[compiler-rt] r318369 - [asan] Fallback to non-ifunc dynamic shadow on android<22.

[Evgeniy Stepanov via llvm-commits]

Author: eugenis
Date: Wed Nov 15 18:52:19 2017
New Revision: 318369

URL: http://llvm.org/viewvc/llvm-project?rev=318369&view=rev
Log:
[asan] Fallback to non-ifunc dynamic shadow on android<22.

Summary: Android < 22 does not support ifunc.

Reviewers: pcc

Subscribers: srhines, kubamracek, hiraditya, llvm-commits

Differential Revision: https://reviews.llvm.org/D40116

Modified:
    compiler-rt/trunk/lib/asan/asan_linux.cc
    compiler-rt/trunk/lib/asan/asan_premap_shadow.cc
    compiler-rt/trunk/lib/asan/asan_premap_shadow.h

Modified: compiler-rt/trunk/lib/asan/asan_linux.cc
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/asan/asan_linux.cc?rev=318369&r1=318368&r2=318369&view=diff
==============================================================================
--- compiler-rt/trunk/lib/asan/asan_linux.cc (original)
+++ compiler-rt/trunk/lib/asan/asan_linux.cc Wed Nov 15 18:52:19 2017
@@ -83,7 +83,7 @@ void *AsanDoesNotSupportStaticLinkage()
 }
 
 #if ASAN_PREMAP_SHADOW
-uptr FindDynamicShadowStart() {
+uptr FindPremappedShadowStart() {
   uptr granularity = GetMmapGranularity();
   uptr shadow_start = reinterpret_cast<uptr>(&__asan_shadow);
   uptr shadow_size = PremapShadowSize();
@@ -93,8 +93,14 @@ uptr FindDynamicShadowStart() {
   IncreaseTotalMmap(shadow_size + granularity);
   return shadow_start;
 }
-#else
+#endif
+
 uptr FindDynamicShadowStart() {
+#if ASAN_PREMAP_SHADOW
+  if (!PremapShadowFailed())
+    return FindPremappedShadowStart();
+#endif
+
   uptr granularity = GetMmapGranularity();
   uptr alignment = granularity * 8;
   uptr left_padding = granularity;
@@ -112,7 +118,6 @@ uptr FindDynamicShadowStart() {
 
   return shadow_start;
 }
-#endif
 
 void AsanApplyToGlobals(globals_op_fptr op, const void *needle) {
   UNIMPLEMENTED();

Modified: compiler-rt/trunk/lib/asan/asan_premap_shadow.cc
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/asan/asan_premap_shadow.cc?rev=318369&r1=318368&r2=318369&view=diff
==============================================================================
--- compiler-rt/trunk/lib/asan/asan_premap_shadow.cc (original)
+++ compiler-rt/trunk/lib/asan/asan_premap_shadow.cc Wed Nov 15 18:52:19 2017
@@ -50,6 +50,15 @@ uptr PremapShadow() {
   return shadow_start;
 }
 
+bool PremapShadowFailed() {
+  uptr shadow = reinterpret_cast<uptr>(&__asan_shadow);
+  uptr resolver = reinterpret_cast<uptr>(&__asan_premap_shadow);
+  // shadow == resolver is how Android KitKat and older handles ifunc.
+  // shadow == 0 just in case.
+  if (shadow == 0 || shadow == resolver)
+    return true;
+  return false;
+}
 } // namespace __asan
 
 extern "C" {

Modified: compiler-rt/trunk/lib/asan/asan_premap_shadow.h
URL: http://llvm.org/viewvc/llvm-project/compiler-rt/trunk/lib/asan/asan_premap_shadow.h?rev=318369&r1=318368&r2=318369&view=diff
==============================================================================
--- compiler-rt/trunk/lib/asan/asan_premap_shadow.h (original)
+++ compiler-rt/trunk/lib/asan/asan_premap_shadow.h Wed Nov 15 18:52:19 2017
@@ -20,9 +20,11 @@
 namespace __asan {
 // Conservative upper limit.
 uptr PremapShadowSize();
+bool PremapShadowFailed();
 }
 #endif
 
 extern "C" INTERFACE_ATTRIBUTE void __asan_shadow();
+extern "C" decltype(__asan_shadow)* __asan_premap_shadow();
 
 #endif // ASAN_PREMAP_SHADOW_H