yggdrasil/llvm-project
1
0
Fork 0
Code Issues Pull Requests Packages Projects Releases Wiki Activity

[lld-macho] Use larger ordinal encoding if import count requires it (#98305)

Browse Source 
The default `dyld_chained_import` entry format only allocates 8 bits to
the library ordinal, of which values 0xF1 - 0xFF are reserved for
special ordinals (`BIND_SPECIAL_DYLIB_*` values). If there are more than
240 imported dylibs (as in the case of component builds of Chromium), we
need to switch to `dyld_chained_import_addend64`, which stores 16-bit
ordinals.
This commit is contained in:
Daniel Bertalan 2024-07-10 18:40:23 +02:00 committed by GitHub
parent e3fe8eee3c
commit 3c8b18bc51
No known key found for this signature in database
GPG Key ID: B5690EEEBB952194
1 changed files with 19 additions and 15 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

34
lld/MachO/SyntheticSections.cpp
View File

@ -544,6 +544,14 @@ static void flushOpcodes(const BindIR &op, raw_svector_ostream &os) {
}
}
static bool needsWeakBind(const Symbol &sym) {
if (auto *dysym = dyn_cast<DylibSymbol>(&sym))
return dysym->isWeakDef();
if (auto *defined = dyn_cast<Defined>(&sym))
return defined->isExternalWeakDef();
return false;
}
// Non-weak bindings need to have their dylib ordinal encoded as well.
static int16_t ordinalForDylibSymbol(const DylibSymbol &dysym) {
if (config->namespaceKind == NamespaceKind::flat || dysym.isDynamicLookup())
@ -553,6 +561,8 @@ static int16_t ordinalForDylibSymbol(const DylibSymbol &dysym) {
}
static int16_t ordinalForSymbol(const Symbol &sym) {
if (config->emitChainedFixups && needsWeakBind(sym))
return BIND_SPECIAL_DYLIB_WEAK_LOOKUP;
if (const auto *dysym = dyn_cast<DylibSymbol>(&sym))
return ordinalForDylibSymbol(*dysym);
assert(cast<Defined>(&sym)->interposable);
@ -2276,14 +2286,6 @@ bool ChainedFixupsSection::isNeeded() const {
return true;
}
static bool needsWeakBind(const Symbol &sym) {
if (auto *dysym = dyn_cast<DylibSymbol>(&sym))
return dysym->isWeakDef();
if (auto *defined = dyn_cast<Defined>(&sym))
return defined->isExternalWeakDef();
return false;
}
void ChainedFixupsSection::addBinding(const Symbol *sym,
const InputSection *isec, uint64_t offset,
int64_t addend) {
@ -2312,7 +2314,7 @@ ChainedFixupsSection::getBinding(const Symbol *sym, int64_t addend) const {
return {it->second, 0};
}
static size_t writeImport(uint8_t *buf, int format, uint32_t libOrdinal,
static size_t writeImport(uint8_t *buf, int format, int16_t libOrdinal,
bool weakRef, uint32_t nameOffset, int64_t addend) {
switch (format) {
case DYLD_CHAINED_IMPORT: {
@ -2430,11 +2432,8 @@ void ChainedFixupsSection::writeTo(uint8_t *buf) const {
uint64_t nameOffset = 0;
for (auto [import, idx] : bindings) {
const Symbol &sym = *import.first;
int16_t libOrdinal = needsWeakBind(sym)
? (int64_t)BIND_SPECIAL_DYLIB_WEAK_LOOKUP
: ordinalForSymbol(sym);
buf += writeImport(buf, importFormat, libOrdinal, sym.isWeakRef(),
nameOffset, import.second);
buf += writeImport(buf, importFormat, ordinalForSymbol(sym),
sym.isWeakRef(), nameOffset, import.second);
nameOffset += sym.getName().size() + 1;
}
@ -2459,7 +2458,12 @@ void ChainedFixupsSection::finalizeContents() {
error("cannot encode chained fixups: imported symbols table size " +
Twine(symtabSize) + " exceeds 4 GiB");
if (needsLargeAddend || !isUInt<23>(symtabSize))
bool needsLargeOrdinal = any_of(bindings, [](const auto &p) {
// 0xF1 - 0xFF are reserved for special ordinals in the 8-bit encoding.
return ordinalForSymbol(*p.first.first) > 0xF0;
});
if (needsLargeAddend || !isUInt<23>(symtabSize) || needsLargeOrdinal)
importFormat = DYLD_CHAINED_IMPORT_ADDEND64;
else if (needsAddend)
importFormat = DYLD_CHAINED_IMPORT_ADDEND;