The Tor Browser: mozglue/linker/CustomElf.cpp@6474c204b198 (annotated)

mozglue/linker/CustomElf.cpp@6474c204b198 (annotated)

mozglue/linker/CustomElf.cpp

Wed, 31 Dec 2014 06:09:35 +0100

author: Michael Schloh von Bennewitz <michael@schloh.com>
date: Wed, 31 Dec 2014 06:09:35 +0100
changeset 0: 6474c204b198
permissions: -rw-r--r--

Cloned upstream origin tor-browser at tor-browser-31.3.0esr-4.5-1-build1
revision ID fc1c9ff7c1b2defdbc039f12214767608f46423f for hacking purpose.

 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this file,
  * You can obtain one at http://mozilla.org/MPL/2.0/. */
 #include <cstring>
 #include <sys/mman.h>
 #include <vector>
 #include <dlfcn.h>
 #include "CustomElf.h"
 #include "Mappable.h"
 #include "Logging.h"
 using namespace Elf;
 using namespace mozilla;
 /* TODO: Fill ElfLoader::Singleton.lastError on errors. */
 /* Function used to report library mappings from the custom linker to Gecko
  * crash reporter */
 #ifdef ANDROID
 extern "C" {
   void report_mapping(char *name, void *base, uint32_t len, uint32_t offset);
 }
 #else
 #define report_mapping(...)
 #endif
 const Ehdr *Ehdr::validate(const void *buf)
 {
   if (!buf || buf == MAP_FAILED)
     return nullptr;
   const Ehdr *ehdr = reinterpret_cast<const Ehdr *>(buf);
   /* Only support ELF executables or libraries for the host system */
   if (memcmp(ELFMAG, &ehdr->e_ident, SELFMAG) ||
       ehdr->e_ident[EI_CLASS] != ELFCLASS ||
       ehdr->e_ident[EI_DATA] != ELFDATA ||
       ehdr->e_ident[EI_VERSION] != 1 ||
       (ehdr->e_ident[EI_OSABI] != ELFOSABI && ehdr->e_ident[EI_OSABI] != ELFOSABI_NONE) ||
 #ifdef EI_ABIVERSION
       ehdr->e_ident[EI_ABIVERSION] != ELFABIVERSION ||
 #endif
       (ehdr->e_type != ET_EXEC && ehdr->e_type != ET_DYN) ||
       ehdr->e_machine != ELFMACHINE ||
       ehdr->e_version != 1 ||
       ehdr->e_phentsize != sizeof(Phdr))
     return nullptr;
   return ehdr;
 }
 namespace {
 void debug_phdr(const char *type, const Phdr *phdr)
 {
   DEBUG_LOG("%s @0x%08" PRIxAddr " ("
             "filesz: 0x%08" PRIxAddr ", "
             "memsz: 0x%08" PRIxAddr ", "
             "offset: 0x%08" PRIxAddr ", "
             "flags: %c%c%c)",
             type, phdr->p_vaddr, phdr->p_filesz, phdr->p_memsz,
             phdr->p_offset, phdr->p_flags & PF_R ? 'r' : '-',
             phdr->p_flags & PF_W ? 'w' : '-', phdr->p_flags & PF_X ? 'x' : '-');
 }
 static int p_flags_to_mprot(Word flags)
 {
   return ((flags & PF_X) ? PROT_EXEC : 0) |
          ((flags & PF_W) ? PROT_WRITE : 0) |
          ((flags & PF_R) ? PROT_READ : 0);
 }
 void
 __void_stub(void)
 {
 }
 } /* anonymous namespace */
 /**
  * RAII wrapper for a mapping of the first page off a Mappable object.
  * This calls Mappable::munmap instead of system munmap.
