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_loc = self.frame().loc;
  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().loc == old_loc {
  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             // Inline assembly can't be interpreted.
 136             InlineAsm { .. } => throw_unsup_format!("inline assembly is not supported"),
 137         }
 138
 139         Ok(())
 140     }
 141
 142     fn check_argument_compat(
 143         rust_abi: bool,
 144         caller: TyAndLayout<'tcx>,
 145         callee: TyAndLayout<'tcx>,
 146     ) -> bool {
 147         if caller.ty == callee.ty {
 148             // No question
 149             return true;
 150         }
 151         if !rust_abi {
 152             // Don't risk anything
 153             return false;
 154         }
 155         // Compare layout
 156         match (&caller.abi, &callee.abi) {
 157             // Different valid ranges are okay (once we enforce validity,
 158             // that will take care to make it UB to leave the range, just
 159             // like for transmute).
 160             (abi::Abi::Scalar(ref caller), abi::Abi::Scalar(ref callee)) => {
 161                 caller.value == callee.value
 162             }
 163             (
 164                 abi::Abi::ScalarPair(ref caller1, ref caller2),
 165                 abi::Abi::ScalarPair(ref callee1, ref callee2),
 166             ) => caller1.value == callee1.value && caller2.value == callee2.value,
 167             // Be conservative
 168             _ => false,
 169         }
 170     }
 171
 172     /// Pass a single argument, checking the types for compatibility.
 173     fn pass_argument(
 174         &mut self,
 175         rust_abi: bool,
 176         caller_arg: &mut impl Iterator<Item = OpTy<'tcx, M::PointerTag>>,
 177         callee_arg: PlaceTy<'tcx, M::PointerTag>,
 178     ) -> InterpResult<'tcx> {
 179         if rust_abi && callee_arg.layout.is_zst() {
 180             // Nothing to do.
 181             trace!("Skipping callee ZST");
 182             return Ok(());
 183         }
 184         let caller_arg = caller_arg.next().ok_or_else(|| {
 185             err_ub_format!("calling a function with fewer arguments than it requires")
 186         })?;
 187         if rust_abi {
 188             assert!(!caller_arg.layout.is_zst(), "ZSTs must have been already filtered out");
 189         }
 190         // Now, check
 191         if !Self::check_argument_compat(rust_abi, caller_arg.layout, callee_arg.layout) {
 192             throw_ub_format!(
 193                 "calling a function with argument of type {:?} passing data of type {:?}",
 194                 callee_arg.layout.ty,
 195                 caller_arg.layout.ty
 196             )
 197         }
 198         // We allow some transmutes here
 199         self.copy_op_transmute(caller_arg, callee_arg)
 200     }
 201
 202     /// Call this function -- pushing the stack frame and initializing the arguments.
 203     fn eval_fn_call(
 204         &mut self,
 205         fn_val: FnVal<'tcx, M::ExtraFnVal>,
 206         caller_abi: Abi,
 207         args: &[OpTy<'tcx, M::PointerTag>],
 208         ret: Option<(PlaceTy<'tcx, M::PointerTag>, mir::BasicBlock)>,
 209         unwind: Option<mir::BasicBlock>,
 210     ) -> InterpResult<'tcx> {
 211         trace!("eval_fn_call: {:#?}", fn_val);
 212
 213         let instance = match fn_val {
 214             FnVal::Instance(instance) => instance,
 215             FnVal::Other(extra) => {
 216                 return M::call_extra_fn(self, extra, args, ret, unwind);
 217             }
 218         };
 219
 220         // ABI check
 221         {
 222             let callee_abi = {
 223                 let instance_ty = instance.ty_env(*self.tcx, self.param_env);
 224                 match instance_ty.kind {
 225                     ty::FnDef(..) => instance_ty.fn_sig(*self.tcx).abi(),
 226                     ty::Closure(..) => Abi::RustCall,
 227                     ty::Generator(..) => Abi::Rust,
 228                     _ => bug!("unexpected callee ty: {:?}", instance_ty),
 229                 }
 230             };
 231             let normalize_abi = |abi| match abi {
 232                 Abi::Rust | Abi::RustCall | Abi::RustIntrinsic | Abi::PlatformIntrinsic =>
 233                 // These are all the same ABI, really.
