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dwarf: add expression writer

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This commit is contained in:
kcbanner
2023-07-05 13:36:28 -04:00
parent ad5f74c0b1
commit 424b1299a8
1 changed files with 483 additions and 20 deletions
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503
lib/std/dwarf/expressions.zig
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@@ -5,17 +5,7 @@ const leb = @import("../leb128.zig");
const dwarf = @import("../dwarf.zig");
const abi = dwarf.abi;
const mem = std.mem;
pub const StackMachineOptions = struct {
/// The address size of the target architecture
addr_size: u8 = @sizeOf(usize),
/// Endianess of the target architecture
endian: std.builtin.Endian = .Little,
/// Restrict the stack machine to a subset of opcodes used in call frame instructions
call_frame_mode: bool = false,
};
const assert = std.debug.assert;
/// Expressions can be evaluated in different contexts, each requiring its own set of inputs.
/// Callers should specify all the fields relevant to their context. If a field is required
@@ -35,10 +25,21 @@ pub const ExpressionContext = struct {
cfa: ?usize,
};
pub const ExpressionOptions = struct {
/// The address size of the target architecture
addr_size: u8 = @sizeOf(usize),
/// Endianess of the target architecture
endian: std.builtin.Endian = .Little,
/// Restrict the stack machine to a subset of opcodes used in call frame instructions
call_frame_mode: bool = false,
};
/// A stack machine that can decode and run DWARF expressions.
/// Expressions can be decoded for non-native address size and endianness,
/// but can only be executed if the current target matches the configuration.
pub fn StackMachine(comptime options: StackMachineOptions) type {
pub fn StackMachine(comptime options: ExpressionOptions) type {
const addr_type = switch (options.addr_size) {
2 => u16,
4 => u32,
@@ -60,6 +61,7 @@ pub fn StackMachine(comptime options: StackMachineOptions) type {
generic: addr_type,
register: u8,
type_size: u8,
branch_offset: i16,
base_register: struct {
base_register: u8,
offset: i64,
@@ -114,7 +116,7 @@ pub fn StackMachine(comptime options: StackMachineOptions) type {
2 => mem.readIntSliceNative(u16, const_type.value_bytes),
4 => mem.readIntSliceNative(u32, const_type.value_bytes),
8 => mem.readIntSliceNative(u64, const_type.value_bytes),
else => return error.InvalidIntegralTypeLength,
else => error.InvalidIntegralTypeLength,
};
},
};
@@ -163,10 +165,10 @@ pub fn StackMachine(comptime options: StackMachineOptions) type {
OP.call2,
=> generic(try reader.readInt(u16, options.endian)),
OP.call4 => generic(try reader.readInt(u32, options.endian)),
OP.const2s,
OP.const2s => generic(try reader.readInt(i16, options.endian)),
OP.bra,
OP.skip,
=> generic(try reader.readInt(i16, options.endian)),
=> .{ .branch_offset = try reader.readInt(i16, options.endian) },
OP.const4u => generic(try reader.readInt(u32, options.endian)),
OP.const4s => generic(try reader.readInt(i32, options.endian)),
OP.const8u => generic(try reader.readInt(u64, options.endian)),
@@ -362,13 +364,21 @@ pub fn StackMachine(comptime options: StackMachineOptions) type {
if (context.ucontext == null) return error.IncompleteExpressionContext;
const base_register = (try readOperand(stream, opcode)).?.base_register;
var value: i64 = @intCast(mem.readIntSliceNative(usize, try abi.regBytes(context.ucontext.?, base_register.base_register, context.reg_ctx)));
var value: i64 = @intCast(mem.readIntSliceNative(usize, try abi.regBytes(
context.ucontext.?,
base_register.base_register,
