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zig/lib/std/dwarf.zig
kcbanner 62598c2187 debug: rework how unwind errors are printed, and add module name lookup for linux 
This change enhances stack trace output to include a note that debug info was missing,
and therefore the stack trace may not be accurate. For example, if the user is using a libc
compiled with -fomit-frame-pointer and doesn't have debug symbols installed, any traces
that begin in a libc function may not unwind correctly. This allows the user to notice this and
potentially install debug symbols to improve the output.
2023-07-20 22:58:14 -04:00

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const builtin = @import("builtin");
const std = @import("std.zig");
const debug = std.debug;
const fs = std.fs;
const io = std.io;
const os = std.os;
const mem = std.mem;
const math = std.math;
const leb = @import("leb128.zig");
const assert = std.debug.assert;
pub const TAG = @import("dwarf/TAG.zig");
pub const AT = @import("dwarf/AT.zig");
pub const OP = @import("dwarf/OP.zig");
pub const LANG = @import("dwarf/LANG.zig");
pub const FORM = @import("dwarf/FORM.zig");
pub const ATE = @import("dwarf/ATE.zig");
pub const EH = @import("dwarf/EH.zig");
pub const abi = @import("dwarf/abi.zig");
pub const call_frame = @import("dwarf/call_frame.zig");
pub const expressions = @import("dwarf/expressions.zig");
pub const LLE = struct {
pub const end_of_list = 0x00;
pub const base_addressx = 0x01;
pub const startx_endx = 0x02;
pub const startx_length = 0x03;
pub const offset_pair = 0x04;
pub const default_location = 0x05;
pub const base_address = 0x06;
pub const start_end = 0x07;
pub const start_length = 0x08;
};
pub const CFA = struct {
pub const advance_loc = 0x40;
pub const offset = 0x80;
pub const restore = 0xc0;
pub const nop = 0x00;
pub const set_loc = 0x01;
pub const advance_loc1 = 0x02;
pub const advance_loc2 = 0x03;
pub const advance_loc4 = 0x04;
pub const offset_extended = 0x05;
pub const restore_extended = 0x06;
pub const @"undefined" = 0x07;
pub const same_value = 0x08;
pub const register = 0x09;
pub const remember_state = 0x0a;
pub const restore_state = 0x0b;
pub const def_cfa = 0x0c;
pub const def_cfa_register = 0x0d;
pub const def_cfa_offset = 0x0e;
// DWARF 3.
pub const def_cfa_expression = 0x0f;
pub const expression = 0x10;
pub const offset_extended_sf = 0x11;
pub const def_cfa_sf = 0x12;
pub const def_cfa_offset_sf = 0x13;
pub const val_offset = 0x14;
pub const val_offset_sf = 0x15;
pub const val_expression = 0x16;
pub const lo_user = 0x1c;
pub const hi_user = 0x3f;
// SGI/MIPS specific.
pub const MIPS_advance_loc8 = 0x1d;
// GNU extensions.
pub const GNU_window_save = 0x2d;
pub const GNU_args_size = 0x2e;
pub const GNU_negative_offset_extended = 0x2f;
};
pub const CHILDREN = struct {
pub const no = 0x00;
pub const yes = 0x01;
};
pub const LNS = struct {
pub const extended_op = 0x00;
pub const copy = 0x01;
pub const advance_pc = 0x02;
pub const advance_line = 0x03;
pub const set_file = 0x04;
pub const set_column = 0x05;
pub const negate_stmt = 0x06;
pub const set_basic_block = 0x07;
pub const const_add_pc = 0x08;
pub const fixed_advance_pc = 0x09;
pub const set_prologue_end = 0x0a;
pub const set_epilogue_begin = 0x0b;
pub const set_isa = 0x0c;
};
pub const LNE = struct {
pub const end_sequence = 0x01;
pub const set_address = 0x02;
pub const define_file = 0x03;
pub const set_discriminator = 0x04;
pub const lo_user = 0x80;
pub const hi_user = 0xff;
};
pub const UT = struct {
pub const compile = 0x01;
pub const @"type" = 0x02;
pub const partial = 0x03;
pub const skeleton = 0x04;
pub const split_compile = 0x05;
pub const split_type = 0x06;
pub const lo_user = 0x80;
pub const hi_user = 0xff;
};
pub const LNCT = struct {
pub const path = 0x1;
pub const directory_index = 0x2;
pub const timestamp = 0x3;
pub const size = 0x4;
pub const MD5 = 0x5;
pub const lo_user = 0x2000;
pub const hi_user = 0x3fff;
};
pub const RLE = struct {
pub const end_of_list = 0x00;
pub const base_addressx = 0x01;
pub const startx_endx = 0x02;
pub const startx_length = 0x03;
pub const offset_pair = 0x04;
pub const base_address = 0x05;
pub const start_end = 0x06;
pub const start_length = 0x07;
};
pub const CC = enum(u8) {
normal = 0x1,
program = 0x2,
nocall = 0x3,
pass_by_reference = 0x4,
pass_by_value = 0x5,
lo_user = 0x40,
hi_user = 0xff,
GNU_renesas_sh = 0x40,
GNU_borland_fastcall_i386 = 0x41,
};
pub const Format = enum { @"32", @"64" };
const PcRange = struct {
start: u64,
end: u64,
};
const Func = struct {
pc_range: ?PcRange,
name: ?[]const u8,
fn deinit(func: *Func, allocator: mem.Allocator) void {
if (func.name) |name| {
allocator.free(name);
}
}
};
const CompileUnit = struct {
version: u16,
is_64: bool,
die: *Die,
pc_range: ?PcRange,
str_offsets_base: usize,
addr_base: usize,
rnglists_base: usize,
loclists_base: usize,
};
const AbbrevTable = std.ArrayList(AbbrevTableEntry);
const AbbrevTableHeader = struct {
// offset from .debug_abbrev
offset: u64,
table: AbbrevTable,
fn deinit(header: *AbbrevTableHeader) void {
for (header.table.items) |*entry| {
entry.deinit();
}
header.table.deinit();
}
};
const AbbrevTableEntry = struct {
has_children: bool,
abbrev_code: u64,
tag_id: u64,
attrs: std.ArrayList(AbbrevAttr),
fn deinit(entry: *AbbrevTableEntry) void {
entry.attrs.deinit();
}
};
const AbbrevAttr = struct {
attr_id: u64,
form_id: u64,
/// Only valid if form_id is .implicit_const
payload: i64,
};
const FormValue = union(enum) {
Address: u64,
AddrOffset: usize,
Block: []u8,
Const: Constant,
ExprLoc: []u8,
Flag: bool,
SecOffset: u64,
Ref: u64,
RefAddr: u64,
String: []const u8,
StrPtr: u64,
StrOffset: usize,
LineStrPtr: u64,
LocListOffset: u64,
RangeListOffset: u64,
data16: [16]u8,
fn getString(fv: FormValue, di: DwarfInfo) ![]const u8 {
switch (fv) {
.String => |s| return s,
.StrPtr => |off| return di.getString(off),
.LineStrPtr => |off| return di.getLineString(off),
else => return badDwarf(),
}
}
fn getUInt(fv: FormValue, comptime U: type) !U {
switch (fv) {
.Const => |c| {
const int = try c.asUnsignedLe();
return math.cast(U, int) orelse return badDwarf();
},
.SecOffset => |x| return math.cast(U, x) orelse return badDwarf(),
else => return badDwarf(),
}
}
fn getData16(fv: FormValue) ![16]u8 {
switch (fv) {
.data16 => |d| return d,
else => return badDwarf(),
}
}
};
const Constant = struct {
payload: u64,
signed: bool,
fn asUnsignedLe(self: Constant) !u64 {
if (self.signed) return badDwarf();
return self.payload;
}
};
const Die = struct {
// Arena for Die's Attr's and FormValue's.
