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1//
2// heapwalk.cpp
3//
4// Copyright (c) Microsoft Corporation. All rights reserved.
5//
6// Implementation of _heapwalk().
7//
8#include <corecrt_internal.h>
9#include <malloc.h>
10
11
12
13// Calls HeapWalk and guards against access violations in case a bad pointer is
14// passed to the CRT _heapwalk function (or in case the heap is corrupt).
15static int __cdecl try_walk(PROCESS_HEAP_ENTRY* const win32_entry) throw()
16{
17 __try
18 {
19 if (HeapWalk(__acrt_heap, win32_entry))
20 return _HEAPOK;
21
22 if (GetLastError() == ERROR_NO_MORE_ITEMS)
23 return _HEAPEND;
24
25 return _HEAPBADNODE;
26 }
27 __except(GetExceptionCode() == EXCEPTION_ACCESS_VIOLATION)
28 {
29 return _HEAPBADNODE;
30 }
31 __endtry
32}
33
34// Walks the heap, returning information on one entry at a time. If there are
35// multiple threads in the process that are allocating using the process heap,
36// the caller must lock the heap for the duration of the heap walk, by calling
37// the Windows API HeapLock. See the documentation of HeapWalk for more
38// information.
39//
40// The return value is one of the following:
41// * _HEAPOK The call completed successfully and returned a node
42// * _HEAPBADPTR The provided 'entry' pointer is invalid
43// * _HEAPBADBEGIN The initial node cannot be found in the heap
44// * _HEAPBADNODE A node was malformed or the heap is corrupt
45// * _HEAPEND The end of the heap was successfully reached
46extern "C" int __cdecl _heapwalk(_HEAPINFO* const entry)
47{
48 // Validation section
49 _VALIDATE_RETURN(entry != nullptr, EINVAL, _HEAPBADPTR);
50
51 PROCESS_HEAP_ENTRY win32_entry = { 0 };
52 win32_entry.wFlags = 0;
53 win32_entry.iRegionIndex = 0;
54 win32_entry.lpData = entry->_pentry;
55
56 // If _pentry is nullptr, then we're just starting the heap walk:
57 if (win32_entry.lpData == nullptr)
58 {
59 if (!HeapWalk(__acrt_heap, &win32_entry))
60 return _HEAPBADBEGIN;
61 }
62 else
63 {
64 if (entry->_useflag == _USEDENTRY)
65 {
66 if (!HeapValidate(__acrt_heap, 0, entry->_pentry))
67 return _HEAPBADNODE;
68
69 win32_entry.wFlags = PROCESS_HEAP_ENTRY_BUSY;
70 }
71
72 int const status = try_walk(&win32_entry);
73 if (status != _HEAPOK)
74 return status;
75 }
76
77 for (;;)
78 {
79 if (win32_entry.wFlags & PROCESS_HEAP_ENTRY_BUSY)
80 {
81 entry->_pentry = static_cast<int*>(win32_entry.lpData);
82 entry->_size = win32_entry.cbData;
83 entry->_useflag = _USEDENTRY;
84 return _HEAPOK;
85 }
86
87 int const status = try_walk(&win32_entry);
88 if (status != _HEAPOK)
89 return status;
90 }
91}