diff options
Diffstat (limited to 'mozglue/linker/CustomElf.cpp')
| -rw-r--r-- | mozglue/linker/CustomElf.cpp | 774 |
1 files changed, 774 insertions, 0 deletions
diff --git a/mozglue/linker/CustomElf.cpp b/mozglue/linker/CustomElf.cpp new file mode 100644 index 000000000..dbab0cf0d --- /dev/null +++ b/mozglue/linker/CustomElf.cpp @@ -0,0 +1,774 @@ +/* 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 <signal.h> +#include <string.h> +#include "CustomElf.h" +#include "BaseElf.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); + void delete_mapping(const char *name); +} +#else +#define report_mapping(...) +#define delete_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); +} + +} /* 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); + } + + RefPtr<Mappable> mappable; +}; + + +already_AddRefed<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 { + ERROR("%s: Multiple PT_DYNAMIC segments detected", elf->GetPath()); + return nullptr; + } + break; + case PT_TLS: + debug_phdr("PT_TLS", phdr); + if (phdr->p_memsz) { + ERROR("%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) { + ERROR("%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: Program header type #%d not handled", + elf->GetPath(), phdr->p_type); + } + } + + if (min_vaddr != 0) { + ERROR("%s: Unsupported minimal virtual address: 0x%08" PRIxAddr, + elf->GetPath(), min_vaddr); + return nullptr; + } + if (!dyn) { + ERROR("%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)) { + ERROR("%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 + + if (MOZ_UNLIKELY(Logging::isVerbose())) { + elf->stats("oneLibLoaded"); + } + DEBUG_LOG("CustomElf::Load(\"%s\", 0x%x) = %p", path, flags, + static_cast<void *>(elf)); + return elf.forget(); +} + +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); + delete_mapping(GetName()); +} + +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 + } else if (symbol[0] == 's' && symbol[1] == 'i') { + if (strcmp(symbol + 2, "gnal") == 0) + return FunctionPtr(signal); + if (strcmp(symbol + 2, "gaction") == 0) + return FunctionPtr(sigaction); + } + + void *sym; + + unsigned long hash = Hash(symbol); + + /* self_elf should never be NULL, but better safe than sorry. */ + if (ElfLoader::Singleton.self_elf) { + /* We consider the library containing this code a permanent LD_PRELOAD, + * so, check if the symbol exists here first. */ + sym = static_cast<BaseElf *>( + ElfLoader::Singleton.self_elf.get())->GetSymbolPtr(symbol, hash); + if (sym) + return sym; + } + + /* 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. */ + for (std::vector<RefPtr<LibHandle> >::const_iterator it = dependencies.begin(); + it < dependencies.end(); ++it) { + /* Skip if it's the library containing this code, since we've already + * looked at it above. */ + if (*it == ElfLoader::Singleton.self_elf) + continue; + if (BaseElf *be = (*it)->AsBaseElf()) { + sym = be->GetSymbolPtr(symbol, hash); + } else { + sym = (*it)->GetSymbolPtr(symbol); + } + if (sym) + return sym; + } + return nullptr; +} + +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) { + ERROR("%s: Failed to mmap", GetPath()); + } else { + ERROR("%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) { + ERROR("%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)) { + ERROR("%s: Unsupported DT_SYMENT", GetPath()); + return false; + } + break; + case DT_TEXTREL: + if (strcmp("libflashplayer.so", GetName()) == 0) { + has_text_relocs = true; + } else { + ERROR("%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): + ERROR("%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)) { + ERROR("%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()) { + ERROR("%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 { + ERROR("%s: Text relocations are not supported", GetPath()); + return false; + } + } + /* we can treat this like having a DT_SYMBOLIC tag */ + flags &= ~DF_SYMBOLIC; + if (flags) + WARN("%s: 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: + WARN("%s: dynamic header type #%" PRIxAddr" not handled", + GetPath(), dyn->d_tag); + } + } + + if (!buckets || !symnum) { + ERROR("%s: Missing or broken DT_HASH", GetPath()); + return false; + } + if (!strtab) { + ERROR("%s: Missing DT_STRTAB", GetPath()); + return false; + } + if (!symtab) { + ERROR("%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) + WARN("%s: 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: + ERROR("%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) { + ERROR("%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) { + if (ELF_ST_BIND(sym.st_info) == STB_WEAK) { + WARN("%s: Relocation to NULL @0x%08" PRIxAddr " for symbol \"%s\"", + GetPath(), + rel->r_offset, strtab.GetStringAt(sym.st_name)); + } else { + ERROR("%s: Relocation to NULL @0x%08" PRIxAddr " for symbol \"%s\"", + GetPath(), + rel->r_offset, strtab.GetStringAt(sym.st_name)); + 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()); +} |