arena: std.heap.ArenaAllocator,
tag_id: u64,
has_children: bool,
attrs: std.ArrayListUnmanaged(Attr) = .{},
const Attr = struct {
id: u64,
value: FormValue,
};
fn deinit(self: *Die, allocator: mem.Allocator) void {
self.arena.deinit();
self.attrs.deinit(allocator);
}
fn getAttr(self: *const Die, id: u64) ?*const FormValue {
for (self.attrs.items) |*attr| {
if (attr.id == id) return &attr.value;
}
return null;
}
fn getAttrAddr(
self: *const Die,
di: *DwarfInfo,
id: u64,
compile_unit: CompileUnit,
) error{ InvalidDebugInfo, MissingDebugInfo }!u64 {
const form_value = self.getAttr(id) orelse return error.MissingDebugInfo;
return switch (form_value.*) {
FormValue.Address => |value| value,
FormValue.AddrOffset => |index| di.readDebugAddr(compile_unit, index),
else => error.InvalidDebugInfo,
};
}
fn getAttrSecOffset(self: *const Die, id: u64) !u64 {
const form_value = self.getAttr(id) orelse return error.MissingDebugInfo;
return form_value.getUInt(u64);
}
fn getAttrUnsignedLe(self: *const Die, id: u64) !u64 {
const form_value = self.getAttr(id) orelse return error.MissingDebugInfo;
return switch (form_value.*) {
FormValue.Const => |value| value.asUnsignedLe(),
else => error.InvalidDebugInfo,
};
}
fn getAttrRef(self: *const Die, id: u64) !u64 {
const form_value = self.getAttr(id) orelse return error.MissingDebugInfo;
return switch (form_value.*) {
FormValue.Ref => |value| value,
else => error.InvalidDebugInfo,
};
}
pub fn getAttrString(
self: *const Die,
di: *DwarfInfo,
id: u64,
opt_str: ?[]const u8,
compile_unit: CompileUnit,
) error{ InvalidDebugInfo, MissingDebugInfo }![]const u8 {
const form_value = self.getAttr(id) orelse return error.MissingDebugInfo;
switch (form_value.*) {
FormValue.String => |value| return value,
FormValue.StrPtr => |offset| return di.getString(offset),
FormValue.StrOffset => |index| {
const debug_str_offsets = di.section(.debug_str_offsets) orelse return badDwarf();
if (compile_unit.str_offsets_base == 0) return badDwarf();
if (compile_unit.is_64) {
const byte_offset = compile_unit.str_offsets_base + 8 * index;
if (byte_offset + 8 > debug_str_offsets.len) return badDwarf();
const offset = mem.readInt(u64, debug_str_offsets[byte_offset..][0..8], di.endian);
return getStringGeneric(opt_str, offset);
} else {
const byte_offset = compile_unit.str_offsets_base + 4 * index;
if (byte_offset + 4 > debug_str_offsets.len) return badDwarf();
const offset = mem.readInt(u32, debug_str_offsets[byte_offset..][0..4], di.endian);
return getStringGeneric(opt_str, offset);
}
},
FormValue.LineStrPtr => |offset| return di.getLineString(offset),
else => return badDwarf(),
}
}
};
const FileEntry = struct {
path: []const u8,
dir_index: u32 = 0,
mtime: u64 = 0,
size: u64 = 0,
md5: [16]u8 = [1]u8{0} ** 16,
};
const LineNumberProgram = struct {
address: u64,
file: usize,
line: i64,
column: u64,
version: u16,
is_stmt: bool,
basic_block: bool,
end_sequence: bool,
default_is_stmt: bool,
target_address: u64,
include_dirs: []const FileEntry,
prev_valid: bool,
prev_address: u64,
prev_file: usize,
prev_line: i64,
prev_column: u64,
prev_is_stmt: bool,
prev_basic_block: bool,
prev_end_sequence: bool,
// Reset the state machine following the DWARF specification
pub fn reset(self: *LineNumberProgram) void {
self.address = 0;
self.file = 1;
self.line = 1;
self.column = 0;
self.is_stmt = self.default_is_stmt;
self.basic_block = false;
self.end_sequence = false;
// Invalidate all the remaining fields
self.prev_valid = false;
self.prev_address = 0;
self.prev_file = undefined;
self.prev_line = undefined;
self.prev_column = undefined;
self.prev_is_stmt = undefined;
self.prev_basic_block = undefined;
self.prev_end_sequence = undefined;
}
pub fn init(
is_stmt: bool,
include_dirs: []const FileEntry,
target_address: u64,
version: u16,
) LineNumberProgram {
return LineNumberProgram{
.address = 0,
.file = 1,
.line = 1,
.column = 0,
.version = version,
.is_stmt = is_stmt,
.basic_block = false,
.end_sequence = false,
.include_dirs = include_dirs,
.default_is_stmt = is_stmt,
.target_address = target_address,
.prev_valid = false,
.prev_address = 0,
.prev_file = undefined,
.prev_line = undefined,
.prev_column = undefined,
.prev_is_stmt = undefined,
.prev_basic_block = undefined,
.prev_end_sequence = undefined,
};
}
pub fn checkLineMatch(
self: *LineNumberProgram,
allocator: mem.Allocator,
file_entries: []const FileEntry,
) !?debug.LineInfo {
if (self.prev_valid and
self.target_address >= self.prev_address and
self.target_address < self.address)
{
const file_index = if (self.version >= 5) self.prev_file else i: {
if (self.prev_file == 0) return missingDwarf();
break :i self.prev_file - 1;
};
if (file_index >= file_entries.len) return badDwarf();
const file_entry = &file_entries[file_index];
if (file_entry.dir_index >= self.include_dirs.len) return badDwarf();
const dir_name = self.include_dirs[file_entry.dir_index].path;
const file_name = try fs.path.join(allocator, &[_][]const u8{
dir_name, file_entry.path,
});
return debug.LineInfo{
.line = if (self.prev_line >= 0) @as(u64, @intCast(self.prev_line)) else 0,
.column = self.prev_column,
.file_name = file_name,
};
}
self.prev_valid = true;
self.prev_address = self.address;
self.prev_file = self.file;
self.prev_line = self.line;
self.prev_column = self.column;
self.prev_is_stmt = self.is_stmt;
self.prev_basic_block = self.basic_block;
self.prev_end_sequence = self.end_sequence;
return null;
}
};
fn readUnitLength(in_stream: anytype, endian: std.builtin.Endian, is_64: *bool) !u64 {
const first_32_bits = try in_stream.readInt(u32, endian);
is_64.* = (first_32_bits == 0xffffffff);
if (is_64.*) {
return in_stream.readInt(u64, endian);
} else {
if (first_32_bits >= 0xfffffff0) return badDwarf();
// TODO this cast should not be needed
return @as(u64, first_32_bits);
}
}
// TODO the nosuspends here are workarounds
fn readAllocBytes(allocator: mem.Allocator, in_stream: anytype, size: usize) ![]u8 {
const buf = try allocator.alloc(u8, size);
errdefer allocator.free(buf);
if ((try nosuspend in_stream.read(buf)) < size) return error.EndOfFile;
return buf;
}
// TODO the nosuspends here are workarounds
fn readAddress(in_stream: anytype, endian: std.builtin.Endian, is_64: bool) !u64 {
return nosuspend if (is_64)
try in_stream.readInt(u64, endian)
else
@as(u64, try in_stream.readInt(u32, endian));
}
fn parseFormValueBlockLen(allocator: mem.Allocator, in_stream: anytype, size: usize) !FormValue {
const buf = try readAllocBytes(allocator, in_stream, size);
return FormValue{ .Block = buf };
}
// TODO the nosuspends here are workarounds
fn parseFormValueBlock(allocator: mem.Allocator, in_stream: anytype, endian: std.builtin.Endian, size: usize) !FormValue {
const block_len = try nosuspend in_stream.readVarInt(usize, endian, size);
return parseFormValueBlockLen(allocator, in_stream, block_len);
}
fn parseFormValueConstant(in_stream: anytype, signed: bool, endian: std.builtin.Endian, comptime size: i32) !FormValue {
// TODO: Please forgive me, I've worked around zig not properly spilling some intermediate values here.
// `nosuspend` should be removed from all the function calls once it is fixed.
return FormValue{
.Const = Constant{
.signed = signed,
.payload = switch (size) {
1 => try nosuspend in_stream.readInt(u8, endian),
2 => try nosuspend in_stream.readInt(u16, endian),
4 => try nosuspend in_stream.readInt(u32, endian),
8 => try nosuspend in_stream.readInt(u64, endian),
-1 => blk: {
if (signed) {
const x = try nosuspend leb.readILEB128(i64, in_stream);
break :blk @as(u64, @bitCast(x));
} else {
const x = try nosuspend leb.readULEB128(u64, in_stream);
break :blk x;
}
},
else => @compileError("Invalid size"),
},
},
};
}
// TODO the nosuspends here are workarounds
fn parseFormValueRef(in_stream: anytype, endian: std.builtin.Endian, size: i32) !FormValue {
return FormValue{
.Ref = switch (size) {
1 => try nosuspend in_stream.readInt(u8, endian),
2 => try nosuspend in_stream.readInt(u16, endian),
4 => try nosuspend in_stream.readInt(u32, endian),
8 => try nosuspend in_stream.readInt(u64, endian),
-1 => try nosuspend leb.readULEB128(u64, in_stream),
else => unreachable,
},
};
}
// TODO the nosuspends here are workarounds
fn parseFormValue(allocator: mem.Allocator, in_stream: anytype, form_id: u64, endian: std.builtin.Endian, is_64: bool) anyerror!FormValue {
return switch (form_id) {
FORM.addr => FormValue{ .Address = try readAddress(in_stream, endian, @sizeOf(usize) == 8) },
FORM.addrx1 => return FormValue{ .AddrOffset = try in_stream.readInt(u8, endian) },
FORM.addrx2 => return FormValue{ .AddrOffset = try in_stream.readInt(u16, endian) },
FORM.addrx3 => return FormValue{ .AddrOffset = try in_stream.readInt(u24, endian) },
FORM.addrx4 => return FormValue{ .AddrOffset = try in_stream.readInt(u32, endian) },
FORM.addrx => return FormValue{ .AddrOffset = try nosuspend leb.readULEB128(usize, in_stream) },
FORM.block1 => parseFormValueBlock(allocator, in_stream, endian, 1),
FORM.block2 => parseFormValueBlock(allocator, in_stream, endian, 2),
FORM.block4 => parseFormValueBlock(allocator, in_stream, endian, 4),
FORM.block => {
const block_len = try nosuspend leb.readULEB128(usize, in_stream);
return parseFormValueBlockLen(allocator, in_stream, block_len);
},
FORM.data1 => parseFormValueConstant(in_stream, false, endian, 1),
FORM.data2 => parseFormValueConstant(in_stream, false, endian, 2),
FORM.data4 => parseFormValueConstant(in_stream, false, endian, 4),
FORM.data8 => parseFormValueConstant(in_stream, false, endian, 8),
FORM.data16 => {
var buf: [16]u8 = undefined;
