From 033d745bb9412c9b546d29395cc9efbbb4fa306e Mon Sep 17 00:00:00 2001 From: David Srbecky Date: Thu, 30 Apr 2015 19:57:35 +0100 Subject: Add binary search table to .eh_frame_hdr The addresses in the search table must be relative to the start of .eh_frame_hdr which results in yet another pointer type to patch. I have moved the Patch method back to elf_writer_quick where it can be specialized to one of the three pointer types. The .eh_frame_hdr takes around 17% of .eh_frame now. Change-Id: I4770d1355ded6cdff9489c33380f6b06c4e3f9fe --- compiler/elf_writer_debug.cc | 37 ++++++++++++++++++++++++++++--------- 1 file changed, 28 insertions(+), 9 deletions(-) (limited to 'compiler/elf_writer_debug.cc') diff --git a/compiler/elf_writer_debug.cc b/compiler/elf_writer_debug.cc index e8c3b6e432..db599c4949 100644 --- a/compiler/elf_writer_debug.cc +++ b/compiler/elf_writer_debug.cc @@ -162,17 +162,20 @@ void WriteEhFrame(const CompilerDriver* compiler, ExceptionHeaderValueApplication address_type, std::vector* eh_frame, std::vector* eh_frame_patches, - std::vector* eh_frame_hdr) { + std::vector* eh_frame_hdr, + std::vector* eh_frame_hdr_patches) { const auto& method_infos = oat_writer->GetMethodDebugInfo(); const InstructionSet isa = compiler->GetInstructionSet(); // Write .eh_frame section. + std::map address_to_fde_offset_map; size_t cie_offset = eh_frame->size(); WriteEhFrameCIE(isa, address_type, eh_frame); for (const OatWriter::DebugInfo& mi : method_infos) { if (!mi.deduped_) { // Only one FDE per unique address. const SwapVector* 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); @@ -183,14 +186,30 @@ void WriteEhFrame(const CompilerDriver* compiler, // Write .eh_frame_hdr section. Writer<> header(eh_frame_hdr); header.PushUint8(1); // Version. - header.PushUint8(DW_EH_PE_pcrel | DW_EH_PE_sdata4); // Encoding of .eh_frame pointer. - header.PushUint8(DW_EH_PE_omit); // Encoding of binary search table size. - header.PushUint8(DW_EH_PE_omit); // Encoding of binary search table addresses. - // .eh_frame pointer - .eh_frame_hdr section is after .eh_frame section, and need to encode - // relative to this location as libunwind doesn't honor datarel for eh_frame_hdr correctly. - header.PushInt32(-static_cast(eh_frame->size() + 4U)); - // Omit binary search table size (number of entries). - // Omit binary search table. + // 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(eh_frame->size()); + header.PushInt32(relative_eh_frame_begin - 4U); + // Binary search table size (number of entries). + header.PushUint32(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; + size_t fde_address = 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); + } } /* -- cgit v1.2.3