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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 
     24 MemoryMappingLayout::MemoryMappingLayout(bool cache_enabled) {
     25   Reset();
     26 }
     27 
     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 
     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
     59 void MemoryMappingLayout::CacheMemoryMappings() {
     60   // No-op on Mac for now.
     61 }
     62 
     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>
     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 
    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 
    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