if ((try nosuspend in_stream.readAll(&buf)) < 16) return error.EndOfFile;
return FormValue{ .data16 = buf };
},
FORM.udata, FORM.sdata => {
const signed = form_id == FORM.sdata;
return parseFormValueConstant(in_stream, signed, endian, -1);
},
FORM.exprloc => {
const size = try nosuspend leb.readULEB128(usize, in_stream);
const buf = try readAllocBytes(allocator, in_stream, size);
return FormValue{ .ExprLoc = buf };
},
FORM.flag => FormValue{ .Flag = (try nosuspend in_stream.readByte()) != 0 },
FORM.flag_present => FormValue{ .Flag = true },
FORM.sec_offset => FormValue{ .SecOffset = try readAddress(in_stream, endian, is_64) },
FORM.ref1 => parseFormValueRef(in_stream, endian, 1),
FORM.ref2 => parseFormValueRef(in_stream, endian, 2),
FORM.ref4 => parseFormValueRef(in_stream, endian, 4),
FORM.ref8 => parseFormValueRef(in_stream, endian, 8),
FORM.ref_udata => parseFormValueRef(in_stream, endian, -1),
FORM.ref_addr => FormValue{ .RefAddr = try readAddress(in_stream, endian, is_64) },
FORM.ref_sig8 => FormValue{ .Ref = try nosuspend in_stream.readInt(u64, endian) },
FORM.string => FormValue{ .String = try in_stream.readUntilDelimiterAlloc(allocator, 0, math.maxInt(usize)) },
FORM.strp => FormValue{ .StrPtr = try readAddress(in_stream, endian, is_64) },
FORM.strx1 => return FormValue{ .StrOffset = try in_stream.readInt(u8, endian) },
FORM.strx2 => return FormValue{ .StrOffset = try in_stream.readInt(u16, endian) },
FORM.strx3 => return FormValue{ .StrOffset = try in_stream.readInt(u24, endian) },
FORM.strx4 => return FormValue{ .StrOffset = try in_stream.readInt(u32, endian) },
FORM.strx => return FormValue{ .StrOffset = try nosuspend leb.readULEB128(usize, in_stream) },
FORM.line_strp => FormValue{ .LineStrPtr = try readAddress(in_stream, endian, is_64) },
FORM.indirect => {
const child_form_id = try nosuspend leb.readULEB128(u64, in_stream);
if (true) {
return parseFormValue(allocator, in_stream, child_form_id, endian, is_64);
}
const F = @TypeOf(async parseFormValue(allocator, in_stream, child_form_id, endian, is_64));
var frame = try allocator.create(F);
defer allocator.destroy(frame);
return await @asyncCall(frame, {}, parseFormValue, .{ allocator, in_stream, child_form_id, endian, is_64 });
},
FORM.implicit_const => FormValue{ .Const = Constant{ .signed = true, .payload = undefined } },
FORM.loclistx => return FormValue{ .LocListOffset = try nosuspend leb.readULEB128(u64, in_stream) },
FORM.rnglistx => return FormValue{ .RangeListOffset = try nosuspend leb.readULEB128(u64, in_stream) },
else => {
//std.debug.print("unrecognized form id: {x}\n", .{form_id});
return badDwarf();
},
};
}
fn getAbbrevTableEntry(abbrev_table: *const AbbrevTable, abbrev_code: u64) ?*const AbbrevTableEntry {
for (abbrev_table.items) |*table_entry| {
if (table_entry.abbrev_code == abbrev_code) return table_entry;
}
return null;
}
pub const DwarfSection = enum {
debug_info,
debug_abbrev,
debug_str,
debug_str_offsets,
debug_line,
debug_line_str,
debug_ranges,
debug_loclists,
debug_rnglists,
debug_addr,
debug_names,
debug_frame,
eh_frame,
eh_frame_hdr,
};
pub const DwarfInfo = struct {
pub const Section = struct {
data: []const u8,
owned: bool,
};
const num_sections = std.enums.directEnumArrayLen(DwarfSection, 0);
pub const SectionArray = [num_sections]?Section;
pub const null_section_array = [_]?Section{null} ** num_sections;
endian: std.builtin.Endian,
sections: SectionArray,
// Filled later by the initializer
abbrev_table_list: std.ArrayListUnmanaged(AbbrevTableHeader) = .{},
compile_unit_list: std.ArrayListUnmanaged(CompileUnit) = .{},
func_list: std.ArrayListUnmanaged(Func) = .{},
eh_frame_hdr: ?ExceptionFrameHeader = null,
// These lookup tables are only used if `eh_frame_hdr` is null
cie_map: std.AutoArrayHashMapUnmanaged(u64, CommonInformationEntry) = .{},
// Sorted by start_pc
fde_list: std.ArrayListUnmanaged(FrameDescriptionEntry) = .{},
is_macho: bool,
pub fn section(di: DwarfInfo, dwarf_section: DwarfSection) ?[]const u8 {
return if (di.sections[@intFromEnum(dwarf_section)]) |s| s.data else null;
}
pub fn deinit(di: *DwarfInfo, allocator: mem.Allocator) void {
for (di.sections) |opt_section| {
if (opt_section) |s| if (s.owned) allocator.free(s.data);
}
for (di.abbrev_table_list.items) |*abbrev| {
abbrev.deinit();
}
di.abbrev_table_list.deinit(allocator);
for (di.compile_unit_list.items) |*cu| {
cu.die.deinit(allocator);
allocator.destroy(cu.die);
}
di.compile_unit_list.deinit(allocator);
for (di.func_list.items) |*func| {
func.deinit(allocator);
}
di.func_list.deinit(allocator);
di.cie_map.deinit(allocator);
di.fde_list.deinit(allocator);
}
pub fn getSymbolName(di: *DwarfInfo, address: u64) ?[]const u8 {
for (di.func_list.items) |*func| {
if (func.pc_range) |range| {
if (address >= range.start and address < range.end) {
return func.name;
}
}
}
return null;
}
fn scanAllFunctions(di: *DwarfInfo, allocator: mem.Allocator) !void {
var stream = io.fixedBufferStream(di.section(.debug_info).?);
const in = stream.reader();
const seekable = &stream.seekableStream();
var this_unit_offset: u64 = 0;
var tmp_arena = std.heap.ArenaAllocator.init(allocator);
defer tmp_arena.deinit();
const arena = tmp_arena.allocator();
while (this_unit_offset < try seekable.getEndPos()) {
try seekable.seekTo(this_unit_offset);
var is_64: bool = undefined;
const unit_length = try readUnitLength(in, di.endian, &is_64);
if (unit_length == 0) return;
const next_offset = unit_length + (if (is_64) @as(usize, 12) else @as(usize, 4));
const version = try in.readInt(u16, di.endian);
if (version < 2 or version > 5) return badDwarf();
var address_size: u8 = undefined;
var debug_abbrev_offset: u64 = undefined;
if (version >= 5) {
const unit_type = try in.readInt(u8, di.endian);
if (unit_type != UT.compile) return badDwarf();
address_size = try in.readByte();
debug_abbrev_offset = if (is_64)
try in.readInt(u64, di.endian)
else
try in.readInt(u32, di.endian);
} else {
debug_abbrev_offset = if (is_64)
try in.readInt(u64, di.endian)
else
try in.readInt(u32, di.endian);
address_size = try in.readByte();
}
if (address_size != @sizeOf(usize)) return badDwarf();
const compile_unit_pos = try seekable.getPos();
const abbrev_table = try di.getAbbrevTable(allocator, debug_abbrev_offset);
try seekable.seekTo(compile_unit_pos);
const next_unit_pos = this_unit_offset + next_offset;
var compile_unit: CompileUnit = undefined;
while ((try seekable.getPos()) < next_unit_pos) {
var die_obj = (try di.parseDie(arena, in, abbrev_table, is_64)) orelse continue;
const after_die_offset = try seekable.getPos();
switch (die_obj.tag_id) {
TAG.compile_unit => {
compile_unit = .{
.version = version,
.is_64 = is_64,
.die = &die_obj,
.pc_range = null,
.str_offsets_base = if (die_obj.getAttr(AT.str_offsets_base)) |fv| try fv.getUInt(usize) else 0,
.addr_base = if (die_obj.getAttr(AT.addr_base)) |fv| try fv.getUInt(usize) else 0,
.rnglists_base = if (die_obj.getAttr(AT.rnglists_base)) |fv| try fv.getUInt(usize) else 0,
.loclists_base = if (die_obj.getAttr(AT.loclists_base)) |fv| try fv.getUInt(usize) else 0,
};
},
TAG.subprogram, TAG.inlined_subroutine, TAG.subroutine, TAG.entry_point => {
const fn_name = x: {
var depth: i32 = 3;
var this_die_obj = die_obj;
// Prevent endless loops
while (depth > 0) : (depth -= 1) {
if (this_die_obj.getAttr(AT.name)) |_| {
const name = try this_die_obj.getAttrString(di, AT.name, di.section(.debug_str), compile_unit);
break :x try allocator.dupe(u8, name);
} else if (this_die_obj.getAttr(AT.abstract_origin)) |_| {
// Follow the DIE it points to and repeat
const ref_offset = try this_die_obj.getAttrRef(AT.abstract_origin);
if (ref_offset > next_offset) return badDwarf();
try seekable.seekTo(this_unit_offset + ref_offset);
this_die_obj = (try di.parseDie(
arena,
in,
abbrev_table,
is_64,
)) orelse return badDwarf();
} else if (this_die_obj.getAttr(AT.specification)) |_| {
// Follow the DIE it points to and repeat
const ref_offset = try this_die_obj.getAttrRef(AT.specification);
if (ref_offset > next_offset) return badDwarf();
try seekable.seekTo(this_unit_offset + ref_offset);
this_die_obj = (try di.parseDie(
arena,
in,
abbrev_table,
is_64,
)) orelse return badDwarf();
} else {
break :x null;
}
}
break :x null;
};
var found_range = if (die_obj.getAttrAddr(di, AT.low_pc, compile_unit)) |low_pc| blk: {
if (die_obj.getAttr(AT.high_pc)) |high_pc_value| {
const pc_end = switch (high_pc_value.*) {
FormValue.Address => |value| value,
FormValue.Const => |value| b: {
const offset = try value.asUnsignedLe();
break :b (low_pc + offset);
},
else => return badDwarf(),
};
try di.func_list.append(allocator, Func{
.name = fn_name,
.pc_range = .{
.start = low_pc,
.end = pc_end,
},
});
}
break :blk true;
} else |err| blk: {
if (err != error.MissingDebugInfo) return err;
break :blk false;
};
if (die_obj.getAttr(AT.ranges)) |ranges_value| blk: {
var iter = DebugRangeIterator.init(ranges_value, di, &compile_unit) catch |err| {
if (err != error.MissingDebugInfo) return err;
break :blk;
};
while (try iter.next()) |range| {
found_range = true;
try di.func_list.append(allocator, Func{
.name = fn_name,
.pc_range = .{
.start = range.start_addr,
.end = range.end_addr,
},
});
}
}
if (!found_range) {
try di.func_list.append(allocator, Func{
.name = fn_name,
.pc_range = null,
});
}
},
else => {},
}
try seekable.seekTo(after_die_offset);
}
this_unit_offset += next_offset;
}
}
fn scanAllCompileUnits(di: *DwarfInfo, allocator: mem.Allocator) !void {
var stream = io.fixedBufferStream(di.section(.debug_info).?);
const in = &stream.reader();
