From db7c82231c32074440d5426870051228435c6bce Mon Sep 17 00:00:00 2001
From: Fangrui Song <i@maskray.me>
Date: Mon, 21 Nov 2022 20:51:52 +0000
Subject: [PATCH] Restore global descriptor demangling after D138095 "[asan]
 Keep Itanium mangled names in global metadata"

This amends commit 00be3578e0841dd9abe408e5b4946180de0bf46b to demangle symbol
names in global descriptors. We keep the mangled name for the `__odr_gen_asan_*`
variables and the runtime __cxa_demangle call site change (which fixed possible
leaks for other scenarios: non-fatal diagnostics).

compiler-rt/lib/sanitizer_common/sanitizer_symbolizer_posix_libcdep.cpp uses
an undefined weak `__cxa_demangle` which does not pull in an archive definition.
A -static-libstdc++ executable link does not get demangled names.

Unfortunately this means we cannot rely on runtime demangling.
See compiler-rt/test/asan/TestCases/global-demangle.cpp
---
 compiler-rt/lib/asan/asan_globals.cpp                     | 4 ++--
 compiler-rt/test/asan/TestCases/Linux/odr_indicators.cpp  | 4 ++--
 llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp  | 9 ++++-----
 llvm/test/Instrumentation/AddressSanitizer/local_alias.ll | 2 +-
 4 files changed, 9 insertions(+), 10 deletions(-)

diff --git a/compiler-rt/lib/asan/asan_globals.cpp b/compiler-rt/lib/asan/asan_globals.cpp
index 69b64dc..2b4a9e0 100644
--- a/compiler-rt/lib/asan/asan_globals.cpp
+++ b/compiler-rt/lib/asan/asan_globals.cpp
@@ -148,7 +148,7 @@ static void CheckODRViolationViaIndicator(const Global *g) {
   for (ListOfGlobals *l = list_of_all_globals; l; l = l->next) {
     if (g->odr_indicator == l->g->odr_indicator &&
         (flags()->detect_odr_violation >= 2 || g->size != l->g->size) &&
-        !IsODRViolationSuppressed(MaybeDemangleGlobalName(g->name)))
+        !IsODRViolationSuppressed(g->name))
       ReportODRViolation(g, FindRegistrationSite(g), l->g,
                          FindRegistrationSite(l->g));
   }
@@ -164,7 +164,7 @@ static void CheckODRViolationViaPoisoning(const Global *g) {
     for (ListOfGlobals *l = list_of_all_globals; l; l = l->next) {
       if (g->beg == l->g->beg &&
           (flags()->detect_odr_violation >= 2 || g->size != l->g->size) &&
-          !IsODRViolationSuppressed(MaybeDemangleGlobalName(g->name)))
+          !IsODRViolationSuppressed(g->name))
         ReportODRViolation(g, FindRegistrationSite(g),
                            l->g, FindRegistrationSite(l->g));
     }
diff --git a/compiler-rt/test/asan/TestCases/Linux/odr_indicators.cpp b/compiler-rt/test/asan/TestCases/Linux/odr_indicators.cpp
index cef6b99..583f6e6 100644
--- a/compiler-rt/test/asan/TestCases/Linux/odr_indicators.cpp
+++ b/compiler-rt/test/asan/TestCases/Linux/odr_indicators.cpp
@@ -11,11 +11,11 @@ int test_global_1;
 // INDICATOR1-DAG: Added Global{{.*}} name=test_global_1{{.*}} odr_indicator={{0x0*[^0]+.*$}}
 
 static int test_global_2;
-// CHECK-DAG: Added Global{{.*}} name=_ZL13test_global_2 {{.*}} odr_indicator={{0xf+$}}
+// CHECK-DAG: Added Global{{.*}} name=test_global_2{{.*}} odr_indicator={{0xf+$}}
 
 namespace {
 static int test_global_3;
-// CHECK-DAG: Added Global{{.*}} name=_ZN12_GLOBAL__N_113test_global_3E {{.*}} odr_indicator={{0xf+$}}
+// CHECK-DAG: Added Global{{.*}} name={{.*}}::test_global_3{{.*}} odr_indicator={{0xf+$}}
 } // namespace
 
 int main() {
diff --git a/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp b/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
index bc8823a..a4d4cc7 100644
--- a/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
+++ b/llvm/lib/Transforms/Instrumentation/AddressSanitizer.cpp
@@ -2264,13 +2264,12 @@ bool ModuleAddressSanitizer::InstrumentGlobals(IRBuilder<> &IRB, Module &M,
     if (G->hasSanitizerMetadata())
       MD = G->getSanitizerMetadata();
 
-    // ASan runtime demangles Itanium mangled names, so keep the original name
-    // to prevent unneeded size increase of the string table.
+    // The runtime library tries demangling symbol names in the descriptor but
+    // functionality like __cxa_demangle may be unavailable (e.g.
+    // -static-libstdc++). So we demangle the symbol names here.
     std::string NameForGlobal = G->getName().str();
-    if (!StringRef(NameForGlobal).startswith("_Z"))
-      NameForGlobal = llvm::demangle(NameForGlobal);
     GlobalVariable *Name =
-        createPrivateGlobalForString(M, NameForGlobal,
+        createPrivateGlobalForString(M, llvm::demangle(NameForGlobal),
                                      /*AllowMerging*/ true, kAsanGenPrefix);
 
     Type *Ty = G->getValueType();
diff --git a/llvm/test/Instrumentation/AddressSanitizer/local_alias.ll b/llvm/test/Instrumentation/AddressSanitizer/local_alias.ll
index 550c2f1..ada8120 100644
--- a/llvm/test/Instrumentation/AddressSanitizer/local_alias.ll
+++ b/llvm/test/Instrumentation/AddressSanitizer/local_alias.ll
@@ -20,7 +20,7 @@ target triple = "x86_64-unknown-linux-gnu"
 ; CHECK-NOALIAS-NOT: private alias
 ; CHECK-INDICATOR: @___asan_gen_.1 = private unnamed_addr constant [2 x i8] c"a\00", align 1
 ; CHECK-INDICATOR: @__odr_asan_gen_a = global i8 0, align 1
-; CHECK-INDICATOR: @___asan_gen_.4 = private unnamed_addr constant [6 x i8] c"_ZL1d\00", align 1
+; CHECK-INDICATOR: @___asan_gen_.4 = private unnamed_addr constant [2 x i8] c"d\00", align 1
 ; CHECK-INDICATOR: @__odr_asan_gen__ZL1d = global i8 0, align 1
 ; CHECK-ALIAS: @0 = private alias { [2 x i32], [24 x i8] }, ptr @a
 
-- 
2.7.4