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Merge "Added test for ifunc support in dynamic linker."

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This commit is contained in:
Dmitriy Ivanov
2014-08-14 00:29:28 +00:00
committed by Gerrit Code Review
parent 9a74e4c15c c5a13efa9b
commit e942b3ed81
7 changed files with 214 additions and 10 deletions
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114
linker/linker.cpp
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@@ -476,6 +476,29 @@ static ElfW(Sym)* soinfo_elf_lookup(soinfo* si, unsigned hash, const char* name,
return NULL;
}
static void resolve_ifunc_symbols(soinfo* si) {
phdr_table_unprotect_segments(si->phdr, si->phnum, si->load_bias);
TRACE_TYPE(IFUNC, "CHECKING FOR IFUNCS AND PERFORMING SYMBOL UPDATES");
for (size_t i = 0; i < si->nchain; ++i) {
ElfW(Sym)* s = &si->symtab[i];
if (ELF_ST_TYPE(s->st_info) == STT_GNU_IFUNC) {
// The address of the ifunc in the symbol table is the address of the
// function that chooses the function to which the ifunc will refer.
// In order to return the proper value, we run the choosing function
// in the linker and then return its result (minus the base offset).
TRACE_TYPE(IFUNC, "FOUND IFUNC");
ElfW(Addr) (*ifunc_ptr)();
ifunc_ptr = reinterpret_cast<ElfW(Addr)(*)()>(s->st_value + si->base);
s->st_value = (ifunc_ptr() - si->base);
TRACE_TYPE(IFUNC, "NEW VALUE IS %p", (void*)s->st_value);
}
}
phdr_table_protect_segments(si->phdr, si->phnum, si->load_bias);
}
static unsigned elfhash(const char* _name) {
const unsigned char* name = reinterpret_cast<const unsigned char*>(_name);
unsigned h = 0, g;
@@ -798,6 +821,10 @@ static soinfo* load_library(const char* name, int dlflags, const android_dlextin
return NULL;
}
// if the library has any ifuncs, we will need to resolve them so that dlsym
// can handle them properly
resolve_ifunc_symbols(si);
return si;
}
@@ -911,6 +938,53 @@ void do_dlclose(soinfo* si) {
protect_data(PROT_READ);
}
// ifuncs are only defined for x86
#if defined(__i386__)
static void soinfo_ifunc_relocate(soinfo* si, ElfW(Rel)* rel, unsigned count, soinfo* needed[]) {
for (size_t idx = 0; idx < count; ++idx, ++rel) {
ElfW(Sym)* s;
soinfo* lsi;
unsigned type = ELFW(R_TYPE)(rel->r_info);
unsigned sym = ELFW(R_SYM)(rel->r_info);
ElfW(Addr) reloc = static_cast<ElfW(Addr)>(rel->r_offset + si->load_bias);
ElfW(Addr) sym_addr = 0;
const char* sym_name = NULL;
sym_name = reinterpret_cast<const char*>(si->strtab + si->symtab[sym].st_name);
s = soinfo_do_lookup(si, sym_name, &lsi, needed);
if (ELF_ST_TYPE(s->st_info) == STT_GNU_IFUNC && type == R_386_JMP_SLOT) {
TRACE("IFUNC RELOCATION, PASS 2: %p", (void*)(sym_addr));
ElfW(Addr) (*ifunc_ptr)();
ifunc_ptr = reinterpret_cast<ElfW(Addr)(*)()>(s->st_value + si->base);
*reinterpret_cast<ElfW(Addr)*>(reloc) = ifunc_ptr();
}
}
}
#endif
#if defined(__x86_64__)
static void soinfo_ifunc_relocate(soinfo* si, ElfW(Rela)* rela, unsigned count, soinfo* needed[]) {
for (size_t idx = 0; idx < count; ++idx, ++rela) {
ElfW(Sym)* s;
soinfo* lsi;
