[PATCH] D30627: [ELF] Properly handle .eh_frame in linker scripts

[Petr Hosek via Phabricator via llvm-commits]

phosek created this revision.
phosek added a project: lld.

Using .eh_frame input section pattern in linker script currently causes a crash; this is because .eh_frame input sections require special handling since they're all combined into a synthetic section rather than regular output section.


Repository:
  rL LLVM

https://reviews.llvm.org/D30627

Files:
  ELF/LinkerScript.cpp
  ELF/OutputSections.cpp
  test/ELF/linkerscript/eh-frame.s


Index: test/ELF/linkerscript/eh-frame.s
===================================================================
--- /dev/null
+++ test/ELF/linkerscript/eh-frame.s
@@ -0,0 +1,19 @@
+# REQUIRES: x86
+# RUN: llvm-mc -filetype=obj -triple=x86_64-unknown-linux %s -o %t
+# RUN: echo "SECTIONS { \
+# RUN:          .eh_frame : { *(.eh_frame) } \
+# RUN:       }" > %t.script
+# RUN: ld.lld -o %t1 --script %t.script %t
+# RUN: llvm-objdump -s -section=".eh_frame" %t1 | FileCheck %s
+
+# CHECK: 0000 14000000 00000000 017a5200 01781001
+# CHECK-NEXT: 0010 1b0c0708 90010000
+
+.global _start
+_start:
+ nop
+
+.section .dah,"ax", at progbits
+.cfi_startproc
+ nop
+.cfi_endproc
Index: ELF/OutputSections.cpp
===================================================================
--- ELF/OutputSections.cpp
+++ ELF/OutputSections.cpp
@@ -326,7 +326,7 @@
 static bool canMergeToProgbits(unsigned Type) {
   return Type == SHT_NOBITS || Type == SHT_PROGBITS || Type == SHT_INIT_ARRAY ||
          Type == SHT_PREINIT_ARRAY || Type == SHT_FINI_ARRAY ||
-         Type == SHT_NOTE;
+         Type == SHT_NOTE || Type == SHT_X86_64_UNWIND;
 }
 
 template <class ELFT> static void reportDiscarded(InputSectionBase *IS) {
@@ -343,6 +343,10 @@
     reportDiscarded<ELFT>(IS);
     return;
   }
+  if (IS->kind() == InputSectionBase::EHFrame) {
+    In<ELFT>::EhFrame->addSection(IS);
+    return;
+  }
 
   SectionKey Key = createKey<ELFT>(IS, OutsecName);
   uint64_t Flags = getOutFlags<ELFT>(IS);
@@ -360,12 +364,7 @@
     }
     Sec->Flags |= Flags;
   } else {
-    uint32_t Type = IS->Type;
-    if (IS->kind() == InputSectionBase::EHFrame) {
-      In<ELFT>::EhFrame->addSection(IS);
-      return;
-    }
-    Sec = make<OutputSection>(Key.Name, Type, Flags);
+    Sec = make<OutputSection>(Key.Name, IS->Type, Flags);
     OutputSections.push_back(Sec);
   }
 
Index: ELF/LinkerScript.cpp
===================================================================
--- ELF/LinkerScript.cpp
+++ ELF/LinkerScript.cpp
@@ -493,6 +493,11 @@
       if (Sec->empty())
         continue;
 
+    // We skip all eh_frame input sections since those are part of and handled
+    // by the EhFrameSection synthetic section.
+    if (IB->kind() == InputSectionBase::EHFrame)
+      continue;
+
     if (!IB->Live)
       continue;
     assert(CurOutSec == IB->OutSec || AlreadyOutputOS.count(IB->OutSec));


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