[PATCH] D100966: [lld-link] Ignore undefined symbols in .addrsig table

[Zequan Wu via Phabricator via llvm-commits]

zequanwu created this revision.
zequanwu added a reviewer: rnk.
zequanwu requested review of this revision.
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Herald added a subscriber: llvm-commits.

Undefined symbols in .addrsig table just mark symbols as addrsig to avoid icf, and not required to be resolved. We could just ignore them.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D100966

Files:
  lld/COFF/Driver.cpp
  lld/COFF/SymbolTable.cpp
  lld/COFF/Symbols.h
  lld/test/COFF/undefined-symbol-addrsig.s


Index: lld/test/COFF/undefined-symbol-addrsig.s
===================================================================
--- /dev/null
+++ lld/test/COFF/undefined-symbol-addrsig.s
@@ -0,0 +1,13 @@
+# REQUIRES: x86
+# RUN: llvm-mc -triple=x86_64-windows-msvc -filetype=obj -o %t.obj %s
+# RUN: lld-link /entry:_start /subsystem:console %t.obj
+
+.text
+.globl _start
+_start:
+  ret
+
+.global bar
+
+.addrsig
+.addrsig_sym bar
Index: lld/COFF/Symbols.h
===================================================================
--- lld/COFF/Symbols.h
+++ lld/COFF/Symbols.h
@@ -104,7 +104,8 @@
       : symbolKind(k), isExternal(true), isCOMDAT(false),
         writtenToSymtab(false), pendingArchiveLoad(false), isGCRoot(false),
         isRuntimePseudoReloc(false), deferUndefined(false), canInline(true),
-        nameSize(n.size()), nameData(n.empty() ? nullptr : n.data()) {}
+        isAddrsig(false), nameSize(n.size()),
+        nameData(n.empty() ? nullptr : n.data()) {}
 
   const unsigned symbolKind : 8;
   unsigned isExternal : 1;
@@ -140,6 +141,10 @@
   // doesn't know the final contents of the symbol.
   unsigned canInline : 1;
 
+  // True if the symbol is in .addrsig table. So we don't report it as undefined
+  // when resolving symbols.
+  unsigned isAddrsig : 1;
+
 protected:
   // Symbol name length. Assume symbol lengths fit in a 32-bit integer.
   uint32_t nameSize;
Index: lld/COFF/SymbolTable.cpp
===================================================================
--- lld/COFF/SymbolTable.cpp
+++ lld/COFF/SymbolTable.cpp
@@ -357,6 +357,8 @@
       ++symIndex;
       if (!sym)
         continue;
+      if (sym->isAddrsig)
+        continue;
       if (undefs.count(sym)) {
         auto it = firstDiag.find(sym);
         if (it == firstDiag.end()) {
Index: lld/COFF/Driver.cpp
===================================================================
--- lld/COFF/Driver.cpp
+++ lld/COFF/Driver.cpp
@@ -1082,6 +1082,7 @@
         if (symIndex >= syms.size())
           fatal(toString(obj) + ": invalid symbol index in addrsig section");
         markAddrsig(syms[symIndex]);
+        syms[symIndex]->isAddrsig = true;
         cur += size;
       }
     } else {
@@ -2099,6 +2100,11 @@
     run();
   }
 
+  // Find symbols in .addrsig table before resolving symbols in case of any of
+  // those symbols is undefined.
+  if (config->doICF != ICFLevel::None)
+    findKeepUniqueSections();
+
   // At this point, we should not have any symbols that cannot be resolved.
   // If we are going to do codegen for link-time optimization, check for
   // unresolvable symbols first, so we don't spend time generating code that
@@ -2224,10 +2230,8 @@
   convertResources();
 
   // Identify identical COMDAT sections to merge them.
-  if (config->doICF != ICFLevel::None) {
-    findKeepUniqueSections();
+  if (config->doICF != ICFLevel::None)
     doICF(symtab->getChunks(), config->doICF);
-  }
 
   // Write the result.
   writeResult();


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