[PATCH] D41551: [ELF] - Allow relocation to a weak undefined symbol when -z notext is given.

[George Rimar via Phabricator via llvm-commits]

grimar created this revision.
grimar added reviewers: ruiu, rafael.

Previously we failed to resolve them:
"relocation R_X86_64_32 cannot be used against shared object; recompile with -fPIC"

This finishes fixing PR35720.


https://reviews.llvm.org/D41551

Files:
  ELF/Relocations.cpp
  test/ELF/znotext-weak-undef.s


Index: test/ELF/znotext-weak-undef.s
===================================================================
--- test/ELF/znotext-weak-undef.s
+++ test/ELF/znotext-weak-undef.s
@@ -0,0 +1,14 @@
+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-pc-linux %s -o %t.o
+# RUN: ld.lld -z notext -shared %t.o -o %t
+# RUN: llvm-readobj -r %t | FileCheck %s
+
+# CHECK:      Relocations [
+# CHECK-NEXT: ]
+
+.text
+.global foo
+.weak foo
+
+_start:
+mov $foo,%eax
Index: ELF/Relocations.cpp
===================================================================
--- ELF/Relocations.cpp
+++ ELF/Relocations.cpp
@@ -591,6 +591,19 @@
   if (S.Flags & SHF_WRITE)
     return Expr;
 
+  // If a relocation can be applied at link-time, we don't need to
+  // create a dynamic relocation in the first place.
+  if (IsConstant)
+    return Expr;
+
+  // If the relocation is to a weak undef, give up on it and produce a
+  // non preemptible 0.
+  if (Sym.isUndefWeak()) {
+    Sym.IsPreemptible = false;
+    IsConstant = true;
+    return Expr;
+  }
+
   // Or, if we are allowed to create dynamic relocations against
   // read-only sections (i.e. when "-z notext" is given),
   // we can create a dynamic relocation as we want, too.
@@ -602,22 +615,9 @@
     return Expr;
   }
 
-  // If a relocation can be applied at link-time, we don't need to
-  // create a dynamic relocation in the first place.
-  if (IsConstant)
-    return Expr;
-
   // If we got here we know that this relocation would require the dynamic
   // linker to write a value to read only memory.
 
-  // If the relocation is to a weak undef, give up on it and produce a
-  // non preemptible 0.
-  if (Sym.isUndefWeak()) {
-    Sym.IsPreemptible = false;
-    IsConstant = true;
-    return Expr;
-  }
-
   // We can hack around it if we are producing an executable and
   // the refered symbol can be preemepted to refer to the executable.
   if (Config->Shared || (Config->Pic && !isRelExpr(Expr))) {


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