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