[PATCH] D91615: [sanitizer_common] Don't try to unmap unaligned memory

[Rainer Orth via Phabricator via llvm-commits]

ro created this revision.
ro added a reviewer: vitalybuka.
ro added a project: Sanitizers.
Herald added subscribers: Sanitizers, fedor.sergeev, jyknight.
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Enabling `sanitizer_common` tests on Solaris (D91606 <https://reviews.llvm.org/D91606>) and SPARC (D91608 <https://reviews.llvm.org/D91608>) uncovered a sparcv9 failure

  SanitizerCommon-Unit :: ./Sanitizer-sparcv9-Test/CompactRingBuffer.int64

like this:

  [ RUN      ] CompactRingBuffer.int64
  ==24576==ERROR: SanitizerTool failed to deallocate 0x2000 (8192) bytes at address 0xffffffff7f59b000
  ==24576==Sanitizer CHECK failed: /vol/llvm/src/llvm-project/local/compiler-rt/lib/sanitizer_common/sanitizer_posix.cpp:61 (("unable to unmap" && 0)) != (0) (0, 0)

The problemis that the original allocation via `MmapAlignedOrDieOnFatalError` is for 4 kB, but the Solaris/sparcv9 pagesize is 8 kB.  So the initial allocation is for 12 kB, rounded to a multiple of the pagesize.  Afterwards, the unneeded rest is unmapped again, but this fails since the address is not pagesize-aligned.

This patch avoids this by only unmapping correctly aligned memory.

The patch still `FAIL`s, but for a different reason, and this part of the issue is generic.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D91615

Files:
  compiler-rt/lib/sanitizer_common/sanitizer_posix.cpp


Index: compiler-rt/lib/sanitizer_common/sanitizer_posix.cpp
===================================================================
--- compiler-rt/lib/sanitizer_common/sanitizer_posix.cpp
+++ compiler-rt/lib/sanitizer_common/sanitizer_posix.cpp
@@ -92,10 +92,11 @@
   uptr res = map_res;
   if (!IsAligned(res, alignment)) {
     res = (map_res + alignment - 1) & ~(alignment - 1);
-    UnmapOrDie((void*)map_res, res - map_res);
+    if (IsAligned(map_res, GetPageSizeCached()))
+      UnmapOrDie((void*)map_res, res - map_res);
   }
   uptr end = res + size;
-  if (end != map_end)
+  if (end != map_end && IsAligned(end, GetPageSizeCached()))
     UnmapOrDie((void*)end, map_end - end);
   return (void*)res;
 }


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