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1 //===-- sanitizer_procmaps_mac.cc -----------------------------------------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // Information about the process mappings (Mac-specific parts).
11 //===----------------------------------------------------------------------===//
12 
13 #include "sanitizer_platform.h"
14 #if SANITIZER_MAC
15 #include "sanitizer_common.h"
16 #include "sanitizer_placement_new.h"
17 #include "sanitizer_procmaps.h"
18 
19 #include <mach-o/dyld.h>
20 #include <mach-o/loader.h>
21 
22 namespace __sanitizer {
23 
MemoryMappingLayout(bool cache_enabled)24 MemoryMappingLayout::MemoryMappingLayout(bool cache_enabled) {
25   Reset();
26 }
27 
~MemoryMappingLayout()28 MemoryMappingLayout::~MemoryMappingLayout() {
29 }
30 
31 // More information about Mach-O headers can be found in mach-o/loader.h
32 // Each Mach-O image has a header (mach_header or mach_header_64) starting with
33 // a magic number, and a list of linker load commands directly following the
34 // header.
35 // A load command is at least two 32-bit words: the command type and the
36 // command size in bytes. We're interested only in segment load commands
37 // (LC_SEGMENT and LC_SEGMENT_64), which tell that a part of the file is mapped
38 // into the task's address space.
39 // The |vmaddr|, |vmsize| and |fileoff| fields of segment_command or
40 // segment_command_64 correspond to the memory address, memory size and the
41 // file offset of the current memory segment.
42 // Because these fields are taken from the images as is, one needs to add
43 // _dyld_get_image_vmaddr_slide() to get the actual addresses at runtime.
44 
Reset()45 void MemoryMappingLayout::Reset() {
46   // Count down from the top.
47   // TODO(glider): as per man 3 dyld, iterating over the headers with
48   // _dyld_image_count is thread-unsafe. We need to register callbacks for
49   // adding and removing images which will invalidate the MemoryMappingLayout
50   // state.
51   current_image_ = _dyld_image_count();
52   current_load_cmd_count_ = -1;
53   current_load_cmd_addr_ = 0;
54   current_magic_ = 0;
55   current_filetype_ = 0;
56 }
57 
58 // static
CacheMemoryMappings()59 void MemoryMappingLayout::CacheMemoryMappings() {
60   // No-op on Mac for now.
61 }
62 
LoadFromCache()63 void MemoryMappingLayout::LoadFromCache() {
64   // No-op on Mac for now.
65 }
66 
67 // Next and NextSegmentLoad were inspired by base/sysinfo.cc in
68 // Google Perftools, https://github.com/gperftools/gperftools.
69 
70 // NextSegmentLoad scans the current image for the next segment load command
71 // and returns the start and end addresses and file offset of the corresponding
72 // segment.
73 // Note that the segment addresses are not necessarily sorted.
74 template<u32 kLCSegment, typename SegmentCommand>
NextSegmentLoad(uptr * start,uptr * end,uptr * offset,char filename[],uptr filename_size,uptr * protection)75 bool MemoryMappingLayout::NextSegmentLoad(
76     uptr *start, uptr *end, uptr *offset,
77     char filename[], uptr filename_size, uptr *protection) {
78   const char* lc = current_load_cmd_addr_;
79   current_load_cmd_addr_ += ((const load_command *)lc)->cmdsize;
80   if (((const load_command *)lc)->cmd == kLCSegment) {
81     const sptr dlloff = _dyld_get_image_vmaddr_slide(current_image_);
82     const SegmentCommand* sc = (const SegmentCommand *)lc;
83     if (start) *start = sc->vmaddr + dlloff;
84     if (protection) {
85       // Return the initial protection.
86       *protection = sc->initprot;
87     }
88     if (end) *end = sc->vmaddr + sc->vmsize + dlloff;
89     if (offset) {
90       if (current_filetype_ == /*MH_EXECUTE*/ 0x2) {
91         *offset = sc->vmaddr;
92       } else {
93         *offset = sc->fileoff;
94       }
95     }
96     if (filename) {
97       internal_strncpy(filename, _dyld_get_image_name(current_image_),
98                        filename_size);
99     }
100     return true;
101   }
102   return false;
103 }
104 
Next(uptr * start,uptr * end,uptr * offset,char filename[],uptr filename_size,uptr * protection)105 bool MemoryMappingLayout::Next(uptr *start, uptr *end, uptr *offset,
106                                char filename[], uptr filename_size,
107                                uptr *protection) {
108   for (; current_image_ >= 0; current_image_--) {
109     const mach_header* hdr = _dyld_get_image_header(current_image_);
110     if (!hdr) continue;
111     if (current_load_cmd_count_ < 0) {
112       // Set up for this image;
113       current_load_cmd_count_ = hdr->ncmds;
114       current_magic_ = hdr->magic;
115       current_filetype_ = hdr->filetype;
116       switch (current_magic_) {
117 #ifdef MH_MAGIC_64
118         case MH_MAGIC_64: {
119           current_load_cmd_addr_ = (char*)hdr + sizeof(mach_header_64);
120           break;
121         }
122 #endif
123         case MH_MAGIC: {
124           current_load_cmd_addr_ = (char*)hdr + sizeof(mach_header);
125           break;
126         }
127         default: {
128           continue;
129         }
130       }
131     }
132 
133     for (; current_load_cmd_count_ >= 0; current_load_cmd_count_--) {
134       switch (current_magic_) {
135         // current_magic_ may be only one of MH_MAGIC, MH_MAGIC_64.
136 #ifdef MH_MAGIC_64
137         case MH_MAGIC_64: {
138           if (NextSegmentLoad<LC_SEGMENT_64, struct segment_command_64>(
139                   start, end, offset, filename, filename_size, protection))
140             return true;
141           break;
142         }
143 #endif
144         case MH_MAGIC: {
145           if (NextSegmentLoad<LC_SEGMENT, struct segment_command>(
146                   start, end, offset, filename, filename_size, protection))
147             return true;
148           break;
149         }
150       }
151     }
152     // If we get here, no more load_cmd's in this image talk about
153     // segments.  Go on to the next image.
154   }
155   return false;
156 }
157 
DumpListOfModules(InternalMmapVector<LoadedModule> * modules)158 void MemoryMappingLayout::DumpListOfModules(
159     InternalMmapVector<LoadedModule> *modules) {
160   Reset();
161   uptr cur_beg, cur_end, prot;
162   InternalScopedString module_name(kMaxPathLength);
163   for (uptr i = 0; Next(&cur_beg, &cur_end, 0, module_name.data(),
164                         module_name.size(), &prot);
165        i++) {
166     const char *cur_name = module_name.data();
167     if (cur_name[0] == '\0')
168       continue;
169     LoadedModule *cur_module = nullptr;
170     if (!modules->empty() &&
171         0 == internal_strcmp(cur_name, modules->back().full_name())) {
172       cur_module = &modules->back();
173     } else {
174       modules->push_back(LoadedModule());
175       cur_module = &modules->back();
176       cur_module->set(cur_name, cur_beg);
177     }
178     cur_module->addAddressRange(cur_beg, cur_end, prot & kProtectionExecute);
179   }
180 }
181 
182 }  // namespace __sanitizer
183 
184 #endif  // SANITIZER_MAC
185