1 //= AArch64WinCOFFObjectWriter.cpp - AArch64 Windows COFF Object Writer C++ =//
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 "AArch64MCTargetDesc.h"
10 #include "MCTargetDesc/AArch64FixupKinds.h"
11 #include "MCTargetDesc/AArch64MCExpr.h"
12 #include "llvm/ADT/Twine.h"
13 #include "llvm/BinaryFormat/COFF.h"
14 #include "llvm/MC/MCAsmBackend.h"
15 #include "llvm/MC/MCContext.h"
16 #include "llvm/MC/MCExpr.h"
17 #include "llvm/MC/MCFixup.h"
18 #include "llvm/MC/MCFixupKindInfo.h"
19 #include "llvm/MC/MCObjectWriter.h"
20 #include "llvm/MC/MCValue.h"
21 #include "llvm/MC/MCWinCOFFObjectWriter.h"
22 #include "llvm/Support/ErrorHandling.h"
23 #include "llvm/Support/raw_ostream.h"
24 #include <cassert>
25 
26 using namespace llvm;
27 
28 namespace {
29 
30 class AArch64WinCOFFObjectWriter : public MCWinCOFFObjectTargetWriter {
31 public:
AArch64WinCOFFObjectWriter()32   AArch64WinCOFFObjectWriter()
33       : MCWinCOFFObjectTargetWriter(COFF::IMAGE_FILE_MACHINE_ARM64) {}
34 
35   ~AArch64WinCOFFObjectWriter() override = default;
36 
37   unsigned getRelocType(MCContext &Ctx, const MCValue &Target,
38                         const MCFixup &Fixup, bool IsCrossSection,
39                         const MCAsmBackend &MAB) const override;
40 
41   bool recordRelocation(const MCFixup &) const override;
42 };
43 
44 } // end anonymous namespace
45 
getRelocType(MCContext & Ctx,const MCValue & Target,const MCFixup & Fixup,bool IsCrossSection,const MCAsmBackend & MAB) const46 unsigned AArch64WinCOFFObjectWriter::getRelocType(
47     MCContext &Ctx, const MCValue &Target, const MCFixup &Fixup,
48     bool IsCrossSection, const MCAsmBackend &MAB) const {
49   unsigned FixupKind = Fixup.getKind();
50   if (IsCrossSection) {
51     // IMAGE_REL_ARM64_REL64 does not exist. We treat FK_Data_8 as FK_PCRel_4 so
52     // that .xword a-b can lower to IMAGE_REL_ARM64_REL32. This allows generic
53     // instrumentation to not bother with the COFF limitation. A negative value
54     // needs attention.
55     if (FixupKind != FK_Data_4 && FixupKind != FK_Data_8) {
56       Ctx.reportError(Fixup.getLoc(), "Cannot represent this expression");
57       return COFF::IMAGE_REL_ARM64_ADDR32;
58     }
59     FixupKind = FK_PCRel_4;
60   }
61 
62   auto Modifier = Target.isAbsolute() ? MCSymbolRefExpr::VK_None
63                                       : Target.getSymA()->getKind();
64   const MCExpr *Expr = Fixup.getValue();
65 
66   if (const AArch64MCExpr *A64E = dyn_cast<AArch64MCExpr>(Expr)) {
67     AArch64MCExpr::VariantKind RefKind = A64E->getKind();
68     switch (AArch64MCExpr::getSymbolLoc(RefKind)) {
69     case AArch64MCExpr::VK_ABS:
70     case AArch64MCExpr::VK_SECREL:
71       // Supported
72       break;
73     default:
74       Ctx.reportError(Fixup.getLoc(), "relocation variant " +
75                                           A64E->getVariantKindName() +
76                                           " unsupported on COFF targets");
77       return COFF::IMAGE_REL_ARM64_ABSOLUTE; // Dummy return value
78     }
79   }
80 
81   switch (FixupKind) {
82   default: {
83     if (const AArch64MCExpr *A64E = dyn_cast<AArch64MCExpr>(Expr)) {
