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/Casting.h"
23 #include "llvm/Support/ErrorHandling.h"
24 #include "llvm/Support/raw_ostream.h"
25 #include <cassert>
26 
27 using namespace llvm;
28 
29 namespace {
30 
31 class AArch64WinCOFFObjectWriter : public MCWinCOFFObjectTargetWriter {
32 public:
AArch64WinCOFFObjectWriter()33   AArch64WinCOFFObjectWriter()
34       : MCWinCOFFObjectTargetWriter(COFF::IMAGE_FILE_MACHINE_ARM64) {}
35 
36   ~AArch64WinCOFFObjectWriter() override = default;
37 
38   unsigned getRelocType(MCContext &Ctx, const MCValue &Target,
39                         const MCFixup &Fixup, bool IsCrossSection,
40                         const MCAsmBackend &MAB) const override;
41 
42   bool recordRelocation(const MCFixup &) const override;
43 };
44 
45 } // end anonymous namespace
46 
getRelocType(MCContext & Ctx,const MCValue & Target,const MCFixup & Fixup,bool IsCrossSection,const MCAsmBackend & MAB) const47 unsigned AArch64WinCOFFObjectWriter::getRelocType(
48     MCContext &Ctx, const MCValue &Target, const MCFixup &Fixup,
49     bool IsCrossSection, const MCAsmBackend &MAB) const {
50   unsigned FixupKind = Fixup.getKind();
51   if (IsCrossSection) {
52     // IMAGE_REL_ARM64_REL64 does not exist. We treat FK_Data_8 as FK_PCRel_4 so
53     // that .xword a-b can lower to IMAGE_REL_ARM64_REL32. This allows generic
54     // instrumentation to not bother with the COFF limitation. A negative value
55     // needs attention.
56     if (FixupKind != FK_Data_4 && FixupKind != FK_Data_8) {
57       Ctx.reportError(Fixup.getLoc(), "Cannot represent this expression");
58       return COFF::IMAGE_REL_ARM64_ADDR32;
59     }
60     FixupKind = FK_PCRel_4;
61   }
62 
63   auto Modifier = Target.isAbsolute() ? MCSymbolRefExpr::VK_None
64                                       : Target.getSymA()->getKind();
65   const MCExpr *Expr = Fixup.getValue();
66 
67   if (const AArch64MCExpr *A64E = dyn_cast<AArch64MCExpr>(Expr)) {
68     AArch64MCExpr::VariantKind RefKind = A64E->getKind();
69     switch (AArch64MCExpr::getSymbolLoc(RefKind)) {
70     case AArch64MCExpr::VK_ABS:
71     case AArch64MCExpr::VK_SECREL:
72       // Supported
73       break;
74     default:
75       Ctx.reportError(Fixup.getLoc(), "relocation variant " +
76                                           A64E->getVariantKindName() +
77                                           " unsupported on COFF targets");
78       return COFF::IMAGE_REL_ARM64_ABSOLUTE; // Dummy return value
79     }
80   }
81 
82   switch (FixupKind) {
83   default: {
84     if (const AArch64MCExpr *A64E = dyn_cast<AArch64MCExpr>(Expr)) {
85       Ctx.reportError(Fixup.getLoc(), "relocation type " +
86                                           A64E->getVariantKindName() +
87                                           " unsupported on COFF targets");
88     } else {
89       const MCFixupKindInfo &Info = MAB.getFixupKindInfo(Fixup.getKind());
90       Ctx.reportError(Fixup.getLoc(), Twine("relocation type ") + Info.Name +
91                                           " unsupported on COFF targets");
92     }
93     return COFF::IMAGE_REL_ARM64_ABSOLUTE; // Dummy return value
94   }
95 
96   case FK_PCRel_4:
97     return COFF::IMAGE_REL_ARM64_REL32;
98 
99   case FK_Data_4:
100     switch (Modifier) {
101     default:
102       return COFF::IMAGE_REL_ARM64_ADDR32;
103     case MCSymbolRefExpr::VK_COFF_IMGREL32:
104       return COFF::IMAGE_REL_ARM64_ADDR32NB;
105     case MCSymbolRefExpr::VK_SECREL:
106       return COFF::IMAGE_REL_ARM64_SECREL;
107     }
108 
109   case FK_Data_8:
110     return COFF::IMAGE_REL_ARM64_ADDR64;
111 
112   case FK_SecRel_2:
113     return COFF::IMAGE_REL_ARM64_SECTION;
114 
115   case FK_SecRel_4:
116     return COFF::IMAGE_REL_ARM64_SECREL;
117 
118   case AArch64::fixup_aarch64_add_imm12:
119     if (const AArch64MCExpr *A64E = dyn_cast<AArch64MCExpr>(Expr)) {
120       AArch64MCExpr::VariantKind RefKind = A64E->getKind();
121       if (RefKind == AArch64MCExpr::VK_SECREL_LO12)
122         return COFF::IMAGE_REL_ARM64_SECREL_LOW12A;
123       if (RefKind == AArch64MCExpr::VK_SECREL_HI12)
124         return COFF::IMAGE_REL_ARM64_SECREL_HIGH12A;
125     }
126     return COFF::IMAGE_REL_ARM64_PAGEOFFSET_12A;
127 
128   case AArch64::fixup_aarch64_ldst_imm12_scale1:
129   case AArch64::fixup_aarch64_ldst_imm12_scale2:
130   case AArch64::fixup_aarch64_ldst_imm12_scale4:
131   case AArch64::fixup_aarch64_ldst_imm12_scale8:
132   case AArch64::fixup_aarch64_ldst_imm12_scale16:
133     if (const AArch64MCExpr *A64E = dyn_cast<AArch64MCExpr>(Expr)) {
134       AArch64MCExpr::VariantKind RefKind = A64E->getKind();
135       if (RefKind == AArch64MCExpr::VK_SECREL_LO12)
136         return COFF::IMAGE_REL_ARM64_SECREL_LOW12L;
137     }
138     return COFF::IMAGE_REL_ARM64_PAGEOFFSET_12L;
139 
140   case AArch64::fixup_aarch64_pcrel_adr_imm21:
141     return COFF::IMAGE_REL_ARM64_REL21;
142 
143   case AArch64::fixup_aarch64_pcrel_adrp_imm21:
144     return COFF::IMAGE_REL_ARM64_PAGEBASE_REL21;
145 
146   case AArch64::fixup_aarch64_pcrel_branch14:
147     return COFF::IMAGE_REL_ARM64_BRANCH14;
148 
149   case AArch64::fixup_aarch64_pcrel_branch19:
150     return COFF::IMAGE_REL_ARM64_BRANCH19;
151 
152   case AArch64::fixup_aarch64_pcrel_branch26:
153   case AArch64::fixup_aarch64_pcrel_call26:
154     return COFF::IMAGE_REL_ARM64_BRANCH26;
155   }
156 }
157 
recordRelocation(const MCFixup & Fixup) const158 bool AArch64WinCOFFObjectWriter::recordRelocation(const MCFixup &Fixup) const {
159   return true;
160 }
161 
createAArch64WinCOFFObjectWriter()162 std::unique_ptr<MCObjectTargetWriter> llvm::createAArch64WinCOFFObjectWriter() {
163   return std::make_unique<AArch64WinCOFFObjectWriter>();
164 }
165