[BOLT] Introduce --disallow-pacret flag

Author: bgergely0

bolt/include/bolt/Utils/CommandLineOpts.h

@@ -78,6 +78,7 @@ extern llvm::cl::opt<std::string> OutputFilename;
 extern llvm::cl::opt<std::string> PerfData;
 extern llvm::cl::opt<bool> PrintCacheMetrics;
 extern llvm::cl::opt<bool> PrintSections;
+extern llvm::cl::opt<bool> DisallowPacret;
 
 // The format to use with -o in aggregation mode (perf2bolt)
 enum ProfileFormatKind { PF_Fdata, PF_YAML };

bolt/lib/Rewrite/BinaryPassManager.cpp

@@ -278,6 +278,15 @@ static cl::opt<bool> ShortenInstructions("shorten-instructions",
                                          cl::desc("shorten instructions"),
                                          cl::init(true),
                                          cl::cat(BoltOptCategory));
+
+// This flag is used to "gate" the negate-ra-state CFI handling.
+// Sometimes, binaries use pac-ret but not contain negate-ra-state CFIs. That
+// should cause no issues for BOLT.
+cl::opt<bool> DisallowPacret(
+    "disallow-pacret",
+    cl::desc("Disable processing binaries containing negate-ra-state DWARF "
+             "CFIs (e.g. binaries using pac-ret hardening)"),
+    cl::cat(BoltOptCategory));
 } // namespace opts
 
 namespace llvm {

bolt/lib/Rewrite/RewriteInstance.cpp

@@ -3520,6 +3520,17 @@ void RewriteInstance::disassembleFunctions() {
       }
     }
 
+    // Check if fillCFIInfoFor removed any OpNegateRAState CFIs from the
+    // function.
+    if (Function.containedNegateRAState()) {
+      if (opts::DisallowPacret) {
+        BC->errs() << "BOLT-ERROR: --disallow-pacret flag was used, but "
+                   << Function.getPrintName()
+                   << " contains .cfi-negate-ra-state.\n";
+        exit(1);
+      }
+    }
+
     // Parse LSDA.
     if (Function.getLSDAAddress() != 0 &&
         !BC->getFragmentsToSkip().count(&Function)) {

bolt/test/AArch64/negate-ra-state-disallow.s

@@ -0,0 +1,25 @@
+# RUN: llvm-mc -filetype=obj -triple aarch64-unknown-unknown %s -o %t.o
+# RUN: %clang %cflags  %t.o -o %t.exe -Wl,-q
+# RUN: not llvm-bolt %t.exe -o %t.exe.bolt --disallow-pacret 2>&1 | FileCheck %s
+
+# CHECK: BOLT-ERROR: --disallow-pacret flag was used, but foo contains .cfi-negate-ra-state.
+
+  .text
+  .globl  foo
+  .p2align        2
+  .type   foo,@function
+foo:
+  .cfi_startproc
+  hint    #25
+  .cfi_negate_ra_state
+  mov x1, #0
+  hint    #29
+  .cfi_negate_ra_state
+  ret
+  .cfi_endproc
+  .size   foo, .-foo
+
+  .global _start
+  .type _start, %function
+_start:
+  b foo