[PATCH] D77280: [ELF] Make --version-script/--dynamic-list work for lazy symbols fetched by LTO libcalls

[Fangrui Song via Phabricator via llvm-commits]

MaskRay updated this revision to Diff 254377.
MaskRay retitled this revision from "[ELF] Make --version-script work for lazy symbols fetched by LTO libcalls" to "[ELF] Make --version-script/--dynamic-list work for lazy symbols fetched by LTO libcalls".
MaskRay edited the summary of this revision.
MaskRay added a comment.

State that this fixes --dynamic-list as well


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D77280/new/

https://reviews.llvm.org/D77280

Files:
  lld/ELF/SymbolTable.cpp
  lld/ELF/Symbols.cpp
  lld/test/ELF/lto/version-libcall.ll


Index: lld/test/ELF/lto/version-libcall.ll
===================================================================
--- /dev/null
+++ lld/test/ELF/lto/version-libcall.ll
@@ -0,0 +1,42 @@
+; REQUIRES: x86
+;; The LTO code generator may create references which will fetch lazy symbols.
+;; Test that version script local: directives can change the binding of such
+;; symbols to STB_LOCAL. This is a bit complex because the LTO code generator
+;; happens after version script scanning and can change symbols from Lazy to Defined.
+
+; RUN: llvm-as %s -o %t.bc
+; RUN: echo '.globl __udivti3; __udivti3:' | llvm-mc -filetype=obj -triple=x86_64 - -o %t1.o
+
+;; An exact pattern can localize a libcall.
+; RUN: echo '{ global: foo; local: __udivti3; };' > %t.exact.ver
+; RUN: ld.lld -shared --version-script %t.exact.ver %t.bc --start-lib %t1.o --end-lib -o %t.exact.so
+; RUN: llvm-nm %t.exact.so | FileCheck %s
+
+;; A wildcard pattern can localize a libcall.
+; RUN: echo '{ global: foo; local: *; };' > %t.wild.ver
+; RUN: ld.lld -shared --version-script %t.wild.ver %t.bc --start-lib %t1.o --end-lib -o %t.wild.so
+; RUN: llvm-nm %t.wild.so | FileCheck %s
+
+; CHECK: t __udivti3
+; CHECK: T foo
+
+;; Test that --dynamic-list works on such libcall fetched symbols.
+; RUN: echo '{ foo; __udivti3; };' > %t.exact.list
+; RUN: ld.lld -pie --dynamic-list %t.exact.list %t.bc --start-lib %t1.o --end-lib -o %t.exact
+; RUN: llvm-nm %t.exact | FileCheck --check-prefix=LIST %s
+; RUN: echo '{ foo; __udiv*; };' > %t.wild.list
+; RUN: ld.lld -pie --dynamic-list %t.wild.list %t.bc --start-lib %t1.o --end-lib -o %t.wild
+; RUN: llvm-nm %t.wild | FileCheck --check-prefix=LIST %s
+
+; LIST: T __udivti3
+; LIST: T foo
+
+target datalayout = "e-m:e-p270:32:32-p271:32:32-p272:64:64-i64:64-f80:128-n8:16:32:64-S128"
+target triple = "x86_64-unknown-linux-gnu"
+
+declare i64 @llvm.udiv.fix.i64(i64, i64, i32)
+
+define i64 @foo(i64 %x, i64 %y) {
+  %ret = call i64 @llvm.udiv.fix.i64(i64 %x, i64 %y, i32 31)
+  ret i64 %ret
+}
Index: lld/ELF/Symbols.cpp
===================================================================
--- lld/ELF/Symbols.cpp
+++ lld/ELF/Symbols.cpp
@@ -276,7 +276,7 @@
   if (config->relocatable)
     return binding;
   if ((visibility != STV_DEFAULT && visibility != STV_PROTECTED) ||
-      versionId == VER_NDX_LOCAL)
+      (versionId == VER_NDX_LOCAL && isDefined()))
     return STB_LOCAL;
   if (!config->gnuUnique && binding == STB_GNU_UNIQUE)
     return STB_GLOBAL;
Index: lld/ELF/SymbolTable.cpp
===================================================================
--- lld/ELF/SymbolTable.cpp
+++ lld/ELF/SymbolTable.cpp
@@ -120,7 +120,7 @@
   if (!demangledSyms) {
     demangledSyms.emplace();
     for (Symbol *sym : symVector) {
-      if (!sym->isDefined() && !sym->isCommon())
+      if (!sym->isDefined() && !sym->isCommon() && !sym->isLazy())
         continue;
       (*demangledSyms)[demangleItanium(sym->getName())].push_back(sym);
     }
@@ -131,8 +131,10 @@
 std::vector<Symbol *> SymbolTable::findByVersion(SymbolVersion ver) {
   if (ver.isExternCpp)
     return getDemangledSyms().lookup(ver.name);
+  // A version script/dynamic list is only meaningful for a Defined symbol.
+  // A lazy symbol can be made Defined if an LTO libcall references it.
   if (Symbol *b = find(ver.name))
-    if (b->isDefined() || b->isCommon())
+    if (b->isDefined() || b->isCommon() || b->isLazy())
       return {b};
   return {};
 }
@@ -148,8 +150,10 @@
     return res;
   }
 
+  // See the comment in findByVersion() for the matched symbols.
   for (Symbol *sym : symVector)
-    if ((sym->isDefined() || sym->isCommon()) && m.match(sym->getName()))
+    if ((sym->isDefined() || sym->isCommon() || sym->isLazy()) &&
+        m.match(sym->getName()))
       res.push_back(sym);
   return res;
 }


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