[asan] Do not instrument globals from special purpose llvm sections

[zaks.anna]

Summary

Do not instrument globals that are placed in sections containing "__llvm" in their name.

ASan interferes with LLVM's PGO, which places its globals into a special section, which is memcpy-ed by the linker as a whole. When those goals are instrumented, ASan's memcpy wrapper reports an issue.

[glider]

These globals aren't intended to be accessed by the user's code, are they?
LGTM

lib/Transforms/Instrumentation/AddressSanitizer.cpp

1145

s/llvm/LLVM ?

[zaks.anna]

These globals aren't intended to be accessed by the user's code, are they?

Correct.

[samsonov]

LGTM

[zaks.anna]

In r240723

lib/Transforms/Instrumentation/AddressSanitizer.cpp

   // For now, just ignore this Global if the alignment is large.
   if (G->getAlignment() > MinRedzoneSizeForGlobal()) return false;
 
   if (G->hasSection()) {
     StringRef Section(G->getSection());
 
     // Globals from llvm.metadata aren't emitted, do not instrument them.
     if (Section == "llvm.metadata") return false;
+    // Do not instrument globals from special llvm sections.
+    if (Section.find("__llvm") != StringRef::npos) return false;
 
     // Callbacks put into the CRT initializer/terminator sections
     // should not be instrumented.
     // See https://code.google.com/p/address-sanitizer/issues/detail?id=305
     // and http://msdn.microsoft.com/en-US/en-en/library/bb918180(v=vs.120).aspx
     if (Section.startswith(".CRT")) {
       DEBUG(dbgs() << "Ignoring a global initializer callback: " << *G << "\n");
       return false;

test/Instrumentation/AddressSanitizer/do-not-instrument-llvm-metadata-darwin.ll

-; This test checks that we are not instrumenting globals in llvm.metadata.
+; This test checks that we are not instrumenting globals in llvm.metadata
+; and other llvm internal globals.
 ; RUN: opt < %s -asan -asan-module -S | FileCheck %s
 
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-apple-macosx10.10.0"
 
 @.str_noinst = private unnamed_addr constant [4 x i8] c"aaa\00", section "llvm.metadata"
+@.str_noinst_prof = private unnamed_addr constant [4 x i8] c"aaa\00", section "__DATA,__llvm_covmap"
 @.str_inst = private unnamed_addr constant [4 x i8] c"aaa\00"
 
 ; CHECK-NOT: {{asan_gen.*str_noinst}}
+; CHECK-NOT: {{asan_gen.*str_noinst_prof}}
 ; CHECK: {{asan_gen.*str_inst}}
 ; CHECK: @asan.module_ctor

test/Instrumentation/AddressSanitizer/do-not-instrument-llvm-metadata.ll

-; This test checks that we are not instrumenting globals in llvm.metadata.
+; This test checks that we are not instrumenting globals in llvm.metadata
+; and other llvm internal globals.
 ; RUN: opt < %s -asan -asan-module -S | FileCheck %s
 
 target datalayout = "e-m:e-i64:64-f80:128-n8:16:32:64-S128"
 target triple = "x86_64-unknown-linux-gnu"
 
 @.str_noinst = private unnamed_addr constant [4 x i8] c"aaa\00", section "llvm.metadata"
+@.str_noinst_prof = private unnamed_addr constant [4 x i8] c"aaa\00", section "__llvm_prf_data"
 @.str_inst = private unnamed_addr constant [4 x i8] c"aaa\00"
 
 ; CHECK-NOT: {{asan_gen.*str_noinst}}
+; CHECK-NOT: {{asan_gen.*str_noinst_prof}}
 ; CHECK: {{asan_gen.*str_inst}}
 ; CHECK: @asan.module_ctor