compiler/rustc_mir/src/interpret/terminator.rs

   1 use std::borrow::Cow;
   2 use std::convert::TryFrom;
   3
   4 use rustc_middle::ty::layout::TyAndLayout;
   5 use rustc_middle::ty::Instance;
   6 use rustc_middle::{mir, ty};
   7 use rustc_target::abi::{self, LayoutOf as _};
   8 use rustc_target::spec::abi::Abi;
   9
  10 use super::{
  11     FnVal, ImmTy, InterpCx, InterpResult, MPlaceTy, Machine, OpTy, PlaceTy, StackPopCleanup,
  12 };
  13
  14 impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
  15     pub(super) fn eval_terminator(
  16         &mut self,
  17         terminator: &mir::Terminator<'tcx>,
  18     ) -> InterpResult<'tcx> {
  19         use rustc_middle::mir::TerminatorKind::*;
  20         match terminator.kind {
  21             Return => {
  22                 self.pop_stack_frame(/* unwinding */ false)?
  23             }
  24
  25             Goto { target } => self.go_to_block(target),
  26
  27             SwitchInt { ref discr, ref targets, switch_ty } => {
  28                 let discr = self.read_immediate(self.eval_operand(discr, None)?)?;
  29                 trace!("SwitchInt({:?})", *discr);
  30                 assert_eq!(discr.layout.ty, switch_ty);
  31
  32                 // Branch to the `otherwise` case by default, if no match is found.
  33                 assert!(!targets.iter().is_empty());
  34                 let mut target_block = targets.otherwise();
  35
  36                 for (const_int, target) in targets.iter() {
  37                     // Compare using binary_op, to also support pointer values
  38                     let res = self
  39                         .overflowing_binary_op(
  40                             mir::BinOp::Eq,
  41                             discr,
  42                             ImmTy::from_uint(const_int, discr.layout),
  43                         )?
  44                         .0;
  45                     if res.to_bool()? {
  46                         target_block = target;
  47                         break;
  48                     }
  49                 }
  50
  51                 self.go_to_block(target_block);
  52             }
  53
  54             Call { ref func, ref args, destination, ref cleanup, from_hir_call: _, fn_span: _ } => {
  55                 let old_stack = self.frame_idx();
  56                 let old_loc = self.frame().loc;
  57                 let func = self.eval_operand(func, None)?;
  58                 let (fn_val, abi) = match *func.layout.ty.kind() {
  59                     ty::FnPtr(sig) => {
  60                         let caller_abi = sig.abi();
  61                         let fn_ptr = self.read_scalar(func)?.check_init()?;
  62                         let fn_val = self.memory.get_fn(fn_ptr)?;
  63                         (fn_val, caller_abi)
  64                     }
  65                     ty::FnDef(def_id, substs) => {
  66                         let sig = func.layout.ty.fn_sig(*self.tcx);
  67                         (
  68                             FnVal::Instance(
  69                                 self.resolve(ty::WithOptConstParam::unknown(def_id), substs)?,
  70                             ),
  71                             sig.abi(),
  72                         )
  73                     }
  74                     _ => span_bug!(
  75                         terminator.source_info.span,
  76                         "invalid callee of type {:?}",
  77                         func.layout.ty
  78                     ),
  79                 };
  80                 let args = self.eval_operands(args)?;
  81                 let ret = match destination {
  82                     Some((dest, ret)) => Some((self.eval_place(dest)?, ret)),
  83                     None => None,
  84                 };
  85                 self.eval_fn_call(fn_val, abi, &args[..], ret, *cleanup)?;
  86                 // Sanity-check that `eval_fn_call` either pushed a new frame or
  87                 // did a jump to another block.
