John F.X. Galea

We also have #2130 pending, which we will address once Umbra tests are in order.

The shadow address of a shadow address is considered as an invalid address in Umbra. However, Umbra (on 64-bit) has checks that ensure the shadow of an app region does...

This is actually a pretty interesting and useful feature!

> @johnfxgalea -- this assumption is seeming untenable, unless we require running with ASLR disabled or sthg extreme, or we set the libdynamorio.so base to cover this gap, or other...

The additional benefit of the above suggestion is that Ubmra's implementation is shared for 32-bit and 64-bit. Again, keeping in mind the cost of runtime performance.

Another option is to keep the current implementation for 64-bit, and find another possible gap that is more suitable, i.e., it does not touch 0x7fff'ff4-0x7fff'ff8 at all, (this also requires...

Blocked by https://github.com/DynamoRIO/drmemory/pull/2310

> Blocked by #2310 Added the fixes to this PR after all.

@derekbruening Not sure if you are aware that this PR is ready for review. No rush though as I am busy with work, so feel free to look at it...

Many thanks for the review. I have tested many of the features in my tools' code-bases. However, I'll write some quick sample tools and include them in this PR.