context.reg_ctx,
)));
value += base_register.offset;
try self.stack.append(allocator, .{ .generic = @intCast(value) });
},
OP.regval_type => {
const register_type = (try readOperand(stream, opcode)).?.register_type;
const value = mem.readIntSliceNative(usize, try abi.regBytes(context.ucontext.?, register_type.register, context.reg_ctx));
const value = mem.readIntSliceNative(usize, try abi.regBytes(
context.ucontext.?,
register_type.register,
context.reg_ctx,
));
try self.stack.append(allocator, .{
.regval_type = .{
.type_offset = register_type.type_offset,
@@ -472,18 +482,242 @@ pub fn StackMachine(comptime options: StackMachineOptions) type {
OP.abs => {
if (self.stack.items.len == 0) return error.InvalidExpression;
const value: isize = @bitCast(try self.stack.items[self.stack.items.len - 1].asIntegral());
self.stack.items[self.stack.items.len - 1] = .{ .generic = std.math.absCast(value) };
self.stack.items[self.stack.items.len - 1] = .{
.generic = std.math.absCast(value),
};
},
OP.@"and" => {
if (self.stack.items.len < 2) return error.InvalidExpression;
const a = try self.stack.pop().asIntegral();
self.stack.items[self.stack.items.len - 1] = .{ .generic = a & try self.stack.items[self.stack.items.len - 1].asIntegral() };
self.stack.items[self.stack.items.len - 1] = .{
.generic = a & try self.stack.items[self.stack.items.len - 1].asIntegral(),
};
},
OP.div => {
if (self.stack.items.len < 2) return error.InvalidExpression;
const a: isize = @bitCast(try self.stack.pop().asIntegral());
const b: isize = @bitCast(try self.stack.items[self.stack.items.len - 1].asIntegral());
self.stack.items[self.stack.items.len - 1] = .{
.generic = @bitCast(try std.math.divTrunc(isize, b, a)),
};
},
OP.minus => {
if (self.stack.items.len < 2) return error.InvalidExpression;
const b = try self.stack.pop().asIntegral();
self.stack.items[self.stack.items.len - 1] = .{
.generic = try std.math.sub(addr_type, try self.stack.items[self.stack.items.len - 1].asIntegral(), b),
};
},
OP.mod => {
if (self.stack.items.len < 2) return error.InvalidExpression;
const a: isize = @bitCast(try self.stack.pop().asIntegral());
const b: isize = @bitCast(try self.stack.items[self.stack.items.len - 1].asIntegral());
self.stack.items[self.stack.items.len - 1] = .{
.generic = @bitCast(@mod(b, a)),
};
},
OP.mul => {
if (self.stack.items.len < 2) return error.InvalidExpression;
const a: isize = @bitCast(try self.stack.pop().asIntegral());
const b: isize = @bitCast(try self.stack.items[self.stack.items.len - 1].asIntegral());
self.stack.items[self.stack.items.len - 1] = .{
.generic = @bitCast(@mulWithOverflow(a, b)[0]),
};
},
OP.neg => {
if (self.stack.items.len == 0) return error.InvalidExpression;
self.stack.items[self.stack.items.len - 1] = .{
.generic = @bitCast(
try std.math.negate(
@as(isize, @bitCast(try self.stack.items[self.stack.items.len - 1].asIntegral())),
),
),
};
},
OP.not => {
if (self.stack.items.len == 0) return error.InvalidExpression;
self.stack.items[self.stack.items.len - 1] = .{
.generic = ~try self.stack.items[self.stack.items.len - 1].asIntegral(),
};
},
OP.@"or" => {
if (self.stack.items.len < 2) return error.InvalidExpression;
const a = try self.stack.pop().asIntegral();
self.stack.items[self.stack.items.len - 1] = .{
.generic = a | try self.stack.items[self.stack.items.len - 1].asIntegral(),
};
},
OP.plus => {
if (self.stack.items.len < 2) return error.InvalidExpression;
const b = try self.stack.pop().asIntegral();
self.stack.items[self.stack.items.len - 1] = .{
.generic = try std.math.add(addr_type, try self.stack.items[self.stack.items.len - 1].asIntegral(), b),