  */
 class Mappable1stPagePtr: public GenericMappedPtr<Mappable1stPagePtr> {
 public:
   Mappable1stPagePtr(Mappable *mappable)
   : GenericMappedPtr<Mappable1stPagePtr>(
       mappable->mmap(nullptr, PageSize(), PROT_READ, MAP_PRIVATE, 0))
   , mappable(mappable)
   {
     /* Ensure the content of this page */
     mappable->ensure(*this);
   }
 private:
   friend class GenericMappedPtr<Mappable1stPagePtr>;
   void munmap(void *buf, size_t length) {
     mappable->munmap(buf, length);
   }
   mozilla::RefPtr<Mappable> mappable;
 };
 TemporaryRef<LibHandle>
 CustomElf::Load(Mappable *mappable, const char *path, int flags)
 {
   DEBUG_LOG("CustomElf::Load(\"%s\", 0x%x) = ...", path, flags);
   if (!mappable)
     return nullptr;
   /* Keeping a RefPtr of the CustomElf is going to free the appropriate
    * resources when returning nullptr */
   RefPtr<CustomElf> elf = new CustomElf(mappable, path);
   /* Map the first page of the Elf object to access Elf and program headers */
   Mappable1stPagePtr ehdr_raw(mappable);
   if (ehdr_raw == MAP_FAILED)
     return nullptr;
   const Ehdr *ehdr = Ehdr::validate(ehdr_raw);
   if (!ehdr)
     return nullptr;
   /* Scan Elf Program Headers and gather some information about them */
   std::vector<const Phdr *> pt_loads;
   Addr min_vaddr = (Addr) -1; // We want to find the lowest and biggest
   Addr max_vaddr = 0;         // virtual address used by this Elf.
   const Phdr *dyn = nullptr;
   const Phdr *first_phdr = reinterpret_cast<const Phdr *>(
                            reinterpret_cast<const char *>(ehdr) + ehdr->e_phoff);
   const Phdr *end_phdr = &first_phdr[ehdr->e_phnum];
 #ifdef __ARM_EABI__
   const Phdr *arm_exidx_phdr = nullptr;
 #endif
   for (const Phdr *phdr = first_phdr; phdr < end_phdr; phdr++) {
     switch (phdr->p_type) {
       case PT_LOAD:
         debug_phdr("PT_LOAD", phdr);
         pt_loads.push_back(phdr);
         if (phdr->p_vaddr < min_vaddr)
           min_vaddr = phdr->p_vaddr;
         if (max_vaddr < phdr->p_vaddr + phdr->p_memsz)
           max_vaddr = phdr->p_vaddr + phdr->p_memsz;
         break;
       case PT_DYNAMIC:
         debug_phdr("PT_DYNAMIC", phdr);
         if (!dyn) {
           dyn = phdr;
         } else {
           LOG("%s: Multiple PT_DYNAMIC segments detected", elf->GetPath());
           return nullptr;
         }
         break;
       case PT_TLS:
         debug_phdr("PT_TLS", phdr);
         if (phdr->p_memsz) {
           LOG("%s: TLS is not supported", elf->GetPath());
           return nullptr;
         }
         break;
       case PT_GNU_STACK:
         debug_phdr("PT_GNU_STACK", phdr);
 // Skip on Android until bug 706116 is fixed
 #ifndef ANDROID
         if (phdr->p_flags & PF_X) {
           LOG("%s: Executable stack is not supported", elf->GetPath());
           return nullptr;
         }
 #endif
         break;
 #ifdef __ARM_EABI__
       case PT_ARM_EXIDX:
         /* We cannot initialize arm_exidx here
            because we don't have a base yet */
         arm_exidx_phdr = phdr;
         break;
 #endif
       default:
         DEBUG_LOG("%s: Warning: program header type #%d not handled",
                   elf->GetPath(), phdr->p_type);
     }
   }
   if (min_vaddr != 0) {
     LOG("%s: Unsupported minimal virtual address: 0x%08" PRIxAddr,
         elf->GetPath(), min_vaddr);
     return nullptr;
   }
   if (!dyn) {
     LOG("%s: No PT_DYNAMIC segment found", elf->GetPath());
     return nullptr;
   }
   /* Reserve enough memory to map the complete virtual address space for this
    * library.