const seekable = &stream.seekableStream();
var this_unit_offset: u64 = 0;
while (this_unit_offset < try seekable.getEndPos()) {
try seekable.seekTo(this_unit_offset);
var is_64: bool = undefined;
const unit_length = try readUnitLength(in, di.endian, &is_64);
if (unit_length == 0) return;
const next_offset = unit_length + (if (is_64) @as(usize, 12) else @as(usize, 4));
const version = try in.readInt(u16, di.endian);
if (version < 2 or version > 5) return badDwarf();
var address_size: u8 = undefined;
var debug_abbrev_offset: u64 = undefined;
if (version >= 5) {
const unit_type = try in.readInt(u8, di.endian);
if (unit_type != UT.compile) return badDwarf();
address_size = try in.readByte();
debug_abbrev_offset = if (is_64)
try in.readInt(u64, di.endian)
else
try in.readInt(u32, di.endian);
} else {
debug_abbrev_offset = if (is_64)
try in.readInt(u64, di.endian)
else
try in.readInt(u32, di.endian);
address_size = try in.readByte();
}
if (address_size != @sizeOf(usize)) return badDwarf();
const compile_unit_pos = try seekable.getPos();
const abbrev_table = try di.getAbbrevTable(allocator, debug_abbrev_offset);
try seekable.seekTo(compile_unit_pos);
const compile_unit_die = try allocator.create(Die);
errdefer allocator.destroy(compile_unit_die);
compile_unit_die.* = (try di.parseDie(allocator, in, abbrev_table, is_64)) orelse
return badDwarf();
if (compile_unit_die.tag_id != TAG.compile_unit) return badDwarf();
var compile_unit: CompileUnit = .{
.version = version,
.is_64 = is_64,
.pc_range = null,
.die = compile_unit_die,
.str_offsets_base = if (compile_unit_die.getAttr(AT.str_offsets_base)) |fv| try fv.getUInt(usize) else 0,
.addr_base = if (compile_unit_die.getAttr(AT.addr_base)) |fv| try fv.getUInt(usize) else 0,
.rnglists_base = if (compile_unit_die.getAttr(AT.rnglists_base)) |fv| try fv.getUInt(usize) else 0,
.loclists_base = if (compile_unit_die.getAttr(AT.loclists_base)) |fv| try fv.getUInt(usize) else 0,
};
compile_unit.pc_range = x: {
if (compile_unit_die.getAttrAddr(di, AT.low_pc, compile_unit)) |low_pc| {
if (compile_unit_die.getAttr(AT.high_pc)) |high_pc_value| {
const pc_end = switch (high_pc_value.*) {
FormValue.Address => |value| value,
FormValue.Const => |value| b: {
const offset = try value.asUnsignedLe();
break :b (low_pc + offset);
},
else => return badDwarf(),
};
break :x PcRange{
.start = low_pc,
.end = pc_end,
};
} else {
break :x null;
}
} else |err| {
if (err != error.MissingDebugInfo) return err;
break :x null;
}
};
try di.compile_unit_list.append(allocator, compile_unit);
this_unit_offset += next_offset;
}
}
const DebugRangeIterator = struct {
base_address: u64,
section_type: DwarfSection,
di: *DwarfInfo,
compile_unit: *const CompileUnit,
stream: io.FixedBufferStream([]const u8),
pub fn init(ranges_value: *const FormValue, di: *DwarfInfo, compile_unit: *const CompileUnit) !@This() {
const section_type = if (compile_unit.version >= 5) DwarfSection.debug_rnglists else DwarfSection.debug_ranges;
const debug_ranges = di.section(section_type) orelse return error.MissingDebugInfo;
const ranges_offset = switch (ranges_value.*) {
.SecOffset => |off| off,
.Const => |c| try c.asUnsignedLe(),
.RangeListOffset => |idx| off: {
if (compile_unit.is_64) {
const offset_loc = @as(usize, @intCast(compile_unit.rnglists_base + 8 * idx));
if (offset_loc + 8 > debug_ranges.len) return badDwarf();
const offset = mem.readInt(u64, debug_ranges[offset_loc..][0..8], di.endian);
break :off compile_unit.rnglists_base + offset;
} else {
const offset_loc = @as(usize, @intCast(compile_unit.rnglists_base + 4 * idx));
if (offset_loc + 4 > debug_ranges.len) return badDwarf();
const offset = mem.readInt(u32, debug_ranges[offset_loc..][0..4], di.endian);
break :off compile_unit.rnglists_base + offset;
}
},
else => return badDwarf(),
};
var stream = io.fixedBufferStream(debug_ranges);
try stream.seekTo(ranges_offset);
// All the addresses in the list are relative to the value
// specified by DW_AT.low_pc or to some other value encoded
// in the list itself.
// If no starting value is specified use zero.
var base_address = compile_unit.die.getAttrAddr(di, AT.low_pc, compile_unit.*) catch |err| switch (err) {
error.MissingDebugInfo => @as(u64, 0), // TODO https://github.com/ziglang/zig/issues/11135
else => return err,
};
return .{
.base_address = base_address,
.section_type = section_type,
.di = di,
.compile_unit = compile_unit,
.stream = stream,
};
}
// Returns the next range in the list, or null if the end was reached.
pub fn next(self: *@This()) !?struct { start_addr: u64, end_addr: u64 } {
const in = self.stream.reader();
switch (self.section_type) {
.debug_rnglists => {
const kind = try in.readByte();
switch (kind) {
RLE.end_of_list => return null,
RLE.base_addressx => {
const index = try leb.readULEB128(usize, in);
self.base_address = try self.di.readDebugAddr(self.compile_unit.*, index);
return try self.next();
},
RLE.startx_endx => {
const start_index = try leb.readULEB128(usize, in);
const start_addr = try self.di.readDebugAddr(self.compile_unit.*, start_index);
const end_index = try leb.readULEB128(usize, in);
const end_addr = try self.di.readDebugAddr(self.compile_unit.*, end_index);
return .{
.start_addr = start_addr,
.end_addr = end_addr,
};
},
RLE.startx_length => {
const start_index = try leb.readULEB128(usize, in);
const start_addr = try self.di.readDebugAddr(self.compile_unit.*, start_index);
const len = try leb.readULEB128(usize, in);
const end_addr = start_addr + len;
return .{
.start_addr = start_addr,
.end_addr = end_addr,
};
},
RLE.offset_pair => {
const start_addr = try leb.readULEB128(usize, in);
const end_addr = try leb.readULEB128(usize, in);
// This is the only kind that uses the base address
return .{
.start_addr = self.base_address + start_addr,
.end_addr = self.base_address + end_addr,
};
},
RLE.base_address => {
self.base_address = try in.readInt(usize, self.di.endian);
return try self.next();
},
RLE.start_end => {
const start_addr = try in.readInt(usize, self.di.endian);
const end_addr = try in.readInt(usize, self.di.endian);
return .{
.start_addr = start_addr,
.end_addr = end_addr,
};
},
RLE.start_length => {
const start_addr = try in.readInt(usize, self.di.endian);
const len = try leb.readULEB128(usize, in);
const end_addr = start_addr + len;
return .{
.start_addr = start_addr,
.end_addr = end_addr,
};
},
else => return badDwarf(),
}
},
.debug_ranges => {
const start_addr = try in.readInt(usize, self.di.endian);
const end_addr = try in.readInt(usize, self.di.endian);
if (start_addr == 0 and end_addr == 0) return null;
// This entry selects a new value for the base address
if (start_addr == math.maxInt(usize)) {
self.base_address = end_addr;
return try self.next();
}
return .{
.start_addr = self.base_address + start_addr,
.end_addr = self.base_address + end_addr,
};
},
else => unreachable,
}
}
};
pub fn findCompileUnit(di: *DwarfInfo, target_address: u64) !*const CompileUnit {
for (di.compile_unit_list.items) |*compile_unit| {
if (compile_unit.pc_range) |range| {
if (target_address >= range.start and target_address < range.end) return compile_unit;
}
const ranges_value = compile_unit.die.getAttr(AT.ranges) orelse continue;
var iter = DebugRangeIterator.init(ranges_value, di, compile_unit) catch continue;
while (try iter.next()) |range| {
if (target_address >= range.start_addr and target_address < range.end_addr) return compile_unit;
}
}
return missingDwarf();
}
/// Gets an already existing AbbrevTable given the abbrev_offset, or if not found,
/// seeks in the stream and parses it.
fn getAbbrevTable(di: *DwarfInfo, allocator: mem.Allocator, abbrev_offset: u64) !*const AbbrevTable {
for (di.abbrev_table_list.items) |*header| {
if (header.offset == abbrev_offset) {
return &header.table;
}
}
try di.abbrev_table_list.append(allocator, AbbrevTableHeader{
.offset = abbrev_offset,
.table = try di.parseAbbrevTable(allocator, abbrev_offset),
});
return &di.abbrev_table_list.items[di.abbrev_table_list.items.len - 1].table;
}
fn parseAbbrevTable(di: *DwarfInfo, allocator: mem.Allocator, offset: u64) !AbbrevTable {
var stream = io.fixedBufferStream(di.section(.debug_abbrev).?);
const in = &stream.reader();
const seekable = &stream.seekableStream();
try seekable.seekTo(offset);
var result = AbbrevTable.init(allocator);
errdefer {
for (result.items) |*entry| {
entry.attrs.deinit();
}
result.deinit();
}
while (true) {
const abbrev_code = try leb.readULEB128(u64, in);
if (abbrev_code == 0) return result;
try result.append(AbbrevTableEntry{
.abbrev_code = abbrev_code,
.tag_id = try leb.readULEB128(u64, in),
.has_children = (try in.readByte()) == CHILDREN.yes,
.attrs = std.ArrayList(AbbrevAttr).init(allocator),
});
const attrs = &result.items[result.items.len - 1].attrs;
while (true) {
const attr_id = try leb.readULEB128(u64, in);
const form_id = try leb.readULEB128(u64, in);
if (attr_id == 0 and form_id == 0) break;
// DW_FORM_implicit_const stores its value immediately after the attribute pair :(
const payload = if (form_id == FORM.implicit_const) try leb.readILEB128(i64, in) else undefined;
try attrs.append(AbbrevAttr{
.attr_id = attr_id,
.form_id = form_id,
.payload = payload,
});
}
}
}
fn parseDie(
di: *DwarfInfo,
allocator: mem.Allocator,
in_stream: anytype,
abbrev_table: *const AbbrevTable,
is_64: bool,
) !?Die {
const abbrev_code = try leb.readULEB128(u64, in_stream);
if (abbrev_code == 0) return null;
const table_entry = getAbbrevTableEntry(abbrev_table, abbrev_code) orelse return badDwarf();
var result = Die{
// Lives as long as the Die.
