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Add support for protected local symbol lookup.

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Bug: http://code.google.com/p/android/issues/detail?id=66048
Change-Id: Ib334223df27adad9477fb241ab099c5e26df4a7d
This commit is contained in:
Dmitriy Ivanov
2014-06-29 12:28:37 -07:00
parent 4ec3bc83c6
commit d97e9f546e
8 changed files with 168 additions and 35 deletions
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51
linker/linker.cpp
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@@ -125,6 +125,11 @@ enum RelocationKind {
kRelocMax
};
enum class SymbolLookupScope {
kAllowLocal,
kExcludeLocal,
};
#if STATS
struct linker_stats_t {
int count[kRelocMax];
@@ -431,7 +436,7 @@ int dl_iterate_phdr(int (*cb)(dl_phdr_info* info, size_t size, void* data), void
return rv;
}
static ElfW(Sym)* soinfo_elf_lookup(soinfo* si, unsigned hash, const char* name) {
static ElfW(Sym)* soinfo_elf_lookup(soinfo* si, unsigned hash, const char* name, const SymbolLookupScope& lookup_scope) {
ElfW(Sym)* symtab = si->symtab;
const char* strtab = si->strtab;
@@ -442,18 +447,30 @@ static ElfW(Sym)* soinfo_elf_lookup(soinfo* si, unsigned hash, const char* name)
ElfW(Sym)* s = symtab + n;
if (strcmp(strtab + s->st_name, name)) continue;
/* only concern ourselves with global and weak symbol definitions */
switch (ELF_ST_BIND(s->st_info)) {
case STB_GLOBAL:
case STB_WEAK:
if (s->st_shndx == SHN_UNDEF) {
continue;
}
continue;
}
TRACE_TYPE(LOOKUP, "FOUND %s in %s (%p) %zd",
TRACE_TYPE(LOOKUP, "FOUND %s in %s (%p) %zd",
name, si->name, reinterpret_cast<void*>(s->st_value),
static_cast<size_t>(s->st_size));
return s;
return s;
case STB_LOCAL:
if (lookup_scope != SymbolLookupScope::kAllowLocal) {
continue;
}
TRACE_TYPE(LOOKUP, "FOUND LOCAL %s in %s (%p) %zd",
name, si->name, reinterpret_cast<void*>(s->st_value),
static_cast<size_t>(s->st_size));
return s;
default:
const char* msg = "FATAL: Unexpected ST_BIND\n";
__libc_format_log(ANDROID_LOG_FATAL, "linker", "%s", msg);
write(2, msg, strlen(msg));
abort();
}
}
@@ -484,7 +501,7 @@ static ElfW(Sym)* soinfo_do_lookup(soinfo* si, const char* name, soinfo** lsi, s
*/
if (si == somain) {
s = soinfo_elf_lookup(si, elf_hash, name);
s = soinfo_elf_lookup(si, elf_hash, name, SymbolLookupScope::kAllowLocal);
if (s != NULL) {
*lsi = si;
goto done;
@@ -501,7 +518,7 @@ static ElfW(Sym)* soinfo_do_lookup(soinfo* si, const char* name, soinfo** lsi, s
if (!si->has_DT_SYMBOLIC) {
DEBUG("%s: looking up %s in executable %s",
si->name, name, somain->name);
s = soinfo_elf_lookup(somain, elf_hash, name);
s = soinfo_elf_lookup(somain, elf_hash, name, SymbolLookupScope::kExcludeLocal);
if (s != NULL) {
*lsi = somain;
goto done;
@@ -518,7 +535,7 @@ static ElfW(Sym)* soinfo_do_lookup(soinfo* si, const char* name, soinfo** lsi, s
* and some the first non-weak definition. This is system dependent.
* Here we return the first definition found for simplicity. */
s = soinfo_elf_lookup(si, elf_hash, name);
s = soinfo_elf_lookup(si, elf_hash, name, SymbolLookupScope::kAllowLocal);
if (s != NULL) {
*lsi = si;
goto done;
@@ -532,7 +549,7 @@ static ElfW(Sym)* soinfo_do_lookup(soinfo* si, const char* name, soinfo** lsi, s
if (si->has_DT_SYMBOLIC) {
DEBUG("%s: looking up %s in executable %s after local scope",
si->name, name, somain->name);
s = soinfo_elf_lookup(somain, elf_hash, name);
s = soinfo_elf_lookup(somain, elf_hash, name, SymbolLookupScope::kExcludeLocal);
if (s != NULL) {
*lsi = somain;
goto done;
@@ -543,7 +560,7 @@ static ElfW(Sym)* soinfo_do_lookup(soinfo* si, const char* name, soinfo** lsi, s
/* Next, look for it in the preloads list */
for (int i = 0; g_ld_preloads[i] != NULL; i++) {
s = soinfo_elf_lookup(g_ld_preloads[i], elf_hash, name);
s = soinfo_elf_lookup(g_ld_preloads[i], elf_hash, name, SymbolLookupScope::kExcludeLocal);
if (s != NULL) {
*lsi = g_ld_preloads[i];
goto done;
@@ -553,7 +570,7 @@ static ElfW(Sym)* soinfo_do_lookup(soinfo* si, const char* name, soinfo** lsi, s
for (int i = 0; needed[i] != NULL; i++) {
DEBUG("%s: looking up %s in %s",
si->name, name, needed[i]->name);
s = soinfo_elf_lookup(needed[i], elf_hash, name);
s = soinfo_elf_lookup(needed[i], elf_hash, name, SymbolLookupScope::kExcludeLocal);
if (s != NULL) {
*lsi = needed[i];
goto done;
@@ -582,8 +599,9 @@ done:
Binary Interface) where in Chapter 5 it discuss resolving "Shared
Object Dependencies" in breadth first search order.
*/
ElfW(Sym)* dlsym_handle_lookup(soinfo* si, const char* name) {
return soinfo_elf_lookup(si, elfhash(name), name);
ElfW(Sym)* dlsym_handle_lookup(soinfo* si, const char* name, soinfo* caller) {
return soinfo_elf_lookup(si, elfhash(name), name,
caller == si ? SymbolLookupScope::kAllowLocal : SymbolLookupScope::kExcludeLocal);
}
/* This is used by dlsym(3) to performs a global symbol lookup. If the
@@ -591,7 +609,7 @@ ElfW(Sym)* dlsym_handle_lookup(soinfo* si, const char* name) {
beginning of the global solist. Otherwise the search starts at the
specified soinfo (for RTLD_NEXT).
*/
ElfW(Sym)* dlsym_linear_lookup(const char* name, soinfo** found, soinfo* start) {
ElfW(Sym)* dlsym_linear_lookup(const char* name, soinfo** found, soinfo* start, soinfo* caller) {
unsigned elf_hash = elfhash(name);
if (start == NULL) {
@@ -600,7 +618,8 @@ ElfW(Sym)* dlsym_linear_lookup(const char* name, soinfo** found, soinfo* start)
ElfW(Sym)* s = NULL;
for (soinfo* si = start; (s == NULL) && (si != NULL); si = si->next) {
s = soinfo_elf_lookup(si, elf_hash, name);
s = soinfo_elf_lookup(si, elf_hash, name,
caller == si ? SymbolLookupScope::kAllowLocal : SymbolLookupScope::kExcludeLocal);
if (s != NULL) {
*found = si;
break;