[PATCH] D35778: Add NetBSD PaX MPROTECT support in allocateMappedMemory

[Kamil Rytarowski via Phabricator via llvm-commits]

krytarowski created this revision.

A user of the Memory::allocateMappedMemory interface
can allocate memory and request additional permission
bits in future. This breaks PaX MPROTECT model on NetBSD,
as these bits have to be reserved with PROT_MPROTECT().

This has been caught by unittests/Support/MemoryTest
and EnabledWrite tests.

This patch fixes these failures and does not introduce
regressions.

Sponsored by <The NetBSD Foundation>


Repository:
  rL LLVM

https://reviews.llvm.org/D35778

Files:
  lib/Support/Unix/Memory.inc


Index: lib/Support/Unix/Memory.inc
===================================================================
--- lib/Support/Unix/Memory.inc
+++ lib/Support/Unix/Memory.inc
@@ -102,6 +102,11 @@
 
   int Protect = getPosixProtectionFlags(PFlags);
 
+#if defined(__NetBSD__) && defined(PROT_MPROTECT)
+  // This is required in order to grant additional protection bits
+  Protect |= PROT_MPROTECT(PROT_READ | PROT_WRITE | PROT_EXEC);
+#endif
+
   // Use any near hint and the page size to set a page-aligned starting address
   uintptr_t Start = NearBlock ? reinterpret_cast<uintptr_t>(NearBlock->base()) +
                                       NearBlock->size() : 0;


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