[lld] 1c00530 - [ELF] Don't set versionId on undefined weak lazy symbols

[Fangrui Song via llvm-commits]

Author: Fangrui Song
Date: 2021-04-20T11:23:10-07:00
New Revision: 1c00530b30e21fd0f5b316401f6485bee08ce850

URL: https://github.com/llvm/llvm-project/commit/1c00530b30e21fd0f5b316401f6485bee08ce850
DIFF: https://github.com/llvm/llvm-project/commit/1c00530b30e21fd0f5b316401f6485bee08ce850.diff

LOG: [ELF] Don't set versionId on undefined weak lazy symbols

An unfetched lazy symbol (undefined weak) should be considered to have its
original versionId which is VER_NDX_GLOBAL, instead of the lazy symbol's
versionId. (The original versionId cannot be non-VER_NDX_GLOBAL because a
undefined versioned symbol is an error.)

The regression was introduced in D77280 when making version scripts work
with lazy symbols fetched by LTO calls.

Fix PR49915

Differential Revision: https://reviews.llvm.org/D100624

Added: 
    

Modified: 
    lld/ELF/SyntheticSections.cpp
    lld/test/ELF/version-script-weak.s

Removed: 
    


################################################################################
diff  --git a/lld/ELF/SyntheticSections.cpp b/lld/ELF/SyntheticSections.cpp
index 79e47176c8b2..36ed89334758 100644
--- a/lld/ELF/SyntheticSections.cpp
+++ b/lld/ELF/SyntheticSections.cpp
@@ -3123,7 +3123,9 @@ size_t VersionTableSection::getSize() const {
 void VersionTableSection::writeTo(uint8_t *buf) {
   buf += 2;
   for (const SymbolTableEntry &s : getPartition().dynSymTab->getSymbols()) {
-    write16(buf, s.sym->versionId);
+    // Use the original versionId for an unfetched lazy symbol (undefined weak),
+    // which must be VER_NDX_GLOBAL (an undefined versioned symbol is an error).
+    write16(buf, s.sym->isLazy() ? VER_NDX_GLOBAL : s.sym->versionId);
     buf += 2;
   }
 }

diff  --git a/lld/test/ELF/version-script-weak.s b/lld/test/ELF/version-script-weak.s
index 7c902eb98bf4..cfa2455ee2bd 100644
--- a/lld/test/ELF/version-script-weak.s
+++ b/lld/test/ELF/version-script-weak.s
@@ -24,6 +24,19 @@
 # CHECK-NEXT:   Section: Undefined
 # CHECK-NEXT: }
 
+## The version of an unfetched lazy symbol is VER_NDX_GLOBAL. It is not affected by version scripts.
+# RUN: echo "v1 { *; };" > %t2.script
+# RUN: ld.lld -shared --version-script %t2.script %t.o --start-lib %t1.o --end-lib -o %t2.so
+# RUN: llvm-readelf --dyn-syms %t2.so | FileCheck %s --check-prefix=CHECK2
+
+# CHECK2: NOTYPE WEAK DEFAULT UND foo{{$}}
+
+# RUN: ld.lld -shared --soname=tshared --version-script %t2.script %t1.o -o %tshared.so
+# RUN: ld.lld -shared --version-script %t2.script %t.o --start-lib %t1.o --end-lib %tshared.so -o %t3.so
+# RUN: llvm-readelf --dyn-syms %t3.so | FileCheck %s --check-prefix=CHECK3
+
+# CHECK3: NOTYPE WEAK DEFAULT UND foo at v1
+
 .text
  callq foo at PLT
 .weak foo