84       Ctx.reportError(Fixup.getLoc(), "relocation type " +
85                                           A64E->getVariantKindName() +
86                                           " unsupported on COFF targets");
87     } else {
88       const MCFixupKindInfo &Info = MAB.getFixupKindInfo(Fixup.getKind());
89       Ctx.reportError(Fixup.getLoc(), Twine("relocation type ") + Info.Name +
90                                           " unsupported on COFF targets");
91     }
92     return COFF::IMAGE_REL_ARM64_ABSOLUTE; // Dummy return value
93   }
94 
95   case FK_PCRel_4:
96     return COFF::IMAGE_REL_ARM64_REL32;
97 
98   case FK_Data_4:
99     switch (Modifier) {
100     default:
101       return COFF::IMAGE_REL_ARM64_ADDR32;
102     case MCSymbolRefExpr::VK_COFF_IMGREL32:
103       return COFF::IMAGE_REL_ARM64_ADDR32NB;
104     case MCSymbolRefExpr::VK_SECREL:
105       return COFF::IMAGE_REL_ARM64_SECREL;
106     }
107 
108   case FK_Data_8:
109     return COFF::IMAGE_REL_ARM64_ADDR64;
110 
111   case FK_SecRel_2:
112     return COFF::IMAGE_REL_ARM64_SECTION;
113 
114   case FK_SecRel_4:
115     return COFF::IMAGE_REL_ARM64_SECREL;
116 
117   case AArch64::fixup_aarch64_add_imm12:
118     if (const AArch64MCExpr *A64E = dyn_cast<AArch64MCExpr>(Expr)) {
119       AArch64MCExpr::VariantKind RefKind = A64E->getKind();
120       if (RefKind == AArch64MCExpr::VK_SECREL_LO12)
121         return COFF::IMAGE_REL_ARM64_SECREL_LOW12A;
122       if (RefKind == AArch64MCExpr::VK_SECREL_HI12)
123         return COFF::IMAGE_REL_ARM64_SECREL_HIGH12A;
124     }
125     return COFF::IMAGE_REL_ARM64_PAGEOFFSET_12A;
126 
127   case AArch64::fixup_aarch64_ldst_imm12_scale1:
128   case AArch64::fixup_aarch64_ldst_imm12_scale2:
129   case AArch64::fixup_aarch64_ldst_imm12_scale4:
130   case AArch64::fixup_aarch64_ldst_imm12_scale8:
131   case AArch64::fixup_aarch64_ldst_imm12_scale16:
132     if (const AArch64MCExpr *A64E = dyn_cast<AArch64MCExpr>(Expr)) {
133       AArch64MCExpr::VariantKind RefKind = A64E->getKind();
134       if (RefKind == AArch64MCExpr::VK_SECREL_LO12)
135         return COFF::IMAGE_REL_ARM64_SECREL_LOW12L;
136     }
137     return COFF::IMAGE_REL_ARM64_PAGEOFFSET_12L;
138 
139   case AArch64::fixup_aarch64_pcrel_adr_imm21:
140     return COFF::IMAGE_REL_ARM64_REL21;
141 
142   case AArch64::fixup_aarch64_pcrel_adrp_imm21:
143     return COFF::IMAGE_REL_ARM64_PAGEBASE_REL21;
144 
145   case AArch64::fixup_aarch64_pcrel_branch14:
146     return COFF::IMAGE_REL_ARM64_BRANCH14;
147 
148   case AArch64::fixup_aarch64_pcrel_branch19:
149     return COFF::IMAGE_REL_ARM64_BRANCH19;
150 
151   case AArch64::fixup_aarch64_pcrel_branch26:
152   case AArch64::fixup_aarch64_pcrel_call26:
153     return COFF::IMAGE_REL_ARM64_BRANCH26;
154   }
155 }
156 
recordRelocation(const MCFixup & Fixup) const157 bool AArch64WinCOFFObjectWriter::recordRelocation(const MCFixup &Fixup) const {
158   return true;
159 }
160 
createAArch64WinCOFFObjectWriter()161 std::unique_ptr<MCObjectTargetWriter> llvm::createAArch64WinCOFFObjectWriter() {
162   return std::make_unique<AArch64WinCOFFObjectWriter>();
163 }
164