[PATCH] D41640: [ELF] - Do not ignore discarding of .rela.plt/.rela.dyn

[George Rimar via Phabricator via llvm-commits]

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

Currently when we build input sections list in linker script
we ignore all rel[a] sections. That was done to support
scripts like `.rela.dyn : { *(.rela.data) }` for emit relocs.

Though as a result following scripts were also silently ignored:

/DISCARD/ : { *(.rela.plt)
/DISCARD/ : { *(.rela.dyn)

and we produced output with this sections. That is not ideal.
Solution this patch suggests is simple: do not ignore synthetic
rel[a] sections. That way we can enable common discarding logic
for them and report proper error.


https://reviews.llvm.org/D41640

Files:
  ELF/LinkerScript.cpp
  test/ELF/linkerscript/discard-section-err.s


Index: test/ELF/linkerscript/discard-section-err.s
===================================================================
--- test/ELF/linkerscript/discard-section-err.s
+++ test/ELF/linkerscript/discard-section-err.s
@@ -22,4 +22,14 @@
 # RUN:   FileCheck -check-prefix=DYNSTR %s
 # DYNSTR: discarding .dynstr section is not allowed
 
+# RUN: echo "SECTIONS { /DISCARD/ : { *(.rela.plt) } }" > %t.script
+# RUN: not ld.lld -pie -o %t --script %t.script %t.o %t.so 2>&1 | \
+# RUN:   FileCheck -check-prefix=RELAPLT %s
+# RELAPLT: discarding .rela.plt section is not allowed
+
+# RUN: echo "SECTIONS { /DISCARD/ : { *(.rela.dyn) } }" > %t.script
+# RUN: not ld.lld -pie -o %t --script %t.script %t.o %t.so 2>&1 | \
+# RUN:   FileCheck -check-prefix=RELADYN %s
+# RELADYN: discarding .rela.dyn section is not allowed
+
 .comm foo,4,4
Index: ELF/LinkerScript.cpp
===================================================================
--- ELF/LinkerScript.cpp
+++ ELF/LinkerScript.cpp
@@ -290,7 +290,8 @@
       // For -emit-relocs we have to ignore entries like
       //   .rela.dyn : { *(.rela.data) }
       // which are common because they are in the default bfd script.
-      if (Sec->Type == SHT_REL || Sec->Type == SHT_RELA)
+      if (!isa<SyntheticSection>(Sec) &&
+          (Sec->Type == SHT_REL || Sec->Type == SHT_RELA))
         continue;
 
       std::string Filename = getFilename(Sec->File);
@@ -315,7 +316,7 @@
 void LinkerScript::discard(ArrayRef<InputSection *> V) {
   for (InputSection *S : V) {
     if (S == InX::ShStrTab || S == InX::Dynamic || S == InX::DynSymTab ||
-        S == InX::DynStrTab)
+        S == InX::DynStrTab || S == InX::RelaPlt || S == InX::RelaDyn)
       error("discarding " + S->Name + " section is not allowed");
 
     S->Assigned = false;


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