falcon-raptor 0.4.8

Higher-level semantics over Falcon IL

raptor is a higher-level il over falcon il


Unknown calls and trashed variables

When raptor detects a call, it sets the trashed variables according to the calling convention. This allows the constants-propagation analysis to propagate certain variables across the call, which is required for recovering future calls.

Imagine in MIPS we save the $gp register on the stack. To determine the locations of functions, we load $gp from the stack, add an offset to it, and load a function pointer from that address into $t9. We then branch to $t9. If we have several calls in a loop, and set all variables to Top after unknown function calls, the stack variable from which $gp is read will become Top, and we will fail to further propagate constants and resolve function calls.

Certain pre-defined functions

Some functions, such as printf/sprintf, take a variable number of arguments. In these cases, 8 arguments are assumed. If more arguments are passed to these functions, this would be a source of unsoundness.