Fix handling of load bias values.

It turns out that for the dwarf information, if a FDE indicates it's pc
relative, then pc has to be incremented by the load bias. If not, then
it should not be incremented.

Previously, the code always subtracted load bias values from pcs, and assumed
that all fdes were incremented by load bias values. The new code actually
reads the fdes and adjusted the pcs in the fde and in the eh frame hdr so
that load bias values are already handled properly.

In addition, add dumping of arm exidx values in unwind_reg_info. This allowed
verifying that the debug frame in those elf files was being handled properly.

Added a new unit test that only has a debug frame that has a non-zero load
bias and has fde entries that do not have pc relative encoding.

Fix a couple of other small bugs.

Bug: 109824792

Test: All libbacktrace/libunwindstack unit tests pass.
Test: Ran ART 137-cfi test and 004-ThreadStress.
Test: Verify that displaying the fde start and end pc actually match the
Test: real data for fde that have pc relative set, and that don't.
Test: Verified that the unwind information for arm exidx matches the
Test: debug frame data.

Change-Id: I707555286b5cb05df9f25489e8c5ede753cfe0fb

1 files changed, 14 insertions, 23 deletions

diff --git a/libunwindstack/ElfInterface.cpp b/libunwindstack/ElfInterface.cpp
index 4c05a1b..954a821 100644
--- a/libunwindstack/ElfInterface.cpp
+++ b/libunwindstack/ElfInterface.cpp
@@ -124,10 +124,10 @@ Memory* ElfInterface::CreateGnuDebugdataMemory() {
 }
 
 template <typename AddressType>
-void ElfInterface::InitHeadersWithTemplate() {
+void ElfInterface::InitHeadersWithTemplate(uint64_t load_bias) {
   if (eh_frame_hdr_offset_ != 0) {
     eh_frame_.reset(new DwarfEhFrameWithHdr<AddressType>(memory_));
-    if (!eh_frame_->Init(eh_frame_hdr_offset_, eh_frame_hdr_size_)) {
+    if (!eh_frame_->Init(eh_frame_hdr_offset_, eh_frame_hdr_size_, load_bias)) {
       eh_frame_.reset(nullptr);
     }
   }
@@ -136,7 +136,7 @@ void ElfInterface::InitHeadersWithTemplate() {
     // If there is an eh_frame section without an eh_frame_hdr section,
     // or using the frame hdr object failed to init.
     eh_frame_.reset(new DwarfEhFrame<AddressType>(memory_));
-    if (!eh_frame_->Init(eh_frame_offset_, eh_frame_size_)) {
+    if (!eh_frame_->Init(eh_frame_offset_, eh_frame_size_, load_bias)) {
       eh_frame_.reset(nullptr);
     }
   }
@@ -150,7 +150,7 @@ void ElfInterface::InitHeadersWithTemplate() {
 
   if (debug_frame_offset_ != 0) {
     debug_frame_.reset(new DwarfDebugFrame<AddressType>(memory_));
-    if (!debug_frame_->Init(debug_frame_offset_, debug_frame_size_)) {
+    if (!debug_frame_->Init(debug_frame_offset_, debug_frame_size_, load_bias)) {
       debug_frame_.reset(nullptr);
       debug_frame_offset_ = 0;
       debug_frame_size_ = static_cast<uint64_t>(-1);
@@ -441,14 +441,14 @@ bool ElfInterface::GetSonameWithTemplate(std::string* soname) {
 }
 
 template <typename SymType>
-bool ElfInterface::GetFunctionNameWithTemplate(uint64_t addr, uint64_t load_bias, std::string* name,
+bool ElfInterface::GetFunctionNameWithTemplate(uint64_t addr, std::string* name,
                                                uint64_t* func_offset) {
   if (symbols_.empty()) {
     return false;
   }
 
   for (const auto symbol : symbols_) {
-    if (symbol->GetName<SymType>(addr, load_bias, memory_, name, func_offset)) {
+    if (symbol->GetName<SymType>(addr, memory_, name, func_offset)) {
       return true;
     }
   }
@@ -469,34 +469,25 @@ bool ElfInterface::GetGlobalVariableWithTemplate(const std::string& name, uint64
   return false;
 }
 
