Generate 3d probe-and-validate wrapper functions

[tahina-pro]

With this PR, 3D can now generate, for a given type T, an unverified wrapper calling a probing function Probe on an address a and then calling the validator for T on the memory area probed by MyProbe.

If for instance in MyModule.3d the user writes:

extern probe MyProbe

entrypoint probe MyProbe 8
typedef struct _T {
  ... 
} T;

Then EverParse/3D generates into MyModuleWrapper.c and MyModuleWrapper.h, in addition to the ordinary MyModuleCheckT validator wrapper function, a probe-and-validate wrapper function:

boolean MyModuleMyProbeCheckT (EVERPARSE_COPY_BUFFER_T probeDest, UINT64 probeAddr);

This probe-and-validate wrapper function takes:

• a destination buffer, probeDest, that still needs to be provided by the caller
• the address value probeAddr, directly (so no need for an extra “fake input buffer” indirection)

When called, the probe-and-validate wrapper function calls the f probing function and, if probing succeeds, calls the T validator on the probed buffer.

The syntax of the entrypoint probe attribute is:

entrypoint probe probeFunctionName size

where the size argument, giving the number of bytes to probe, is either an integer literal or a global integer variable defined with #define. The value of size must be at most a 32-bit unsigned integer.

[nikswamy]

Thanks Tahina! A few things we discussed:

• Let's make it (length=8), so that it's more explicit and matches the existing probe syntax.
• It would also be nice if instead of a constant or defined symbol, it could also be sizeof(T)
• The name of the wrapper should be MyModule[f]ValidateT, typically this would produce MyModuleProbeAndCopyValidateT
  * [ ] Aside from these cosmetic things, it would be great if the generated .h file only includes the probing version of the entrypoint, since the non-probing one would be unsafe to call with a user pointer. Reading a bit more, I see there are legitimate uses where we want to have both entry points, with and without probes. So, let's not change this for now.