[PowerPC][msan] Update msan to handle changed memory layouts in newer kernels

[seurer]

Summary

[PowerPC][msan] Update msan to handle changed memory layouts in newer kernels

In more recent Linux kernels (including those with 47 bit VMAs) the layout of
virtual memory for powerpc64 changed causing the memory sanitizer to not
work properly. This patch adjusts a bit mask in the memory sanitizer to work
on the newer kernels while continuing to work on the older ones as well.

This is the non-runtime part of the patch and finishes it. ref: r317802

Tested on several 4.x and 3.x kernel releases.

[nemanjai]

LGTM.
I am far from an expert on this, but the modification seems to make perfect sense. Perhaps @eugenis can have a look as well, but if not, I'd say that we should go ahead with this since:

• It seems to make perfect sense (and shouldn't affect 46 and 45 bit VMA kernels)
• You've tested it on multiple kernels
• It's been up for review for around two weeks
• This is blocking us from running on 47 bit VMA kernels

[eugenis]

Sorry I missed this patch.

[nemanjai]

It appears to me that this was committed in https://reviews.llvm.org/rL318045.
@seurer If I'm wrong about this, please reopen/commit.

lib/Transforms/Instrumentation/MemorySanitizer.cpp

static const MemoryMapParams Linux_MIPS64_MemoryMapParams = {
   0,               // AndMask (not used)
   0x008000000000,  // XorMask
   0,               // ShadowBase (not used)
   0x002000000000,  // OriginBase
 };
 
 // ppc64 Linux
 static const MemoryMapParams Linux_PowerPC64_MemoryMapParams = {
-  0x200000000000,  // AndMask
+  0xE00000000000,  // AndMask
   0x100000000000,  // XorMask
   0x080000000000,  // ShadowBase
   0x1C0000000000,  // OriginBase
 };
 
 // aarch64 Linux
 static const MemoryMapParams Linux_AArch64_MemoryMapParams = {
   0,               // AndMask (not used)