Relocate DWARF using .oat_patches.
The current solution is to hard-code knowledge of DWARF in the linker.
This works for simple use of DWARF, but breaks as soon as I try to do
anything more complex. Making the linker fully support DWARF would be
non-trivial task and would be essentially rewrite. Using .oat_patches
is much easier solution.
Relocating .debug_* sections required extending .oat_patches to support
more sections than just .text. I have encoded each section as
null-terminated section name followed by ULEB128 deltas.
The ULEB128 encoding shrinks .oat_patches for .text by factor of
about 6 with 64-bit compiler, and factor of 3 with 32-bit compiler.
On the other hand, it grows by the extra .oat_patches for DWARF which
were not present before (if debug symbols are included).
Overall, it is still a clear improvement even with the DWARF patches.
Change-Id: I78ffeda0f8a3da03341995a3b5ef15c954e16e9f
diff --git a/compiler/elf_writer_debug.cc b/compiler/elf_writer_debug.cc
index 5e8e24b..6df5ea9 100644
--- a/compiler/elf_writer_debug.cc
+++ b/compiler/elf_writer_debug.cc
@@ -159,7 +159,7 @@
* @param debug_line Line number table.
*/
void WriteDebugSections(const CompilerDriver* compiler,
- const OatWriter* oat_writer,
+ OatWriter* oat_writer,
uint32_t text_section_offset,
std::vector<uint8_t>* eh_frame,
std::vector<uint8_t>* debug_info,
@@ -176,6 +176,7 @@
}
// Write .eh_frame section.
+ auto* eh_frame_patches = oat_writer->GetAbsolutePatchLocationsFor(".eh_frame");
size_t cie_offset = eh_frame->size();
WriteEhFrameCIE(isa, eh_frame);
for (const OatWriter::DebugInfo& mi : method_infos) {
@@ -183,7 +184,7 @@
if (opcodes != nullptr) {
WriteEhFrameFDE(Is64BitInstructionSet(isa), cie_offset,
text_section_offset + mi.low_pc_, mi.high_pc_ - mi.low_pc_,
- opcodes, eh_frame);
+ opcodes, eh_frame, eh_frame_patches);
}
}
@@ -211,7 +212,8 @@
info.EndTag(); // DW_TAG_subprogram
}
info.EndTag(); // DW_TAG_compile_unit
- WriteDebugInfoCU(debug_abbrev_offset, info, debug_info);
+ auto* debug_info_patches = oat_writer->GetAbsolutePatchLocationsFor(".debug_info");
+ WriteDebugInfoCU(debug_abbrev_offset, info, debug_info, debug_info_patches);
// TODO: in gdb info functions <regexp> - reports Java functions, but
// source file is <unknown> because .debug_line is formed as one
@@ -353,7 +355,8 @@
}
opcodes.AdvancePC(text_section_offset + cunit_high_pc);
opcodes.EndSequence();
- WriteDebugLineTable(directories, files, opcodes, debug_line);
+ auto* debug_line_patches = oat_writer->GetAbsolutePatchLocationsFor(".debug_line");
+ WriteDebugLineTable(directories, files, opcodes, debug_line, debug_line_patches);
}
} // namespace dwarf