1 //===- FaultMaps.cpp ------------------------------------------------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #include "llvm/CodeGen/FaultMaps.h"
10 #include "llvm/ADT/Twine.h"
11 #include "llvm/CodeGen/AsmPrinter.h"
12 #include "llvm/MC/MCContext.h"
13 #include "llvm/MC/MCExpr.h"
14 #include "llvm/MC/MCObjectFileInfo.h"
15 #include "llvm/MC/MCStreamer.h"
16 #include "llvm/Support/Debug.h"
17 #include "llvm/Support/ErrorHandling.h"
18 
19 using namespace llvm;
20 
21 #define DEBUG_TYPE "faultmaps"
22 
23 static const int FaultMapVersion = 1;
24 const char *FaultMaps::WFMP = "Fault Maps: ";
25 
26 FaultMaps::FaultMaps(AsmPrinter &AP) : AP(AP) {}
27 
28 void FaultMaps::recordFaultingOp(FaultKind FaultTy,
29                                  const MCSymbol *FaultingLabel,
30                                  const MCSymbol *HandlerLabel) {
31   MCContext &OutContext = AP.OutStreamer->getContext();
32 
33   const MCExpr *FaultingOffset = MCBinaryExpr::createSub(
34       MCSymbolRefExpr::create(FaultingLabel, OutContext),
35       MCSymbolRefExpr::create(AP.CurrentFnSymForSize, OutContext), OutContext);
36 
37   const MCExpr *HandlerOffset = MCBinaryExpr::createSub(
38       MCSymbolRefExpr::create(HandlerLabel, OutContext),
39       MCSymbolRefExpr::create(AP.CurrentFnSymForSize, OutContext), OutContext);
40 
41   FunctionInfos[AP.CurrentFnSym].emplace_back(FaultTy, FaultingOffset,
42                                               HandlerOffset);
43 }
44 
45 void FaultMaps::serializeToFaultMapSection() {
46   if (FunctionInfos.empty())
47     return;
48 
49   MCContext &OutContext = AP.OutStreamer->getContext();
50   MCStreamer &OS = *AP.OutStreamer;
51 
52   // Create the section.
53   MCSection *FaultMapSection =
54       OutContext.getObjectFileInfo()->getFaultMapSection();
55   OS.switchSection(FaultMapSection);
56 
57   // Emit a dummy symbol to force section inclusion.
58   OS.emitLabel(OutContext.getOrCreateSymbol(Twine("__LLVM_FaultMaps")));
59 
60   LLVM_DEBUG(dbgs() << "********** Fault Map Output **********\n");
61 
62   // Header
63   OS.emitIntValue(FaultMapVersion, 1); // Version.
64   OS.emitIntValue(0, 1);               // Reserved.
65   OS.emitInt16(0);                     // Reserved.
66 
67   LLVM_DEBUG(dbgs() << WFMP << "#functions = " << FunctionInfos.size() << "\n");
68   OS.emitInt32(FunctionInfos.size());
69 
70   LLVM_DEBUG(dbgs() << WFMP << "functions:\n");
71 
72   for (const auto &FFI : FunctionInfos)
73     emitFunctionInfo(FFI.first, FFI.second);
74 }
75 
76 void FaultMaps::emitFunctionInfo(const MCSymbol *FnLabel,
77                                  const FunctionFaultInfos &FFI) {
78   MCStreamer &OS = *AP.OutStreamer;
79 
80   LLVM_DEBUG(dbgs() << WFMP << "  function addr: " << *FnLabel << "\n");
81   OS.emitSymbolValue(FnLabel, 8);
82 
83   LLVM_DEBUG(dbgs() << WFMP << "  #faulting PCs: " << FFI.size() << "\n");
84   OS.emitInt32(FFI.size());
85 
86   OS.emitInt32(0); // Reserved
87 
88   for (const auto &Fault : FFI) {
89     LLVM_DEBUG(dbgs() << WFMP << "    fault type: "
90                       << faultTypeToString(Fault.Kind) << "\n");
91     OS.emitInt32(Fault.Kind);
92 
93     LLVM_DEBUG(dbgs() << WFMP << "    faulting PC offset: "
94                       << *Fault.FaultingOffsetExpr << "\n");
95     OS.emitValue(Fault.FaultingOffsetExpr, 4);
96 
97     LLVM_DEBUG(dbgs() << WFMP << "    fault handler PC offset: "
98                       << *Fault.HandlerOffsetExpr << "\n");
99     OS.emitValue(Fault.HandlerOffsetExpr, 4);
100   }
101 }
102 
103 const char *FaultMaps::faultTypeToString(FaultMaps::FaultKind FT) {
104   switch (FT) {
105   default:
106     llvm_unreachable("unhandled fault type!");
107   case FaultMaps::FaultingLoad:
108     return "FaultingLoad";
109   case FaultMaps::FaultingLoadStore:
110     return "FaultingLoadStore";
111   case FaultMaps::FaultingStore:
112     return "FaultingStore";
113   }
114 }
115