[BOLT] Reintroduce allow-stripped

[Amir]

Summary

Reject stripped binaries as a policy.

The core issue with stripped binaries is that we can't detect the presence
of split functions which require extra handling. Therefore BOLT can't ensure
functional correctness of produced binary if the input stripped binary contains
split functions. Supporting such cases is an interesting problem but it goes
against BOLT's intended goal of achieving peak program performance.

[maksfb]

bolt/lib/Rewrite/RewriteInstance.cpp

1670–1671

Since we are existing without generating the output, this should be an abnormal behavior and hence we should issue an error.

[Amir]

Report error

[Amir]

Dash

[maksfb]

Test case has to be updated as well.

bolt/lib/Rewrite/RewriteInstance.cpp

1671

bolt/test/X86/broken_dynsym.test

6

[Amir]

Update tests

[maksfb]

bolt/lib/Rewrite/RewriteInstance.cpp

1671

nit: drop the trailing period in the message.

[Amir]

dot

bolt/lib/Rewrite/RewriteInstance.cpp

 extern cl::list<std::string> HotTextMoveSections;
 extern cl::opt<bool> Hugify;
 extern cl::opt<bool> Instrument;
 extern cl::opt<JumpTableSupportLevel> JumpTables;
 extern cl::list<std::string> ReorderData;
 extern cl::opt<bolt::ReorderFunctions::ReorderType> ReorderFunctions;
 extern cl::opt<bool> TimeBuild;
 
+cl::opt<bool> AllowStripped("allow-stripped",
+                            cl::desc("allow processing of stripped binaries"),
+                            cl::Hidden, cl::cat(BoltCategory));
+
 static cl::opt<bool> ForceToDataRelocations(
     "force-data-relocations",
     cl::desc("force relocations to data sections to always be processed"),
 
     cl::Hidden, cl::cat(BoltCategory));
 
 cl::opt<std::string>
     BoltID("bolt-id",
if (opts::RelocationMode == cl::BOU_TRUE && !HasTextRelocations) {
     exit(1);
   }
 
   BC->HasRelocations =
       HasTextRelocations && (opts::RelocationMode != cl::BOU_FALSE);
 
   BC->IsStripped = !HasSymbolTable;
 
+  if (BC->IsStripped && !opts::AllowStripped) {
+    errs() << "BOLT-ERROR: stripped binaries are not supported. If you know "
+              "what you're doing, use --allow-stripped to proceed";
+    exit(1);
+  }
+
   // Force non-relocation mode for heatmap generation
   if (opts::HeatmapMode)
     BC->HasRelocations = false;
 
   if (BC->HasRelocations)
     outs() << "BOLT-INFO: enabling " << (opts::StrictMode ? "strict " : "")
            << "relocation mode\n";
 
-  if (BC->IsStripped)
-    outs() << "BOLT-INFO: input binary is stripped. The support is limited and "
-           << "is considered experimental.\n";
-
   // Read EH frame for function boundaries info.
   Expected<const DWARFDebugFrame *> EHFrameOrError = BC->DwCtx->getEHFrame();
   if (!EHFrameOrError)
     report_error("expected valid eh_frame section", EHFrameOrError.takeError());
   CFIRdWrt.reset(new CFIReaderWriter(*EHFrameOrError.get()));
 
   // Parse build-id
   parseBuildID();

bolt/test/X86/broken_dynsym.test

 # This test checks if BOLT can process stripped binaries, where symbol's section
 # header index is corrupted due to strip tool.
 
 # RUN: yaml2obj %p/Inputs/broken_dynsym.yaml -o %t
 # RUN: llvm-strip -s %t
-# RUN: llvm-bolt %t -o %t.bolt | FileCheck %s
+# RUN: llvm-bolt %t -o %t.bolt --allow-stripped | FileCheck %s
 
 # CHECK-NOT: section index out of bounds 

bolt/test/X86/is-strip.s

 # This test checks whether a binary is stripped or not.
 
 # RUN: %clang++ %cflags %p/Inputs/linenumber.cpp -o %t -Wl,-q
 # RUN: llvm-bolt %t -o %t.out 2>&1 | FileCheck %s -check-prefix=CHECK-NOSTRIP
 # RUN: cp %t %t.stripped
 # RUN: llvm-strip -s %t.stripped
-# RUN: llvm-bolt %t.stripped -o %t.out 2>&1 | FileCheck %s -check-prefix=CHECK-STRIP
+# RUN: not llvm-bolt %t.stripped -o %t.out 2>&1 | FileCheck %s -check-prefix=CHECK-STRIP
+# RUN: llvm-bolt %t.stripped -o %t.out --allow-stripped 2>&1 | FileCheck %s -check-prefix=CHECK-NOSTRIP
 
-# CHECK-NOSTRIP-NOT: BOLT-INFO: input binary is stripped. The support is limited and is considered experimental.
-# CHECK-STRIP: BOLT-INFO: input binary is stripped. The support is limited and is considered experimental.
+# CHECK-NOSTRIP-NOT: BOLT-ERROR: stripped binaries are not supported.
+# CHECK-STRIP: BOLT-ERROR: stripped binaries are not supported.