--- a/lld/ELF/MarkLive.cpp	Mon May 25 11:55:54 2020 +0900
+++ b/lld/ELF/MarkLive.cpp	Tue Jun 08 06:07:14 2021 +0900
@@ -56,7 +56,7 @@
   void mark();
 
   template <class RelTy>
-  void resolveReloc(InputSectionBase &sec, RelTy &rel, bool isLSDA);
+  void resolveReloc(InputSectionBase &sec, RelTy &rel, bool fromFDE);
 
   template <class RelTy>
   void scanEhFrameSection(EhInputSection &eh, ArrayRef<RelTy> rels);
@@ -65,7 +65,7 @@
   unsigned partition;
 
   // A list of sections to visit.
-  SmallVector<InputSection *, 256> queue;
+  SmallVector<InputSection *, 0> queue;
 
   // There are normally few input sections whose names are valid C
   // identifiers, so we just store a std::vector instead of a multimap.
@@ -89,7 +89,7 @@
 template <class ELFT>
 template <class RelTy>
 void MarkLive<ELFT>::resolveReloc(InputSectionBase &sec, RelTy &rel,
-                                  bool isLSDA) {
+                                  bool fromFDE) {
   Symbol &sym = sec.getFile<ELFT>()->getRelocTargetSym(rel);
 
   // If a symbol is referenced in a live section, it is used.
@@ -104,7 +104,16 @@
     if (d->isSection())
       offset += getAddend<ELFT>(sec, rel);
 
-    if (!isLSDA || !(relSec->flags & SHF_EXECINSTR))
+    // fromFDE being true means this is referenced by a FDE in a .eh_frame
+    // piece. The relocation points to the described function or to a LSDA. We
+    // only need to keep the LSDA live, so ignore anything that points to
+    // executable sections. If the LSDA is in a section group or has the
+    // SHF_LINK_ORDER flag, we ignore the relocation as well because (a) if the
+    // associated text section is live, the LSDA will be retained due to section
+    // group/SHF_LINK_ORDER rules (b) if the associated text section should be
+    // discarded, marking the LSDA will unnecessarily retain the text section.
+    if (!(fromFDE && ((relSec->flags & (SHF_EXECINSTR | SHF_LINK_ORDER)) ||
+                      relSec->nextInSectionGroup)))
       enqueue(relSec, offset);
     return;
   }
@@ -148,13 +157,10 @@
       continue;
     }
 
-    // This is a FDE. The relocations point to the described function or to
-    // a LSDA. We only need to keep the LSDA alive, so ignore anything that
-    // points to executable sections.
     uint64_t pieceEnd = piece.inputOff + piece.size;
-    for (size_t j = firstRelI, end2 = rels.size(); j < end2; ++j)
-      if (rels[j].r_offset < pieceEnd)
-        resolveReloc(eh, rels[j], true);
+    for (size_t j = firstRelI, end2 = rels.size();
+         j < end2 && rels[j].r_offset < pieceEnd; ++j)
+      resolveReloc(eh, rels[j], true);
   }
 }
 
@@ -255,12 +261,20 @@
         scanEhFrameSection(*eh, eh->template rels<ELFT>());
     }
 
+    if (sec->flags & SHF_GNU_RETAIN) {
+      enqueue(sec, 0);
+      continue;
+    }
     if (sec->flags & SHF_LINK_ORDER)
       continue;
 
     if (isReserved(sec) || script->shouldKeep(sec)) {
       enqueue(sec, 0);
-    } else if (isValidCIdentifier(sec->name)) {
+    } else if ((!config->zStartStopGC || sec->name.startswith("__libc_")) &&
+               isValidCIdentifier(sec->name)) {
+      // As a workaround for glibc libc.a before 2.34
+      // (https://sourceware.org/PR27492), retain __libc_atexit and similar
+      // sections regardless of zStartStopGC.
       cNamedSections[saver.save("__start_" + sec->name)].push_back(sec);
       cNamedSections[saver.save("__stop_" + sec->name)].push_back(sec);
     }
@@ -339,16 +353,16 @@
 
   // Otherwise, do mark-sweep GC.
   //
-  // The -gc-sections option works only for SHF_ALLOC sections
-  // (sections that are memory-mapped at runtime). So we can
-  // unconditionally make non-SHF_ALLOC sections alive except
-  // SHF_LINK_ORDER and SHT_REL/SHT_RELA sections.
+  // The -gc-sections option works only for SHF_ALLOC sections (sections that
+  // are memory-mapped at runtime). So we can unconditionally make non-SHF_ALLOC
+  // sections alive except SHF_LINK_ORDER, SHT_REL/SHT_RELA sections, and
+  // sections in a group.
   //
   // Usually, non-SHF_ALLOC sections are not removed even if they are
-  // unreachable through relocations because reachability is not
-  // a good signal whether they are garbage or not (e.g. there is
-  // usually no section referring to a .comment section, but we
-  // want to keep it.).
+  // unreachable through relocations because reachability is not a good signal
+  // whether they are garbage or not (e.g. there is usually no section referring
+  // to a .comment section, but we want to keep it.) When a non-SHF_ALLOC
+  // section is retained, we also retain sections dependent on it.
   //
   // Note on SHF_LINK_ORDER: Such sections contain metadata and they
   // have a reverse dependency on the InputSection they are linked with.
@@ -370,8 +384,11 @@
     bool isLinkOrder = (sec->flags & SHF_LINK_ORDER);
     bool isRel = (sec->type == SHT_REL || sec->type == SHT_RELA);
 
-    if (!isAlloc && !isLinkOrder && !isRel && !sec->nextInSectionGroup)
+    if (!isAlloc && !isLinkOrder && !isRel && !sec->nextInSectionGroup) {
       sec->markLive();
+      for (InputSection *isec : sec->dependentSections)
+        isec->markLive();
+    }
   }
 
   // Follow the graph to mark all live sections.