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Add support for printing DWARF location attributes
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@chaoticgd
chaoticgd committed Nov 19, 2024
1 parent 54c7083 commit 813e9b7
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Showing 2 changed files with 174 additions and 37 deletions.
180 changes: 143 additions & 37 deletions src/ccc/dwarf_section.cpp
View file
Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@
#include "dwarf_section.h"

#include "importer_flags.h"
#include "registers.h"

namespace ccc::dwarf {

Expand Down Expand Up @@ -351,6 +352,66 @@ Result<AttributeTuple> DIE::parse_attribute(u32& offset) const
return result;
}

// *****************************************************************************

LocationDescription::LocationDescription(std::span<const u8> block)
: m_block(block) {}

Result<void> LocationDescription::print(FILE* out)
{
fprintf(out, "{");

u32 offset = 0;
while (offset < m_block.size()) {
if (offset != 0) {
fprintf(out, ",");
}

Result<LocationAtom> atom = parse_atom(offset);
CCC_RETURN_IF_ERROR(atom);

const char* op_name = location_op_to_string(atom->op);
CCC_ASSERT(op_name);

fprintf(out, "%s", op_name);

if (atom->value.has_value()) {
if ((atom->op == OP_REG || atom->op == OP_BASEREG) && *atom->value < 32) {
fprintf(out, "(%s)", mips::GPR_STRINGS[*atom->value]);
} else {
fprintf(out, "(0x%x)", *atom->value);
}
}
}

fprintf(out, "}");

return Result<void>();
}

Result<LocationAtom> LocationDescription::parse_atom(u32& offset) const
{
LocationAtom atom;

const u8* op = get_unaligned<u8>(m_block, offset);
CCC_CHECK(op, "Invalid location description (cannot read op).");
offset += sizeof(u8);

const char* op_name = location_op_to_string(*op);
CCC_CHECK(op_name, "Invalid location description (unknown op 0x%hhx).", *op);

atom.op = static_cast<LocationOp>(*op);

if (*op == OP_REG || *op == OP_BASEREG || *op == OP_ADDR || *op == OP_CONST || *op == OP_80) {
const u32* value = get_unaligned<u32>(m_block, offset);
CCC_CHECK(value, "Invalid location descripton (cannot read value).");
offset += sizeof(u32);

atom.value = *value;
}

return atom;
}

// *****************************************************************************

Expand Down Expand Up @@ -432,47 +493,14 @@ Result<void> SectionReader::print_attributes(FILE* out, const DIE& die) const
break;
}
case FORM_REF: {
Result<std::optional<DIE>> referenced_die = DIE::parse(m_debug, value.reference(), NO_IMPORTER_FLAGS);
if (referenced_die.success()) {
if (referenced_die->has_value()) {
const char* referenced_die_tag = tag_to_string((*referenced_die)->tag());
if (referenced_die_tag) {
fprintf(out, "%s", referenced_die_tag);
} else {
fprintf(out, "unknown(%hx)", (*referenced_die)->tag());
}
} else {
// The DIE was less than 8 bytes in size.
fprintf(out, "null");
}
} else {
// The DIE could not be read.
fprintf(out, "???");
}

fprintf(out, "@%x", value.reference());
Result<void> ref_result = print_ref_value(out, value);
CCC_RETURN_IF_ERROR(ref_result);
break;
}
case FORM_BLOCK2:
case FORM_BLOCK4: {
fprintf(out, "{");

size_t max_bytes_to_display = 3;
std::span<const u8> block = value.block();

for (size_t i = 0; i < std::min(block.size(), max_bytes_to_display); i++) {
if (i != 0) {
fprintf(out, ",");
}
fprintf(out, "%02hhx", block[i]);
}

if (block.size() > max_bytes_to_display) {
fprintf(out, ",...");
}

fprintf(out, "}@%x", offset);

Result<void> block_result = print_block_value(out, offset, attribute, value);
CCC_RETURN_IF_ERROR(block_result);
break;
}
case FORM_DATA2:
Expand All @@ -492,6 +520,67 @@ Result<void> SectionReader::print_attributes(FILE* out, const DIE& die) const
return Result<void>();
}