  88                 if self.frame_idx() == old_stack && self.frame().loc == old_loc {
  89                     span_bug!(terminator.source_info.span, "evaluating this call made no progress");
  90                 }
  91             }
  92
  93             Drop { place, target, unwind } => {
  94                 let place = self.eval_place(place)?;
  95                 let ty = place.layout.ty;
  96                 trace!("TerminatorKind::drop: {:?}, type {}", place, ty);
  97
  98                 let instance = Instance::resolve_drop_in_place(*self.tcx, ty);
  99                 self.drop_in_place(place, instance, target, unwind)?;
 100             }
 101
 102             Assert { ref cond, expected, ref msg, target, cleanup } => {
 103                 let cond_val =
 104                     self.read_immediate(self.eval_operand(cond, None)?)?.to_scalar()?.to_bool()?;
 105                 if expected == cond_val {
 106                     self.go_to_block(target);
 107                 } else {
 108                     M::assert_panic(self, msg, cleanup)?;
 109                 }
 110             }
 111
 112             Abort => {
 113                 M::abort(self)?;
 114             }
 115
 116             // When we encounter Resume, we've finished unwinding
 117             // cleanup for the current stack frame. We pop it in order
 118             // to continue unwinding the next frame
 119             Resume => {
 120                 trace!("unwinding: resuming from cleanup");
 121                 // By definition, a Resume terminator means
 122                 // that we're unwinding
 123                 self.pop_stack_frame(/* unwinding */ true)?;
 124                 return Ok(());
 125             }
 126
 127             // It is UB to ever encounter this.
 128             Unreachable => throw_ub!(Unreachable),
 129
 130             // These should never occur for MIR we actually run.
 131             DropAndReplace { .. }
 132             | FalseEdge { .. }
 133             | FalseUnwind { .. }
 134             | Yield { .. }
 135             | GeneratorDrop => span_bug!(
 136                 terminator.source_info.span,
 137                 "{:#?} should have been eliminated by MIR pass",
 138                 terminator.kind
 139             ),
 140
 141             // Inline assembly can't be interpreted.
 142             InlineAsm { .. } => throw_unsup_format!("inline assembly is not supported"),
 143         }
 144
 145         Ok(())
 146     }
 147
 148     fn check_argument_compat(
 149         rust_abi: bool,
 150         caller: TyAndLayout<'tcx>,
 151         callee: TyAndLayout<'tcx>,
 152     ) -> bool {
 153         if caller.ty == callee.ty {
 154             // No question
 155             return true;
 156         }
 157         if !rust_abi {
 158             // Don't risk anything
 159             return false;
 160         }
 161         // Compare layout
 162         match (&caller.abi, &callee.abi) {
 163             // Different valid ranges are okay (once we enforce validity,
 164             // that will take care to make it UB to leave the range, just
 165             // like for transmute).
 166             (abi::Abi::Scalar(ref caller), abi::Abi::Scalar(ref callee)) => {
 167                 caller.value == callee.value
 168             }
 169             (
 170                 abi::Abi::ScalarPair(ref caller1, ref caller2),
 171                 abi::Abi::ScalarPair(ref callee1, ref callee2),
 172             ) => caller1.value == callee1.value && caller2.value == callee2.value,
 173             // Be conservative
 174             _ => false,
 175         }
 176     }
 177
 178     /// Pass a single argument, checking the types for compatibility.
 179     fn pass_argument(
 180         &mut self,
 181         rust_abi: bool,
 182         caller_arg: &mut impl Iterator<Item = OpTy<'tcx, M::PointerTag>>,
 183         callee_arg: PlaceTy<'tcx, M::PointerTag>,
 184     ) -> InterpResult<'tcx> {
 185         if rust_abi && callee_arg.layout.is_zst() {
 186             // Nothing to do.
