[llvm] r303239 - [RuntimeDyld] Fix debug section relocation (pr20457)

[Pavel Labath via llvm-commits]

Author: labath
Date: Wed May 17 03:47:28 2017
New Revision: 303239

URL: http://llvm.org/viewvc/llvm-project?rev=303239&view=rev
Log:
[RuntimeDyld] Fix debug section relocation (pr20457)

Summary:
Debug info sections, (or non-SHF_ALLOC sections in general) should be
linked as if their load address was zero to emulate the behavior of the
static linker.

This bug was discovered because it was breaking lldb expression evaluation on
linux.

Reviewers: lhames

Subscribers: aprantl, eugene, clayborg, lldb-commits, llvm-commits

Differential Revision: https://reviews.llvm.org/D32899

Added:
    llvm/trunk/test/ExecutionEngine/RuntimeDyld/X86/ELF_x86-64_debug_frame.s
Modified:
    llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp

Modified: llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp?rev=303239&r1=303238&r2=303239&view=diff
==============================================================================
--- llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp (original)
+++ llvm/trunk/lib/ExecutionEngine/RuntimeDyld/RuntimeDyld.cpp Wed May 17 03:47:28 2017
@@ -705,7 +705,7 @@ RuntimeDyldImpl::emitSection(const Objec
   unsigned Alignment = (unsigned)Alignment64 & 0xffffffffL;
   unsigned PaddingSize = 0;
   unsigned StubBufSize = 0;
-  bool IsRequired = isRequiredForExecution(Section) || ProcessAllSections;
+  bool IsRequired = isRequiredForExecution(Section);
   bool IsVirtual = Section.isVirtual();
   bool IsZeroInit = isZeroInit(Section);
   bool IsReadOnly = isReadOnlyData(Section);
@@ -745,8 +745,8 @@ RuntimeDyldImpl::emitSection(const Objec
     Alignment = std::max(Alignment, getStubAlignment());
 
   // Some sections, such as debug info, don't need to be loaded for execution.
-  // Leave those where they are.
-  if (IsRequired) {
+  // Process those only if explicitly requested.
+  if (IsRequired || ProcessAllSections) {
     Allocate = DataSize + PaddingSize + StubBufSize;
     if (!Allocate)
       Allocate = 1;
@@ -790,6 +790,10 @@ RuntimeDyldImpl::emitSection(const Objec
   Sections.push_back(
       SectionEntry(Name, Addr, DataSize, Allocate, (uintptr_t)pData));
 
+  // Debug info sections are linked as if their load address was zero
+  if (!IsRequired)
+    Sections.back().setLoadAddress(0);
+
   if (Checker)
     Checker->registerSection(Obj.getFileName(), SectionID);
 

Added: llvm/trunk/test/ExecutionEngine/RuntimeDyld/X86/ELF_x86-64_debug_frame.s
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/test/ExecutionEngine/RuntimeDyld/X86/ELF_x86-64_debug_frame.s?rev=303239&view=auto
==============================================================================
--- llvm/trunk/test/ExecutionEngine/RuntimeDyld/X86/ELF_x86-64_debug_frame.s (added)
+++ llvm/trunk/test/ExecutionEngine/RuntimeDyld/X86/ELF_x86-64_debug_frame.s Wed May 17 03:47:28 2017
@@ -0,0 +1,20 @@
+# RUN: llvm-mc -triple=x86_64-pc-linux -filetype=obj -o %T/ELF_x86-64_debug_frame.o %s
+# RUN: llvm-rtdyld -triple=x86_64-pc-linux -verify -check=%s %T/ELF_x86-64_debug_frame.o
+
+        .text
+        .file   "debug_frame_test.c"
+        .align  16, 0x90
+        .type   foo, at function
+foo:
+        .cfi_startproc
+        retq
+.Ltmp0:
+        .size   foo, .Ltmp0-foo
+        .cfi_endproc
+        .cfi_sections .debug_frame
+
+# Check that .debug_frame is mapped to 0.
+# rtdyld-check: section_addr(ELF_x86-64_debug_frame.o, .debug_frame) = 0
+
+# Check that The relocated FDE's CIE offset also points to zero.
+# rtdyld-check: *{4}(section_addr(ELF_x86-64_debug_frame.o, .debug_frame) + 0x1C) = 0