.arena = std.heap.ArenaAllocator.init(allocator),
.tag_id = table_entry.tag_id,
.has_children = table_entry.has_children,
};
try result.attrs.resize(allocator, table_entry.attrs.items.len);
for (table_entry.attrs.items, 0..) |attr, i| {
result.attrs.items[i] = Die.Attr{
.id = attr.attr_id,
.value = try parseFormValue(
result.arena.allocator(),
in_stream,
attr.form_id,
di.endian,
is_64,
),
};
if (attr.form_id == FORM.implicit_const) {
result.attrs.items[i].value.Const.payload = @as(u64, @bitCast(attr.payload));
}
}
return result;
}
pub fn getLineNumberInfo(
di: *DwarfInfo,
allocator: mem.Allocator,
compile_unit: CompileUnit,
target_address: u64,
) !debug.LineInfo {
var stream = io.fixedBufferStream(di.section(.debug_line).?);
const in = &stream.reader();
const seekable = &stream.seekableStream();
const compile_unit_cwd = try compile_unit.die.getAttrString(di, AT.comp_dir, di.section(.debug_line_str), compile_unit);
const line_info_offset = try compile_unit.die.getAttrSecOffset(AT.stmt_list);
try seekable.seekTo(line_info_offset);
var is_64: bool = undefined;
const unit_length = try readUnitLength(in, di.endian, &is_64);
if (unit_length == 0) {
return missingDwarf();
}
const next_offset = unit_length + (if (is_64) @as(usize, 12) else @as(usize, 4));
const version = try in.readInt(u16, di.endian);
if (version < 2) return badDwarf();
var addr_size: u8 = if (is_64) 8 else 4;
var seg_size: u8 = 0;
if (version >= 5) {
addr_size = try in.readByte();
seg_size = try in.readByte();
}
const prologue_length = if (is_64) try in.readInt(u64, di.endian) else try in.readInt(u32, di.endian);
const prog_start_offset = (try seekable.getPos()) + prologue_length;
const minimum_instruction_length = try in.readByte();
if (minimum_instruction_length == 0) return badDwarf();
if (version >= 4) {
// maximum_operations_per_instruction
_ = try in.readByte();
}
const default_is_stmt = (try in.readByte()) != 0;
const line_base = try in.readByteSigned();
const line_range = try in.readByte();
if (line_range == 0) return badDwarf();
const opcode_base = try in.readByte();
const standard_opcode_lengths = try allocator.alloc(u8, opcode_base - 1);
defer allocator.free(standard_opcode_lengths);
{
var i: usize = 0;
while (i < opcode_base - 1) : (i += 1) {
standard_opcode_lengths[i] = try in.readByte();
}
}
var tmp_arena = std.heap.ArenaAllocator.init(allocator);
defer tmp_arena.deinit();
const arena = tmp_arena.allocator();
var include_directories = std.ArrayList(FileEntry).init(arena);
var file_entries = std.ArrayList(FileEntry).init(arena);
if (version < 5) {
try include_directories.append(.{ .path = compile_unit_cwd });
while (true) {
const dir = try in.readUntilDelimiterAlloc(arena, 0, math.maxInt(usize));
if (dir.len == 0) break;
try include_directories.append(.{ .path = dir });
}
while (true) {
const file_name = try in.readUntilDelimiterAlloc(arena, 0, math.maxInt(usize));
if (file_name.len == 0) break;
const dir_index = try leb.readULEB128(u32, in);
const mtime = try leb.readULEB128(u64, in);
const size = try leb.readULEB128(u64, in);
try file_entries.append(FileEntry{
.path = file_name,
.dir_index = dir_index,
.mtime = mtime,
.size = size,
});
}
} else {
const FileEntFmt = struct {
content_type_code: u8,
form_code: u16,
};
{
var dir_ent_fmt_buf: [10]FileEntFmt = undefined;
const directory_entry_format_count = try in.readByte();
if (directory_entry_format_count > dir_ent_fmt_buf.len) return badDwarf();
for (dir_ent_fmt_buf[0..directory_entry_format_count]) |*ent_fmt| {
ent_fmt.* = .{
.content_type_code = try leb.readULEB128(u8, in),
.form_code = try leb.readULEB128(u16, in),
};
}
const directories_count = try leb.readULEB128(usize, in);
try include_directories.ensureUnusedCapacity(directories_count);
{
var i: usize = 0;
while (i < directories_count) : (i += 1) {
var e: FileEntry = .{ .path = &.{} };
for (dir_ent_fmt_buf[0..directory_entry_format_count]) |ent_fmt| {
const form_value = try parseFormValue(
arena,
in,
ent_fmt.form_code,
di.endian,
is_64,
);
switch (ent_fmt.content_type_code) {
LNCT.path => e.path = try form_value.getString(di.*),
LNCT.directory_index => e.dir_index = try form_value.getUInt(u32),
LNCT.timestamp => e.mtime = try form_value.getUInt(u64),
LNCT.size => e.size = try form_value.getUInt(u64),
LNCT.MD5 => e.md5 = try form_value.getData16(),
else => continue,
}
}
include_directories.appendAssumeCapacity(e);
}
}
}
var file_ent_fmt_buf: [10]FileEntFmt = undefined;
const file_name_entry_format_count = try in.readByte();
if (file_name_entry_format_count > file_ent_fmt_buf.len) return badDwarf();
for (file_ent_fmt_buf[0..file_name_entry_format_count]) |*ent_fmt| {
ent_fmt.* = .{
.content_type_code = try leb.readULEB128(u8, in),
.form_code = try leb.readULEB128(u16, in),
};
}
const file_names_count = try leb.readULEB128(usize, in);
try file_entries.ensureUnusedCapacity(file_names_count);
{
var i: usize = 0;
while (i < file_names_count) : (i += 1) {
var e: FileEntry = .{ .path = &.{} };
for (file_ent_fmt_buf[0..file_name_entry_format_count]) |ent_fmt| {
const form_value = try parseFormValue(
arena,
in,
ent_fmt.form_code,
di.endian,
is_64,
);
switch (ent_fmt.content_type_code) {
LNCT.path => e.path = try form_value.getString(di.*),
LNCT.directory_index => e.dir_index = try form_value.getUInt(u32),
LNCT.timestamp => e.mtime = try form_value.getUInt(u64),
LNCT.size => e.size = try form_value.getUInt(u64),
LNCT.MD5 => e.md5 = try form_value.getData16(),
else => continue,
}
}
file_entries.appendAssumeCapacity(e);
}
}
}
var prog = LineNumberProgram.init(
default_is_stmt,
include_directories.items,
target_address,
version,
);
try seekable.seekTo(prog_start_offset);
const next_unit_pos = line_info_offset + next_offset;
while ((try seekable.getPos()) < next_unit_pos) {
const opcode = try in.readByte();
if (opcode == LNS.extended_op) {
const op_size = try leb.readULEB128(u64, in);
if (op_size < 1) return badDwarf();
var sub_op = try in.readByte();
switch (sub_op) {
LNE.end_sequence => {
prog.end_sequence = true;
if (try prog.checkLineMatch(allocator, file_entries.items)) |info| return info;
prog.reset();
},
LNE.set_address => {
const addr = try in.readInt(usize, di.endian);
prog.address = addr;
},
LNE.define_file => {
const path = try in.readUntilDelimiterAlloc(arena, 0, math.maxInt(usize));
const dir_index = try leb.readULEB128(u32, in);
const mtime = try leb.readULEB128(u64, in);
const size = try leb.readULEB128(u64, in);
try file_entries.append(FileEntry{
.path = path,
.dir_index = dir_index,
.mtime = mtime,
.size = size,
});
},
else => {
const fwd_amt = math.cast(isize, op_size - 1) orelse return badDwarf();
try seekable.seekBy(fwd_amt);
},
}
} else if (opcode >= opcode_base) {
// special opcodes
const adjusted_opcode = opcode - opcode_base;
const inc_addr = minimum_instruction_length * (adjusted_opcode / line_range);
const inc_line = @as(i32, line_base) + @as(i32, adjusted_opcode % line_range);
prog.line += inc_line;
prog.address += inc_addr;
if (try prog.checkLineMatch(allocator, file_entries.items)) |info| return info;
prog.basic_block = false;
} else {
switch (opcode) {
LNS.copy => {
if (try prog.checkLineMatch(allocator, file_entries.items)) |info| return info;
prog.basic_block = false;
},
LNS.advance_pc => {
const arg = try leb.readULEB128(usize, in);
prog.address += arg * minimum_instruction_length;
},
LNS.advance_line => {
const arg = try leb.readILEB128(i64, in);
prog.line += arg;
},
LNS.set_file => {
const arg = try leb.readULEB128(usize, in);
prog.file = arg;
},
LNS.set_column => {
const arg = try leb.readULEB128(u64, in);
prog.column = arg;
},
LNS.negate_stmt => {
prog.is_stmt = !prog.is_stmt;
},
LNS.set_basic_block => {
prog.basic_block = true;
},
LNS.const_add_pc => {
const inc_addr = minimum_instruction_length * ((255 - opcode_base) / line_range);
prog.address += inc_addr;
},
LNS.fixed_advance_pc => {
const arg = try in.readInt(u16, di.endian);
prog.address += arg;
},
LNS.set_prologue_end => {},
else => {
if (opcode - 1 >= standard_opcode_lengths.len) return badDwarf();
const len_bytes = standard_opcode_lengths[opcode - 1];
try seekable.seekBy(len_bytes);
},
}
}
}
return missingDwarf();
}
fn getString(di: DwarfInfo, offset: u64) ![]const u8 {
return getStringGeneric(di.section(.debug_str), offset);
}
fn getLineString(di: DwarfInfo, offset: u64) ![]const u8 {
return getStringGeneric(di.section(.debug_line_str), offset);
}
fn readDebugAddr(di: DwarfInfo, compile_unit: CompileUnit, index: u64) !u64 {
const debug_addr = di.section(.debug_addr) orelse return badDwarf();
// addr_base points to the first item after the header, however we
// need to read the header to know the size of each item. Empirically,
// it may disagree with is_64 on the compile unit.
