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/dwarf/dwarf_constants.h b/compiler/dwarf/dwarf_constants.h
index 61a44cd..3b570e5 100644
--- a/compiler/dwarf/dwarf_constants.h
+++ b/compiler/dwarf/dwarf_constants.h
@@ -680,6 +680,14 @@
DW_EH_PE_aligned = 0x50,
};
+enum CFIFormat : uint8_t {
+ // This is the original format as defined by the specification.
+ // It is used for the .debug_frame section.
+ DW_DEBUG_FRAME_FORMAT,
+ // Slightly modified format used for the .eh_frame section.
+ DW_EH_FRAME_FORMAT
+};
+
} // namespace dwarf
} // namespace art
diff --git a/compiler/dwarf/dwarf_test.cc b/compiler/dwarf/dwarf_test.cc
index edba00a..4971f0e 100644
--- a/compiler/dwarf/dwarf_test.cc
+++ b/compiler/dwarf/dwarf_test.cc
@@ -26,6 +26,8 @@
namespace art {
namespace dwarf {
+constexpr CFIFormat kCFIFormat = DW_DEBUG_FRAME_FORMAT;
+
// Run the tests only on host since we need objdump.
#ifndef HAVE_ANDROID_OS
@@ -120,30 +122,30 @@
DW_CHECK_NEXT("DW_CFA_restore: r5 (ebp)");
DebugFrameOpCodeWriter<> initial_opcodes;
- WriteEhFrameCIE(is64bit, DW_EH_PE_absptr, Reg(is64bit ? 16 : 8),
- initial_opcodes, &eh_frame_data_);
- std::vector<uintptr_t> eh_frame_patches;
+ WriteDebugFrameCIE(is64bit, DW_EH_PE_absptr, Reg(is64bit ? 16 : 8),
+ initial_opcodes, kCFIFormat, &debug_frame_data_);
+ std::vector<uintptr_t> debug_frame_patches;
std::vector<uintptr_t> expected_patches { 28 }; // NOLINT
- WriteEhFrameFDE(is64bit, 0, 0x01000000, 0x01000000, opcodes.data(),
- &eh_frame_data_, &eh_frame_patches);
+ WriteDebugFrameFDE(is64bit, 0, 0x01000000, 0x01000000, opcodes.data(),
+ kCFIFormat, &debug_frame_data_, &debug_frame_patches);
- EXPECT_EQ(expected_patches, eh_frame_patches);
+ EXPECT_EQ(expected_patches, debug_frame_patches);
CheckObjdumpOutput(is64bit, "-W");
}
TEST_F(DwarfTest, DebugFrame64) {
constexpr bool is64bit = true;
DebugFrameOpCodeWriter<> initial_opcodes;
- WriteEhFrameCIE(is64bit, DW_EH_PE_absptr, Reg(16),
- initial_opcodes, &eh_frame_data_);
+ WriteDebugFrameCIE(is64bit, DW_EH_PE_absptr, Reg(16),
+ initial_opcodes, kCFIFormat, &debug_frame_data_);
DebugFrameOpCodeWriter<> opcodes;
- std::vector<uintptr_t> eh_frame_patches;
+ std::vector<uintptr_t> debug_frame_patches;
std::vector<uintptr_t> expected_patches { 32 }; // NOLINT
- WriteEhFrameFDE(is64bit, 0, 0x0100000000000000, 0x0200000000000000,
- opcodes.data(), &eh_frame_data_, &eh_frame_patches);
+ WriteDebugFrameFDE(is64bit, 0, 0x0100000000000000, 0x0200000000000000,
+ opcodes.data(), kCFIFormat, &debug_frame_data_, &debug_frame_patches);
DW_CHECK("FDE cie=00000000 pc=100000000000000..300000000000000");
- EXPECT_EQ(expected_patches, eh_frame_patches);
+ EXPECT_EQ(expected_patches, debug_frame_patches);
CheckObjdumpOutput(is64bit, "-W");
}
@@ -173,11 +175,11 @@
DW_CHECK_NEXT("DW_CFA_offset: r14 (r14)");
DW_CHECK_NEXT("DW_CFA_offset: r15 (r15)");
DebugFrameOpCodeWriter<> initial_opcodes;
- WriteEhFrameCIE(is64bit, DW_EH_PE_absptr, Reg(16),
- initial_opcodes, &eh_frame_data_);
- std::vector<uintptr_t> eh_frame_patches;
- WriteEhFrameFDE(is64bit, 0, 0x0100000000000000, 0x0200000000000000,
- opcodes.data(), &eh_frame_data_, &eh_frame_patches);
+ WriteDebugFrameCIE(is64bit, DW_EH_PE_absptr, Reg(16),
+ initial_opcodes, kCFIFormat, &debug_frame_data_);
+ std::vector<uintptr_t> debug_frame_patches;
+ WriteDebugFrameFDE(is64bit, 0, 0x0100000000000000, 0x0200000000000000,
+ opcodes.data(), kCFIFormat, &debug_frame_data_, &debug_frame_patches);
CheckObjdumpOutput(is64bit, "-W");
}
diff --git a/compiler/dwarf/dwarf_test.h b/compiler/dwarf/dwarf_test.h
index 230ebe3..3afb5ea 100644
--- a/compiler/dwarf/dwarf_test.h
+++ b/compiler/dwarf/dwarf_test.h
@@ -69,7 +69,7 @@
RawSection debug_abbrev(".debug_abbrev", SHT_PROGBITS, 0, nullptr, 0, 1, 0);
RawSection debug_str(".debug_str", SHT_PROGBITS, 0, nullptr, 0, 1, 0);
RawSection debug_line(".debug_line", SHT_PROGBITS, 0, nullptr, 0, 1, 0);
- RawSection eh_frame(".eh_frame", SHT_PROGBITS, SHF_ALLOC, nullptr, 0, kPageSize, 0);
+ RawSection debug_frame(".debug_frame", SHT_PROGBITS, 0, nullptr, 0, 8, 0);
if (!debug_info_data_.empty()) {
debug_info.SetBuffer(debug_info_data_);
builder.RegisterSection(&debug_info);
@@ -86,9 +86,9 @@
debug_line.SetBuffer(debug_line_data_);
builder.RegisterSection(&debug_line);
}
- if (!eh_frame_data_.empty()) {
- eh_frame.SetBuffer(eh_frame_data_);
- builder.RegisterSection(&eh_frame);
+ if (!debug_frame_data_.empty()) {
+ debug_frame.SetBuffer(debug_frame_data_);
+ builder.RegisterSection(&debug_frame);
}
ScratchFile file;
builder.Write(file.GetFile());
@@ -167,7 +167,7 @@
}
// Buffers which are going to assembled into ELF file and passed to objdump.