 187             trace!("Skipping callee ZST");
 188             return Ok(());
 189         }
 190         let caller_arg = caller_arg.next().ok_or_else(|| {
 191             err_ub_format!("calling a function with fewer arguments than it requires")
 192         })?;
 193         if rust_abi {
 194             assert!(!caller_arg.layout.is_zst(), "ZSTs must have been already filtered out");
 195         }
 196         // Now, check
 197         if !Self::check_argument_compat(rust_abi, caller_arg.layout, callee_arg.layout) {
 198             throw_ub_format!(
 199                 "calling a function with argument of type {:?} passing data of type {:?}",
 200                 callee_arg.layout.ty,
 201                 caller_arg.layout.ty
 202             )
 203         }
 204         // We allow some transmutes here
 205         self.copy_op_transmute(caller_arg, callee_arg)
 206     }
 207
 208     /// Call this function -- pushing the stack frame and initializing the arguments.
 209     fn eval_fn_call(
 210         &mut self,
 211         fn_val: FnVal<'tcx, M::ExtraFnVal>,
 212         caller_abi: Abi,
 213         args: &[OpTy<'tcx, M::PointerTag>],
 214         ret: Option<(PlaceTy<'tcx, M::PointerTag>, mir::BasicBlock)>,
 215         unwind: Option<mir::BasicBlock>,
 216     ) -> InterpResult<'tcx> {
 217         trace!("eval_fn_call: {:#?}", fn_val);
 218
 219         let instance = match fn_val {
 220             FnVal::Instance(instance) => instance,
 221             FnVal::Other(extra) => {
 222                 return M::call_extra_fn(self, extra, args, ret, unwind);
 223             }
 224         };
 225
 226         // ABI check
 227         {
 228             let callee_abi = {
 229                 let instance_ty = instance.ty(*self.tcx, self.param_env);
 230                 match instance_ty.kind() {
 231                     ty::FnDef(..) => instance_ty.fn_sig(*self.tcx).abi(),
 232                     ty::Closure(..) => Abi::RustCall,
 233                     ty::Generator(..) => Abi::Rust,
 234                     _ => span_bug!(self.cur_span(), "unexpected callee ty: {:?}", instance_ty),
 235                 }
 236             };
 237             let normalize_abi = |abi| match abi {
 238                 Abi::Rust | Abi::RustCall | Abi::RustIntrinsic | Abi::PlatformIntrinsic =>
 239                 // These are all the same ABI, really.
 240                 {
 241                     Abi::Rust
 242                 }
 243                 abi => abi,
 244             };
 245             if normalize_abi(caller_abi) != normalize_abi(callee_abi) {
 246                 throw_ub_format!(
 247                     "calling a function with ABI {:?} using caller ABI {:?}",
 248                     callee_abi,
 249                     caller_abi
 250                 )
 251             }
 252         }
 253
 254         match instance.def {
 255             ty::InstanceDef::Intrinsic(..) => {
 256                 assert!(caller_abi == Abi::RustIntrinsic || caller_abi == Abi::PlatformIntrinsic);
 257                 M::call_intrinsic(self, instance, args, ret, unwind)
 258             }
 259             ty::InstanceDef::VtableShim(..)
 260             | ty::InstanceDef::ReifyShim(..)
 261             | ty::InstanceDef::ClosureOnceShim { .. }
 262             | ty::InstanceDef::FnPtrShim(..)
 263             | ty::InstanceDef::DropGlue(..)
 264             | ty::InstanceDef::CloneShim(..)
 265             | ty::InstanceDef::Item(_) => {
 266                 // We need MIR for this fn
 267                 let body = match M::find_mir_or_eval_fn(self, instance, args, ret, unwind)? {
 268                     Some(body) => body,
 269                     None => return Ok(()),
 270                 };
 271
 272                 self.push_stack_frame(
 273                     instance,
 274                     body,
 275                     ret.map(|p| p.0),
 276                     StackPopCleanup::Goto { ret: ret.map(|p| p.1), unwind },
 277                 )?;
 278
 279                 // If an error is raised here, pop the frame again to get an accurate backtrace.
 280                 // To this end, we wrap it all in a `try` block.