// The header is 8 or 12 bytes depending on is_64.
if (compile_unit.addr_base < 8) return badDwarf();
const version = mem.readInt(u16, debug_addr[compile_unit.addr_base - 4 ..][0..2], di.endian);
if (version != 5) return badDwarf();
const addr_size = debug_addr[compile_unit.addr_base - 2];
const seg_size = debug_addr[compile_unit.addr_base - 1];
const byte_offset = @as(usize, @intCast(compile_unit.addr_base + (addr_size + seg_size) * index));
if (byte_offset + addr_size > debug_addr.len) return badDwarf();
return switch (addr_size) {
1 => debug_addr[byte_offset],
2 => mem.readInt(u16, debug_addr[byte_offset..][0..2], di.endian),
4 => mem.readInt(u32, debug_addr[byte_offset..][0..4], di.endian),
8 => mem.readInt(u64, debug_addr[byte_offset..][0..8], di.endian),
else => badDwarf(),
};
}
pub fn scanAllUnwindInfo(di: *DwarfInfo, allocator: mem.Allocator, binary_mem: []const u8) !void {
if (di.section(.eh_frame_hdr)) |eh_frame_hdr| blk: {
var stream = io.fixedBufferStream(eh_frame_hdr);
const reader = stream.reader();
const version = try reader.readByte();
if (version != 1) break :blk;
const eh_frame_ptr_enc = try reader.readByte();
if (eh_frame_ptr_enc == EH.PE.omit) break :blk;
const fde_count_enc = try reader.readByte();
if (fde_count_enc == EH.PE.omit) break :blk;
const table_enc = try reader.readByte();
if (table_enc == EH.PE.omit) break :blk;
const eh_frame_ptr = std.math.cast(usize, try readEhPointer(reader, eh_frame_ptr_enc, @sizeOf(usize), .{
.pc_rel_base = @intFromPtr(&eh_frame_hdr[stream.pos]),
.follow_indirect = true,
}, builtin.cpu.arch.endian()) orelse return badDwarf()) orelse return badDwarf();
const fde_count = std.math.cast(usize, try readEhPointer(reader, fde_count_enc, @sizeOf(usize), .{
.pc_rel_base = @intFromPtr(&eh_frame_hdr[stream.pos]),
.follow_indirect = true,
}, builtin.cpu.arch.endian()) orelse return badDwarf()) orelse return badDwarf();
const entry_size = try ExceptionFrameHeader.entrySize(table_enc);
const entries_len = fde_count * entry_size;
if (entries_len > eh_frame_hdr.len - stream.pos) return badDwarf();
di.eh_frame_hdr = .{
.eh_frame_ptr = eh_frame_ptr,
.table_enc = table_enc,
.fde_count = fde_count,
.entries = eh_frame_hdr[stream.pos..][0..entries_len],
};
// No need to scan .eh_frame, we have a binary search table already
return;
}
const frame_sections = [2]DwarfSection{ .eh_frame, .debug_frame };
for (frame_sections) |frame_section| {
if (di.section(frame_section)) |eh_frame| {
var stream = io.fixedBufferStream(eh_frame);
while (stream.pos < stream.buffer.len) {
const entry_header = try EntryHeader.read(&stream, frame_section, di.endian);
switch (entry_header.type) {
.cie => {
const cie = try CommonInformationEntry.parse(
entry_header.entry_bytes,
-@as(i64, @intCast(@intFromPtr(binary_mem.ptr))),
true,
frame_section,
entry_header.length_offset,
@sizeOf(usize),
di.endian,
);
try di.cie_map.put(allocator, entry_header.length_offset, cie);
},
.fde => |cie_offset| {
const cie = di.cie_map.get(cie_offset) orelse return badDwarf();
const fde = try FrameDescriptionEntry.parse(
entry_header.entry_bytes,
-@as(i64, @intCast(@intFromPtr(binary_mem.ptr))),
true,
cie,
@sizeOf(usize),
di.endian,
);
try di.fde_list.append(allocator, fde);
},
.terminator => break,
}
}
std.mem.sort(FrameDescriptionEntry, di.fde_list.items, {}, struct {
fn lessThan(ctx: void, a: FrameDescriptionEntry, b: FrameDescriptionEntry) bool {
_ = ctx;
return a.pc_begin < b.pc_begin;
}
}.lessThan);
}
}
}
pub fn unwindFrame(di: *const DwarfInfo, allocator: mem.Allocator, context: *UnwindContext, module_base_address: usize) !usize {
if (!comptime abi.isSupportedArch(builtin.target.cpu.arch)) return error.UnsupportedCpuArchitecture;
if (context.pc == 0) return 0;
// TODO: Handle unwinding from a signal frame (ie. use_prev_instr in libunwind)
// Find the FDE and CIE
var cie: CommonInformationEntry = undefined;
var fde: FrameDescriptionEntry = undefined;
// In order to support reading .eh_frame from the ELF file (vs using the already-mapped section),
// scanAllUnwindInfo has already mapped any pc-relative offsets such that they we be relative to zero
// instead of the actual base address of the module. When using .eh_frame_hdr, PC can be used directly
// as pointers will be decoded relative to the alreayd-mapped .eh_frame.
var mapped_pc: usize = undefined;
if (di.eh_frame_hdr) |header| {
const eh_frame_len = if (di.section(.eh_frame)) |eh_frame| eh_frame.len else null;
mapped_pc = context.pc;
try header.findEntry(
context.isValidMemory,
eh_frame_len,
@intFromPtr(di.section(.eh_frame_hdr).?.ptr),
mapped_pc,
&cie,
&fde,
);
} else {
mapped_pc = context.pc - module_base_address;
const index = std.sort.binarySearch(FrameDescriptionEntry, mapped_pc, di.fde_list.items, {}, struct {
pub fn compareFn(_: void, pc: usize, mid_item: FrameDescriptionEntry) std.math.Order {
if (pc < mid_item.pc_begin) {
return .lt;
} else {
const range_end = mid_item.pc_begin + mid_item.pc_range;
if (pc < range_end) {
return .eq;
}
return .gt;
}
}
}.compareFn);
fde = if (index) |i| di.fde_list.items[i] else return error.MissingFDE;
cie = di.cie_map.get(fde.cie_length_offset) orelse return error.MissingCIE;
}
context.vm.reset();
context.reg_ctx.eh_frame = cie.version != 4;
_ = try context.vm.runToNative(allocator, mapped_pc, cie, fde);
const row = &context.vm.current_row;
context.cfa = switch (row.cfa.rule) {
.val_offset => |offset| blk: {
const register = row.cfa.register orelse return error.InvalidCFARule;
const value = mem.readIntSliceNative(usize, try abi.regBytes(&context.ucontext, register, context.reg_ctx));
break :blk try call_frame.applyOffset(value, offset);
},
.expression => |expression| {
// TODO: Evaluate expression
_ = expression;
return error.UnimplementedTODO;
},
else => return error.InvalidCFARule,
};
if (!context.isValidMemory(context.cfa.?)) return error.InvalidCFA;
// Update the context with the previous frame's values
var next_ucontext = context.ucontext;
var has_next_ip = false;
for (context.vm.rowColumns(row.*)) |column| {
if (column.register) |register| {
const dest = try abi.regBytes(&next_ucontext, register, context.reg_ctx);
if (register == cie.return_address_register) {
has_next_ip = column.rule != .undefined;
}
try column.resolveValue(context.*, dest);
}
}
context.ucontext = next_ucontext;
if (has_next_ip) {
context.pc = mem.readIntSliceNative(usize, try abi.regBytes(&context.ucontext, comptime abi.ipRegNum(), context.reg_ctx));
} else {
context.pc = 0;
}
mem.writeIntSliceNative(usize, try abi.regBytes(&context.ucontext, abi.spRegNum(context.reg_ctx), context.reg_ctx), context.cfa.?);
// The call instruction will have pushed the address of the instruction that follows the call as the return address
// However, this return address may be past the end of the function if the caller was `noreturn`.
