1 //===- X86PLT.cpp -----------------------------------------------------------===//
2 //
3 // The MCLinker Project
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 #include "X86GOT.h"
10 #include "X86PLT.h"
11 #include <llvm/Support/raw_ostream.h>
12 #include <llvm/Support/ErrorHandling.h>
13 #include <llvm/Support/ELF.h>
14 #include <mcld/MC/MCLDOutput.h>
15 #include <new>
16
17 namespace {
18
19 const uint8_t x86_dyn_plt0[] = {
20 0xff, 0xb3, 0x04, 0, 0, 0, // pushl 0x4(%ebx)
21 0xff, 0xa3, 0x08, 0, 0, 0, // jmp *0x8(%ebx)
22 0xf, 0x1f, 0x4, 0 // nopl 0(%eax)
23 };
24
25 const uint8_t x86_dyn_plt1[] = {
26 0xff, 0xa3, 0, 0, 0, 0, // jmp *sym@GOT(%ebx)
27 0x68, 0, 0, 0, 0, // pushl $offset
28 0xe9, 0, 0, 0, 0 // jmp plt0
29 };
30
31 const uint8_t x86_exec_plt0[] = {
32 0xff, 0x35, 0, 0, 0, 0, // pushl .got + 4
33 0xff, 0x25, 0, 0, 0, 0, // jmp *(.got + 8)
34 0xf, 0x1f, 0x4, 0 // nopl 0(%eax)
35 };
36
37 const uint8_t x86_exec_plt1[] = {
38 0xff, 0x25, 0, 0, 0, 0, // jmp *(sym in .got)
39 0x68, 0, 0, 0, 0, // pushl $offset
40 0xe9, 0, 0, 0, 0 // jmp plt0
41 };
42
43 }
44
45 namespace mcld {
46
X86PLT0(llvm::MCSectionData * pParent,unsigned int pSize)47 X86PLT0::X86PLT0(llvm::MCSectionData* pParent, unsigned int pSize)
48 : PLTEntry(pSize, pParent) { }
49
X86PLT1(llvm::MCSectionData * pParent,unsigned int pSize)50 X86PLT1::X86PLT1(llvm::MCSectionData* pParent, unsigned int pSize)
51 : PLTEntry(pSize, pParent) { }
52
53 //===----------------------------------------------------------------------===//
54 // X86PLT
55
X86PLT(LDSection & pSection,llvm::MCSectionData & pSectionData,X86GOT & pGOTPLT,const Output & pOutput)56 X86PLT::X86PLT(LDSection& pSection,
57 llvm::MCSectionData& pSectionData,
58 X86GOT &pGOTPLT,
59 const Output& pOutput)
60 : PLT(pSection, pSectionData), m_GOT(pGOTPLT), m_PLTEntryIterator()
61 {
62 assert (Output::DynObj == pOutput.type() || Output::Exec == pOutput.type());
63 if (Output::DynObj == pOutput.type()) {
64 m_PLT0 = x86_dyn_plt0;
65 m_PLT1 = x86_dyn_plt1;
66 m_PLT0Size = sizeof (x86_dyn_plt0);
67 m_PLT1Size = sizeof (x86_dyn_plt1);
68 }
69 else {
70 m_PLT0 = x86_exec_plt0;
71 m_PLT1 = x86_exec_plt1;
72 m_PLT0Size = sizeof (x86_exec_plt0);
73 m_PLT1Size = sizeof (x86_exec_plt1);
74 }
75 X86PLT0* plt0_entry = new X86PLT0(&m_SectionData, m_PLT0Size);
76
77 m_Section.setSize(m_Section.size() + plt0_entry->getEntrySize());
78
79 m_PLTEntryIterator = pSectionData.begin();
80 }
81
~X86PLT()82 X86PLT::~X86PLT()
83 {
84 }
85
reserveEntry(size_t pNum)86 void X86PLT::reserveEntry(size_t pNum)
87 {
88 X86PLT1* plt1_entry = 0;