 281                 let res: InterpResult<'tcx> = try {
 282                     trace!(
 283                         "caller ABI: {:?}, args: {:#?}",
 284                         caller_abi,
 285                         args.iter()
 286                             .map(|arg| (arg.layout.ty, format!("{:?}", **arg)))
 287                             .collect::<Vec<_>>()
 288                     );
 289                     trace!(
 290                         "spread_arg: {:?}, locals: {:#?}",
 291                         body.spread_arg,
 292                         body.args_iter()
 293                             .map(|local| (
 294                                 local,
 295                                 self.layout_of_local(self.frame(), local, None).unwrap().ty
 296                             ))
 297                             .collect::<Vec<_>>()
 298                     );
 299
 300                     // Figure out how to pass which arguments.
 301                     // The Rust ABI is special: ZST get skipped.
 302                     let rust_abi = match caller_abi {
 303                         Abi::Rust | Abi::RustCall => true,
 304                         _ => false,
 305                     };
 306                     // We have two iterators: Where the arguments come from,
 307                     // and where they go to.
 308
 309                     // For where they come from: If the ABI is RustCall, we untuple the
 310                     // last incoming argument.  These two iterators do not have the same type,
 311                     // so to keep the code paths uniform we accept an allocation
 312                     // (for RustCall ABI only).
 313                     let caller_args: Cow<'_, [OpTy<'tcx, M::PointerTag>]> =
 314                         if caller_abi == Abi::RustCall && !args.is_empty() {
 315                             // Untuple
 316                             let (&untuple_arg, args) = args.split_last().unwrap();
 317                             trace!("eval_fn_call: Will pass last argument by untupling");
 318                             Cow::from(
 319                                 args.iter()
 320                                     .map(|&a| Ok(a))
 321                                     .chain(
 322                                         (0..untuple_arg.layout.fields.count())
 323                                             .map(|i| self.operand_field(untuple_arg, i)),
 324                                     )
 325                                     .collect::<InterpResult<'_, Vec<OpTy<'tcx, M::PointerTag>>>>(
 326                                     )?,
 327                             )
 328                         } else {
 329                             // Plain arg passing
 330                             Cow::from(args)
 331                         };
 332                     // Skip ZSTs
 333                     let mut caller_iter =
 334                         caller_args.iter().filter(|op| !rust_abi || !op.layout.is_zst()).copied();
 335
 336                     // Now we have to spread them out across the callee's locals,
 337                     // taking into account the `spread_arg`.  If we could write
 338                     // this is a single iterator (that handles `spread_arg`), then
 339                     // `pass_argument` would be the loop body. It takes care to
 340                     // not advance `caller_iter` for ZSTs.
 341                     for local in body.args_iter() {
 342                         let dest = self.eval_place(mir::Place::from(local))?;
 343                         if Some(local) == body.spread_arg {
 344                             // Must be a tuple
 345                             for i in 0..dest.layout.fields.count() {
 346                                 let dest = self.place_field(dest, i)?;
 347                                 self.pass_argument(rust_abi, &mut caller_iter, dest)?;
 348                             }
 349                         } else {
 350                             // Normal argument
 351                             self.pass_argument(rust_abi, &mut caller_iter, dest)?;
 352                         }
 353                     }
 354                     // Now we should have no more caller args
 355                     if caller_iter.next().is_some() {
 356                         throw_ub_format!("calling a function with more arguments than it expected")
 357                     }
 358                     // Don't forget to check the return type!
