Support generation of CFI in .debug_frame format.
.debug_frame section is almost identical to .eh_frame section.
There are only minor differences in the CIE and FDE headers.
The main difference is that .eh_frame is intended to be used
at runtime for exception handling and is therefore allocated
within the running program whereas .debug_frame is not.
This makes .debug_frame easier to remove using standard tools.
"objcopy --strip-debug" removes .debug_frame, but not .eh_frame.
(although objcopy can be still be forced to remove .eh_frame)
Similarly, we might want to separate the CFI to separate debug
file or include it as compressed .gnu_debugdata section.
It is more appropriate to use .debug_frame for this purpose.
Bug:20556771
Change-Id: I9d91a333b9fb37523fd6fafccfad89b21d2477af
diff --git a/compiler/elf_writer_debug.cc b/compiler/elf_writer_debug.cc
index 5e9cf76..a1aabc3 100644
--- a/compiler/elf_writer_debug.cc
+++ b/compiler/elf_writer_debug.cc
@@ -29,9 +29,10 @@
namespace art {
namespace dwarf {
-static void WriteEhFrameCIE(InstructionSet isa,
- ExceptionHeaderValueApplication addr_type,
- std::vector<uint8_t>* eh_frame) {
+static void WriteDebugFrameCIE(InstructionSet isa,
+ ExceptionHeaderValueApplication addr_type,
+ CFIFormat format,
+ std::vector<uint8_t>* eh_frame) {
// Scratch registers should be marked as undefined. This tells the
// debugger that its value in the previous frame is not recoverable.
bool is64bit = Is64BitInstructionSet(isa);
@@ -57,7 +58,8 @@
}
}
auto return_reg = Reg::ArmCore(14); // R14(LR).
- WriteEhFrameCIE(is64bit, addr_type, return_reg, opcodes, eh_frame);
+ WriteDebugFrameCIE(is64bit, addr_type, return_reg,
+ opcodes, format, eh_frame);
return;
}
case kArm64: {
@@ -80,7 +82,8 @@
}
}
auto return_reg = Reg::Arm64Core(30); // R30(LR).
- WriteEhFrameCIE(is64bit, addr_type, return_reg, opcodes, eh_frame);
+ WriteDebugFrameCIE(is64bit, addr_type, return_reg,
+ opcodes, format, eh_frame);
return;
}
case kMips:
@@ -96,7 +99,8 @@
}
}
auto return_reg = Reg::MipsCore(31); // R31(RA).
- WriteEhFrameCIE(is64bit, addr_type, return_reg, opcodes, eh_frame);
+ WriteDebugFrameCIE(is64bit, addr_type, return_reg,
+ opcodes, format, eh_frame);
return;
}
case kX86: {
@@ -122,7 +126,8 @@
}
}
auto return_reg = Reg::X86Core(8); // R8(EIP).
- WriteEhFrameCIE(is64bit, addr_type, return_reg, opcodes, eh_frame);
+ WriteDebugFrameCIE(is64bit, addr_type, return_reg,
+ opcodes, format, eh_frame);
return;
}
case kX86_64: {
@@ -148,7 +153,8 @@
}
}
auto return_reg = Reg::X86_64Core(16); // R16(RIP).
- WriteEhFrameCIE(is64bit, addr_type, return_reg, opcodes, eh_frame);
+ WriteDebugFrameCIE(is64bit, addr_type, return_reg,
+ opcodes, format, eh_frame);
return;
}
case kNone:
@@ -158,58 +164,61 @@
UNREACHABLE();
}
-void WriteEhFrame(const CompilerDriver* compiler,
- const OatWriter* oat_writer,
- ExceptionHeaderValueApplication address_type,
- std::vector<uint8_t>* eh_frame,
- std::vector<uintptr_t>* eh_frame_patches,
- std::vector<uint8_t>* eh_frame_hdr,
- std::vector<uintptr_t>* eh_frame_hdr_patches) {
+void WriteCFISection(const CompilerDriver* compiler,
+ const OatWriter* oat_writer,
+ ExceptionHeaderValueApplication address_type,
+ CFIFormat format,
+ std::vector<uint8_t>* debug_frame,
+ std::vector<uintptr_t>* debug_frame_patches,
+ std::vector<uint8_t>* eh_frame_hdr,
+ std::vector<uintptr_t>* eh_frame_hdr_patches) {
const auto& method_infos = oat_writer->GetMethodDebugInfo();
const InstructionSet isa = compiler->GetInstructionSet();
- // Write .eh_frame section.
