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:
33   AArch64WinCOFFObjectWriter(const Triple &TheTriple)
34       : MCWinCOFFObjectTargetWriter(TheTriple.isWindowsArm64EC()
35                                         ? COFF::IMAGE_FILE_MACHINE_ARM64EC
36                                         : COFF::IMAGE_FILE_MACHINE_ARM64) {}
37 
38   ~AArch64WinCOFFObjectWriter() override = default;
39 
40   unsigned getRelocType(MCContext &Ctx, const MCValue &Target,
41                         const MCFixup &Fixup, bool IsCrossSection,
42                         const MCAsmBackend &MAB) const override;
43 
44   bool recordRelocation(const MCFixup &) const override;
45 };
46 
47 } // end anonymous namespace
48 
49 unsigned AArch64WinCOFFObjectWriter::getRelocType(
50     MCContext &Ctx, const MCValue &Target, const MCFixup &Fixup,
51     bool IsCrossSection, const MCAsmBackend &MAB) const {
52   unsigned FixupKind = Fixup.getKind();
53   if (IsCrossSection) {
54     // IMAGE_REL_ARM64_REL64 does not exist. We treat FK_Data_8 as FK_PCRel_4 so
55     // that .xword a-b can lower to IMAGE_REL_ARM64_REL32. This allows generic
56     // instrumentation to not bother with the COFF limitation. A negative value
57     // needs attention.
58     if (FixupKind != FK_Data_4 && FixupKind != FK_Data_8) {
59       Ctx.reportError(Fixup.getLoc(), "Cannot represent this expression");
60       return COFF::IMAGE_REL_ARM64_ADDR32;
61     }
62     FixupKind = FK_PCRel_4;
63   }
64 
65   auto Modifier = Target.isAbsolute() ? MCSymbolRefExpr::VK_None
66                                       : Target.getSymA()->getKind();
67   const MCExpr *Expr = Fixup.getValue();
68 
69   if (const AArch64MCExpr *A64E = dyn_cast<AArch64MCExpr>(Expr)) {
70     AArch64MCExpr::VariantKind RefKind = A64E->getKind();
71     switch (AArch64MCExpr::getSymbolLoc(RefKind)) {
72     case AArch64MCExpr::VK_ABS:
73     case AArch64MCExpr::VK_SECREL:
74       // Supported
75       break;
76     default:
77       Ctx.reportError(Fixup.getLoc(), "relocation variant " +
78                                           A64E->getVariantKindName() +
79                                           " unsupported on COFF targets");
80       return COFF::IMAGE_REL_ARM64_ABSOLUTE; // Dummy return value
81     }
82   }
83 
84   switch (FixupKind) {
85   default: {
86     if (const AArch64MCExpr *A64E = dyn_cast<AArch64MCExpr>(Expr)) {
87       Ctx.reportError(Fixup.getLoc(), "relocation type " +
88                                           A64E->getVariantKindName() +
89                                           " unsupported on COFF targets");
90     } else {
91       const MCFixupKindInfo &Info = MAB.getFixupKindInfo(Fixup.getKind());
92       Ctx.reportError(Fixup.getLoc(), Twine("relocation type ") + Info.Name +
93                                           " unsupported on COFF targets");
94     }
95     return COFF::IMAGE_REL_ARM64_ABSOLUTE; // Dummy return value
96   }
97 
98   case FK_PCRel_4:
99     return COFF::IMAGE_REL_ARM64_REL32;
100 
101   case FK_Data_4:
102     switch (Modifier) {
103     default:
104       return COFF::IMAGE_REL_ARM64_ADDR32;
105     case MCSymbolRefExpr::VK_COFF_IMGREL32:
106       return COFF::IMAGE_REL_ARM64_ADDR32NB;
107     case MCSymbolRefExpr::VK_SECREL:
108       return COFF::IMAGE_REL_ARM64_SECREL;
109     }
110 
111   case FK_Data_8:
112     return COFF::IMAGE_REL_ARM64_ADDR64;
113 
114   case FK_SecRel_2:
115     return COFF::IMAGE_REL_ARM64_SECTION;
116 
117   case FK_SecRel_4:
118     return COFF::IMAGE_REL_ARM64_SECREL;
119 
120   case AArch64::fixup_aarch64_add_imm12:
121     if (const AArch64MCExpr *A64E = dyn_cast<AArch64MCExpr>(Expr)) {
122       AArch64MCExpr::VariantKind RefKind = A64E->getKind();
123       if (RefKind == AArch64MCExpr::VK_SECREL_LO12)
124         return COFF::IMAGE_REL_ARM64_SECREL_LOW12A;
125       if (RefKind == AArch64MCExpr::VK_SECREL_HI12)
126         return COFF::IMAGE_REL_ARM64_SECREL_HIGH12A;
127     }
128     return COFF::IMAGE_REL_ARM64_PAGEOFFSET_12A;
129 
130   case AArch64::fixup_aarch64_ldst_imm12_scale1:
131   case AArch64::fixup_aarch64_ldst_imm12_scale2:
132   case AArch64::fixup_aarch64_ldst_imm12_scale4:
133   case AArch64::fixup_aarch64_ldst_imm12_scale8:
134   case AArch64::fixup_aarch64_ldst_imm12_scale16:
135     if (const AArch64MCExpr *A64E = dyn_cast<AArch64MCExpr>(Expr)) {
136       AArch64MCExpr::VariantKind RefKind = A64E->getKind();
137       if (RefKind == AArch64MCExpr::VK_SECREL_LO12)
138         return COFF::IMAGE_REL_ARM64_SECREL_LOW12L;
139     }
140     return COFF::IMAGE_REL_ARM64_PAGEOFFSET_12L;
141 
142   case AArch64::fixup_aarch64_pcrel_adr_imm21:
143     return COFF::IMAGE_REL_ARM64_REL21;
144 
145   case AArch64::fixup_aarch64_pcrel_adrp_imm21:
146     return COFF::IMAGE_REL_ARM64_PAGEBASE_REL21;
147 
148   case AArch64::fixup_aarch64_pcrel_branch14:
149     return COFF::IMAGE_REL_ARM64_BRANCH14;
150 
151   case AArch64::fixup_aarch64_pcrel_branch19:
152     return COFF::IMAGE_REL_ARM64_BRANCH19;
153 
154   case AArch64::fixup_aarch64_pcrel_branch26:
155   case AArch64::fixup_aarch64_pcrel_call26:
156     return COFF::IMAGE_REL_ARM64_BRANCH26;
157   }
158 }
159 
160 bool AArch64WinCOFFObjectWriter::recordRelocation(const MCFixup &Fixup) const {
161   return true;
162 }
163 
164 std::unique_ptr<MCObjectTargetWriter>
165 llvm::createAArch64WinCOFFObjectWriter(const Triple &TheTriple) {
166   return std::make_unique<AArch64WinCOFFObjectWriter>(TheTriple);
167 }
168