-bool ElfInterface::Step(uint64_t pc, uint64_t load_bias, Regs* regs, Memory* process_memory,
-                        bool* finished) {
+bool ElfInterface::Step(uint64_t pc, Regs* regs, Memory* process_memory, bool* finished) {
   last_error_.code = ERROR_NONE;
   last_error_.address = 0;
 
-  // Adjust the load bias to get the real relative pc.
-  if (pc < load_bias) {
-    last_error_.code = ERROR_UNWIND_INFO;
-    return false;
-  }
-  uint64_t adjusted_pc = pc - load_bias;
-
   // Try the debug_frame first since it contains the most specific unwind
   // information.
   DwarfSection* debug_frame = debug_frame_.get();
-  if (debug_frame != nullptr && debug_frame->Step(adjusted_pc, regs, process_memory, finished)) {
+  if (debug_frame != nullptr && debug_frame->Step(pc, regs, process_memory, finished)) {
     return true;
   }
 
   // Try the eh_frame next.
   DwarfSection* eh_frame = eh_frame_.get();
-  if (eh_frame != nullptr && eh_frame->Step(adjusted_pc, regs, process_memory, finished)) {
+  if (eh_frame != nullptr && eh_frame->Step(pc, regs, process_memory, finished)) {
     return true;
   }
 
-  // Finally try the gnu_debugdata interface, but always use a zero load bias.
   if (gnu_debugdata_interface_ != nullptr &&
-      gnu_debugdata_interface_->Step(pc, 0, regs, process_memory, finished)) {
+      gnu_debugdata_interface_->Step(pc, regs, process_memory, finished)) {
     return true;
   }
 
@@ -559,8 +550,8 @@ void ElfInterface::GetMaxSizeWithTemplate(Memory* memory, uint64_t* size) {
 }
 
 // Instantiate all of the needed template functions.
-template void ElfInterface::InitHeadersWithTemplate<uint32_t>();
-template void ElfInterface::InitHeadersWithTemplate<uint64_t>();
+template void ElfInterface::InitHeadersWithTemplate<uint32_t>(uint64_t);
+template void ElfInterface::InitHeadersWithTemplate<uint64_t>(uint64_t);
 
 template bool ElfInterface::ReadAllHeaders<Elf32_Ehdr, Elf32_Phdr, Elf32_Shdr>(uint64_t*);
 template bool ElfInterface::ReadAllHeaders<Elf64_Ehdr, Elf64_Phdr, Elf64_Shdr>(uint64_t*);
@@ -574,9 +565,9 @@ template bool ElfInterface::ReadSectionHeaders<Elf64_Ehdr, Elf64_Shdr>(const Elf
 template bool ElfInterface::GetSonameWithTemplate<Elf32_Dyn>(std::string*);
 template bool ElfInterface::GetSonameWithTemplate<Elf64_Dyn>(std::string*);
 
-template bool ElfInterface::GetFunctionNameWithTemplate<Elf32_Sym>(uint64_t, uint64_t, std::string*,
+template bool ElfInterface::GetFunctionNameWithTemplate<Elf32_Sym>(uint64_t, std::string*,
                                                                    uint64_t*);
-template bool ElfInterface::GetFunctionNameWithTemplate<Elf64_Sym>(uint64_t, uint64_t, std::string*,
+template bool ElfInterface::GetFunctionNameWithTemplate<Elf64_Sym>(uint64_t, std::string*,
                                                                    uint64_t*);
 
 template bool ElfInterface::GetGlobalVariableWithTemplate<Elf32_Sym>(const std::string&, uint64_t*);