[tsan] re-exec when ASLR is enabled for x86_64 as well

[enh]

compiler-rt/lib/tsan/rtl/tsan_platform_linux.cpp

302

do we know the corresponding x86-64 patch?

[pirama]

compiler-rt/lib/tsan/rtl/tsan_platform_linux.cpp

302

https://android.googlesource.com/platform/system/core/+/master/init/security.cpp#100 points to 9e08f57d684a x86: mm: support ARCH_MMAP_RND_BITS as the equivalent for x86.

319

This function seems to be needed only for aarch64 [1]? Add a separate #if guard around this call with the old check #if SANITIZER_LINUX && defined(__aarch64__).

[1] https://github.com/llvm/llvm-project/blob/main/compiler-rt/lib/tsan/rtl/tsan_platform_linux.cpp#L432

[pirama]

compiler-rt/lib/tsan/rtl/tsan_platform_linux.cpp

319

For clarity, I'd duplicate the SANITIZER_LINUX here instead of nesting the pre-processor checks - because the ASLR personality check is unrelated to initializing the longjmp key.

[fmayer]

compiler-rt/lib/tsan/rtl/tsan_platform_linux.cpp

306

nit

[vitalybuka]

compiler-rt/lib/tsan/rtl/tsan_platform_linux.cpp

302

Is this 39-bit VA specific?
Can you please update comment to cover x86

I guess it's android only?
So it should be SANITIZER_ANDROID.

I was recently notoced internal that ASLR is not working on TSAN arm64 linux, and want to undo this reexec

[pirama]

compiler-rt/lib/tsan/rtl/tsan_platform_linux.cpp

302

I was recently notoced internal that ASLR is not working on TSAN arm64 linux, and want to undo this reexec

If I'm reading this correctly, TSAN for arm64-linux doesn't need the re-exec? It's possible the address mappings here are for a different VA address space. Can you confirm if it's ok to relax the re-exec for all linux systems?

[ZijunZhao]

Use SANITIZER_ANDROID in line 293 instead of SANITIZER_LINUX and fix the nit.

compiler-rt/lib/tsan/rtl/tsan_platform_linux.cpp

#if !SANITIZER_GO
 
     if (!AddressSpaceIsUnlimited()) {
       Report("WARNING: Program is run with limited virtual address space,"
              " which wouldn't work with ThreadSanitizer.\n");
       Report("Re-execing with unlimited virtual address space.\n");
       SetAddressSpaceUnlimited();
       reexec = true;
     }
-#if SANITIZER_LINUX && defined(__aarch64__)
+#if SANITIZER_ANDROID && (defined(__aarch64__) || defined(__x86_64__))
     // After patch "arm64: mm: support ARCH_MMAP_RND_BITS." is introduced in
     // linux kernel, the random gap between stack and mapped area is increased
     // from 128M to 36G on 39-bit aarch64. As it is almost impossible to cover
     // this big range, we should disable randomized virtual space on aarch64.
+    // ASLR personality check.
     int old_personality = personality(0xffffffff);
     if (old_personality != -1 && (old_personality & ADDR_NO_RANDOMIZE) == 0) {
       VReport(1, "WARNING: Program is run with randomized virtual address "
               "space, which wouldn't work with ThreadSanitizer.\n"
               "Re-execing with fixed virtual address space.\n");
       CHECK_NE(personality(old_personality | ADDR_NO_RANDOMIZE), -1);
       reexec = true;
     }
+
+#endif
+#if SANITIZER_LINUX && defined(__aarch64__)
     // Initialize the xor key used in {sig}{set,long}jump.
     InitializeLongjmpXorKey();
 #endif
     if (reexec)
       ReExec();
   }
 
   CheckAndProtect();
   InitTlsSize();
 #endif  // !SANITIZER_GO