[PATCH] D29273: [ELF] - Added support of linkerscript's "/DISCARD/" for --emit-relocs

[George Rimar via Phabricator via llvm-commits]

grimar updated this revision to Diff 88324.
grimar retitled this revision from "[ELF] - Added partial support for --emit-relocs (no --gc-section case)" to "[ELF] - Added support of linkerscript's "/DISCARD/" for --emit-relocs".
grimar edited the summary of this revision.
grimar added a comment.

- Rebased.


https://reviews.llvm.org/D29273

Files:
  ELF/InputFiles.cpp
  ELF/LinkerScript.cpp
  test/ELF/linkerscript/emit-reloc-discard.s


Index: test/ELF/linkerscript/emit-reloc-discard.s
===================================================================
--- test/ELF/linkerscript/emit-reloc-discard.s
+++ test/ELF/linkerscript/emit-reloc-discard.s
@@ -0,0 +1,14 @@
+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t.o
+# RUN: echo "SECTIONS { /DISCARD/ : { *(.bbb) } }" > %t.script
+# RUN: ld.lld --emit-relocs --script %t.script %t.o -o %t1
+# RUN: llvm-readobj -r %t1 | FileCheck %s
+
+# CHECK:      Relocations [
+# CHECK-NEXT: ]
+
+.section .aaa,"", at progbits
+.Lfoo:
+
+.section .bbb,"", at progbits
+.long .Lfoo
Index: ELF/LinkerScript.cpp
===================================================================
--- ELF/LinkerScript.cpp
+++ ELF/LinkerScript.cpp
@@ -272,6 +272,15 @@
   for (InputSectionBase<ELFT> *S : V) {
     S->Live = false;
     reportDiscarded(S);
+
+    // If we discard a section, we also should discard a dependent section.
+    // For example if linkerscript discards .text section,
+    // code below will discard .rel[a].text dependent section, which
+    // is impossible and useless to keep then. Used for --emit-relocs.
+    InputSection<ELFT> *IS = dyn_cast<InputSection<ELFT>>(S);
+    if (!IS || !IS->DependentSection || !IS->DependentSection->Live)
+      continue;
+    discard({IS->DependentSection});
   }
 }
 
Index: ELF/InputFiles.cpp
===================================================================
--- ELF/InputFiles.cpp
+++ ELF/InputFiles.cpp
@@ -404,8 +404,14 @@
     // from the output, so returning `nullptr` for the normal case.
     // However, if -emit-relocs is given, we need to leave them in the output.
     // (Some post link analysis tools need this information.)
-    if (Config->EmitRelocs)
-      return make<InputSection<ELFT>>(this, &Sec, Name);
+    if (Config->EmitRelocs) {
+      if (!isa<InputSection<ELFT>>(Target))
+        fatal(toString(this) + ": --emit-relocs for relocations sections "
+                               "pointing to .eh_frame is not supported");
+      InputSection<ELFT> *RelocSec = make<InputSection<ELFT>>(this, &Sec, Name);
+      cast<InputSection<ELFT>>(Target)->DependentSection = RelocSec;
+      return RelocSec;
+    }
     return nullptr;
   }
   }


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