    * As we are using the base address from here to mmap something else with
    * MAP_FIXED | MAP_SHARED, we need to make sure these mmaps will work. For
    * instance, on armv6, MAP_SHARED mappings require a 16k alignment, but mmap
    * MAP_PRIVATE only returns a 4k aligned address. So we first get a base
    * address with MAP_SHARED, which guarantees the kernel returns an address
    * that we'll be able to use with MAP_FIXED, and then remap MAP_PRIVATE at
    * the same address, because of some bad side effects of keeping it as
    * MAP_SHARED. */
   elf->base.Assign(MemoryRange::mmap(nullptr, max_vaddr, PROT_NONE,
                                      MAP_SHARED | MAP_ANONYMOUS, -1, 0));
   if ((elf->base == MAP_FAILED) ||
       (mmap(elf->base, max_vaddr, PROT_NONE,
             MAP_PRIVATE | MAP_ANONYMOUS | MAP_FIXED, -1, 0) != elf->base)) {
     LOG("%s: Failed to mmap", elf->GetPath());
     return nullptr;
   }
   /* Load and initialize library */
   for (std::vector<const Phdr *>::iterator it = pt_loads.begin();
        it < pt_loads.end(); ++it)
     if (!elf->LoadSegment(*it))
       return nullptr;
   /* We're not going to mmap anymore */
   mappable->finalize();
   report_mapping(const_cast<char *>(elf->GetName()), elf->base,
                  (max_vaddr + PAGE_SIZE - 1) & PAGE_MASK, 0);
   elf->l_addr = elf->base;
   elf->l_name = elf->GetPath();
   elf->l_ld = elf->GetPtr<Dyn>(dyn->p_vaddr);
   ElfLoader::Singleton.Register(elf);
   if (!elf->InitDyn(dyn))
     return nullptr;
   if (elf->has_text_relocs) {
     for (std::vector<const Phdr *>::iterator it = pt_loads.begin();
          it < pt_loads.end(); ++it)
       mprotect(PageAlignedPtr(elf->GetPtr((*it)->p_vaddr)),
                PageAlignedEndPtr((*it)->p_memsz),
                p_flags_to_mprot((*it)->p_flags) | PROT_WRITE);
   }
   if (!elf->Relocate() || !elf->RelocateJumps())
     return nullptr;
   if (elf->has_text_relocs) {
     for (std::vector<const Phdr *>::iterator it = pt_loads.begin();
          it < pt_loads.end(); ++it)
       mprotect(PageAlignedPtr(elf->GetPtr((*it)->p_vaddr)),
                PageAlignedEndPtr((*it)->p_memsz),
                p_flags_to_mprot((*it)->p_flags));
   }
   if (!elf->CallInit())
     return nullptr;
 #ifdef __ARM_EABI__
   if (arm_exidx_phdr)
     elf->arm_exidx.InitSize(elf->GetPtr(arm_exidx_phdr->p_vaddr),
                             arm_exidx_phdr->p_memsz);
 #endif
   elf->stats("oneLibLoaded");
   DEBUG_LOG("CustomElf::Load(\"%s\", 0x%x) = %p", path, flags,
             static_cast<void *>(elf));
   return elf;
 }
 CustomElf::~CustomElf()
 {
   DEBUG_LOG("CustomElf::~CustomElf(%p [\"%s\"])",
             reinterpret_cast<void *>(this), GetPath());
   CallFini();
   /* Normally, __cxa_finalize is called by the .fini function. However,
    * Android NDK before r6b doesn't do that. Our wrapped cxa_finalize only
    * calls destructors once, so call it in all cases. */
   ElfLoader::__wrap_cxa_finalize(this);
   ElfLoader::Singleton.Forget(this);
 }
 namespace {
 /**
  * Hash function for symbol lookup, as defined in ELF standard for System V
  */
 unsigned long
 ElfHash(const char *symbol)
 {
   const unsigned char *sym = reinterpret_cast<const unsigned char *>(symbol);
   unsigned long h = 0, g;
   while (*sym) {
     h = (h << 4) + *sym++;
     if ((g = h & 0xf0000000))
       h ^= g >> 24;
     h &= ~g;
   }
   return h;
 }
 } /* anonymous namespace */
 void *
 CustomElf::GetSymbolPtr(const char *symbol) const
 {
   return GetSymbolPtr(symbol, ElfHash(symbol));
 }
 void *
 CustomElf::GetSymbolPtr(const char *symbol, unsigned long hash) const
 {