// TODO: Check this on non-x86_64
const return_address = context.pc;
if (context.pc > 0) context.pc -= 1;
return return_address;
}
};
pub const UnwindContext = struct {
cfa: ?usize,
pc: usize,
ucontext: os.ucontext_t,
reg_ctx: abi.RegisterContext,
isValidMemory: *const fn (address: usize) bool,
vm: call_frame.VirtualMachine = .{},
pub fn init(ucontext: *const os.ucontext_t, isValidMemory: *const fn (address: usize) bool) !UnwindContext {
const pc = mem.readIntSliceNative(usize, try abi.regBytes(ucontext, abi.ipRegNum(), null));
return .{
.cfa = null,
.pc = pc,
.ucontext = ucontext.*,
.reg_ctx = undefined,
.isValidMemory = isValidMemory,
};
}
pub fn deinit(self: *UnwindContext, allocator: mem.Allocator) void {
self.vm.deinit(allocator);
}
pub fn getFp(self: *const UnwindContext) !usize {
return mem.readIntSliceNative(usize, try abi.regBytes(&self.ucontext, abi.fpRegNum(self.reg_ctx), self.reg_ctx));
}
};
/// Initialize DWARF info. The caller has the responsibility to initialize most
/// the DwarfInfo fields before calling. `binary_mem` is the raw bytes of the
/// main binary file (not the secondary debug info file).
pub fn openDwarfDebugInfo(di: *DwarfInfo, allocator: mem.Allocator, binary_mem: []const u8) !void {
try di.scanAllFunctions(allocator);
try di.scanAllCompileUnits(allocator);
// Unwind info is not required
di.scanAllUnwindInfo(allocator, binary_mem) catch {};
}
/// This function is to make it handy to comment out the return and make it
/// into a crash when working on this file.
fn badDwarf() error{InvalidDebugInfo} {
//std.os.abort(); // can be handy to uncomment when working on this file
return error.InvalidDebugInfo;
}
fn missingDwarf() error{MissingDebugInfo} {
//std.os.abort(); // can be handy to uncomment when working on this file
return error.MissingDebugInfo;
}
fn getStringGeneric(opt_str: ?[]const u8, offset: u64) ![:0]const u8 {
const str = opt_str orelse return badDwarf();
if (offset > str.len) return badDwarf();
const casted_offset = math.cast(usize, offset) orelse return badDwarf();
// Valid strings always have a terminating zero byte
const last = mem.indexOfScalarPos(u8, str, casted_offset, 0) orelse return badDwarf();
return str[casted_offset..last :0];
}
const EhPointerContext = struct {
// The address of the pointer field itself
pc_rel_base: u64,
// Whether or not to follow indirect pointers. This should only be
// used when decoding pointers at runtime using the current process's
// debug info
follow_indirect: bool,
// These relative addressing modes are only used in specific cases, and
// might not be available / required in all parsing contexts
data_rel_base: ?u64 = null,
text_rel_base: ?u64 = null,
function_rel_base: ?u64 = null,
};
fn readEhPointer(reader: anytype, enc: u8, addr_size_bytes: u8, ctx: EhPointerContext, endian: std.builtin.Endian) !?u64 {
if (enc == EH.PE.omit) return null;
const value: union(enum) {
signed: i64,
unsigned: u64,
} = switch (enc & EH.PE.type_mask) {
EH.PE.absptr => .{
.unsigned = switch (addr_size_bytes) {
2 => try reader.readInt(u16, endian),
4 => try reader.readInt(u32, endian),
8 => try reader.readInt(u64, endian),
else => return error.InvalidAddrSize,
},
},
EH.PE.uleb128 => .{ .unsigned = try leb.readULEB128(u64, reader) },
EH.PE.udata2 => .{ .unsigned = try reader.readInt(u16, endian) },
EH.PE.udata4 => .{ .unsigned = try reader.readInt(u32, endian) },
EH.PE.udata8 => .{ .unsigned = try reader.readInt(u64, endian) },
EH.PE.sleb128 => .{ .signed = try leb.readILEB128(i64, reader) },
EH.PE.sdata2 => .{ .signed = try reader.readInt(i16, endian) },
EH.PE.sdata4 => .{ .signed = try reader.readInt(i32, endian) },
EH.PE.sdata8 => .{ .signed = try reader.readInt(i64, endian) },
else => return badDwarf(),
};
var base = switch (enc & EH.PE.rel_mask) {
EH.PE.pcrel => ctx.pc_rel_base,
EH.PE.textrel => ctx.text_rel_base orelse return error.PointerBaseNotSpecified,
EH.PE.datarel => ctx.data_rel_base orelse return error.PointerBaseNotSpecified,
EH.PE.funcrel => ctx.function_rel_base orelse return error.PointerBaseNotSpecified,
else => null,
};
const ptr = if (base) |b| switch (value) {
.signed => |s| @as(u64, @intCast(s + @as(i64, @intCast(b)))),
.unsigned => |u| u + b,
} else switch (value) {
.signed => |s| @as(u64, @intCast(s)),
.unsigned => |u| u,
};
if ((enc & EH.PE.indirect) > 0 and ctx.follow_indirect) {
if (@sizeOf(usize) != addr_size_bytes) {
// See the documentation for `follow_indirect`
return error.NonNativeIndirection;
}
const native_ptr = math.cast(usize, ptr) orelse return error.PointerOverflow;
return switch (addr_size_bytes) {
2, 4, 8 => return @as(*const usize, @ptrFromInt(native_ptr)).*,
else => return error.UnsupportedAddrSize,
};
} else {
return ptr;
}
}
/// This represents the decoded .eh_frame_hdr header
pub const ExceptionFrameHeader = struct {
eh_frame_ptr: usize,
table_enc: u8,
fde_count: usize,
entries: []const u8,
pub fn entrySize(table_enc: u8) !u8 {
return switch (table_enc & EH.PE.type_mask) {
EH.PE.udata2,
EH.PE.sdata2,
=> 4,
EH.PE.udata4,
EH.PE.sdata4,
=> 8,
EH.PE.udata8,
EH.PE.sdata8,
=> 16,
// This is a binary search table, so all entries must be the same length
else => return badDwarf(),
};
}
fn isValidPtr(
self: ExceptionFrameHeader,
ptr: usize,
isValidMemory: *const fn (address: usize) bool,
eh_frame_len: ?usize,
) bool {
if (eh_frame_len) |len| {
return ptr >= self.eh_frame_ptr and ptr < self.eh_frame_ptr + len;
} else {
return isValidMemory(ptr);
}
}
/// Find an entry by binary searching the eh_frame_hdr section.
///
/// Since the length of the eh_frame section (`eh_frame_len`) may not be known by the caller,
/// `isValidMemory` will be called before accessing any memory referenced by
/// the header entries. If `eh_frame_len` is provided, then these checks can be skipped.
pub fn findEntry(
self: ExceptionFrameHeader,
isValidMemory: *const fn (address: usize) bool,
eh_frame_len: ?usize,
eh_frame_hdr_ptr: usize,
pc: usize,
cie: *CommonInformationEntry,
fde: *FrameDescriptionEntry,
) !void {
const entry_size = try entrySize(self.table_enc);
var left: usize = 0;
var len: usize = self.fde_count;
var stream = io.fixedBufferStream(self.entries);
const reader = stream.reader();
while (len > 1) {
const mid = left + len / 2;
try stream.seekTo(mid * entry_size);
const pc_begin = try readEhPointer(reader, self.table_enc, @sizeOf(usize), .{
.pc_rel_base = @intFromPtr(&self.entries[stream.pos]),
.follow_indirect = true,
.data_rel_base = eh_frame_hdr_ptr,
}, builtin.cpu.arch.endian()) orelse return badDwarf();
if (pc < pc_begin) {
len /= 2;
} else {
left = mid;
if (pc == pc_begin) break;
len -= len / 2;
}
}
try stream.seekTo(left * entry_size);
// Read past the pc_begin field of the entry
_ = try readEhPointer(reader, self.table_enc, @sizeOf(usize), .{
.pc_rel_base = @intFromPtr(&self.entries[stream.pos]),
.follow_indirect = true,
.data_rel_base = eh_frame_hdr_ptr,
}, builtin.cpu.arch.endian()) orelse return badDwarf();
const fde_ptr = math.cast(usize, try readEhPointer(reader, self.table_enc, @sizeOf(usize), .{
.pc_rel_base = @intFromPtr(&self.entries[stream.pos]),
.follow_indirect = true,
.data_rel_base = eh_frame_hdr_ptr,
}, builtin.cpu.arch.endian()) orelse return badDwarf()) orelse return badDwarf();
// Verify the length fields of the FDE header are readable
if (!self.isValidPtr(fde_ptr, isValidMemory, eh_frame_len) or fde_ptr < self.eh_frame_ptr) return badDwarf();
var fde_entry_header_len: usize = 4;
if (!self.isValidPtr(fde_ptr + 3, isValidMemory, eh_frame_len)) return badDwarf();
if (self.isValidPtr(fde_ptr + 11, isValidMemory, eh_frame_len)) fde_entry_header_len = 12;
// Even if eh_frame_len is not specified, all ranges accssed are checked by isValidPtr
const eh_frame = @as([*]const u8, @ptrFromInt(self.eh_frame_ptr))[0 .. eh_frame_len orelse math.maxInt(u32)];
const fde_offset = fde_ptr - self.eh_frame_ptr;
var eh_frame_stream = io.fixedBufferStream(eh_frame);
try eh_frame_stream.seekTo(fde_offset);
const fde_entry_header = try EntryHeader.read(&eh_frame_stream, .eh_frame, builtin.cpu.arch.endian());
if (!self.isValidPtr(@intFromPtr(&fde_entry_header.entry_bytes[fde_entry_header.entry_bytes.len - 1]), isValidMemory, eh_frame_len)) return badDwarf();
if (fde_entry_header.type != .fde) return badDwarf();
// CIEs always come before FDEs (the offset is a subtration), so we can assume this memory is readable
const cie_offset = fde_entry_header.type.fde;
try eh_frame_stream.seekTo(cie_offset);
const cie_entry_header = try EntryHeader.read(&eh_frame_stream, .eh_frame, builtin.cpu.arch.endian());
if (!self.isValidPtr(@intFromPtr(&cie_entry_header.entry_bytes[cie_entry_header.entry_bytes.len - 1]), isValidMemory, eh_frame_len)) return badDwarf();
if (cie_entry_header.type != .cie) return badDwarf();
cie.* = try CommonInformationEntry.parse(
cie_entry_header.entry_bytes,
0,
true,
.eh_frame,
cie_entry_header.length_offset,
@sizeOf(usize),
builtin.cpu.arch.endian(),
);
fde.* = try FrameDescriptionEntry.parse(
fde_entry_header.entry_bytes,
0,
true,
cie.*,
@sizeOf(usize),
builtin.cpu.arch.endian(),
);
}
};
pub const EntryHeader = struct {
/// Offset of the length field in the backing buffer
length_offset: usize,
is_64: bool,
type: union(enum) {
cie,
/// Value is the offset of the corresponding CIE
fde: u64,
terminator: void,
},
/// The entry's contents, not including the ID field
entry_bytes: []const u8,
/// Reads a header for either an FDE or a CIE, then advances the stream to the position after the trailing structure.
