STACKLEAK Plug-In Being Reattempted For Inclusion In Linux 4.20

Originally attempted for the Linux 4.19 kernel but not merged that cycle was the STACKLEAK GCC plug-in that was ported for the mainline code-base from the Linux GrSecurity patch-set. That plug-in is now trying to get into the Linux 4.20 (or perhaps relabeled as 5.0) kernel.

The STACKLEAK GCC plug-in provides efficient stack content poisoning on system call exits. This functionality can fend off possible attacks around uninitialized stack usage and stack content exposure.

The 4.19 version also advertised support for fending off stack exhaustion / guard-page skipping flaws, but that has been removed with the last of the VLA usage being dropped from the kernel this cycle and thus not making that protection necessary.

The new pull request gets the STACKLEAK support into shape for x86 architectures and ARM64/