89 GOTEntry* got_entry = 0;
90
91 for (size_t i = 0; i < pNum; ++i) {
92 plt1_entry = new (std::nothrow) X86PLT1(&m_SectionData, m_PLT1Size);
93
94 if (!plt1_entry)
95 llvm::report_fatal_error("Allocating new memory for X86PLT1 failed!");
96
97 m_Section.setSize(m_Section.size() + plt1_entry->getEntrySize());
98
99 got_entry= new (std::nothrow) GOTEntry(0, m_GOT.getEntrySize(),
100 &(m_GOT.m_SectionData));
101
102 if (!got_entry)
103 llvm::report_fatal_error("Allocating new memory for GOT failed!");
104
105 m_GOT.m_Section.setSize(m_GOT.m_Section.size() + m_GOT.f_EntrySize);
106
107 ++(m_GOT.m_GOTPLTNum);
108 ++(m_GOT.m_GeneralGOTIterator);
109 }
110 }
111
getPLTEntry(const ResolveInfo & pSymbol,bool & pExist)112 PLTEntry* X86PLT::getPLTEntry(const ResolveInfo& pSymbol, bool& pExist)
113 {
114 X86PLT1 *&PLTEntry = m_PLTEntryMap[&pSymbol];
115
116 pExist = 1;
117
118 if (!PLTEntry) {
119 GOTEntry *&GOTPLTEntry = m_GOT.m_GOTPLTMap[&pSymbol];
120 assert(!GOTPLTEntry && "PLT entry and got.plt entry doesn't match!");
121
122 pExist = 0;
123
124 // This will skip PLT0.
125 ++m_PLTEntryIterator;
126 assert(m_PLTEntryIterator != m_SectionData.end() &&
127 "The number of PLT Entries and ResolveInfo doesn't match");
128 ++(m_GOT.m_GOTPLTIterator);
129
130 PLTEntry = llvm::cast<X86PLT1>(&(*m_PLTEntryIterator));
131 GOTPLTEntry = llvm::cast<GOTEntry>(&(*(m_GOT.m_GOTPLTIterator)));
132 }
133
134 return PLTEntry;
135 }
136
getGOTPLTEntry(const ResolveInfo & pSymbol,bool & pExist)137 GOTEntry* X86PLT::getGOTPLTEntry(const ResolveInfo& pSymbol, bool& pExist)
138 {
139 GOTEntry *&GOTPLTEntry = m_GOT.m_GOTPLTMap[&pSymbol];
140
141 pExist = 1;
142
143 if (!GOTPLTEntry) {
144 X86PLT1 *&PLTEntry = m_PLTEntryMap[&pSymbol];
145 assert(!PLTEntry && "PLT entry and got.plt entry doesn't match!");
146
147 pExist = 0;
148
149 // This will skip PLT0.
150 ++m_PLTEntryIterator;
151 assert(m_PLTEntryIterator != m_SectionData.end() &&
152 "The number of PLT Entries and ResolveInfo doesn't match");
153 ++(m_GOT.m_GOTPLTIterator);
154
155 PLTEntry = llvm::cast<X86PLT1>(&(*m_PLTEntryIterator));
156 GOTPLTEntry = llvm::cast<GOTEntry>(&(*(m_GOT.m_GOTPLTIterator)));
157 }
158
159 return GOTPLTEntry;
160 }
161
getPLT0() const162 X86PLT0* X86PLT::getPLT0() const {
163
164 iterator first = m_SectionData.getFragmentList().begin();
165 iterator end = m_SectionData.getFragmentList().end();
166
167 assert(first!=end && "FragmentList is empty, getPLT0 failed!");
168
169 X86PLT0* plt0 = &(llvm::cast<X86PLT0>(*first));
170
171 return plt0;
172 }
173
174 // FIXME: It only works on little endian machine.
