[sanitizers] Add ASAN support for AArch64 42-bit VMA

[zatrazz]

Summary

This patch adds support for asan on aarch64-linux with 42-bit VMA
(current default config for 64K pagesize kernels). The support is
enabled by defining the SANITIZER_AARCH64_VMA to 42 at build time
for both clang/llvm and compiler-rt. The default VMA is 39 bits.

The patch is sent along with a compiler-rt one to enable the same
functionality for aarch64. The same compiler flag is used.

[rengolin]

lib/Transforms/Instrumentation/AddressSanitizer.cpp

87

#elif defined SANITIZER_AARCH64_VMA
#error "Srsly?"
#endif

[zatrazz]

Updated patch with missing default VMA value.

[rengolin]

lib/Transforms/Instrumentation/AddressSanitizer.cpp

67

Same comment as in the RT side: make sure that, if the value is defined, it is sane.

[zatrazz]

Updated patch based on comments:

• Add failsafe check for invalid SANITIZER_AARCH64_VMA values.

[rengolin]

LGTM, with an additional "(unsupported)" comment after 48.

lib/Transforms/Instrumentation/AddressSanitizer.cpp

 #include <algorithm>
 #include <string>
 #include <system_error>
 
 using namespace llvm;
 
 #define DEBUG_TYPE "asan"
 
+// VMA size definition for architecture that support multiple sizes.
+// AArch64 has 3 VMA sizes: 39, 42 and 48.
+#if SANITIZER_AARCH64_VMA != 39 && SANITIZER_AARCH64_VMA != 42
+# error "invalid SANITIZER_AARCH64_VMA size"
+#endif
+#ifndef SANITIZER_AARCH64_VMA
+# define SANITIZER_AARCH64_VMA 39
+#endif
+
 static const uint64_t kDefaultShadowScale = 3;
 static const uint64_t kDefaultShadowOffset32 = 1ULL << 29;
 static const uint64_t kIOSShadowOffset32 = 1ULL << 30;
 static const uint64_t kDefaultShadowOffset64 = 1ULL << 44;
 static const uint64_t kSmallX86_64ShadowOffset = 0x7FFF8000;  // < 2G.
 static const uint64_t kLinuxKasan_ShadowOffset64 = 0xdffffc0000000000;
 static const uint64_t kPPC64_ShadowOffset64 = 1ULL << 41;
 static const uint64_t kMIPS32_ShadowOffset32 = 0x0aaa0000;
 static const uint64_t kMIPS64_ShadowOffset64 = 1ULL << 37;
+#if SANITIZER_AARCH64_VMA == 39
 static const uint64_t kAArch64_ShadowOffset64 = 1ULL << 36;
+#elif SANITIZER_AARCH64_VMA == 42
+static const uint64_t kAArch64_ShadowOffset64 = 1ULL << 39;
+#endif
 static const uint64_t kFreeBSD_ShadowOffset32 = 1ULL << 30;
 static const uint64_t kFreeBSD_ShadowOffset64 = 1ULL << 46;
 static const uint64_t kWindowsShadowOffset32 = 3ULL << 28;
 
 static const size_t kMinStackMallocSize = 1 << 6;   // 64B
 static const size_t kMaxStackMallocSize = 1 << 16;  // 64K
 static const uintptr_t kCurrentStackFrameMagic = 0x41B58AB3;
 static const uintptr_t kRetiredStackFrameMagic = 0x45E0360E;