 234                 {
 235                     Abi::Rust
 236                 }
 237                 abi => abi,
 238             };
 239             if normalize_abi(caller_abi) != normalize_abi(callee_abi) {
 240                 throw_ub_format!(
 241                     "calling a function with ABI {:?} using caller ABI {:?}",
 242                     callee_abi,
 243                     caller_abi
 244                 )
 245             }
 246         }
 247
 248         match instance.def {
 249             ty::InstanceDef::Intrinsic(..) => {
 250                 assert!(caller_abi == Abi::RustIntrinsic || caller_abi == Abi::PlatformIntrinsic);
 251                 M::call_intrinsic(self, instance, args, ret, unwind)
 252             }
 253             ty::InstanceDef::VtableShim(..)
 254             | ty::InstanceDef::ReifyShim(..)
 255             | ty::InstanceDef::ClosureOnceShim { .. }
 256             | ty::InstanceDef::FnPtrShim(..)
 257             | ty::InstanceDef::DropGlue(..)
 258             | ty::InstanceDef::CloneShim(..)
 259             | ty::InstanceDef::Item(_) => {
 260                 // We need MIR for this fn
 261                 let body = match M::find_mir_or_eval_fn(self, instance, args, ret, unwind)? {
 262                     Some(body) => body,
 263                     None => return Ok(()),
 264                 };
 265
 266                 self.push_stack_frame(
 267                     instance,
 268                     body,
 269                     ret.map(|p| p.0),
 270                     StackPopCleanup::Goto { ret: ret.map(|p| p.1), unwind },
 271                 )?;
 272
 273                 // If an error is raised here, pop the frame again to get an accurate backtrace.
 274                 // To this end, we wrap it all in a `try` block.
 275                 let res: InterpResult<'tcx> = try {
 276                     trace!(
 277                         "caller ABI: {:?}, args: {:#?}",
 278                         caller_abi,
 279                         args.iter()
 280                             .map(|arg| (arg.layout.ty, format!("{:?}", **arg)))
 281                             .collect::<Vec<_>>()
 282                     );
 283                     trace!(
 284                         "spread_arg: {:?}, locals: {:#?}",
 285                         body.spread_arg,
 286                         body.args_iter()
 287                             .map(|local| (
 288                                 local,
 289                                 self.layout_of_local(self.frame(), local, None).unwrap().ty
 290                             ))
 291                             .collect::<Vec<_>>()
 292                     );
 293
 294                     // Figure out how to pass which arguments.
 295                     // The Rust ABI is special: ZST get skipped.
 296                     let rust_abi = match caller_abi {
 297                         Abi::Rust | Abi::RustCall => true,
 298                         _ => false,
 299                     };
 300                     // We have two iterators: Where the arguments come from,
 301                     // and where they go to.
 302
 303                     // For where they come from: If the ABI is RustCall, we untuple the
 304                     // last incoming argument.  These two iterators do not have the same type,
 305                     // so to keep the code paths uniform we accept an allocation
 306                     // (for RustCall ABI only).
 307                     let caller_args: Cow<'_, [OpTy<'tcx, M::PointerTag>]> =
 308                         if caller_abi == Abi::RustCall && !args.is_empty() {
 309                             // Untuple
 310                             let (&untuple_arg, args) = args.split_last().unwrap();
 311                             trace!("eval_fn_call: Will pass last argument by untupling");
 312                             Cow::from(
 313                                 args.iter()
 314                                     .map(|&a| Ok(a))
 315                                     .chain(
 316                                         (0..untuple_arg.layout.fields.count())
 317                                             .map(|i| self.operand_field(untuple_arg, i)),
 318                                     )
 319                                     .collect::<InterpResult<'_, Vec<OpTy<'tcx, M::PointerTag>>>>(
 320                                     )?,
 321                             )
 322                         } else {
 323                             // Plain arg passing
 324                             Cow::from(args)
 325                         };
 326                     // Skip ZSTs
 327                     let mut caller_iter =
 328                         caller_args.iter().filter(|op| !rust_abi || !op.layout.is_zst()).copied();
 329
 330                     // Now we have to spread them out across the callee's locals,
 331                     // taking into account the `spread_arg`.  If we could write
 332                     // this is a single iterator (that handles `spread_arg`), then
 333                     // `pass_argument` would be the loop body. It takes care to
 334                     // not advance `caller_iter` for ZSTs.