 359                     if let Some((caller_ret, _)) = ret {
 360                         let callee_ret = self.eval_place(mir::Place::return_place())?;
 361                         if !Self::check_argument_compat(
 362                             rust_abi,
 363                             caller_ret.layout,
 364                             callee_ret.layout,
 365                         ) {
 366                             throw_ub_format!(
 367                                 "calling a function with return type {:?} passing \
 368                                      return place of type {:?}",
 369                                 callee_ret.layout.ty,
 370                                 caller_ret.layout.ty
 371                             )
 372                         }
 373                     } else {
 374                         let local = mir::RETURN_PLACE;
 375                         let callee_layout = self.layout_of_local(self.frame(), local, None)?;
 376                         if !callee_layout.abi.is_uninhabited() {
 377                             throw_ub_format!("calling a returning function without a return place")
 378                         }
 379                     }
 380                 };
 381                 match res {
 382                     Err(err) => {
 383                         self.stack_mut().pop();
 384                         Err(err)
 385                     }
 386                     Ok(()) => Ok(()),
 387                 }
 388             }
 389             // cannot use the shim here, because that will only result in infinite recursion
 390             ty::InstanceDef::Virtual(_, idx) => {
 391                 let mut args = args.to_vec();
 392                 // We have to implement all "object safe receivers".  Currently we
 393                 // support built-in pointers `(&, &mut, Box)` as well as unsized-self.  We do
 394                 // not yet support custom self types.
 395                 // Also see `compiler/rustc_codegen_llvm/src/abi.rs` and `compiler/rustc_codegen_ssa/src/mir/block.rs`.
 396                 let receiver_place = match args[0].layout.ty.builtin_deref(true) {
 397                     Some(_) => {
 398                         // Built-in pointer.
 399                         self.deref_operand(args[0])?
 400                     }
 401                     None => {
 402                         // Unsized self.
 403                         args[0].assert_mem_place(self)
 404                     }
 405                 };
 406                 // Find and consult vtable
 407                 let vtable = receiver_place.vtable();
 408                 let drop_fn = self.get_vtable_slot(vtable, u64::try_from(idx).unwrap())?;
 409
 410                 // `*mut receiver_place.layout.ty` is almost the layout that we
 411                 // want for args[0]: We have to project to field 0 because we want
 412                 // a thin pointer.
 413                 assert!(receiver_place.layout.is_unsized());
 414                 let receiver_ptr_ty = self.tcx.mk_mut_ptr(receiver_place.layout.ty);
 415                 let this_receiver_ptr = self.layout_of(receiver_ptr_ty)?.field(self, 0)?;
 416                 // Adjust receiver argument.
 417                 args[0] =
 418                     OpTy::from(ImmTy::from_immediate(receiver_place.ptr.into(), this_receiver_ptr));
 419                 trace!("Patched self operand to {:#?}", args[0]);
 420                 // recurse with concrete function
 421                 self.eval_fn_call(drop_fn, caller_abi, &args, ret, unwind)
 422             }
 423         }
 424     }
 425
 426     fn drop_in_place(
 427         &mut self,
 428         place: PlaceTy<'tcx, M::PointerTag>,
 429         instance: ty::Instance<'tcx>,
 430         target: mir::BasicBlock,
 431         unwind: Option<mir::BasicBlock>,
 432     ) -> InterpResult<'tcx> {
 433         trace!("drop_in_place: {:?},\n  {:?}, {:?}", *place, place.layout.ty, instance);
 434         // We take the address of the object.  This may well be unaligned, which is fine
 435         // for us here.  However, unaligned accesses will probably make the actual drop
 436         // implementation fail -- a problem shared by rustc.
 437         let place = self.force_allocation(place)?;
 438
 439         let (instance, place) = match place.layout.ty.kind() {
 440             ty::Dynamic(..) => {
 441                 // Dropping a trait object.
 442                 self.unpack_dyn_trait(place)?
 443             }
 444             _ => (instance, place),
 445         };
 446
 447         let arg = ImmTy::from_immediate(
 448             place.to_ref(),
 449             self.layout_of(self.tcx.mk_mut_ptr(place.layout.ty))?,
 450         );
 451
 452         let ty = self.tcx.mk_unit(); // return type is ()
 453         let dest = MPlaceTy::dangling(self.layout_of(ty)?, self);
 454
 455         self.eval_fn_call(
 456             FnVal::Instance(instance),
 457             Abi::Rust,
 458             &[arg.into()],
 459             Some((dest.into(), target)),
 460             unwind,
 461         )
 462     }
 463 }