};
},
OP.plus_uconst => {
if (self.stack.items.len == 0) return error.InvalidExpression;
const constant = (try readOperand(stream, opcode)).?.generic;
self.stack.items[self.stack.items.len - 1] = .{
.generic = try std.math.add(addr_type, try self.stack.items[self.stack.items.len - 1].asIntegral(), constant),
};
},
OP.shl => {
if (self.stack.items.len < 2) return error.InvalidExpression;
const a = try self.stack.pop().asIntegral();
const b = try self.stack.items[self.stack.items.len - 1].asIntegral();
self.stack.items[self.stack.items.len - 1] = .{
.generic = std.math.shl(usize, b, a),
};
},
OP.shr => {
if (self.stack.items.len < 2) return error.InvalidExpression;
const a = try self.stack.pop().asIntegral();
const b = try self.stack.items[self.stack.items.len - 1].asIntegral();
self.stack.items[self.stack.items.len - 1] = .{
.generic = std.math.shr(usize, b, a),
};
},
OP.shra => {
if (self.stack.items.len < 2) return error.InvalidExpression;
const a = try self.stack.pop().asIntegral();
const b: isize = @bitCast(try self.stack.items[self.stack.items.len - 1].asIntegral());
self.stack.items[self.stack.items.len - 1] = .{
.generic = @bitCast(std.math.shr(isize, b, a)),
};
},
OP.xor => {
if (self.stack.items.len < 2) return error.InvalidExpression;
const a = try self.stack.pop().asIntegral();
self.stack.items[self.stack.items.len - 1] = .{
.generic = a ^ try self.stack.items[self.stack.items.len - 1].asIntegral(),
};
},
// 2.5.1.5: Control Flow Operations
OP.le,
OP.ge,
OP.eq,
OP.lt,
OP.gt,
OP.ne,
=> {
if (self.stack.items.len < 2) return error.InvalidExpression;
const a = self.stack.pop();
const b = self.stack.items[self.stack.items.len - 1];
if (a == .generic and b == .generic) {
const a_int: isize = @bitCast(a.asIntegral() catch unreachable);
const b_int: isize = @bitCast(b.asIntegral() catch unreachable);
const result = @intFromBool(switch (opcode) {
OP.le => b_int < a_int,
OP.ge => b_int >= a_int,
OP.eq => b_int == a_int,
OP.lt => b_int < a_int,
OP.gt => b_int > a_int,
OP.ne => b_int != a_int,
else => unreachable,
});
self.stack.items[self.stack.items.len - 1] = .{ .generic = result };
} else {
// TODO: Load the types referenced by these values, find their comparison operator, and run it
return error.UnimplementedTypedComparison;
}
},
OP.skip, OP.bra => {
const branch_offset = (try readOperand(stream, opcode)).?.branch_offset;
const condition = if (opcode == OP.bra) blk: {
if (self.stack.items.len == 0) return error.InvalidExpression;
break :blk try self.stack.pop().asIntegral() != 0;
} else true;
if (condition) {
const new_pos = std.math.cast(
usize,
try std.math.add(isize, @as(isize, @intCast(stream.pos)), branch_offset),
) orelse return error.InvalidExpression;
if (new_pos < 0 or new_pos >= stream.buffer.len) return error.InvalidExpression;
stream.pos = new_pos;
}
},
OP.call2,
OP.call4,
OP.call_ref,
=> {
const debug_info_offset = (try readOperand(stream, opcode)).?.generic;
_ = debug_info_offset;
// TODO: Load a DIE entry at debug_info_offset in a .debug_info section (the spec says that it
// can be in a separate exe / shared object from the one containing this expression).
// Transfer control to the DW_AT_location attribute, with the current stack as input.
return error.UnimplementedExpressionCall;
},
// 2.5.1.6: Type Conversions
OP.convert => {
if (self.stack.items.len == 0) return error.InvalidExpression;
const type_offset = (try readOperand(stream, opcode)).?.generic;
_ = type_offset;
// TODO: Load the DW_TAG_base_type entry in context.compile_unit, find a conversion operator
// from the old type to the new type, run it.
