1 //===- MarkLive.cpp -------------------------------------------------------===//
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
7 //===----------------------------------------------------------------------===//
19 #include "mach-o/compact_unwind_encoding.h"
28   // Keep track of the entry that caused us to mark `isec` as live.
35 // Type-erased interface to MarkLiveImpl. Used for adding roots to the liveness
47   // -why_live is a rarely used option, so we don't want support for that flag
48   // to slow down the main -dead_strip code path. As such, we employ templates
66   // We build up a worklist of sections which have been marked as live. We
78   if (isec->isLive(off))  in enqueue()
80   isec->markLive(off);  in enqueue()
82     assert(!s->isCoalescedWeak());  in enqueue()
88   std::string out = toString(*s) + " from " + toString(s->getFile());  in printWhyLive()
91        entry = entry->prev, indent += 2) {  in printWhyLive()
92     const TinyPtrVector<Defined *> &symbols = entry->isec->symbols;  in printWhyLive()
97              " from " + toString(symbols.front()->getFile());  in printWhyLive()
106   if (s->used)  in addSym()
108   s->used = true;  in addSym()
110     if (!config->whyLive.empty() && config->whyLive.match(s->getName()))  in addSym()
113     if (d->isec())  in addSym()
114       enqueue(d->isec(), d->value, prev);  in addSym()
115     if (d->unwindEntry())  in addSym()
116       enqueue(d->unwindEntry(), 0, prev);  in addSym()
124     return entry->isec;  in getInputSection()
148     // Mark things reachable from GC roots as live.  in markTransitively()
156       assert(isec->live && "We mark as live when pushing onto the worklist!");  in markTransitively()
159       for (const Reloc &r : isec->relocs) {  in markTransitively()
165       for (Defined *d : getInputSection(entry)->symbols)  in markTransitively()
169     // S_ATTR_LIVE_SUPPORT sections are live if they point _to_ a live  in markTransitively()
170     // section. Process them in a second pass.  in markTransitively()
172       // FIXME: Check if copying all S_ATTR_LIVE_SUPPORT sections into a  in markTransitively()
174       if (!(isec->getFlags() & S_ATTR_LIVE_SUPPORT) || isec->live)  in markTransitively()
177       for (const Reloc &r : isec->relocs) {  in markTransitively()
179           if (s->isLive()) {  in markTransitively()
182               referentIsec = d->isec();  in markTransitively()
187           if (referentIsec->isLive(r.addend))  in markTransitively()
193     // S_ATTR_LIVE_SUPPORT could have marked additional sections live,  in markTransitively()
194     // which in turn could mark additional S_ATTR_LIVE_SUPPORT sections live.  in markTransitively()
196     // S_ATTR_LIVE_SUPPORT sections live.  in markTransitively()
200 // Set live bit on for each reachable chunk. Unmarked (unreachable)
206   if (config->whyLive.empty())  in markLive()
211   if (config->entry)  in markLive()
212     marker->addSym(config->entry);  in markLive()
213   for (Symbol *sym : symtab->getSymbols()) {  in markLive()
215       // -exported_symbol(s_list)  in markLive()
216       if (!config->exportedSymbols.empty() &&  in markLive()
217           config->exportedSymbols.match(defined->getName())) {  in markLive()
218         // NOTE: Even though exporting private externs is an ill-defined  in markLive()
221         // extern symbols as live, irrespective of whether they are autohide.  in markLive()
222         marker->addSym(defined);  in markLive()
227       if (defined->referencedDynamically || defined->noDeadStrip) {  in markLive()
228         marker->addSym(defined);  in markLive()
234       // * -reexported_symbol(s_list)  in markLive()
235       // * -alias_list  in markLive()
236       // * -init  in markLive()
238       // In dylibs and bundles and in executables with -export_dynamic,  in markLive()
241           config->outputType != MH_EXECUTE || config->exportDynamic;  in markLive()
242       if (externsAreRoots && !defined->privateExtern) {  in markLive()
243         marker->addSym(defined);  in markLive()
248   // -u symbols  in markLive()
249   for (Symbol *sym : config->explicitUndefineds)  in markLive()
250     marker->addSym(sym);  in markLive()
254       for (Symbol *sym : objFile->symbols)  in markLive()
256           if (!defined->isExternal() && defined->noDeadStrip)  in markLive()
257             marker->addSym(defined);  in markLive()
259           dyn_cast_or_null<DylibSymbol>(symtab->find("dyld_stub_binder")))  in markLive()
260     marker->addSym(stubBinder);  in markLive()
263     if (isec->getFlags() & S_ATTR_NO_DEAD_STRIP) {  in markLive()
264       marker->enqueue(isec, 0);  in markLive()
269     if (sectionType(isec->getFlags()) == S_MOD_INIT_FUNC_POINTERS ||  in markLive()
270         sectionType(isec->getFlags()) == S_MOD_TERM_FUNC_POINTERS) {  in markLive()
271       assert(!config->emitInitOffsets ||  in markLive()
272              sectionType(isec->getFlags()) != S_MOD_INIT_FUNC_POINTERS);  in markLive()
273       marker->enqueue(isec, 0);  in markLive()
278   for (ConcatInputSection *isec : in.initOffsets->inputs())  in markLive()
279     marker->enqueue(isec, 0);  in markLive()
281   marker->markTransitively();  in markLive()