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 ~ARMELFObjectWriter() override;
36
37 unsigned getRelocType(MCContext &Ctx, const MCValue &Target,
38 const MCFixup &Fixup, bool IsPCRel) const override;
39
40 bool needsRelocateWithSymbol(const MCSymbol &Sym,
41 unsigned Type) const override;
42 };
43 }
44
ARMELFObjectWriter(uint8_t OSABI)45 ARMELFObjectWriter::ARMELFObjectWriter(uint8_t OSABI)
46 : MCELFObjectTargetWriter(/*Is64Bit*/ false, OSABI,
47 ELF::EM_ARM,
48 /*HasRelocationAddend*/ false) {}
49
~ARMELFObjectWriter()50 ARMELFObjectWriter::~ARMELFObjectWriter() {}
51
needsRelocateWithSymbol(const MCSymbol & Sym,unsigned Type) const52 bool ARMELFObjectWriter::needsRelocateWithSymbol(const MCSymbol &Sym,
53 unsigned Type) const {
54 // FIXME: This is extremely conservative. This really needs to use a
55 // whitelist with a clear explanation for why each realocation needs to
56 // point to the symbol, not to the section.
57 switch (Type) {
58 default:
59 return true;
60
61 case ELF::R_ARM_PREL31:
62 case ELF::R_ARM_ABS32:
63 return false;
64 }
65 }
66
67 // Need to examine the Fixup when determining whether to
68 // emit the relocation as an explicit symbol or as a section relative
69 // offset
getRelocType(MCContext & Ctx,const MCValue & Target,const MCFixup & Fixup,bool IsPCRel) const70 unsigned ARMELFObjectWriter::getRelocType(MCContext &Ctx, const MCValue &Target,
71 const MCFixup &Fixup,
72 bool IsPCRel) const {
73 return GetRelocTypeInner(Target, Fixup, IsPCRel);
74 }
75
GetRelocTypeInner(const MCValue & Target,const MCFixup & Fixup,bool IsPCRel) const76 unsigned ARMELFObjectWriter::GetRelocTypeInner(const MCValue &Target,
77 const MCFixup &Fixup,
78 bool IsPCRel) const {
79 MCSymbolRefExpr::VariantKind Modifier = Target.getAccessVariant();
80
81 unsigned Type = 0;
82 if (IsPCRel) {
83 switch ((unsigned)Fixup.getKind()) {
84 default:
85 report_fatal_error("unsupported relocation on symbol");
86 return ELF::R_ARM_NONE;
87 case FK_Data_4:
88 switch (Modifier) {
89 default: llvm_unreachable("Unsupported Modifier");
90 case MCSymbolRefExpr::VK_None:
91 Type = ELF::R_ARM_REL32;
92 break;
93 case MCSymbolRefExpr::VK_TLSGD:
94 llvm_unreachable("unimplemented");
95 case MCSymbolRefExpr::VK_GOTTPOFF:
96 Type = ELF::R_ARM_TLS_IE32;
97 break;
98 case MCSymbolRefExpr::VK_ARM_GOT_PREL:
99 Type = ELF::R_ARM_GOT_PREL;
100 break;
101 case MCSymbolRefExpr::VK_ARM_PREL31:
102 Type = ELF::R_ARM_PREL31;
103 break;
104 }
105 break;
106 case ARM::fixup_arm_blx:
107 case ARM::fixup_arm_uncondbl:
108 switch (Modifier) {
109 case MCSymbolRefExpr::VK_PLT:
110 Type = ELF::R_ARM_CALL;
111 break;
112 case MCSymbolRefExpr::VK_TLSCALL:
113 Type = ELF::R_ARM_TLS_CALL;
114 break;
115 default:
116 Type = ELF::R_ARM_CALL;
117 break;
118 }
119 break;
120 case ARM::fixup_arm_condbl:
121 case ARM::fixup_arm_condbranch:
122 case ARM::fixup_arm_uncondbranch:
123 Type = ELF::R_ARM_JUMP24;
124 break;
125 case ARM::fixup_t2_condbranch:
126 Type = ELF::R_ARM_THM_JUMP19;
127 break;
128 case ARM::fixup_t2_uncondbranch:
129 Type = ELF::R_ARM_THM_JUMP24;
130 break;
131 case ARM::fixup_arm_movt_hi16:
132 Type = ELF::R_ARM_MOVT_PREL;
133 break;
134 case ARM::fixup_arm_movw_lo16:
135 Type = ELF::R_ARM_MOVW_PREL_NC;
136 break;
137 case ARM::fixup_t2_movt_hi16:
138 Type = ELF::R_ARM_THM_MOVT_PREL;
139 break;
140 case ARM::fixup_t2_movw_lo16:
141 Type = ELF::R_ARM_THM_MOVW_PREL_NC;
142 break;
143 case ARM::fixup_arm_thumb_bl:
144 case ARM::fixup_arm_thumb_blx:
145 switch (Modifier) {
146 case MCSymbolRefExpr::VK_TLSCALL:
147 Type = ELF::R_ARM_THM_TLS_CALL;
148 break;
149 default:
150 Type = ELF::R_ARM_THM_CALL;
151 break;
152 }
153 break;
154 }
155 } else {
156 switch ((unsigned)Fixup.getKind()) {
157 default:
158 report_fatal_error("unsupported relocation on symbol");
159 return ELF::R_ARM_NONE;
160 case FK_Data_1:
161 switch (Modifier) {
162 default: llvm_unreachable("unsupported Modifier");
163 case MCSymbolRefExpr::VK_None:
164 Type = ELF::R_ARM_ABS8;
165 break;
166 }
167 break;
168 case FK_Data_2:
169 switch (Modifier) {
170 default: llvm_unreachable("unsupported modifier");
171 case MCSymbolRefExpr::VK_None:
172 Type = ELF::R_ARM_ABS16;
173 break;
174 }
175 break;
176 case FK_Data_4:
177 switch (Modifier) {
178 default: llvm_unreachable("Unsupported Modifier");
179 case MCSymbolRefExpr::VK_ARM_NONE:
180 Type = ELF::R_ARM_NONE;
181 break;
182 case MCSymbolRefExpr::VK_GOT:
183 Type = ELF::R_ARM_GOT_BREL;
184 break;
185 case MCSymbolRefExpr::VK_TLSGD:
186 Type = ELF::R_ARM_TLS_GD32;
187 break;
188 case MCSymbolRefExpr::VK_TPOFF:
189 Type = ELF::R_ARM_TLS_LE32;
190 break;
191 case MCSymbolRefExpr::VK_GOTTPOFF:
192 Type = ELF::R_ARM_TLS_IE32;
193 break;
194 case MCSymbolRefExpr::VK_None:
195 Type = ELF::R_ARM_ABS32;
196 break;
197 case MCSymbolRefExpr::VK_GOTOFF:
198 Type = ELF::R_ARM_GOTOFF32;
199 break;
200 case MCSymbolRefExpr::VK_ARM_GOT_PREL:
201 Type = ELF::R_ARM_GOT_PREL;
202 break;
203 case MCSymbolRefExpr::VK_ARM_TARGET1:
204 Type = ELF::R_ARM_TARGET1;
205 break;
206 case MCSymbolRefExpr::VK_ARM_TARGET2:
207 Type = ELF::R_ARM_TARGET2;
208 break;
209 case MCSymbolRefExpr::VK_ARM_PREL31:
210 Type = ELF::R_ARM_PREL31;
211 break;
212 case MCSymbolRefExpr::VK_ARM_SBREL:
213 Type = ELF::R_ARM_SBREL32;
214 break;
215 case MCSymbolRefExpr::VK_ARM_TLSLDO:
216 Type = ELF::R_ARM_TLS_LDO32;
217 break;
218 case MCSymbolRefExpr::VK_TLSCALL:
219 Type = ELF::R_ARM_TLS_CALL;
220 break;
221 case MCSymbolRefExpr::VK_TLSDESC:
222 Type = ELF::R_ARM_TLS_GOTDESC;
223 break;
224 case MCSymbolRefExpr::VK_ARM_TLSDESCSEQ:
225 Type = ELF::R_ARM_TLS_DESCSEQ;
226 break;
227 }
228 break;
229 case ARM::fixup_arm_ldst_pcrel_12:
230 case ARM::fixup_arm_pcrel_10:
231 case ARM::fixup_arm_adr_pcrel_12:
232 case ARM::fixup_arm_thumb_bl:
233 case ARM::fixup_arm_thumb_cb:
234 case ARM::fixup_arm_thumb_cp:
235 case ARM::fixup_arm_thumb_br:
236 llvm_unreachable("Unimplemented");
237 case ARM::fixup_arm_condbranch:
238 case ARM::fixup_arm_uncondbranch:
239 Type = ELF::R_ARM_JUMP24;
240 break;
241 case ARM::fixup_arm_movt_hi16:
242 Type = ELF::R_ARM_MOVT_ABS;
243 break;
244 case ARM::fixup_arm_movw_lo16:
245 Type = ELF::R_ARM_MOVW_ABS_NC;
246 break;
247 case ARM::fixup_t2_movt_hi16:
248 Type = ELF::R_ARM_THM_MOVT_ABS;
249 break;
250 case ARM::fixup_t2_movw_lo16:
251 Type = ELF::R_ARM_THM_MOVW_ABS_NC;
252 break;
253 }
254 }
255
256 return Type;
257 }
258
createARMELFObjectWriter(raw_pwrite_stream & OS,uint8_t OSABI,bool IsLittleEndian)259 MCObjectWriter *llvm::createARMELFObjectWriter(raw_pwrite_stream &OS,
260 uint8_t OSABI,
261 bool IsLittleEndian) {
262 MCELFObjectTargetWriter *MOTW = new ARMELFObjectWriter(OSABI);
263 return createELFObjectWriter(MOTW, OS, IsLittleEndian);
264 }
265