return error.UnimplementedTypeConversion;
},
OP.reinterpret => {
if (self.stack.items.len == 0) return error.InvalidExpression;
const type_offset = (try readOperand(stream, opcode)).?.generic;
// TODO: Load the DW_TAG_base_type entries in context.compile_unit and verify both types are the same size
const value = self.stack.items[self.stack.items.len - 1];
if (type_offset == 0) {
self.stack.items[self.stack.items.len - 1] = .{ .generic = try value.asIntegral() };
} else {
self.stack.items[self.stack.items.len - 1] = switch (value) {
.generic => |v| .{
.regval_type = .{
.type_offset = type_offset,
.type_size = @sizeOf(addr_type),
.value = v,
},
},
.regval_type => |r| .{
.regval_type = .{
.type_offset = type_offset,
.type_size = r.type_size,
.value = r.value,
},
},
.const_type => |c| .{
.const_type = .{
.type_offset = type_offset,
.value_bytes = c.value_bytes,
},
},
};
}
},
// 2.5.1.7: Special Operations
OP.nop => {},
OP.entry_value => {
const block = (try readOperand(stream, opcode)).?.block;
_ = block;
// TODO: If block is an expression, run it on a new stack. Push the resulting value onto this stack.
// TODO: If block is a register location, push the value that location had before running this program onto this stack.
// This implies capturing all register values before executing this block, in case this program modifies them.
// TODO: If the block contains, OP.push_object_address, treat it as OP.nop
return error.UnimplementedSubExpression;
},
// These have already been handled by readOperand
OP.lo_user...OP.hi_user => unreachable,
else => {
//std.debug.print("Unimplemented DWARF expression opcode: {x}\n", .{opcode});
//std.debug.print("Unknown DWARF expression opcode: {x}\n", .{opcode});
return error.UnknownExpressionOpcode;
},
}
@@ -492,3 +726,232 @@ pub fn StackMachine(comptime options: StackMachineOptions) type {
}
};
}
pub fn Writer(options: ExpressionOptions) type {
const addr_type = switch (options.addr_size) {
2 => u16,
4 => u32,
8 => u64,
else => @compileError("Unsupported address size of " ++ options.addr_size),
};
return struct {
/// Zero-operand instructions
pub fn writeOpcode(writer: anytype, comptime opcode: u8) !void {
switch (opcode) {
OP.dup,
OP.drop,
OP.over,
OP.swap,
OP.rot,
OP.deref,
OP.xderef,
OP.push_object_address,
OP.form_tls_address,
OP.call_frame_cfa,
OP.abs,
OP.@"and",
OP.div,
OP.minus,
OP.mod,
OP.mul,
OP.neg,
OP.not,
OP.@"or",
OP.plus,
OP.shl,
OP.shr,
OP.shra,
OP.xor,
OP.le,
OP.ge,
OP.eq,
OP.lt,
OP.gt,
OP.ne,
OP.nop,
=> try writer.writeByte(opcode),
else => @compileError("This opcode requires operands, use write<Opcode>() instead"),
}
}
// 2.5.1.1: Literal Encodings
pub fn writeLiteral(writer: anytype, literal: u8) !void {
switch (literal) {
0...31 => |n| try writer.writeByte(n + OP.lit0),
else => return error.InvalidLiteral,
}
}
pub fn writeConst(writer: anytype, comptime T: type, value: T) !void {
if (@typeInfo(T) != .Int) @compileError("Constants must be integers");
switch (T) {
u8, i8, u16, i16, u32, i32, u64, i64 => {
try writer.writeByte(switch (T) {
u8 => OP.const1u,
i8 => OP.const1s,
u16 => OP.const2u,
i16 => OP.const2s,
u32 => OP.const4u,
i32 => OP.const4s,
u64 => OP.const8u,
i64 => OP.const8s,
});
try writer.writeInt(T, value, options.endian);
},
else => switch (@typeInfo(T).Int.signedness) {
.unsigned => {
try writer.writeByte(OP.constu);
try leb.writeULEB128(writer, value);
},
.signed => {
try writer.writeByte(OP.consts);
try leb.writeILEB128(writer, value);
},
},
}
}
pub fn writeConstx(writer: anytype, debug_addr_offset: anytype) !void {
try writer.writeByte(OP.constx);
try leb.writeULEB128(writer, debug_addr_offset);
}
pub fn writeConstType(writer: anytype, die_offset: anytype, size: u8, value_bytes: []const u8) !void {