- std::vector<uint8_t> eh_frame_data_;
+ std::vector<uint8_t> debug_frame_data_;
std::vector<uint8_t> debug_info_data_;
std::vector<uint8_t> debug_abbrev_data_;
std::vector<uint8_t> debug_str_data_;
diff --git a/compiler/dwarf/headers.h b/compiler/dwarf/headers.h
index 9f64766..ad315ee 100644
--- a/compiler/dwarf/headers.h
+++ b/compiler/dwarf/headers.h
@@ -35,17 +35,18 @@
// and compilers are expected *not* to use it by default.
// In particular, it is not related to machine architecture.
-// Write common information entry (CIE) to .eh_frame section.
+// Write common information entry (CIE) to .debug_frame or .eh_frame section.
template<typename Allocator>
-void WriteEhFrameCIE(bool is64bit,
- ExceptionHeaderValueApplication address_type,
- Reg return_address_register,
- const DebugFrameOpCodeWriter<Allocator>& opcodes,
- std::vector<uint8_t>* eh_frame) {
- Writer<> writer(eh_frame);
+void WriteDebugFrameCIE(bool is64bit,
+ ExceptionHeaderValueApplication address_type,
+ Reg return_address_register,
+ const DebugFrameOpCodeWriter<Allocator>& opcodes,
+ CFIFormat format,
+ std::vector<uint8_t>* debug_frame) {
+ Writer<> writer(debug_frame);
size_t cie_header_start_ = writer.data()->size();
writer.PushUint32(0); // Length placeholder.
- writer.PushUint32(0); // CIE id.
+ writer.PushUint32((format == DW_EH_FRAME_FORMAT) ? 0 : 0xFFFFFFFF); // CIE id.
writer.PushUint8(1); // Version.
writer.PushString("zR");
writer.PushUleb128(DebugFrameOpCodeWriter<Allocator>::kCodeAlignmentFactor);
@@ -62,20 +63,26 @@
writer.UpdateUint32(cie_header_start_, writer.data()->size() - cie_header_start_ - 4);
}
-// Write frame description entry (FDE) to .eh_frame section.
+// Write frame description entry (FDE) to .debug_frame or .eh_frame section.
template<typename Allocator>
-void WriteEhFrameFDE(bool is64bit, size_t cie_offset,
- uint64_t initial_address, uint64_t address_range,
- const std::vector<uint8_t, Allocator>* opcodes,
- std::vector<uint8_t>* eh_frame,
- std::vector<uintptr_t>* eh_frame_patches) {
- Writer<> writer(eh_frame);
+void WriteDebugFrameFDE(bool is64bit, size_t cie_offset,
+ uint64_t initial_address, uint64_t address_range,
+ const std::vector<uint8_t, Allocator>* opcodes,
+ CFIFormat format,
+ std::vector<uint8_t>* debug_frame,
+ std::vector<uintptr_t>* debug_frame_patches) {
+ Writer<> writer(debug_frame);
size_t fde_header_start = writer.data()->size();
writer.PushUint32(0); // Length placeholder.
- uint32_t cie_pointer = writer.data()->size() - cie_offset;
- writer.PushUint32(cie_pointer);
+ if (format == DW_EH_FRAME_FORMAT) {
+ uint32_t cie_pointer = writer.data()->size() - cie_offset;
+ writer.PushUint32(cie_pointer);
+ } else {
+ uint32_t cie_pointer = cie_offset;
+ writer.PushUint32(cie_pointer);
+ }
// Relocate initial_address, but not address_range (it is size).
- eh_frame_patches->push_back(writer.data()->size());
+ debug_frame_patches->push_back(writer.data()->size());
if (is64bit) {
writer.PushUint64(initial_address);
writer.PushUint64(address_range);