[llvm] [BOLT][binary-analysis] Fix pac-ret scanner's "major limitation" (PR #136664)

[Gergely Bálint via llvm-commits]

https://github.com/bgergely0 updated https://github.com/llvm/llvm-project/pull/136664

>From 15bc0cbb1c12469596590ab446859ec8f3a1889b Mon Sep 17 00:00:00 2001
From: Gergely Balint <gergely.balint at arm.com>
Date: Tue, 29 Apr 2025 10:04:58 +0200
Subject: [PATCH] [BOLT][AArch64] Allow binary-analysis and heatmaptool to run
 with pac-ret binaries

- OpNegateRAState support is only needed for tools that
    produce binaries.
---
 bolt/docs/BinaryAnalysis.md      |  6 ------
 bolt/lib/Core/BinaryFunction.cpp | 26 +++++++++++++++++++++++---
 2 files changed, 23 insertions(+), 9 deletions(-)

diff --git a/bolt/docs/BinaryAnalysis.md b/bolt/docs/BinaryAnalysis.md
index 9f0f018980517..b13410cd96355 100644
--- a/bolt/docs/BinaryAnalysis.md
+++ b/bolt/docs/BinaryAnalysis.md
@@ -180,12 +180,6 @@ The following are current known cases of false negatives:
    [prototype branch](
    https://github.com/llvm/llvm-project/compare/main...kbeyls:llvm-project:bolt-gadget-scanner-prototype).
 
-BOLT cannot currently handle functions with `cfi_negate_ra_state` correctly,
-i.e. any binaries built with `-mbranch-protection=pac-ret`. The scanner is meant
-to be used on specifically such binaries, so this is a major limitation! Work is
-going on in PR [#120064](https://github.com/llvm/llvm-project/pull/120064) to
-fix this.
-
 ## How to add your own binary analysis
 
 _TODO: this section needs to be written. Ideally, we should have a simple
diff --git a/bolt/lib/Core/BinaryFunction.cpp b/bolt/lib/Core/BinaryFunction.cpp
index 184a4462b356a..6c98984b0de6e 100644
--- a/bolt/lib/Core/BinaryFunction.cpp
+++ b/bolt/lib/Core/BinaryFunction.cpp
@@ -65,6 +65,8 @@ extern cl::opt<bool> StrictMode;
 extern cl::opt<bool> UpdateDebugSections;
 extern cl::opt<unsigned> Verbosity;
 
+extern bool BinaryAnalysisMode;
+extern bool HeatmapMode;
 extern bool processAllFunctions();
 
 static cl::opt<bool> CheckEncoding(
@@ -2760,13 +2762,19 @@ struct CFISnapshot {
     }
     case MCCFIInstruction::OpAdjustCfaOffset:
     case MCCFIInstruction::OpWindowSave:
-    case MCCFIInstruction::OpNegateRAState:
     case MCCFIInstruction::OpNegateRAStateWithPC:
     case MCCFIInstruction::OpLLVMDefAspaceCfa:
     case MCCFIInstruction::OpLabel:
     case MCCFIInstruction::OpValOffset:
       llvm_unreachable("unsupported CFI opcode");
       break;
+    case MCCFIInstruction::OpNegateRAState:
+      if (!(opts::BinaryAnalysisMode || opts::HeatmapMode)) {
+        llvm_unreachable("BOLT-ERROR: binaries using pac-ret hardening (e.g. "
+                         "as produced by '-mbranch-protection=pac-ret') are "
+                         "currently not supported by BOLT\n");
+      }
+      break;
     case MCCFIInstruction::OpRememberState:
     case MCCFIInstruction::OpRestoreState:
     case MCCFIInstruction::OpGnuArgsSize:
@@ -2900,13 +2908,19 @@ struct CFISnapshotDiff : public CFISnapshot {
       return CFAReg == Instr.getRegister() && CFAOffset == Instr.getOffset();
     case MCCFIInstruction::OpAdjustCfaOffset:
     case MCCFIInstruction::OpWindowSave:
-    case MCCFIInstruction::OpNegateRAState:
     case MCCFIInstruction::OpNegateRAStateWithPC:
     case MCCFIInstruction::OpLLVMDefAspaceCfa:
     case MCCFIInstruction::OpLabel:
     case MCCFIInstruction::OpValOffset:
       llvm_unreachable("unsupported CFI opcode");
       return false;
+    case MCCFIInstruction::OpNegateRAState:
+      if (!(opts::BinaryAnalysisMode || opts::HeatmapMode)) {
+        llvm_unreachable("BOLT-ERROR: binaries using pac-ret hardening (e.g. "
+                         "as produced by '-mbranch-protection=pac-ret') are "
+                         "currently not supported by BOLT\n");
+      }
+      break;
     case MCCFIInstruction::OpRememberState:
     case MCCFIInstruction::OpRestoreState:
     case MCCFIInstruction::OpGnuArgsSize:
@@ -3051,13 +3065,19 @@ BinaryFunction::unwindCFIState(int32_t FromState, int32_t ToState,
       break;
     case MCCFIInstruction::OpAdjustCfaOffset:
     case MCCFIInstruction::OpWindowSave:
-    case MCCFIInstruction::OpNegateRAState:
     case MCCFIInstruction::OpNegateRAStateWithPC:
     case MCCFIInstruction::OpLLVMDefAspaceCfa:
     case MCCFIInstruction::OpLabel:
     case MCCFIInstruction::OpValOffset:
       llvm_unreachable("unsupported CFI opcode");
       break;
+    case MCCFIInstruction::OpNegateRAState:
+      if (!(opts::BinaryAnalysisMode || opts::HeatmapMode)) {
+        llvm_unreachable("BOLT-ERROR: binaries using pac-ret hardening (e.g. "
+                         "as produced by '-mbranch-protection=pac-ret') are "
+                         "currently not supported by BOLT\n");
+      }
+      break;
     case MCCFIInstruction::OpGnuArgsSize:
       // do not affect CFI state
       break;