if (size != value_bytes.len) return error.InvalidValueSize;
try writer.writeByte(OP.const_type);
try leb.writeULEB128(writer, die_offset);
try writer.writeByte(size);
try writer.writeAll(value_bytes);
}
pub fn writeAddr(writer: anytype, value: addr_type) !void {
try writer.writeByte(OP.addr);
try writer.writeInt(addr_type, value, options.endian);
}
pub fn writeAddrx(writer: anytype, debug_addr_offset: anytype) !void {
try writer.writeByte(OP.addrx);
try leb.writeULEB128(writer, debug_addr_offset);
}
// 2.5.1.2: Register Values
pub fn writeFbreg(writer: anytype, offset: anytype) !void {
try writer.writeByte(OP.fbreg);
try leb.writeILEB128(writer, offset);
}
pub fn writeBreg(writer: anytype, register: u8, offset: anytype) !void {
if (register > 31) return error.InvalidRegister;
try writer.writeByte(OP.reg0 + register);
try leb.writeILEB128(writer, offset);
}
pub fn writeBregx(writer: anytype, register: anytype, offset: anytype) !void {
try writer.writeByte(OP.bregx);
try leb.writeULEB128(writer, register);
try leb.writeILEB128(writer, offset);
}
pub fn writeRegvalType(writer: anytype, register: anytype, offset: anytype) !void {
try writer.writeByte(OP.bregx);
try leb.writeULEB128(writer, register);
try leb.writeULEB128(writer, offset);
}
// 2.5.1.3: Stack Operations
pub fn writePick(writer: anytype, index: u8) !void {
try writer.writeByte(OP.pick);
try writer.writeByte(index);
}
pub fn writeDerefSize(writer: anytype, size: u8) !void {
try writer.writeByte(OP.deref_size);
try writer.writeByte(size);
}
pub fn writeXDerefSize(writer: anytype, size: u8) !void {
try writer.writeByte(OP.xderef_size);
try writer.writeByte(size);
}
pub fn writeDerefType(writer: anytype, size: u8, die_offset: anytype) !void {
try writer.writeByte(OP.deref_type);
try writer.writeByte(size);
try leb.writeULEB128(writer, die_offset);
}
pub fn writeXDerefType(writer: anytype, size: u8, die_offset: anytype) !void {
try writer.writeByte(OP.xderef_type);
try writer.writeByte(size);
try leb.writeULEB128(writer, die_offset);
}
// 2.5.1.4: Arithmetic and Logical Operations
pub fn writePlusUconst(writer: anytype, uint_value: anytype) !void {
try writer.writeByte(OP.plus_uconst);
try leb.writeULEB128(writer, uint_value);
}
// 2.5.1.5: Control Flow Operations
pub fn writeSkip(writer: anytype, offset: i16) !void {
try writer.writeByte(OP.skip);
try writer.writeInt(i16, offset, options.endian);
}
pub fn writeBra(writer: anytype, offset: i16) !void {
try writer.writeByte(OP.bra);
try writer.writeInt(i16, offset, options.endian);
}
pub fn writeCall(writer: anytype, comptime T: type, offset: T) !void {
switch (T) {
u16 => try writer.writeByte(OP.call2),
u32 => try writer.writeByte(OP.call4),
else => @compileError("Call operand must be a 2 or 4 byte offset"),
}
try writer.writeInt(T, offset, options.endian);
}
pub fn writeCallRef(writer: anytype, debug_info_offset: addr_type) !void {
try writer.writeByte(OP.call_ref);
try writer.writeInt(addr_type, debug_info_offset, options.endian);
}
pub fn writeConvert(writer: anytype, die_offset: anytype) !void {
try writer.writeByte(OP.convert);
try leb.writeULEB128(writer, die_offset);
}
pub fn writeReinterpret(writer: anytype, die_offset: anytype) !void {
try writer.writeByte(OP.reinterpret);
try leb.writeULEB128(writer, die_offset);
}
// 2.5.1.7: Special Operations
pub fn writeEntryValue(writer: anytype, expression: []const u8) !void {
try writer.writeByte(OP.entry_value);
try leb.writeULEB128(writer, expression.len);
try writer.writeAll(expression);
}
// 2.6: Location Descriptions
// TODO
};
}
test "DWARF expressions" {
const allocator = std.testing.allocator;
const options = ExpressionOptions{};
const stack_machine = StackMachine(options){};
defer stack_machine.deinit(allocator);
}