Result<void> SectionReader::print_ref_value(FILE* out, const Value& value) const
{
Result<std::optional<DIE>> referenced_die = DIE::parse(m_debug, value.reference(), NO_IMPORTER_FLAGS);
if (referenced_die.success()) {
if (referenced_die->has_value()) {
const char* referenced_die_tag = tag_to_string((*referenced_die)->tag());
if (referenced_die_tag) {
fprintf(out, "%s", referenced_die_tag);
} else {
fprintf(out, "unknown(%hx)", (*referenced_die)->tag());
}
} else {
// The DIE was less than 8 bytes in size.
fprintf(out, "null");
}
} else {
// The DIE could not be read.
fprintf(out, "???");
}

fprintf(out, "@%x", value.reference());

return Result<void>();
}

Result<void> SectionReader::print_block_value(FILE* out, u32 offset, Attribute attribute, const Value& value) const
{
std::span<const u8> block = value.block();

switch (attribute) {
case AT_location: {
LocationDescription location(value.block());

Result<void> print_result = location.print(out);
CCC_RETURN_IF_ERROR(print_result);

break;
}
default: {
fprintf(out, "{");

size_t max_bytes_to_display = 3;

for (size_t i = 0; i < std::min(block.size(), max_bytes_to_display); i++) {
if (i != 0) {
fprintf(out, ",");
}
fprintf(out, "%02hhx", block[i]);
}

if (block.size() > max_bytes_to_display) {
fprintf(out, ",...");
}

fprintf(out, "}@%x", offset);
}
}

return Result<void>();
}

const char* tag_to_string(u32 tag)
{
switch (tag) {
Expand Down Expand Up @@ -599,11 +688,28 @@ const char* attribute_to_string(u32 attribute)
case AT_stride_size: return "stride_size";
case AT_upper_bound: return "upper_bound";
case AT_virtual: return "virtual";
case AT_mangled_name: return "mangled_name";
case AT_overlay_id: return "overlay_id";
case AT_overlay_name: return "overlay_name";
}

return nullptr;
}

const char* location_op_to_string(u32 op)
{
switch (op) {
case OP_REG: return "reg";
case OP_BASEREG: return "basereg";
case OP_ADDR: return "addr";
case OP_CONST: return "const";
case OP_DEREF2: return "deref2";
case OP_DEREF: return "deref";
case OP_ADD: return "add";
case OP_80: return "op80";
}

return nullptr;
}

}
31 changes: 31 additions & 0 deletions src/ccc/dwarf_section.h
View file
Original file line number Diff line number Diff line change
Expand Up @@ -237,6 +237,34 @@ class DIE {
u32 m_importer_flags;
};

enum LocationOp : u8 {
OP_REG = 0x01,
OP_BASEREG = 0x02,
OP_ADDR = 0x03,
OP_CONST = 0x04,
OP_DEREF2 = 0x05,
OP_DEREF = 0x06,
OP_ADD = 0x07,
OP_80 = 0x80
};

struct LocationAtom {
LocationOp op;
std::optional<u32> value;
};

class LocationDescription {
public:
LocationDescription(std::span<const u8> block);

Result<void> print(FILE* out);

protected:
Result<LocationAtom> parse_atom(u32& offset) const;

std::span<const u8> m_block;
};

class SectionReader {
public:
SectionReader(std::span<const u8> debug, std::span<const u8> line);
Expand All @@ -245,6 +273,8 @@ class SectionReader {

Result<void> print_dies(FILE* out, DIE die, s32 depth) const;
Result<void> print_attributes(FILE* out, const DIE& die) const;
Result<void> print_ref_value(FILE* out, const Value& value) const;
Result<void> print_block_value(FILE* out, u32 offset, Attribute attribute, const Value& value) const;

protected:
std::span<const u8> m_debug;
Expand All @@ -254,5 +284,6 @@ class SectionReader {
const char* tag_to_string(u32 tag);
const char* form_to_string(u32 form);
const char* attribute_to_string(u32 attribute);
const char* location_op_to_string(u32 op);

}

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