1 //===-- ARMELFObjectWriter.cpp - ARM ELF Writer ---------------------------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9
10 #include "MCTargetDesc/ARMMCTargetDesc.h"
11 #include "MCTargetDesc/ARMFixupKinds.h"
12 #include "llvm/ADT/Statistic.h"
13 #include "llvm/ADT/StringSwitch.h"
14 #include "llvm/MC/MCELFObjectWriter.h"
15 #include "llvm/MC/MCExpr.h"
16 #include "llvm/MC/MCSectionELF.h"
17 #include "llvm/MC/MCValue.h"
18 #include "llvm/Support/Debug.h"
19 #include "llvm/Support/ErrorHandling.h"
20 #include "llvm/Support/raw_ostream.h"
21
22 using namespace llvm;
23
24 namespace {
25 class ARMELFObjectWriter : public MCELFObjectTargetWriter {
26 enum { DefaultEABIVersion = 0x05000000U };
27 unsigned GetRelocTypeInner(const MCValue &Target,
28 const MCFixup &Fixup,
29 bool IsPCRel) const;
30
31
32 public:
33 ARMELFObjectWriter(uint8_t OSABI);
34
35 virtual ~ARMELFObjectWriter();
36
37 unsigned GetRelocType(const MCValue &Target, const MCFixup &Fixup,
38 bool IsPCRel) const override;
39
40 bool needsRelocateWithSymbol(unsigned Type) const override;
41 };
42 }
43
ARMELFObjectWriter(uint8_t OSABI)44 ARMELFObjectWriter::ARMELFObjectWriter(uint8_t OSABI)
45 : MCELFObjectTargetWriter(/*Is64Bit*/ false, OSABI,
46 ELF::EM_ARM,
47 /*HasRelocationAddend*/ false) {}
48
~ARMELFObjectWriter()49 ARMELFObjectWriter::~ARMELFObjectWriter() {}
50
needsRelocateWithSymbol(unsigned Type) const51 bool ARMELFObjectWriter::needsRelocateWithSymbol(unsigned Type) const {
52 // FIXME: This is extremelly conservative. This really needs to use a
53 // whitelist with a clear explanation for why each realocation needs to
54 // point to the symbol, not to the section.
55 switch (Type) {
56 default:
57 return true;
58
59 case ELF::R_ARM_PREL31:
60 case ELF::R_ARM_ABS32:
61 return false;
62 }
63 }
64
65 // Need to examine the Fixup when determining whether to
66 // emit the relocation as an explicit symbol or as a section relative
67 // offset
GetRelocType(const MCValue & Target,const MCFixup & Fixup,bool IsPCRel) const68 unsigned ARMELFObjectWriter::GetRelocType(const MCValue &Target,
69 const MCFixup &Fixup,
70 bool IsPCRel) const {
71 return GetRelocTypeInner(Target, Fixup, IsPCRel);
72 }
73
GetRelocTypeInner(const MCValue & Target,const MCFixup & Fixup,bool IsPCRel) const74 unsigned ARMELFObjectWriter::GetRelocTypeInner(const MCValue &Target,
75 const MCFixup &Fixup,
76 bool IsPCRel) const {
77 MCSymbolRefExpr::VariantKind Modifier = Target.getAccessVariant();
78
79 unsigned Type = 0;
80 if (IsPCRel) {
81 switch ((unsigned)Fixup.getKind()) {
82 default: llvm_unreachable("Unimplemented");
83 case FK_Data_4:
84 switch (Modifier) {
85 default: llvm_unreachable("Unsupported Modifier");
86 case MCSymbolRefExpr::VK_None:
87 Type = ELF::R_ARM_REL32;
88 break;
89 case MCSymbolRefExpr::VK_TLSGD:
90 llvm_unreachable("unimplemented");
91 case MCSymbolRefExpr::VK_GOTTPOFF:
92 Type = ELF::R_ARM_TLS_IE32;
93 break;
94 case MCSymbolRefExpr::VK_GOTPCREL:
95 Type = ELF::R_ARM_GOT_PREL;
96 break;
97 }
98 break;
99 case ARM::fixup_arm_blx:
100 case ARM::fixup_arm_uncondbl:
101 switch (Modifier) {
102 case MCSymbolRefExpr::VK_PLT:
103 Type = ELF::R_ARM_PLT32;
104 break;
105 case MCSymbolRefExpr::VK_ARM_TLSCALL:
106 Type = ELF::R_ARM_TLS_CALL;
107 break;
108 default:
109 Type = ELF::R_ARM_CALL;
110 break;
111 }
112 break;
113 case ARM::fixup_arm_condbl:
114 case ARM::fixup_arm_condbranch:
115 case ARM::fixup_arm_uncondbranch:
116 Type = ELF::R_ARM_JUMP24;
117 break;
118 case ARM::fixup_t2_condbranch:
119 case ARM::fixup_t2_uncondbranch:
120 Type = ELF::R_ARM_THM_JUMP24;
121 break;
122 case ARM::fixup_arm_movt_hi16:
123 Type = ELF::R_ARM_MOVT_PREL;
124 break;
125 case ARM::fixup_arm_movw_lo16:
126 Type = ELF::R_ARM_MOVW_PREL_NC;
127 break;
128 case ARM::fixup_t2_movt_hi16:
129 Type = ELF::R_ARM_THM_MOVT_PREL;
130 break;
131 case ARM::fixup_t2_movw_lo16:
132 Type = ELF::R_ARM_THM_MOVW_PREL_NC;
133 break;
134 case ARM::fixup_arm_thumb_bl:
135 case ARM::fixup_arm_thumb_blx:
136 switch (Modifier) {
137 case MCSymbolRefExpr::VK_ARM_TLSCALL:
138 Type = ELF::R_ARM_THM_TLS_CALL;
139 break;
140 default:
141 Type = ELF::R_ARM_THM_CALL;
142 break;
143 }
144 break;
145 }
146 } else {
147 switch ((unsigned)Fixup.getKind()) {
148 default: llvm_unreachable("invalid fixup kind!");
149 case FK_Data_4:
150 switch (Modifier) {
151 default: llvm_unreachable("Unsupported Modifier");
152 case MCSymbolRefExpr::VK_ARM_NONE:
153 Type = ELF::R_ARM_NONE;
154 break;
155 case MCSymbolRefExpr::VK_GOT:
156 Type = ELF::R_ARM_GOT_BREL;
157 break;
158 case MCSymbolRefExpr::VK_TLSGD:
159 Type = ELF::R_ARM_TLS_GD32;
160 break;
161 case MCSymbolRefExpr::VK_TPOFF:
162 Type = ELF::R_ARM_TLS_LE32;
163 break;
164 case MCSymbolRefExpr::VK_GOTTPOFF:
165 Type = ELF::R_ARM_TLS_IE32;
166 break;
167 case MCSymbolRefExpr::VK_None:
168 Type = ELF::R_ARM_ABS32;
169 break;
170 case MCSymbolRefExpr::VK_GOTOFF:
171 Type = ELF::R_ARM_GOTOFF32;
172 break;
173 case MCSymbolRefExpr::VK_GOTPCREL:
174 Type = ELF::R_ARM_GOT_PREL;
175 break;
176 case MCSymbolRefExpr::VK_ARM_TARGET1:
177 Type = ELF::R_ARM_TARGET1;
178 break;
179 case MCSymbolRefExpr::VK_ARM_TARGET2:
180 Type = ELF::R_ARM_TARGET2;
181 break;
182 case MCSymbolRefExpr::VK_ARM_PREL31:
183 Type = ELF::R_ARM_PREL31;
184 break;
185 case MCSymbolRefExpr::VK_ARM_TLSLDO:
186 Type = ELF::R_ARM_TLS_LDO32;
187 break;
188 case MCSymbolRefExpr::VK_ARM_TLSCALL:
189 Type = ELF::R_ARM_TLS_CALL;
190 break;
191 case MCSymbolRefExpr::VK_ARM_TLSDESC:
192 Type = ELF::R_ARM_TLS_GOTDESC;
193 break;
194 case MCSymbolRefExpr::VK_ARM_TLSDESCSEQ:
195 Type = ELF::R_ARM_TLS_DESCSEQ;
196 break;
197 }
198 break;
199 case ARM::fixup_arm_ldst_pcrel_12:
200 case ARM::fixup_arm_pcrel_10:
201 case ARM::fixup_arm_adr_pcrel_12:
202 case ARM::fixup_arm_thumb_bl:
203 case ARM::fixup_arm_thumb_cb:
204 case ARM::fixup_arm_thumb_cp:
205 case ARM::fixup_arm_thumb_br:
206 llvm_unreachable("Unimplemented");
207 case ARM::fixup_arm_condbranch:
208 case ARM::fixup_arm_uncondbranch:
209 Type = ELF::R_ARM_JUMP24;
210 break;
211 case ARM::fixup_arm_movt_hi16:
212 Type = ELF::R_ARM_MOVT_ABS;
213 break;
214 case ARM::fixup_arm_movw_lo16:
215 Type = ELF::R_ARM_MOVW_ABS_NC;
216 break;
217 case ARM::fixup_t2_movt_hi16:
218 Type = ELF::R_ARM_THM_MOVT_ABS;
219 break;
220 case ARM::fixup_t2_movw_lo16:
221 Type = ELF::R_ARM_THM_MOVW_ABS_NC;
222 break;
223 }
224 }
225
226 return Type;
227 }
228
createARMELFObjectWriter(raw_ostream & OS,uint8_t OSABI,bool IsLittleEndian)229 MCObjectWriter *llvm::createARMELFObjectWriter(raw_ostream &OS,
230 uint8_t OSABI,
231 bool IsLittleEndian) {
232 MCELFObjectTargetWriter *MOTW = new ARMELFObjectWriter(OSABI);
233 return createELFObjectWriter(MOTW, OS, IsLittleEndian);
234 }
235