1 //===-- X86WinCOFFObjectWriter.cpp - X86 Win COFF Writer ------------------===//
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 "MCTargetDesc/X86FixupKinds.h"
10 #include "MCTargetDesc/X86MCTargetDesc.h"
11 #include "llvm/BinaryFormat/COFF.h"
12 #include "llvm/MC/MCContext.h"
13 #include "llvm/MC/MCExpr.h"
14 #include "llvm/MC/MCFixup.h"
15 #include "llvm/MC/MCObjectWriter.h"
16 #include "llvm/MC/MCValue.h"
17 #include "llvm/MC/MCWinCOFFObjectWriter.h"
18 #include "llvm/Support/ErrorHandling.h"
19 
20 using namespace llvm;
21 
22 namespace {
23 
24 class X86WinCOFFObjectWriter : public MCWinCOFFObjectTargetWriter {
25 public:
26   X86WinCOFFObjectWriter(bool Is64Bit);
27   ~X86WinCOFFObjectWriter() override = default;
28 
29   unsigned getRelocType(MCContext &Ctx, const MCValue &Target,
30                         const MCFixup &Fixup, bool IsCrossSection,
31                         const MCAsmBackend &MAB) const override;
32 };
33 
34 } // end anonymous namespace
35 
36 X86WinCOFFObjectWriter::X86WinCOFFObjectWriter(bool Is64Bit)
37     : MCWinCOFFObjectTargetWriter(Is64Bit ? COFF::IMAGE_FILE_MACHINE_AMD64
38                                           : COFF::IMAGE_FILE_MACHINE_I386) {}
39 
40 unsigned X86WinCOFFObjectWriter::getRelocType(MCContext &Ctx,
41                                               const MCValue &Target,
42                                               const MCFixup &Fixup,
43                                               bool IsCrossSection,
44                                               const MCAsmBackend &MAB) const {
45   const bool Is64Bit = getMachine() == COFF::IMAGE_FILE_MACHINE_AMD64;
46   unsigned FixupKind = Fixup.getKind();
47   if (IsCrossSection) {
48     // IMAGE_REL_AMD64_REL64 does not exist. We treat FK_Data_8 as FK_PCRel_4 so
49     // that .quad a-b can lower to IMAGE_REL_AMD64_REL32. This allows generic
50     // instrumentation to not bother with the COFF limitation. A negative value
51     // needs attention.
52     if (FixupKind == FK_Data_4 || FixupKind == llvm::X86::reloc_signed_4byte ||
53         (FixupKind == FK_Data_8 && Is64Bit)) {
54       FixupKind = FK_PCRel_4;
55     } else {
56       Ctx.reportError(Fixup.getLoc(), "Cannot represent this expression");
57       return COFF::IMAGE_REL_AMD64_ADDR32;
58     }
59   }
60 
61   MCSymbolRefExpr::VariantKind Modifier = Target.isAbsolute() ?
62     MCSymbolRefExpr::VK_None : Target.getSymA()->getKind();
63 
64   if (Is64Bit) {
65     switch (FixupKind) {
66     case FK_PCRel_4:
67     case X86::reloc_riprel_4byte:
68     case X86::reloc_riprel_4byte_movq_load:
69     case X86::reloc_riprel_4byte_relax:
70     case X86::reloc_riprel_4byte_relax_rex:
71     case X86::reloc_branch_4byte_pcrel:
72       return COFF::IMAGE_REL_AMD64_REL32;
73     case FK_Data_4:
74     case X86::reloc_signed_4byte:
75     case X86::reloc_signed_4byte_relax:
76       if (Modifier == MCSymbolRefExpr::VK_COFF_IMGREL32)
77         return COFF::IMAGE_REL_AMD64_ADDR32NB;
78       if (Modifier == MCSymbolRefExpr::VK_SECREL)
79         return COFF::IMAGE_REL_AMD64_SECREL;
80       return COFF::IMAGE_REL_AMD64_ADDR32;
81     case FK_Data_8:
82       return COFF::IMAGE_REL_AMD64_ADDR64;
83     case FK_SecRel_2:
84       return COFF::IMAGE_REL_AMD64_SECTION;
85     case FK_SecRel_4:
86       return COFF::IMAGE_REL_AMD64_SECREL;
87     default:
88       Ctx.reportError(Fixup.getLoc(), "unsupported relocation type");
89       return COFF::IMAGE_REL_AMD64_ADDR32;
90     }
91   } else if (getMachine() == COFF::IMAGE_FILE_MACHINE_I386) {
92     switch (FixupKind) {
93     case FK_PCRel_4:
94     case X86::reloc_riprel_4byte:
95     case X86::reloc_riprel_4byte_movq_load:
96       return COFF::IMAGE_REL_I386_REL32;
97     case FK_Data_4:
98     case X86::reloc_signed_4byte:
99     case X86::reloc_signed_4byte_relax:
100       if (Modifier == MCSymbolRefExpr::VK_COFF_IMGREL32)
101         return COFF::IMAGE_REL_I386_DIR32NB;
102       if (Modifier == MCSymbolRefExpr::VK_SECREL)
103         return COFF::IMAGE_REL_AMD64_SECREL;
104       return COFF::IMAGE_REL_I386_DIR32;
105     case FK_SecRel_2:
106       return COFF::IMAGE_REL_I386_SECTION;
107     case FK_SecRel_4:
108       return COFF::IMAGE_REL_I386_SECREL;
109     default:
110       Ctx.reportError(Fixup.getLoc(), "unsupported relocation type");
111       return COFF::IMAGE_REL_I386_DIR32;
112     }
113   } else
114     llvm_unreachable("Unsupported COFF machine type.");
115 }
116 
117 std::unique_ptr<MCObjectTargetWriter>
118 llvm::createX86WinCOFFObjectWriter(bool Is64Bit) {
119   return std::make_unique<X86WinCOFFObjectWriter>(Is64Bit);
120 }
121