   const Sym *sym = GetSymbol(symbol, hash);
   void *ptr = nullptr;
   if (sym && sym->st_shndx != SHN_UNDEF)
     ptr = GetPtr(sym->st_value);
   DEBUG_LOG("CustomElf::GetSymbolPtr(%p [\"%s\"], \"%s\") = %p",
             reinterpret_cast<const void *>(this), GetPath(), symbol, ptr);
   return ptr;
 }
 void *
 CustomElf::GetSymbolPtrInDeps(const char *symbol) const
 {
   /* Resolve dlopen and related functions to point to ours */
   if (symbol[0] == 'd' && symbol[1] == 'l') {
     if (strcmp(symbol + 2, "open") == 0)
       return FunctionPtr(__wrap_dlopen);
     if (strcmp(symbol + 2, "error") == 0)
       return FunctionPtr(__wrap_dlerror);
     if (strcmp(symbol + 2, "close") == 0)
       return FunctionPtr(__wrap_dlclose);
     if (strcmp(symbol + 2, "sym") == 0)
       return FunctionPtr(__wrap_dlsym);
     if (strcmp(symbol + 2, "addr") == 0)
       return FunctionPtr(__wrap_dladdr);
     if (strcmp(symbol + 2, "_iterate_phdr") == 0)
       return FunctionPtr(__wrap_dl_iterate_phdr);
   } else if (symbol[0] == '_' && symbol[1] == '_') {
   /* Resolve a few C++ ABI specific functions to point to ours */
 #ifdef __ARM_EABI__
     if (strcmp(symbol + 2, "aeabi_atexit") == 0)
       return FunctionPtr(&ElfLoader::__wrap_aeabi_atexit);
 #else
     if (strcmp(symbol + 2, "cxa_atexit") == 0)
       return FunctionPtr(&ElfLoader::__wrap_cxa_atexit);
 #endif
     if (strcmp(symbol + 2, "cxa_finalize") == 0)
       return FunctionPtr(&ElfLoader::__wrap_cxa_finalize);
     if (strcmp(symbol + 2, "dso_handle") == 0)
       return const_cast<CustomElf *>(this);
     if (strcmp(symbol + 2, "moz_linker_stats") == 0)
       return FunctionPtr(&ElfLoader::stats);
 #ifdef __ARM_EABI__
     if (strcmp(symbol + 2, "gnu_Unwind_Find_exidx") == 0)
       return FunctionPtr(__wrap___gnu_Unwind_Find_exidx);
 #endif
   }
 #define MISSING_FLASH_SYMNAME_START "_ZN7android10VectorImpl19reservedVectorImpl"
   // Android changed some symbols that Flash depended on in 4.4,
   // so stub those out here
   if (strncmp(symbol,
               MISSING_FLASH_SYMNAME_START,
               sizeof(MISSING_FLASH_SYMNAME_START) - 1) == 0) {
     return FunctionPtr(__void_stub);
   }
   void *sym;
   /* Search the symbol in the main program. Note this also tries all libraries
    * the system linker will have loaded RTLD_GLOBAL. Unfortunately, that doesn't
    * work with bionic, but its linker doesn't normally search the main binary
    * anyways. Moreover, on android, the main binary is dalvik. */
 #ifdef __GLIBC__
   sym = dlsym(RTLD_DEFAULT, symbol);
   DEBUG_LOG("dlsym(RTLD_DEFAULT, \"%s\") = %p", symbol, sym);
   if (sym)
     return sym;
 #endif
   /* Then search the symbol in our dependencies. Since we already searched in
    * libraries the system linker loaded, skip those (on glibc systems). We
    * also assume the symbol is to be found in one of the dependent libraries
    * directly, not in their own dependent libraries. Building libraries with
    * --no-allow-shlib-undefined ensures such indirect symbol dependency don't
    * happen. */
   unsigned long hash = ElfHash(symbol);
   for (std::vector<RefPtr<LibHandle> >::const_iterator it = dependencies.begin();
        it < dependencies.end(); ++it) {
     if (!(*it)->IsSystemElf()) {
       sym = reinterpret_cast<CustomElf *>((*it).get())->GetSymbolPtr(symbol, hash);
 #ifndef __GLIBC__
     } else {
       sym = (*it)->GetSymbolPtr(symbol);
 #endif
     }
     if (sym)
       return sym;
   }
   return nullptr;
 }
 const Sym *
 CustomElf::GetSymbol(const char *symbol, unsigned long hash) const
 {
   /* Search symbol with the buckets and chains tables.
