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gecko-dev/mozglue/linker/CustomElf.cpp

772 строки
25 KiB
C++
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/* 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);
}
#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);
}
} /* 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);
}
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());
}
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