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1 // Copyright 2019 The Go Authors. All rights reserved.
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2 // Use of this source code is governed by a BSD-style
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3 // license that can be found in the LICENSE file.
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4
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5 // +build ignore
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6
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7 package runtime
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8
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9 import "unsafe"
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10
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11 type ptrAlignError struct {
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12 ptr unsafe.Pointer
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13 elem *_type
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14 n uintptr
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15 }
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16
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17 func (e ptrAlignError) RuntimeError() {}
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18
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19 func (e ptrAlignError) Error() string {
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20 return "runtime error: unsafe pointer conversion"
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21 }
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22
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23 func checkptrAlignment(p unsafe.Pointer, elem *_type, n uintptr) {
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24 // Check that (*[n]elem)(p) is appropriately aligned.
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25 // TODO(mdempsky): What about fieldAlign?
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26 if uintptr(p)&(uintptr(elem.align)-1) != 0 {
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27 panic(ptrAlignError{p, elem, n})
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28 }
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29
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30 // Check that (*[n]elem)(p) doesn't straddle multiple heap objects.
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31 if size := n * elem.size; size > 1 && checkptrBase(p) != checkptrBase(add(p, size-1)) {
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32 panic(ptrAlignError{p, elem, n})
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33 }
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34 }
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35
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36 type ptrArithError struct {
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37 ptr unsafe.Pointer
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38 originals []unsafe.Pointer
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39 }
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40
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41 func (e ptrArithError) RuntimeError() {}
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42
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43 func (e ptrArithError) Error() string {
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44 return "runtime error: unsafe pointer arithmetic"
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45 }
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46
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47 func checkptrArithmetic(p unsafe.Pointer, originals []unsafe.Pointer) {
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48 if 0 < uintptr(p) && uintptr(p) < minLegalPointer {
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49 panic(ptrArithError{p, originals})
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50 }
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51
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52 // Check that if the computed pointer p points into a heap
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53 // object, then one of the original pointers must have pointed
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54 // into the same object.
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55 base := checkptrBase(p)
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56 if base == 0 {
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57 return
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58 }
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59
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60 for _, original := range originals {
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61 if base == checkptrBase(original) {
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62 return
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63 }
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64 }
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65
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66 panic(ptrArithError{p, originals})
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67 }
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68
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69 // checkptrBase returns the base address for the allocation containing
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70 // the address p.
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71 //
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72 // Importantly, if p1 and p2 point into the same variable, then
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73 // checkptrBase(p1) == checkptrBase(p2). However, the converse/inverse
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74 // is not necessarily true as allocations can have trailing padding,
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75 // and multiple variables may be packed into a single allocation.
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76 func checkptrBase(p unsafe.Pointer) uintptr {
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77 // stack
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78 if gp := getg(); gp.stack.lo <= uintptr(p) && uintptr(p) < gp.stack.hi {
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79 // TODO(mdempsky): Walk the stack to identify the
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80 // specific stack frame or even stack object that p
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81 // points into.
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82 //
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83 // In the mean time, use "1" as a pseudo-address to
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84 // represent the stack. This is an invalid address on
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85 // all platforms, so it's guaranteed to be distinct
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86 // from any of the addresses we might return below.
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87 return 1
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88 }
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89
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90 // heap (must check after stack because of #35068)
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91 if base, _, _ := findObject(uintptr(p), 0, 0); base != 0 {
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92 return base
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93 }
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94
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95 // data or bss
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96 for _, datap := range activeModules() {
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97 if datap.data <= uintptr(p) && uintptr(p) < datap.edata {
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98 return datap.data
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99 }
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100 if datap.bss <= uintptr(p) && uintptr(p) < datap.ebss {
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101 return datap.bss
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102 }
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103 }
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104
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105 return 0
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106 }
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