gem5  v20.1.0.0
emulenv.cc
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37 
38 #include "arch/x86/emulenv.hh"
39 
40 #include <cassert>
41 
42 #include "base/logging.hh"
43 
44 using namespace X86ISA;
45 
46 void EmulEnv::doModRM(const ExtMachInst & machInst)
47 {
48  assert(machInst.modRM.mod != 3);
49  //Use the SIB byte for addressing if the modrm byte calls for it.
50  if (machInst.modRM.rm == 4 && machInst.addrSize != 2) {
51  scale = 1 << machInst.sib.scale;
52  index = machInst.sib.index | (machInst.rex.x << 3);
53  base = machInst.sib.base | (machInst.rex.b << 3);
54  //In this special case, we don't use a base. The displacement also
55  //changes, but that's managed by the decoder.
56  if (machInst.sib.base == INTREG_RBP && machInst.modRM.mod == 0)
57  base = NUM_INTREGS;
58  //In -this- special case, we don't use an index.
59  if (index == INTREG_RSP)
61  } else {
62  if (machInst.addrSize == 2) {
63  unsigned rm = machInst.modRM.rm;
64  if (rm <= 3) {
65  scale = 1;
66  if (rm < 2) {
67  base = INTREG_RBX;
68  } else {
69  base = INTREG_RBP;
70  }
71  index = (rm % 2) ? INTREG_RDI : INTREG_RSI;
72  } else {
73  scale = 0;
74  switch (rm) {
75  case 4:
76  base = INTREG_RSI;
77  break;
78  case 5:
79  base = INTREG_RDI;
80  break;
81  case 6:
82  base = INTREG_RBP;
83  break;
84  case 7:
85  base = INTREG_RBX;
86  break;
87  }
88  }
89  } else {
90  scale = 0;
91  base = machInst.modRM.rm | (machInst.rex.b << 3);
92  if (machInst.modRM.mod == 0 && machInst.modRM.rm == 5) {
93  //Since we need to use a different encoding of this
94  //instruction anyway, just ignore the base in those cases
95  base = NUM_INTREGS;
96  }
97  }
98  }
99  //Figure out what segment to use. This won't be entirely accurate since
100  //the presence of a displacement is supposed to make the instruction
101  //default to the data segment.
102  if ((base != INTREG_RBP && base != INTREG_RSP) || machInst.dispSize) {
104  //Handle any segment override that might have been in the instruction
105  int segFromInst = machInst.legacy.seg;
106  if (segFromInst)
107  seg = (SegmentRegIndex)(segFromInst - 1);
108  } else {
110  }
111 }
112 
113 void EmulEnv::setSeg(const ExtMachInst & machInst)
114 {
116  //Handle any segment override that might have been in the instruction
117  int segFromInst = machInst.legacy.seg;
118  if (segFromInst)
119  seg = (SegmentRegIndex)(segFromInst - 1);
120 }
X86ISA::EmulEnv::doModRM
void doModRM(const ExtMachInst &machInst)
Definition: emulenv.cc:46
X86ISA::EmulEnv::base
RegIndex base
Definition: emulenv.hh:55
X86ISA::EmulEnv::setSeg
void setSeg(const ExtMachInst &machInst)
Definition: emulenv.cc:113
X86ISA::EmulEnv::index
RegIndex index
Definition: emulenv.hh:54
X86ISA::ExtMachInst::addrSize
uint8_t addrSize
Definition: types.hh:226
X86ISA::ExtMachInst
Definition: types.hh:198
X86ISA::SegmentRegIndex
SegmentRegIndex
Definition: segment.hh:43
X86ISA
This is exposed globally, independent of the ISA.
Definition: acpi.hh:55
X86ISA::ExtMachInst::modRM
ModRM modRM
Definition: types.hh:217
X86ISA::EmulEnv::scale
uint8_t scale
Definition: emulenv.hh:53
X86ISA::SEGMENT_REG_DS
@ SEGMENT_REG_DS
Definition: segment.hh:48
X86ISA::SEGMENT_REG_SS
@ SEGMENT_REG_SS
Definition: segment.hh:47
emulenv.hh
ArmISA::NUM_INTREGS
@ NUM_INTREGS
Definition: intregs.hh:123
X86ISA::ExtMachInst::rex
Rex rex
Definition: types.hh:206
logging.hh
X86ISA::ExtMachInst::sib
Sib sib
Definition: types.hh:218
X86ISA::ExtMachInst::dispSize
uint8_t dispSize
Definition: types.hh:230
X86ISA::ExtMachInst::legacy
LegacyPrefixVector legacy
Definition: types.hh:205
X86ISA::rm
Bitfield< 2, 0 > rm
Definition: types.hh:88
X86ISA::EmulEnv::seg
SegmentRegIndex seg
Definition: emulenv.hh:52

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