[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

4 files changed, 58 insertions, 22 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");
   }
 }
 
diff --git a/lib/sanitizer_common/sanitizer_getauxval.h b/lib/sanitizer_common/sanitizer_getauxval.h
new file mode 100644
index 000000000..d0287f02c
--- /dev/null
+++ b/lib/sanitizer_common/sanitizer_getauxval.h
@@ -0,0 +1,40 @@
+//===-- sanitizer_getauxval.h -----------------------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// Common getauxval() guards and definitions.
+// getauxval() is not defined until glbc version 2.16.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef SANITIZER_GETAUXVAL_H
+#define SANITIZER_GETAUXVAL_H
+
+#include "sanitizer_platform.h"
+
+#if SANITIZER_LINUX
+
+#include <features.h>
+
+#ifndef __GLIBC_PREREQ
+#define __GLIBC_PREREQ(x, y) 0
+#endif
+
+#if __GLIBC_PREREQ(2, 16)
+# define SANITIZER_USE_GETAUXVAL 1
+#else
+# define SANITIZER_USE_GETAUXVAL 0
+#endif
+
+#if SANITIZER_USE_GETAUXVAL
+#include <sys/auxv.h>
+#endif
+
+#endif // SANITIZER_LINUX
+
+#endif // SANITIZER_GETAUXVAL_H
diff --git a/lib/sanitizer_common/sanitizer_linux.cc b/lib/sanitizer_common/sanitizer_linux.cc
index 6ea185817..5199aa601 100644
--- a/lib/sanitizer_common/sanitizer_linux.cc
+++ b/lib/sanitizer_common/sanitizer_linux.cc
@@ -18,6 +18,7 @@
 
 #include "sanitizer_common.h"
 #include "sanitizer_flags.h"
+#include "sanitizer_getauxval.h"
 #include "sanitizer_internal_defs.h"
 #include "sanitizer_libc.h"
 #include "sanitizer_linux.h"
@@ -95,20 +96,6 @@ extern struct ps_strings *__ps_strings;
 #include <sys/signal.h>
 #endif
 
-#ifndef __GLIBC_PREREQ
-#define __GLIBC_PREREQ(x, y) 0
-#endif
-
-#if SANITIZER_LINUX && __GLIBC_PREREQ(2, 16)
-# define SANITIZER_USE_GETAUXVAL 1
-#else
-# define SANITIZER_USE_GETAUXVAL 0
-#endif
-
-#if SANITIZER_USE_GETAUXVAL
-#include <sys/auxv.h>
-#endif
-
 #if SANITIZER_LINUX
 // <linux/time.h>
 struct kernel_timeval {