[Lldb-commits] [PATCH] D129489: [lldb][AArch64] Add support for memory tags in core files

[David Spickett via Phabricator via lldb-commits]

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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 <https://reviews.llvm.org/D129487>


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D129489

Files:
  lldb/include/lldb/Target/Process.h
  lldb/source/Plugins/Process/elf-core/ProcessElfCore.cpp
  lldb/source/Plugins/Process/elf-core/ProcessElfCore.h
  lldb/test/API/linux/aarch64/mte_core_file/TestAArch64LinuxMTEMemoryTagCoreFile.py
  lldb/test/API/linux/aarch64/mte_core_file/core.mte
  lldb/test/API/linux/aarch64/mte_core_file/core.nomte
  lldb/test/API/linux/aarch64/mte_core_file/main.c
  llvm/include/llvm/BinaryFormat/ELF.h

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