    * The hash computed from the symbol name gives an index in the buckets
    * table. The corresponding value in the bucket table is an index in the
    * symbols table and in the chains table.
    * If the corresponding symbol in the symbols table matches, we're done.
    * Otherwise, the corresponding value in the chains table is a new index
    * in both tables, which corresponding symbol is tested and so on and so
    * forth */
   size_t bucket = hash % buckets.numElements();
   for (size_t y = buckets[bucket]; y != STN_UNDEF; y = chains[y]) {
     if (strcmp(symbol, strtab.GetStringAt(symtab[y].st_name)))
       continue;
     return &symtab[y];
   }
   return nullptr;
 }
 bool
 CustomElf::Contains(void *addr) const
 {
   return base.Contains(addr);
 }
 #ifdef __ARM_EABI__
 const void *
 CustomElf::FindExidx(int *pcount) const
 {
   if (arm_exidx) {
     *pcount = arm_exidx.numElements();
     return arm_exidx;
   }
   *pcount = 0;
   return nullptr;
 }
 #endif
 void
 CustomElf::stats(const char *when) const
 {
   mappable->stats(when, GetPath());
 }
 bool
 CustomElf::LoadSegment(const Phdr *pt_load) const
 {
   if (pt_load->p_type != PT_LOAD) {
     DEBUG_LOG("%s: Elf::LoadSegment only takes PT_LOAD program headers", GetPath());
     return false;;
   }
   int prot = p_flags_to_mprot(pt_load->p_flags);
   /* Mmap at page boundary */
   Addr align = PageSize();
   Addr align_offset;
   void *mapped, *where;
   do {
     align_offset = pt_load->p_vaddr - AlignedPtr(pt_load->p_vaddr, align);
     where = GetPtr(pt_load->p_vaddr - align_offset);
     DEBUG_LOG("%s: Loading segment @%p %c%c%c", GetPath(), where,
                                                 prot & PROT_READ ? 'r' : '-',
                                                 prot & PROT_WRITE ? 'w' : '-',
                                                 prot & PROT_EXEC ? 'x' : '-');
     mapped = mappable->mmap(where, pt_load->p_filesz + align_offset,
                             prot, MAP_PRIVATE | MAP_FIXED,
                             pt_load->p_offset - align_offset);
     if ((mapped != MAP_FAILED) || (pt_load->p_vaddr == 0) ||
         (pt_load->p_align == align))
       break;
     /* The virtual address space for the library is properly aligned at
      * 16k on ARMv6 (see CustomElf::Load), and so is the first segment
      * (p_vaddr == 0). But subsequent segments may not be 16k aligned
      * and fail to mmap. In such case, try to mmap again at the p_align
      * boundary instead of page boundary. */
     DEBUG_LOG("%s: Failed to mmap, retrying", GetPath());
     align = pt_load->p_align;
   } while (1);
   if (mapped != where) {
     if (mapped == MAP_FAILED) {
       LOG("%s: Failed to mmap", GetPath());
     } else {
       LOG("%s: Didn't map at the expected location (wanted: %p, got: %p)",
           GetPath(), where, mapped);
     }
     return false;
   }
   /* Ensure the availability of all pages within the mapping if on-demand
    * decompression is disabled (MOZ_LINKER_ONDEMAND=0 or signal handler not
    * registered). */
   const char *ondemand = getenv("MOZ_LINKER_ONDEMAND");
   if (!ElfLoader::Singleton.hasRegisteredHandler() ||
       (ondemand && !strncmp(ondemand, "0", 2 /* Including '\0' */))) {
     for (Addr off = 0; off < pt_load->p_filesz + align_offset;
          off += PageSize()) {
       mappable->ensure(reinterpret_cast<char *>(mapped) + off);
     }
   }
   /* When p_memsz is greater than p_filesz, we need to have nulled out memory
    * after p_filesz and before p_memsz.