+ // Write .eh_frame/.debug_frame section.
std::map<uint32_t, size_t> address_to_fde_offset_map;
- size_t cie_offset = eh_frame->size();
- WriteEhFrameCIE(isa, address_type, eh_frame);
+ size_t cie_offset = debug_frame->size();
+ WriteDebugFrameCIE(isa, address_type, format, debug_frame);
for (const OatWriter::DebugInfo& mi : method_infos) {
if (!mi.deduped_) { // Only one FDE per unique address.
const SwapVector<uint8_t>* opcodes = mi.compiled_method_->GetCFIInfo();
if (opcodes != nullptr) {
- address_to_fde_offset_map.emplace(mi.low_pc_, eh_frame->size());
- WriteEhFrameFDE(Is64BitInstructionSet(isa), cie_offset,
- mi.low_pc_, mi.high_pc_ - mi.low_pc_,
- opcodes, eh_frame, eh_frame_patches);
+ address_to_fde_offset_map.emplace(mi.low_pc_, debug_frame->size());
+ WriteDebugFrameFDE(Is64BitInstructionSet(isa), cie_offset,
+ mi.low_pc_, mi.high_pc_ - mi.low_pc_,
+ opcodes, format, debug_frame, debug_frame_patches);
}
}
}
- // Write .eh_frame_hdr section.
- Writer<> header(eh_frame_hdr);
- header.PushUint8(1); // Version.
- // Encoding of .eh_frame pointer - libunwind does not honor datarel here,
- // so we have to use pcrel which means relative to the pointer's location.
- header.PushUint8(DW_EH_PE_pcrel | DW_EH_PE_sdata4);
- // Encoding of binary search table size.
- header.PushUint8(DW_EH_PE_udata4);
- // Encoding of binary search table addresses - libunwind supports only this
- // specific combination, which means relative to the start of .eh_frame_hdr.
- header.PushUint8(DW_EH_PE_datarel | DW_EH_PE_sdata4);
- // .eh_frame pointer - .eh_frame_hdr section is after .eh_frame section
- const int32_t relative_eh_frame_begin = -static_cast<int32_t>(eh_frame->size());
- header.PushInt32(relative_eh_frame_begin - 4U);
- // Binary search table size (number of entries).
- header.PushUint32(dchecked_integral_cast<uint32_t>(address_to_fde_offset_map.size()));
- // Binary search table.
- for (const auto& address_to_fde_offset : address_to_fde_offset_map) {
- u_int32_t code_address = address_to_fde_offset.first;
- int32_t fde_address = dchecked_integral_cast<int32_t>(address_to_fde_offset.second);
- eh_frame_hdr_patches->push_back(header.data()->size());
- header.PushUint32(code_address);
- // We know the exact layout (eh_frame is immediately before eh_frame_hdr)
- // and the data is relative to the start of the eh_frame_hdr,
- // so patching isn't necessary (in contrast to the code address above).
- header.PushInt32(relative_eh_frame_begin + fde_address);
+ if (format == DW_EH_FRAME_FORMAT) {
+ // Write .eh_frame_hdr section.
+ Writer<> header(eh_frame_hdr);
+ header.PushUint8(1); // Version.
+ // Encoding of .eh_frame pointer - libunwind does not honor datarel here,
+ // so we have to use pcrel which means relative to the pointer's location.
+ header.PushUint8(DW_EH_PE_pcrel | DW_EH_PE_sdata4);
+ // Encoding of binary search table size.
+ header.PushUint8(DW_EH_PE_udata4);
+ // Encoding of binary search table addresses - libunwind supports only this
+ // specific combination, which means relative to the start of .eh_frame_hdr.
+ header.PushUint8(DW_EH_PE_datarel | DW_EH_PE_sdata4);
+ // .eh_frame pointer - .eh_frame_hdr section is after .eh_frame section
+ const int32_t relative_eh_frame_begin = -static_cast<int32_t>(debug_frame->size());
+ header.PushInt32(relative_eh_frame_begin - 4U);
+ // Binary search table size (number of entries).
+ header.PushUint32(dchecked_integral_cast<uint32_t>(address_to_fde_offset_map.size()));
+ // Binary search table.
+ for (const auto& address_to_fde_offset : address_to_fde_offset_map) {
+ u_int32_t code_address = address_to_fde_offset.first;
+ int32_t fde_address = dchecked_integral_cast<int32_t>(address_to_fde_offset.second);
+ eh_frame_hdr_patches->push_back(header.data()->size());
+ header.PushUint32(code_address);
+ // We know the exact layout (eh_frame is immediately before eh_frame_hdr)
+ // and the data is relative to the start of the eh_frame_hdr,
+ // so patching isn't necessary (in contrast to the code address above).
+ header.PushInt32(relative_eh_frame_begin + fde_address);
+ }
}
}