked into the binary, for instance, then this requirement would not detect it.