    * Above the end of the last page, and up to p_memsz, we already have nulled
    * out memory because we mapped anonymous memory on the whole library virtual
    * address space. We just need to adjust this anonymous memory protection
    * flags. */
   if (pt_load->p_memsz > pt_load->p_filesz) {
     Addr file_end = pt_load->p_vaddr + pt_load->p_filesz;
     Addr mem_end = pt_load->p_vaddr + pt_load->p_memsz;
     Addr next_page = PageAlignedEndPtr(file_end);
     if (next_page > file_end) {
       /* The library is not registered at this point, so we can't rely on
        * on-demand decompression to handle missing pages here. */
       void *ptr = GetPtr(file_end);
       mappable->ensure(ptr);
       memset(ptr, 0, next_page - file_end);
     }
     if (mem_end > next_page) {
       if (mprotect(GetPtr(next_page), mem_end - next_page, prot) < 0) {
         LOG("%s: Failed to mprotect", GetPath());
         return false;
       }
     }
   }
   return true;
 }
 namespace {
 void debug_dyn(const char *type, const Dyn *dyn)
 {
   DEBUG_LOG("%s 0x%08" PRIxAddr, type, dyn->d_un.d_val);
 }
 } /* anonymous namespace */
 bool
 CustomElf::InitDyn(const Phdr *pt_dyn)
 {
   /* Scan PT_DYNAMIC segment and gather some information */
   const Dyn *first_dyn = GetPtr<Dyn>(pt_dyn->p_vaddr);
   const Dyn *end_dyn = GetPtr<Dyn>(pt_dyn->p_vaddr + pt_dyn->p_filesz);
   std::vector<Word> dt_needed;
   size_t symnum = 0;
   for (const Dyn *dyn = first_dyn; dyn < end_dyn && dyn->d_tag; dyn++) {
     switch (dyn->d_tag) {
       case DT_NEEDED:
         debug_dyn("DT_NEEDED", dyn);
         dt_needed.push_back(dyn->d_un.d_val);
         break;
       case DT_HASH:
         {
           debug_dyn("DT_HASH", dyn);
           const Word *hash_table_header = GetPtr<Word>(dyn->d_un.d_ptr);
           symnum = hash_table_header[1];
           buckets.Init(&hash_table_header[2], hash_table_header[0]);
           chains.Init(&*buckets.end());
         }
         break;
       case DT_STRTAB:
         debug_dyn("DT_STRTAB", dyn);
         strtab.Init(GetPtr(dyn->d_un.d_ptr));
         break;
       case DT_SYMTAB:
         debug_dyn("DT_SYMTAB", dyn);
         symtab.Init(GetPtr(dyn->d_un.d_ptr));
         break;
       case DT_SYMENT:
         debug_dyn("DT_SYMENT", dyn);
         if (dyn->d_un.d_val != sizeof(Sym)) {
           LOG("%s: Unsupported DT_SYMENT", GetPath());
           return false;
         }
         break;
       case DT_TEXTREL:
         if (strcmp("libflashplayer.so", GetName()) == 0) {
           has_text_relocs = true;
         } else {
           LOG("%s: Text relocations are not supported", GetPath());
           return false;
         }
         break;
       case DT_STRSZ: /* Ignored */
         debug_dyn("DT_STRSZ", dyn);
         break;
       case UNSUPPORTED_RELOC():
       case UNSUPPORTED_RELOC(SZ):
       case UNSUPPORTED_RELOC(ENT):
         LOG("%s: Unsupported relocations", GetPath());
         return false;
       case RELOC():
         debug_dyn(STR_RELOC(), dyn);
         relocations.Init(GetPtr(dyn->d_un.d_ptr));
         break;
       case RELOC(SZ):
         debug_dyn(STR_RELOC(SZ), dyn);
         relocations.InitSize(dyn->d_un.d_val);
         break;
       case RELOC(ENT):
         debug_dyn(STR_RELOC(ENT), dyn);
         if (dyn->d_un.d_val != sizeof(Reloc)) {
           LOG("%s: Unsupported DT_RELENT", GetPath());
           return false;
         }
         break;
       case DT_JMPREL:
         debug_dyn("DT_JMPREL", dyn);
         jumprels.Init(GetPtr(dyn->d_un.d_ptr));
         break;
       case DT_PLTRELSZ:
         debug_dyn("DT_PLTRELSZ", dyn);
         jumprels.InitSize(dyn->d_un.d_val);
         break;
       case DT_PLTGOT:
         debug_dyn("DT_PLTGOT", dyn);
         break;
