[LSan] Detect dynamic loader by its base address.

Summary:
Relanding D38600, which was reverted due to various PPC bot failures.

If it breaks something again, please provide some pointers to broken
bots, not just revert it, otherwise it's very hard to reason what's
wrong with this commit.

Whenever possible (Linux + glibc 2.16+), detect dynamic loader module by
its base address, not by the module name matching. The current name
matching approach fails on some configurations.

Reviewers: eugenis

Subscribers: kubamracek, llvm-commits

Differential Revision: https://reviews.llvm.org/D39275

git-svn-id: https://llvm.org/svn/llvm-project/compiler-rt/trunk@317512 91177308-0d34-0410-b5e6-96231b3b80d8

2 files changed, 17 insertions, 8 deletions

diff --git a/lib/lsan/lsan_common.cc b/lib/lsan/lsan_common.cc
index 622aae734..651bbe1f3 100644
--- a/lib/lsan/lsan_common.cc
+++ b/lib/lsan/lsan_common.cc
@@ -411,8 +411,9 @@ static void MarkInvalidPCCb(uptr chunk, void *arg) {
   }
 }
 
-// On Linux, handles dynamically allocated TLS blocks by treating all chunks
-// allocated from ld-linux.so as reachable.
+// On Linux, treats all chunks allocated from ld-linux.so as reachable, which
+// covers dynamically allocated TLS blocks, internal dynamic loader's loaded
+// modules accounting etc.
 // Dynamic TLS blocks contain the TLS variables of dynamically loaded modules.
 // They are allocated with a __libc_memalign() call in allocate_and_init()
 // (elf/dl-tls.c). Glibc won't tell us the address ranges occupied by those
diff --git a/lib/lsan/lsan_common_linux.cc b/lib/lsan/lsan_common_linux.cc
index 5042c7b3a..cdd7f032a 100644
--- a/lib/lsan/lsan_common_linux.cc
+++ b/lib/lsan/lsan_common_linux.cc
@@ -20,6 +20,7 @@
 
 #include "sanitizer_common/sanitizer_common.h"
 #include "sanitizer_common/sanitizer_flags.h"
+#include "sanitizer_common/sanitizer_getauxval.h"
 #include "sanitizer_common/sanitizer_linux.h"
 #include "sanitizer_common/sanitizer_stackdepot.h"
 
@@ -30,8 +31,12 @@ static const char kLinkerName[] = "ld";
 static char linker_placeholder[sizeof(LoadedModule)] ALIGNED(64);
 static LoadedModule *linker = nullptr;
 
-static bool IsLinker(const char* full_name) {
-  return LibraryNameIs(full_name, kLinkerName);
+static bool IsLinker(const LoadedModule& module) {
+#if SANITIZER_USE_GETAUXVAL
+  return module.base_address() == getauxval(AT_BASE);
+#else
+  return LibraryNameIs(module.full_name(), kLinkerName);
+#endif  // SANITIZER_USE_GETAUXVAL
 }
 
 __attribute__((tls_model("initial-exec")))
@@ -49,22 +54,25 @@ void InitializePlatformSpecificModules() {
   ListOfModules modules;
   modules.init();
   for (LoadedModule &module : modules) {
-    if (!IsLinker(module.full_name())) continue;
+    if (!IsLinker(module))
+      continue;
     if (linker == nullptr) {
       linker = reinterpret_cast<LoadedModule *>(linker_placeholder);
       *linker = module;
       module = LoadedModule();
     } else {
       VReport(1, "LeakSanitizer: Multiple modules match \"%s\". "
-              "TLS will not be handled correctly.\n", kLinkerName);
+              "TLS and other allocations originating from linker might be "
+              "falsely reported as leaks.\n", kLinkerName);
       linker->clear();
       linker = nullptr;
       return;
     }
   }
   if (linker == nullptr) {
-    VReport(1, "LeakSanitizer: Dynamic linker not found. "
-               "TLS will not be handled correctly.\n");
+    VReport(1, "LeakSanitizer: Dynamic linker not found. TLS and other "
+               "allocations originating from linker might be falsely reported "
+                "as leaks.\n");
   }
 }