This teaches ProcessElfCore to recognise the MTE tag segments.
https://www.kernel.org/doc/html/latest/arm64/memory-tagging-extension.html#core-dump-support
These segments contain all the tags for a matching memory segment
which will have the same size in virtual address terms. In real terms
it's 2 tags per byte so the data in the segment is much smaller.
Since MTE is the only tag type supported I have hardcoded some
things to those values. We could and should support more formats
as they appear but doing so now would leave code untested until that
happens.
A few things to note:
* /proc/pid/smaps is not in the core file, only the details you have
in "maps". Meaning we mark a region tagged only if it has a tag segment.
* A core file supports memory tagging if it has at least 1 memory
tag segment, there is no other flag we can check to tell if memory
tagging was enabled. (unlike a live process that can support memory
tagging even if there are currently no tagged memory regions)
Tests have been added at the commands level for a core file with
mte and without.
There is a lot of overlap between the "memory tag read" tests here and the unit tests for
MemoryTagManagerAArch64MTE::UnpackTagsFromCoreFileSegment, but I think it's
worth keeping to check ProcessElfCore doesn't cause an assert.
Depends on D129487
Reviewed By: omjavaid
Differential Revision: https://reviews.llvm.org/D129489
2f9fa9ef53