[compiler-rt] [asan] Enable DFSan for AArch64/42-bit VMA

[zatrazz]

Summary

This patch adds support for dfsan 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.

[rengolin]

lib/dfsan/dfsan.cc

132

This looks wrong with the table above?

[zatrazz]

lib/dfsan/dfsan.cc

132

In fact is the contraty, the comment needs update. I'll change it.

[rengolin]

lib/dfsan/dfsan.h

52

Do you need the same trick with defining it to 39 when undef? Or is this getting from the same header as the other sans?

[zatrazz]

The SANITIZER_AARCH64_VMA is defined in a common header (lib/sanitizer_common/sanitizer_platform.h) used by all sanitizers.

[rengolin]

LGTM after updating the comment. Thanks!

lib/dfsan/dfsan.cc

132

makes sense, this is 3 bits to the left. :)

lib/dfsan/dfsan.h

 void InitializeInterceptors();
 
 inline dfsan_label *shadow_for(void *ptr) {
 #if defined(__x86_64__)
   return (dfsan_label *) ((((uptr) ptr) & ~0x700000000000) << 1);
 #elif defined(__mips64)
   return (dfsan_label *) ((((uptr) ptr) & ~0xF000000000) << 1);
 #elif defined(__aarch64__)
+# if SANITIZER_AARCH64_VMA == 39
   return (dfsan_label *) ((((uptr) ptr) & ~0x7800000000) << 1);
+# elif SANITIZER_AARCH64_VMA == 42
+  return (dfsan_label *) ((((uptr) ptr) & ~0x3c000000000) << 1);
+# endif
 #endif
 }
 
 inline const dfsan_label *shadow_for(const void *ptr) {
   return shadow_for(const_cast<void *>(ptr));
 }
 
 struct Flags {

lib/dfsan/dfsan.cc

 // +--------------------+ 0x1200000000 (kUnusedAddr)
 // |    union table     |
 // +--------------------+ 0x1000000000 (kUnionTableAddr)
 // |   shadow memory    |
 // +--------------------+ 0x0000010000 (kShadowAddr)
 // | reserved by kernel |
 // +--------------------+ 0x0000000000
 
+// On Linux/AArch64 (42-bit VMA), memory is laid out as follow:
+//
+// +--------------------+ 0x40000000000 (top of memory)
+// | application memory |
+// +--------------------+ 0x3ff00008000 (kAppAddr)
+// |                    |
+// |       unused       |
+// |                    |
+// +--------------------+ 0x1200000000 (kUnusedAddr)
+// |    union table     |
+// +--------------------+ 0x1000000000 (kUnionTableAddr)
+// |   shadow memory    |
+// +--------------------+ 0x0000010000 (kShadowAddr)
+// | reserved by kernel |
+// +--------------------+ 0x0000000000
+
 typedef atomic_dfsan_label dfsan_union_table_t[kNumLabels][kNumLabels];
 
 #if defined(__x86_64__)
 static const uptr kShadowAddr = 0x10000;
 static const uptr kUnionTableAddr = 0x200000000000;
 static const uptr kUnusedAddr = kUnionTableAddr + sizeof(dfsan_union_table_t);
 static const uptr kAppAddr = 0x700000008000;
 #elif defined(__mips64)
 static const uptr kShadowAddr = 0x10000;
 static const uptr kUnionTableAddr = 0x2000000000;
 static const uptr kUnusedAddr = kUnionTableAddr + sizeof(dfsan_union_table_t);
 static const uptr kAppAddr = 0xF000008000;
 #elif defined(__aarch64__)
 static const uptr kShadowAddr = 0x10000;
+# if SANITIZER_AARCH64_VMA == 39
 static const uptr kUnionTableAddr = 0x1000000000;
+# elif SANITIZER_AARCH64_VMA == 42
+static const uptr kUnionTableAddr = 0x8000000000;
+# endif
 static const uptr kUnusedAddr = kUnionTableAddr + sizeof(dfsan_union_table_t);
+# if SANITIZER_AARCH64_VMA == 39
 static const uptr kAppAddr = 0x7000008000;
+# elif SANITIZER_AARCH64_VMA == 42
+static const uptr kAppAddr = 0x3ff00008000;
+# endif
 #else
 # error "DFSan not supported for this platform!"
 #endif
 
 static atomic_dfsan_label *union_table(dfsan_label l1, dfsan_label l2) {
   return &(*(dfsan_union_table_t *) kUnionTableAddr)[l1][l2];
 }