applyPLT0()175 void X86PLT::applyPLT0() {
176
177 iterator first = m_SectionData.getFragmentList().begin();
178 iterator end = m_SectionData.getFragmentList().end();
179
180 assert(first!=end && "FragmentList is empty, applyPLT0 failed!");
181
182 X86PLT0* plt0 = &(llvm::cast<X86PLT0>(*first));
183
184 unsigned char* data = 0;
185 data = static_cast<unsigned char*>(malloc(plt0->getEntrySize()));
186
187 if (!data)
188 llvm::report_fatal_error("Allocating new memory for plt0 failed!");
189
190 memcpy(data, m_PLT0, plt0->getEntrySize());
191
192 if (m_PLT0 == x86_exec_plt0) {
193 uint64_t got_base = m_GOT.getSection().addr();
194 assert(got_base && ".got base address is NULL!");
195 uint32_t *offset = reinterpret_cast<uint32_t*>(data + 2);
196 *offset = got_base + 4;
197 offset = reinterpret_cast<uint32_t*>(data + 8);
198 *offset = got_base + 8;
199 }
200
201 plt0->setContent(data);
202 }
203
204 // FIXME: It only works on little endian machine.
applyPLT1()205 void X86PLT::applyPLT1() {
206
207 uint64_t plt_base = m_Section.addr();
208 assert(plt_base && ".plt base address is NULL!");
209
210 uint64_t got_base = m_GOT.getSection().addr();
211 assert(got_base && ".got base address is NULL!");
212
213 X86PLT::iterator it = m_SectionData.begin();
214 X86PLT::iterator ie = m_SectionData.end();
215 assert(it!=ie && "FragmentList is empty, applyPLT1 failed!");
216
217 uint64_t GOTEntrySize = m_GOT.getEntrySize();
218
219 // Skip GOT0
220 uint64_t GOTEntryOffset = GOTEntrySize * X86GOT0Num;
221
222 //skip PLT0
223 uint64_t PLTEntryOffset = m_PLT0Size;
224 ++it;
225
226 X86PLT1* plt1 = 0;
227
228 uint64_t PLTRelOffset = 0;
229
230 while (it != ie) {
231 plt1 = &(llvm::cast<X86PLT1>(*it));
232 unsigned char *data;
233 data = static_cast<unsigned char*>(malloc(plt1->getEntrySize()));
234
235 if (!data)
236 llvm::report_fatal_error("Allocating new memory for plt1 failed!");
237
238 memcpy(data, m_PLT1, plt1->getEntrySize());
239
240 uint32_t* offset;
241
242 offset = reinterpret_cast<uint32_t*>(data + 2);
243 *offset = GOTEntryOffset;
244 GOTEntryOffset += GOTEntrySize;
245
246 offset = reinterpret_cast<uint32_t*>(data + 7);
247 *offset = PLTRelOffset;
248 PLTRelOffset += sizeof (llvm::ELF::Elf32_Rel);
249
250 offset = reinterpret_cast<uint32_t*>(data + 12);
251 *offset = -(PLTEntryOffset + 12 + 4);
252 PLTEntryOffset += m_PLT1Size;
253
254 plt1->setContent(data);
255 ++it;
256 }
257
258 unsigned int GOTPLTNum = m_GOT.getGOTPLTNum();
259
260 if (GOTPLTNum != 0) {
261 X86GOT::iterator gotplt_it = m_GOT.getLastGOT0();
262 X86GOT::iterator list_ie = m_GOT.getSectionData().getFragmentList().end();
263
264 ++gotplt_it;
265 uint64_t PLTEntryAddress = plt_base + m_PLT0Size;
266 for (unsigned int i = 0; i < GOTPLTNum; ++i) {
267 if (gotplt_it == list_ie)
268 llvm::report_fatal_error(
269 "The number of got.plt entries is inconsistent!");
270
271 llvm::cast<GOTEntry>(*gotplt_it).setContent(PLTEntryAddress + 6);
272 PLTEntryAddress += m_PLT1Size;
273 ++gotplt_it;
274 }
275 }
276 }
277
278 } // end namespace mcld
279