[Tsan] Fix guessing data range on FreeBSD

[dvyukov]

LGTM

Closed by commit rL220672 (authored by vkutuzov).

lib/tsan/rtl/tsan_platform_linux.cc

 //===-- tsan_platform_linux.cc --------------------------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 //
 // This file is a part of ThreadSanitizer (TSan), a race detector.
 //
-// Linux-specific code.
+// Linux- and FreeBSD-specific code.
 //===----------------------------------------------------------------------===//
 
 
 #include "sanitizer_common/sanitizer_platform.h"
 #if SANITIZER_LINUX || SANITIZER_FREEBSD
 
 #include "sanitizer_common/sanitizer_common.h"
 #include "sanitizer_common/sanitizer_libc.h"
#endif
 
   MapRodata();
 }
 
 static void InitDataSeg() {
   MemoryMappingLayout proc_maps(true);
   uptr start, end, offset;
   char name[128];
+#if SANITIZER_FREEBSD
+  // On FreeBSD BSS is usually the last block allocated within the
+  // low range and heap is the last block allocated within the range
+  // 0x800000000-0x8ffffffff.
+  while (proc_maps.Next(&start, &end, &offset, name, ARRAY_SIZE(name),
+                        /*protection*/ 0)) {
+    DPrintf("%p-%p %p %s\n", start, end, offset, name);
+    if ((start & 0xffff00000000ULL) == 0 && (end & 0xffff00000000ULL) == 0 &&
+        name[0] == '\0') {
+      g_data_start = start;
+      g_data_end = end;
+    }
+  }
+#else
   bool prev_is_data = false;
   while (proc_maps.Next(&start, &end, &offset, name, ARRAY_SIZE(name),
                         /*protection*/ 0)) {
     DPrintf("%p-%p %p %s\n", start, end, offset, name);
     bool is_data = offset != 0 && name[0] != 0;
     // BSS may get merged with [heap] in /proc/self/maps. This is not very
     // reliable.
     bool is_bss = offset == 0 &&
       (name[0] == 0 || internal_strcmp(name, "[heap]") == 0) && prev_is_data;
     if (g_data_start == 0 && is_data)
       g_data_start = start;
     if (is_bss)
       g_data_end = end;
     prev_is_data = is_data;
   }
+#endif
   DPrintf("guessed data_start=%p data_end=%p\n",  g_data_start, g_data_end);
   CHECK_LT(g_data_start, g_data_end);
   CHECK_GE((uptr)&g_data_start, g_data_start);
   CHECK_LT((uptr)&g_data_start, g_data_end);
 }
 
 static void CheckAndProtect() {
   // Ensure that the binary is indeed compiled with -pie.
int call_pthread_cancel_with_cleanup(int(*fn)(void *c, void *m,
   res = fn(c, m, abstime);
   pthread_cleanup_pop(0);
   return res;
 }
 #endif
 
 }  // namespace __tsan
 
-#endif  // SANITIZER_LINUX
+#endif  // SANITIZER_LINUX || SANITIZER_FREEBSD