From 0b5d6e5d0e093377e3b212093b999c3fec9c2b69 Mon Sep 17 00:00:00 2001
From: Hafiz Abid Qadeer <hafiz_abid@mentor.com>
Date: Thu, 25 May 2017 10:21:29 +0000
Subject: [PATCH] Fix FDE indexing while scan debug_info section.

There are some differences between eh_frame and debug_frame formats that
are not considered by DWARFCallFrameInfo::GetFDEIndex. An FDE entry
contains CIE_pointer in debug_frame in same place as cie_id in eh_frame.
As described in dwarf standard (section 6.4.1), CIE_pointer is an
"offset into the .debug_frame section". So, variable cie_offset should
be equal cie_id for debug_frame.

FDE entries with zeroth CIE pointer (which is actually placed in cie_id
variable) shouldn't be ignored also.

I have also added a little change which allow to use debug_info section
when eh_frame is absent. This case really can take place on some platforms.

Patch from tatyana-krasnukha.
https://reviews.llvm.org/D33504

llvm-svn: 303847
---
 lldb/source/Symbol/DWARFCallFrameInfo.cpp | 31 ++++++++++++++++++++-----------
 lldb/source/Symbol/UnwindTable.cpp        |  7 +++++++
 2 files changed, 27 insertions(+), 11 deletions(-)

diff --git a/lldb/source/Symbol/DWARFCallFrameInfo.cpp b/lldb/source/Symbol/DWARFCallFrameInfo.cpp
index 015ecd856..df8a8cf 100644
--- a/lldb/source/Symbol/DWARFCallFrameInfo.cpp
+++ b/lldb/source/Symbol/DWARFCallFrameInfo.cpp
@@ -461,11 +461,25 @@ void DWARFCallFrameInfo::GetFDEIndex() {
       m_fde_index_initialized = true;
       return;
     }
+
+    // An FDE entry contains CIE_pointer in debug_frame in same place as cie_id
+    // in eh_frame. CIE_pointer is an offset into the .debug_frame section.
+    // So, variable cie_offset should be equal cie_id for debug_frame.
+    // FDE entries with cie_id == 0 shouldn't be ignored for it.
+    if ((cie_id == 0 && m_is_eh_frame) || cie_id == UINT32_MAX || len == 0) {
+      m_cie_map[current_entry] = ParseCIE(current_entry);
+      offset = next_entry;
+      continue;
+    }
+
+    if (!m_is_eh_frame)
+      cie_offset = cie_id;
+
     if (cie_offset > m_cfi_data.GetByteSize()) {
-      Host::SystemLog(
-          Host::eSystemLogError,
-          "error: Invalid cie offset of 0x%x found in cie/fde at 0x%x\n",
-          cie_offset, current_entry);
+      Host::SystemLog(Host::eSystemLogError,
+                      "error: Invalid cie offset of 0x%x "
+                      "found in cie/fde at 0x%x\n",
+                      cie_offset, current_entry);
       // Don't trust anything in this eh_frame section if we find blatantly
       // invalid data.
       m_fde_index.Clear();
@@ -473,12 +487,6 @@ void DWARFCallFrameInfo::GetFDEIndex() {
       return;
     }
 
-    if (cie_id == 0 || cie_id == UINT32_MAX || len == 0) {
-      m_cie_map[current_entry] = ParseCIE(current_entry);
-      offset = next_entry;
-      continue;
-    }
-
     const CIE *cie = GetCIE(cie_offset);
     if (cie) {
       const lldb::addr_t pc_rel_addr = m_section_sp->GetFileAddress();
@@ -531,7 +539,8 @@ bool DWARFCallFrameInfo::FDEToUnwindPlan(dw_offset_t dwarf_offset,
     cie_offset = m_cfi_data.GetU32(&offset);
   }
 
-  assert(cie_offset != 0 && cie_offset != UINT32_MAX);
+  // FDE entries with zero cie_offset may occur for debug_frame.
+  assert(!(m_is_eh_frame && 0 == cie_offset) && cie_offset != UINT32_MAX);
 
   // Translate the CIE_id from the eh_frame format, which
   // is relative to the FDE offset, into a __eh_frame section
diff --git a/lldb/source/Symbol/UnwindTable.cpp b/lldb/source/Symbol/UnwindTable.cpp
index 336f0c3..f417f35 100644
--- a/lldb/source/Symbol/UnwindTable.cpp
+++ b/lldb/source/Symbol/UnwindTable.cpp
@@ -51,6 +51,13 @@ void UnwindTable::Initialize() {
     if (sect.get()) {
       m_eh_frame_up.reset(new DWARFCallFrameInfo(m_object_file, sect,
                                                  eRegisterKindEHFrame, true));
+    } else {
+      // Try to find .debug_frame section if .eh_frame doesn't exist.
+      sect = sl->FindSectionByType(eSectionTypeDWARFDebugFrame, true);
+      if (sect.get()) {
+        m_eh_frame_up.reset(new DWARFCallFrameInfo(m_object_file, sect,
+                                                   eRegisterKindDWARF, false));
+      }
     }
     sect = sl->FindSectionByType(eSectionTypeCompactUnwind, true);
     if (sect.get()) {
-- 
2.7.4