unsigned type = ELFW(R_TYPE)(rela->r_info);
unsigned sym = ELFW(R_SYM)(rela->r_info);
ElfW(Addr) reloc = static_cast<ElfW(Addr)>(rela->r_offset + si->load_bias);
ElfW(Addr) sym_addr = 0;
const char* sym_name = NULL;
sym_name = reinterpret_cast<const char*>(si->strtab + si->symtab[sym].st_name);
s = soinfo_do_lookup(si, sym_name, &lsi, needed);
if (ELF_ST_TYPE(s->st_info) == STT_GNU_IFUNC && type == R_X86_64_JUMP_SLOT) {
TRACE("IFUNC RELOCATION, PASS 2: %p", (void*)(sym_addr + rela->r_addend));
ElfW(Addr) (*ifunc_ptr)();
ifunc_ptr = reinterpret_cast<ElfW(Addr)(*)()>(s->st_value + si->base);
*reinterpret_cast<ElfW(Addr)*>(reloc) = ifunc_ptr();
}
}
}
#endif
#if defined(USE_RELA)
static int soinfo_relocate(soinfo* si, ElfW(Rela)* rela, unsigned count, soinfo* needed[]) {
ElfW(Sym)* s;
@@ -1122,7 +1196,11 @@ static int soinfo_relocate(soinfo* si, ElfW(Rela)* rela, unsigned count, soinfo*
MARK(rela->r_offset);
TRACE_TYPE(RELO, "RELO JMP_SLOT %08zx <- %08zx %s", static_cast<size_t>(reloc),
static_cast<size_t>(sym_addr + rela->r_addend), sym_name);
*reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend;
if (ELF_ST_TYPE(s->st_info) == STT_GNU_IFUNC) {
si->set_has_ifuncs(true);
} else {
*reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr + rela->r_addend;
}
break;
case R_X86_64_GLOB_DAT:
count_relocation(kRelocAbsolute);
@@ -1301,7 +1379,11 @@ static int soinfo_relocate(soinfo* si, ElfW(Rel)* rel, unsigned count, soinfo* n
count_relocation(kRelocAbsolute);
MARK(rel->r_offset);
TRACE_TYPE(RELO, "RELO JMP_SLOT %08x <- %08x %s", reloc, sym_addr, sym_name);
*reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr;
if (ELF_ST_TYPE(s->st_info) == STT_GNU_IFUNC) {
si->set_has_ifuncs(true);
} else {
*reinterpret_cast<ElfW(Addr)*>(reloc) = sym_addr;
}
break;
case R_386_GLOB_DAT:
count_relocation(kRelocAbsolute);
@@ -1561,6 +1643,14 @@ void soinfo::set_st_ino(ino_t ino) {
st_ino = ino;
}
void soinfo::set_has_ifuncs(bool ifuncs) {
if ((this->flags & FLAG_NEW_SOINFO) == 0) {
return;
}
has_ifuncs = ifuncs;
}
dev_t soinfo::get_st_dev() {
if ((this->flags & FLAG_NEW_SOINFO) == 0) {
return 0;
@@ -1577,6 +1667,14 @@ ino_t soinfo::get_st_ino() {
return st_ino;
}
bool soinfo::get_has_ifuncs() {
if ((this->flags & FLAG_NEW_SOINFO) == 0) {
return false;
}
return has_ifuncs;
}
// This is a return on get_children() in case
// 'this->flags' does not have FLAG_NEW_SOINFO set.
static soinfo::soinfo_list_t g_empty_list;
@@ -1961,6 +2059,18 @@ static bool soinfo_link_image(soinfo* si, const android_dlextinfo* extinfo) {
}
#endif
// if there are ifuncs, we need to do an additional relocation pass.
// they cannot be resolved until the rest of the relocations are done
// because we need to call the resolution function which may be waiting
// on relocations.
if(si->get_has_ifuncs()) {
#if defined(__i386__)
soinfo_ifunc_relocate(si, si->plt_rel, si->plt_rel_count, needed);
#elif defined(__x86_64__)
soinfo_ifunc_relocate(si, si->plt_rela, si->plt_rela_count, needed);
#endif
}
#if defined(__mips__)
if (!mips_relocate_got(si, needed)) {
return false;