THMToARMStub.cpp revision 0dea6bc96bb52346737966839ac68644f7939f58 
1//===- THMToARMStub.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
10#include "THMToARMStub.h"
11#include "ARMLDBackend.h"
12
13#include <llvm/Support/ELF.h>
14#include <mcld/LD/ResolveInfo.h>
15#include <mcld/LD/LDSymbol.h>
16#include <mcld/Fragment/Relocation.h>
17
18using namespace mcld;
19
20//===----------------------------------------------------------------------===//
21// THMToARMStub
22//===----------------------------------------------------------------------===//
23const uint32_t THMToARMStub::PIC_TEMPLATE[] = {
24  0x46c04778, // bx    pc ... nop
25  0xe59fc000, // ldr   ip, [pc, #0]
26  0xe08cf00f, // add   pc, ip, pc
27  0x0         // dcd   R_ARM_REL32(X)
28};
29
30const uint32_t THMToARMStub::TEMPLATE[] = {
31  0x46c04778, // bx    pc ... nop
32  0xe51ff004, // ldr   pc, [pc, #-4]
33  0x0         // dcd   R_ARM_ABS32(X)
34};
35
36THMToARMStub::THMToARMStub(bool pIsOutputPIC, bool pUsingThumb2)
37 : m_pData(NULL),
38   m_Name("T2A_prototype"),
39   m_Size(0x0),
40   m_bUsingThumb2(pUsingThumb2)
41{
42  if (pIsOutputPIC) {
43    m_pData = PIC_TEMPLATE;
44    m_Size = sizeof(PIC_TEMPLATE);
45    addFixup(12u, -4, llvm::ELF::R_ARM_REL32);
46  } else {
47    m_pData = TEMPLATE;
48    m_Size = sizeof(TEMPLATE);
49    addFixup(8u, 0x0, llvm::ELF::R_ARM_ABS32);
50  }
51}
52
53/// for doClone
54THMToARMStub::THMToARMStub(const uint32_t* pData,
55                           size_t pSize,
56                           const_fixup_iterator pBegin,
57                           const_fixup_iterator pEnd,
58                           bool pUsingThumb2)
59 : m_pData(pData),
60   m_Name("T2A_veneer"),
61   m_Size(pSize),
62   m_bUsingThumb2(pUsingThumb2)
63{
64  for (const_fixup_iterator it = pBegin, ie = pEnd; it != ie; ++it)
65    addFixup(**it);
66}
67
68THMToARMStub::~THMToARMStub()
69{
70}
71
72bool THMToARMStub::isMyDuty(const class Relocation& pReloc,
73                            uint64_t pSource,
74                            uint64_t pTargetSymValue) const
75{
76  bool result = false;
77  // Check if the branch target is ARM
78  if ((pTargetSymValue & 0x1) == 0x0) {
79    switch (pReloc.type()) {
80      case llvm::ELF::R_ARM_THM_CALL: {
81        // FIXME: Assuming blx is available (i.e., target is armv5 or above!)
82        // then, we do not need a stub unless the branch target is too far.
83        uint64_t dest = pTargetSymValue + pReloc.addend() + 4u;
84        int64_t branch_offset = static_cast<int64_t>(dest) - pSource;
85        if (m_bUsingThumb2) {
86          if ((branch_offset > ARMGNULDBackend::THM2_MAX_FWD_BRANCH_OFFSET) ||
87              (branch_offset < ARMGNULDBackend::THM2_MAX_BWD_BRANCH_OFFSET)) {
88            result = true;
89            break;
90          }
91        } else {
92          if ((branch_offset > ARMGNULDBackend::THM_MAX_FWD_BRANCH_OFFSET) ||
93              (branch_offset < ARMGNULDBackend::THM_MAX_BWD_BRANCH_OFFSET)) {
94            result = true;
95            break;
96          }
97        }
98        break;
99      }
100      case llvm::ELF::R_ARM_THM_JUMP24: {
101        // always need a stub to switch mode
102        result = true;
103        break;
104      }
105      default:
106        break;
107    }
108  }
109  return result;
110}
111
112const std::string& THMToARMStub::name() const
113{
114  return m_Name;
115}
116
117const uint8_t* THMToARMStub::getContent() const
118{
119  return reinterpret_cast<const uint8_t*>(m_pData);
120}
121
122size_t THMToARMStub::size() const
123{
124  return m_Size;
125}
126
127size_t THMToARMStub::alignment() const
128{
129  return 4u;
130}
131
132// for T bit of this stub
133uint64_t THMToARMStub::initSymValue() const
134{
135  return 0x1;
136}
137
138Stub* THMToARMStub::doClone()
139{
140  return new THMToARMStub(m_pData,
141                          m_Size,
142                          fixup_begin(),
143                          fixup_end(),
144                          m_bUsingThumb2);
145}
146