       case DT_INIT:
         debug_dyn("DT_INIT", dyn);
         init = dyn->d_un.d_ptr;
         break;
       case DT_INIT_ARRAY:
         debug_dyn("DT_INIT_ARRAY", dyn);
         init_array.Init(GetPtr(dyn->d_un.d_ptr));
         break;
       case DT_INIT_ARRAYSZ:
         debug_dyn("DT_INIT_ARRAYSZ", dyn);
         init_array.InitSize(dyn->d_un.d_val);
         break;
       case DT_FINI:
         debug_dyn("DT_FINI", dyn);
         fini = dyn->d_un.d_ptr;
         break;
       case DT_FINI_ARRAY:
         debug_dyn("DT_FINI_ARRAY", dyn);
         fini_array.Init(GetPtr(dyn->d_un.d_ptr));
         break;
       case DT_FINI_ARRAYSZ:
         debug_dyn("DT_FINI_ARRAYSZ", dyn);
         fini_array.InitSize(dyn->d_un.d_val);
         break;
       case DT_PLTREL:
         if (dyn->d_un.d_val != RELOC()) {
           LOG("%s: Error: DT_PLTREL is not " STR_RELOC(), GetPath());
           return false;
         }
         break;
       case DT_FLAGS:
         {
            Addr flags = dyn->d_un.d_val;
            /* Treat as a DT_TEXTREL tag */
            if (flags & DF_TEXTREL) {
              if (strcmp("libflashplayer.so", GetName()) == 0) {
                has_text_relocs = true;
              } else {
                LOG("%s: Text relocations are not supported", GetPath());
                return false;
              }
            }
            /* we can treat this like having a DT_SYMBOLIC tag */
            flags &= ~DF_SYMBOLIC;
            if (flags)
              LOG("%s: Warning: unhandled flags #%" PRIxAddr" not handled",
                  GetPath(), flags);
         }
         break;
       case DT_SONAME: /* Should match GetName(), but doesn't matter */
       case DT_SYMBOLIC: /* Indicates internal symbols should be looked up in
                          * the library itself first instead of the executable,
                          * which is actually what this linker does by default */
       case RELOC(COUNT): /* Indicates how many relocations are relative, which
                           * is usually used to skip relocations on prelinked
                           * libraries. They are not supported anyways. */
       case UNSUPPORTED_RELOC(COUNT): /* This should error out, but it doesn't
                                       * really matter. */
       case DT_FLAGS_1: /* Additional linker-internal flags that we don't care about. See
                         * DF_1_* values in src/include/elf/common.h in binutils. */
       case DT_VERSYM: /* DT_VER* entries are used for symbol versioning, which */
       case DT_VERDEF: /* this linker doesn't support yet. */
       case DT_VERDEFNUM:
       case DT_VERNEED:
       case DT_VERNEEDNUM:
         /* Ignored */
         break;
       default:
         LOG("%s: Warning: dynamic header type #%" PRIxAddr" not handled",
             GetPath(), dyn->d_tag);
     }
   }
   if (!buckets || !symnum) {
     LOG("%s: Missing or broken DT_HASH", GetPath());
     return false;
   }
   if (!strtab) {
     LOG("%s: Missing DT_STRTAB", GetPath());
     return false;
   }
   if (!symtab) {
     LOG("%s: Missing DT_SYMTAB", GetPath());
     return false;
   }
   /* Load dependent libraries */
   for (size_t i = 0; i < dt_needed.size(); i++) {
     const char *name = strtab.GetStringAt(dt_needed[i]);
     RefPtr<LibHandle> handle =
       ElfLoader::Singleton.Load(name, RTLD_GLOBAL | RTLD_LAZY, this);
     if (!handle)
       return false;
     dependencies.push_back(handle);
   }
   return true;
 }
 bool
 CustomElf::Relocate()
 {
   DEBUG_LOG("Relocate %s @%p", GetPath(), static_cast<void *>(base));
   uint32_t symtab_index = (uint32_t) -1;
   void *symptr = nullptr;
   for (Array<Reloc>::iterator rel = relocations.begin();
