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334
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1
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335
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2 import struct
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334
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3 from .objectfile import ObjectFile
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335
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4 from . import CompilerError
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5
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6 def align(x, m):
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7 while ((x % m) != 0):
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8 x = x + 1
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9 return x
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10
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11 def wrap_negative(x, bits):
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12 b = struct.unpack('<I', struct.pack('<i', x))[0]
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13 mask = (1 << bits) - 1
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14 return b & mask
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15
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16 reloc_map = {}
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17
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18 def reloc(t):
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19 def f(c):
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20 reloc_map[t] = c
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21 return f
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22
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23
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24 @reloc('lit_add_8')
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25 class LitAdd8:
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26 def apply(self):
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27 pass
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28
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334
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29
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30 class Linker:
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31 def set_symbol(self, sym):
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335
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32 self.dst.add_symbol(sym.name, sym.value, sym.section)
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334
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33
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34 def link(self, objs):
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335
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35 # Create new object file to store output:
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334
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36 self.dst = ObjectFile()
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335
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37 self.dst.get_section('code').address = 0x08000000
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38
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334
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39 # First copy all sections into output sections:
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40 for iobj in objs:
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335
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41 offsets = {}
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42 # Merge sections:
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43 for in_s in iobj.sections.values():
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44 out_s = self.dst.get_section(in_s.name)
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45 offsets[in_s.name] = out_s.address + out_s.Size
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46 out_s.add_data(in_s.data)
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47 # TODO: align section
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48
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49 # Merge symbols:
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50 for sym in iobj.symbols.values():
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334
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51 self.set_symbol(sym)
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335
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52
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53 # Merge relocations:
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54 for reloc in iobj.relocations:
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55 self.dst.add_relocation(reloc.sym, reloc.offset, reloc.typ, reloc.section)
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56
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334
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57 # Check that there are no more unresolved symbols:
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335
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58 # Perform relocations:
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59 for reloc in self.dst.relocations:
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60 # Lookup symbol:
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61 if reloc.sym not in self.dst.symbols:
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62 raise CompilerError('Undefined reference "{}"'.format(reloc.sym))
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63 sym = self.dst.symbols[reloc.sym]
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64 # patch up:
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65 section = self.dst.get_section(reloc.section)
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66
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67 if reloc.typ == 'lit_add_8':
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68 assert sym.value % 4 == 0
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69 offset = (sym.value - (align(reloc.offset + 2, 4)))
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70 assert offset in range(0, 1024, 4)
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71 rel8 = offset >> 2
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72 section.data[reloc.offset] = rel8
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73 elif reloc.typ == 'wrap_new11':
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74 offset = sym.value - (align(reloc.offset, 2) + 4)
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75 assert offset in range(-2048, 2046, 2)
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76 imm11 = wrap_negative(offset >> 1, 11)
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77 section.data[reloc.offset] = (imm11 & 0xff)
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78 section.data[reloc.offset + 1] |= (imm11 >> 8) & 0x7
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79 elif reloc.typ == 'rel8':
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80 assert sym.value % 2 == 0
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81 offset = sym.value - (align(reloc.offset, 2) + 4)
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82 assert offset in range(-256, 254, 2), str(offset) + str(reloc)
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83 imm8 = wrap_negative(offset >> 1, 8)
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84 section.data[reloc.offset] = imm8
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85 elif reloc.typ == 'bl_imm11_imm10':
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86 assert sym.value % 2 == 0
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87 offset = sym.value - (align(reloc.offset, 2) + 4)
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88 assert offset in range(-16777216, 16777214, 2), str(offset)
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89 imm32 = wrap_negative(offset >> 1, 32)
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90 imm11 = imm32 & 0x7FF
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91 imm10 = (imm32 >> 11) & 0x3FF
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92 s = (imm32 >> 24) & 0x1
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93 section.data[reloc.offset + 2] = imm11 & 0xFF
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94 section.data[reloc.offset + 3] |= (imm11 >> 8) & 0x7
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95 section.data[reloc.offset] = imm10 & 0xff
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96 section.data[reloc.offset + 1] |= ((imm10 >> 8) & 0x3) | (s << 2)
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97 elif reloc.typ == 'b_imm11_imm6':
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98 assert sym.value % 2 == 0
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99 offset = sym.value - (align(reloc.offset, 2) + 4)
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100 assert offset in range(-1048576, 1048574, 2), str(offset)
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101 imm32 = wrap_negative(offset >> 1, 32)
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102 imm11 = imm32 & 0x7FF
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103 imm6 = (imm32 >> 11) & 0x3F
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104 s = (imm32 >> 24) & 0x1
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105 section.data[reloc.offset + 2] = imm11 & 0xFF
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106 section.data[reloc.offset + 3] |= (imm11 >> 8) & 0x7
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107 section.data[reloc.offset] |= imm6
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108 section.data[reloc.offset + 1] |= (s << 2)
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109 else:
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110 raise NotImplementedError('Unknown relocation type {}'.format(reloc.typ))
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111
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334
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112 return self.dst
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