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gecko/mozglue/linker/CustomElf.cpp
Mike Hommey 49c12e0023 Bug 1081034 part 2 - Move initialization of self_elf to its own separate class. r=nfroyd 
The new class is kind of like SystemElf, but using our linker's own symbol
resolution. This also adds some initialization from ELF program headers that
weren't done previously for self_elf, as well as registration as for CustomElf
instances.
2014-10-16 09:20:06 +09:00

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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);
}
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 {
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;
}
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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