        rel < relocations.end(); ++rel) {
     /* Location of the relocation */
     void *ptr = GetPtr(rel->r_offset);
     /* R_*_RELATIVE relocations apply directly at the given location */
     if (ELF_R_TYPE(rel->r_info) == R_RELATIVE) {
       *(void **) ptr = GetPtr(rel->GetAddend(base));
       continue;
     }
     /* Other relocation types need a symbol resolution */
     /* Avoid symbol resolution when it's the same symbol as last iteration */
     if (symtab_index != ELF_R_SYM(rel->r_info)) {
       symtab_index = ELF_R_SYM(rel->r_info);
       const Sym sym = symtab[symtab_index];
       if (sym.st_shndx != SHN_UNDEF) {
         symptr = GetPtr(sym.st_value);
       } else {
         /* TODO: handle symbol resolving to nullptr vs. being undefined. */
         symptr = GetSymbolPtrInDeps(strtab.GetStringAt(sym.st_name));
       }
     }
     if (symptr == nullptr)
       LOG("%s: Warning: relocation to NULL @0x%08" PRIxAddr,
           GetPath(), rel->r_offset);
     /* Apply relocation */
     switch (ELF_R_TYPE(rel->r_info)) {
     case R_GLOB_DAT:
       /* R_*_GLOB_DAT relocations simply use the symbol value */
       *(void **) ptr = symptr;
       break;
     case R_ABS:
       /* R_*_ABS* relocations add the relocation added to the symbol value */
       *(const char **) ptr = (const char *)symptr + rel->GetAddend(base);
       break;
     default:
       LOG("%s: Unsupported relocation type: 0x%" PRIxAddr,
           GetPath(), ELF_R_TYPE(rel->r_info));
       return false;
     }
   }
   return true;
 }
 bool
 CustomElf::RelocateJumps()
 {
   /* TODO: Dynamic symbol resolution */
   for (Array<Reloc>::iterator rel = jumprels.begin();
        rel < jumprels.end(); ++rel) {
     /* Location of the relocation */
     void *ptr = GetPtr(rel->r_offset);
     /* Only R_*_JMP_SLOT relocations are expected */
     if (ELF_R_TYPE(rel->r_info) != R_JMP_SLOT) {
       LOG("%s: Jump relocation type mismatch", GetPath());
       return false;
     }
     /* TODO: Avoid code duplication with the relocations above */
     const Sym sym = symtab[ELF_R_SYM(rel->r_info)];
     void *symptr;
     if (sym.st_shndx != SHN_UNDEF)
       symptr = GetPtr(sym.st_value);
     else
       symptr = GetSymbolPtrInDeps(strtab.GetStringAt(sym.st_name));
     if (symptr == nullptr) {
       LOG("%s: %s: relocation to NULL @0x%08" PRIxAddr " for symbol \"%s\"",
           GetPath(),
           (ELF_ST_BIND(sym.st_info) == STB_WEAK) ? "Warning" : "Error",
           rel->r_offset, strtab.GetStringAt(sym.st_name));
       if (ELF_ST_BIND(sym.st_info) != STB_WEAK)
         return false;
     }
     /* Apply relocation */
     *(void **) ptr = symptr;
   }
   return true;
 }
 bool
 CustomElf::CallInit()
 {
   if (init)
     CallFunction(init);
   for (Array<void *>::iterator it = init_array.begin();
        it < init_array.end(); ++it) {
     /* Android x86 NDK wrongly puts 0xffffffff in INIT_ARRAY */
     if (*it && *it != reinterpret_cast<void *>(-1))
       CallFunction(*it);
   }
   initialized = true;
   return true;
 }
 void
 CustomElf::CallFini()
 {
   if (!initialized)
     return;
   for (Array<void *>::reverse_iterator it = fini_array.rbegin();
        it < fini_array.rend(); ++it) {
     /* Android x86 NDK wrongly puts 0xffffffff in FINI_ARRAY */
     if (*it && *it != reinterpret_cast<void *>(-1))
       CallFunction(*it);
   }
   if (fini)
     CallFunction(fini);
 }
 Mappable *
 CustomElf::GetMappable() const
 {
   if (!mappable)
     return nullptr;
   if (mappable->GetKind() == Mappable::MAPPABLE_EXTRACT_FILE)
     return mappable;
   return ElfLoader::GetMappableFromPath(GetPath());
 }

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mozglue/linker/CustomElf.cpp@6474c204b198 (annotated)

mozglue/linker/CustomElf.cpp