/// `stream` must be a stream backed by either the .eh_frame or .debug_frame sections.
pub fn read(stream: *std.io.FixedBufferStream([]const u8), dwarf_section: DwarfSection, endian: std.builtin.Endian) !EntryHeader {
assert(dwarf_section == .eh_frame or dwarf_section == .debug_frame);
const reader = stream.reader();
const length_offset = stream.pos;
var is_64: bool = undefined;
const length = math.cast(usize, try readUnitLength(reader, endian, &is_64)) orelse return badDwarf();
if (length == 0) return .{
.length_offset = length_offset,
.is_64 = is_64,
.type = .{ .terminator = {} },
.entry_bytes = &.{},
};
const id_len = @as(u8, if (is_64) 8 else 4);
const id = if (is_64) try reader.readInt(u64, endian) else try reader.readInt(u32, endian);
const entry_bytes = stream.buffer[stream.pos..][0 .. length - id_len];
const cie_id: u64 = switch (dwarf_section) {
.eh_frame => CommonInformationEntry.eh_id,
.debug_frame => if (is_64) CommonInformationEntry.dwarf64_id else CommonInformationEntry.dwarf32_id,
else => unreachable,
};
const result = EntryHeader{
.length_offset = length_offset,
.is_64 = is_64,
.type = if (id == cie_id) .{ .cie = {} } else .{
.fde = switch (dwarf_section) {
.eh_frame => stream.pos - id_len - id,
.debug_frame => id,
else => unreachable,
},
},
.entry_bytes = entry_bytes,
};
stream.pos += entry_bytes.len;
return result;
}
/// The length of the entry including the ID field, but not the length field itself
pub fn entryLength(self: EntryHeader) usize {
return self.entry_bytes.len + @as(u8, if (self.is_64) 8 else 4);
}
};
pub const CommonInformationEntry = struct {
// Used in .eh_frame
pub const eh_id = 0;
// Used in .debug_frame (DWARF32)
pub const dwarf32_id = math.maxInt(u32);
// Used in .debug_frame (DWARF64)
pub const dwarf64_id = math.maxInt(u64);
// Offset of the length field of this entry in the eh_frame section.
// This is the key that FDEs use to reference CIEs.
length_offset: u64,
version: u8,
address_size: u8,
// Only present in version 4
segment_selector_size: ?u8,
code_alignment_factor: u32,
data_alignment_factor: i32,
return_address_register: u8,
aug_str: []const u8,
aug_data: []const u8,
lsda_pointer_enc: u8,
personality_enc: ?u8,
personality_routine_pointer: ?u64,
fde_pointer_enc: u8,
initial_instructions: []const u8,
pub fn isSignalFrame(self: CommonInformationEntry) bool {
for (self.aug_str) |c| if (c == 'S') return true;
return false;
}
pub fn addressesSignedWithBKey(self: CommonInformationEntry) bool {
for (self.aug_str) |c| if (c == 'B') return true;
return false;
}
pub fn mteTaggedFrame(self: CommonInformationEntry) bool {
for (self.aug_str) |c| if (c == 'G') return true;
return false;
}
/// This function expects to read the CIE starting with the version field.
/// The returned struct references memory backed by cie_bytes.
///
/// See the FrameDescriptionEntry.parse documentation for the description
/// of `pc_rel_offset` and `is_runtime`.
///
/// `length_offset` specifies the offset of this CIE's length field in the
/// .eh_frame / .debug_framesection.
pub fn parse(
cie_bytes: []const u8,
pc_rel_offset: i64,
is_runtime: bool,
dwarf_section: DwarfSection,
length_offset: u64,
addr_size_bytes: u8,
endian: std.builtin.Endian,
) !CommonInformationEntry {
if (addr_size_bytes > 8) return error.UnsupportedAddrSize;
var stream = io.fixedBufferStream(cie_bytes);
const reader = stream.reader();
const version = try reader.readByte();
switch (dwarf_section) {
.eh_frame => if (version != 1 and version != 3) return error.UnsupportedDwarfVersion,
.debug_frame => if (version != 4) return error.UnsupportedDwarfVersion,
else => return error.UnsupportedDwarfSection,
}
var has_eh_data = false;
var has_aug_data = false;
var aug_str_len: usize = 0;
var aug_str_start = stream.pos;
var aug_byte = try reader.readByte();
while (aug_byte != 0) : (aug_byte = try reader.readByte()) {
switch (aug_byte) {
'z' => {
if (aug_str_len != 0) return badDwarf();
has_aug_data = true;
},
'e' => {
if (has_aug_data or aug_str_len != 0) return badDwarf();
if (try reader.readByte() != 'h') return badDwarf();
has_eh_data = true;
},
else => if (has_eh_data) return badDwarf(),
}
aug_str_len += 1;
}
if (has_eh_data) {
// legacy data created by older versions of gcc - unsupported here
for (0..addr_size_bytes) |_| _ = try reader.readByte();
}
const address_size = if (version == 4) try reader.readByte() else addr_size_bytes;
const segment_selector_size = if (version == 4) try reader.readByte() else null;
const code_alignment_factor = try leb.readULEB128(u32, reader);
const data_alignment_factor = try leb.readILEB128(i32, reader);
const return_address_register = if (version == 1) try reader.readByte() else try leb.readULEB128(u8, reader);
var lsda_pointer_enc: u8 = EH.PE.omit;
var personality_enc: ?u8 = null;
var personality_routine_pointer: ?u64 = null;
var fde_pointer_enc: u8 = EH.PE.absptr;
var aug_data: []const u8 = &[_]u8{};
const aug_str = if (has_aug_data) blk: {
const aug_data_len = try leb.readULEB128(usize, reader);
const aug_data_start = stream.pos;
aug_data = cie_bytes[aug_data_start..][0..aug_data_len];
const aug_str = cie_bytes[aug_str_start..][0..aug_str_len];
for (aug_str[1..]) |byte| {
switch (byte) {
'L' => {
lsda_pointer_enc = try reader.readByte();
},
'P' => {
personality_enc = try reader.readByte();
personality_routine_pointer = try readEhPointer(
reader,
personality_enc.?,
addr_size_bytes,
.{
.pc_rel_base = try pcRelBase(@intFromPtr(&cie_bytes[stream.pos]), pc_rel_offset),
.follow_indirect = is_runtime,
},
endian,
);
},
'R' => {
fde_pointer_enc = try reader.readByte();
},
'S', 'B', 'G' => {},
else => return badDwarf(),
}
}
// aug_data_len can include padding so the CIE ends on an address boundary
try stream.seekTo(aug_data_start + aug_data_len);
break :blk aug_str;
} else &[_]u8{};
const initial_instructions = cie_bytes[stream.pos..];
return .{
.length_offset = length_offset,
.version = version,
.address_size = address_size,
.segment_selector_size = segment_selector_size,
.code_alignment_factor = code_alignment_factor,
.data_alignment_factor = data_alignment_factor,
.return_address_register = return_address_register,
.aug_str = aug_str,
.aug_data = aug_data,
.lsda_pointer_enc = lsda_pointer_enc,
.personality_enc = personality_enc,
.personality_routine_pointer = personality_routine_pointer,
.fde_pointer_enc = fde_pointer_enc,
.initial_instructions = initial_instructions,
};
}
};
pub const FrameDescriptionEntry = struct {
// Offset into eh_frame where the CIE for this FDE is stored
cie_length_offset: u64,
pc_begin: u64,
pc_range: u64,
lsda_pointer: ?u64,
aug_data: []const u8,
instructions: []const u8,
/// This function expects to read the FDE starting at the PC Begin field.
/// The returned struct references memory backed by fde_bytes.
///
/// `pc_rel_offset` specifies an offset to be applied to pc_rel_base values
/// used when decoding pointers. This should be set to zero if fde_bytes is
/// backed by the memory of the .eh_frame section in the running executable.
///
/// Otherwise, it should be the relative offset to translate addresses from
/// where the section is currently stored in memory, to where it *would* be
/// stored at runtime: section runtime offset - backing section data base ptr.
///
/// Similarly, `is_runtime` specifies this function is being called on a runtime section, and so
/// indirect pointers can be followed.
pub fn parse(
fde_bytes: []const u8,
pc_rel_offset: i64,
is_runtime: bool,
cie: CommonInformationEntry,
addr_size_bytes: u8,
endian: std.builtin.Endian,
) !FrameDescriptionEntry {
if (addr_size_bytes > 8) return error.InvalidAddrSize;
var stream = io.fixedBufferStream(fde_bytes);
const reader = stream.reader();
const pc_begin = try readEhPointer(
reader,
cie.fde_pointer_enc,
addr_size_bytes,
.{
.pc_rel_base = try pcRelBase(@intFromPtr(&fde_bytes[stream.pos]), pc_rel_offset),
.follow_indirect = is_runtime,
},
endian,
) orelse return badDwarf();
const pc_range = try readEhPointer(
reader,
cie.fde_pointer_enc,
addr_size_bytes,
.{
.pc_rel_base = 0,
.follow_indirect = false,
},
endian,
) orelse return badDwarf();
var aug_data: []const u8 = &[_]u8{};
const lsda_pointer = if (cie.aug_str.len > 0) blk: {
const aug_data_len = try leb.readULEB128(usize, reader);
const aug_data_start = stream.pos;
aug_data = fde_bytes[aug_data_start..][0..aug_data_len];
const lsda_pointer = if (cie.lsda_pointer_enc != EH.PE.omit)
try readEhPointer(
reader,
cie.lsda_pointer_enc,
addr_size_bytes,
.{
.pc_rel_base = try pcRelBase(@intFromPtr(&fde_bytes[stream.pos]), pc_rel_offset),
.follow_indirect = is_runtime,
},
endian,
)
else
null;
try stream.seekTo(aug_data_start + aug_data_len);
break :blk lsda_pointer;
} else null;
const instructions = fde_bytes[stream.pos..];
return .{
.cie_length_offset = cie.length_offset,
.pc_begin = pc_begin,
.pc_range = pc_range,
.lsda_pointer = lsda_pointer,
.aug_data = aug_data,
.instructions = instructions,
};
}
};
fn pcRelBase(field_ptr: usize, pc_rel_offset: i64) !usize {
if (pc_rel_offset < 0) {
return math.sub(usize, field_ptr, @as(usize, @intCast(-pc_rel_offset)));
} else {
return math.add(usize, field_ptr, @as(usize, @intCast(pc_rel_offset)));
}
}
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