 335                     for local in body.args_iter() {
 336                         let dest = self.eval_place(mir::Place::from(local))?;
 337                         if Some(local) == body.spread_arg {
 338                             // Must be a tuple
 339                             for i in 0..dest.layout.fields.count() {
 340                                 let dest = self.place_field(dest, i)?;
 341                                 self.pass_argument(rust_abi, &mut caller_iter, dest)?;
 342                             }
 343                         } else {
 344                             // Normal argument
 345                             self.pass_argument(rust_abi, &mut caller_iter, dest)?;
 346                         }
 347                     }
 348                     // Now we should have no more caller args
 349                     if caller_iter.next().is_some() {
 350                         throw_ub_format!("calling a function with more arguments than it expected")
 351                     }
 352                     // Don't forget to check the return type!
 353                     if let Some((caller_ret, _)) = ret {
 354                         let callee_ret = self.eval_place(mir::Place::return_place())?;
 355                         if !Self::check_argument_compat(
 356                             rust_abi,
 357                             caller_ret.layout,
 358                             callee_ret.layout,
 359                         ) {
 360                             throw_ub_format!(
 361                                 "calling a function with return type {:?} passing \
 362                                      return place of type {:?}",
 363                                 callee_ret.layout.ty,
 364                                 caller_ret.layout.ty
 365                             )
 366                         }
 367                     } else {
 368                         let local = mir::RETURN_PLACE;
 369                         let callee_layout = self.layout_of_local(self.frame(), local, None)?;
 370                         if !callee_layout.abi.is_uninhabited() {
 371                             throw_ub_format!("calling a returning function without a return place")
 372                         }
 373                     }
 374                 };
 375                 match res {
 376                     Err(err) => {
 377                         self.stack_mut().pop();
 378                         Err(err)
 379                     }
 380                     Ok(()) => Ok(()),
 381                 }
 382             }
 383             // cannot use the shim here, because that will only result in infinite recursion
 384             ty::InstanceDef::Virtual(_, idx) => {
 385                 let mut args = args.to_vec();
 386                 // We have to implement all "object safe receivers".  Currently we
 387                 // support built-in pointers (&, &mut, Box) as well as unsized-self.  We do
 388                 // not yet support custom self types.
 389                 // Also see librustc_codegen_llvm/abi.rs and librustc_codegen_llvm/mir/block.rs.
 390                 let receiver_place = match args[0].layout.ty.builtin_deref(true) {
 391                     Some(_) => {
 392                         // Built-in pointer.
 393                         self.deref_operand(args[0])?
 394                     }
 395                     None => {
 396                         // Unsized self.
 397                         args[0].assert_mem_place(self)
 398                     }
 399                 };
 400                 // Find and consult vtable
 401                 let vtable = receiver_place.vtable();
 402                 let drop_fn = self.get_vtable_slot(vtable, u64::try_from(idx).unwrap())?;
 403
 404                 // `*mut receiver_place.layout.ty` is almost the layout that we
 405                 // want for args[0]: We have to project to field 0 because we want
 406                 // a thin pointer.
 407                 assert!(receiver_place.layout.is_unsized());
 408                 let receiver_ptr_ty = self.tcx.mk_mut_ptr(receiver_place.layout.ty);
 409                 let this_receiver_ptr = self.layout_of(receiver_ptr_ty)?.field(self, 0)?;
 410                 // Adjust receiver argument.
 411                 args[0] =
 412                     OpTy::from(ImmTy::from_immediate(receiver_place.ptr.into(), this_receiver_ptr));
 413                 trace!("Patched self operand to {:#?}", args[0]);
 414                 // recurse with concrete function
 415                 self.eval_fn_call(drop_fn, caller_abi, &args, ret, unwind)
 416             }
 417         }
 418     }
 419
 420     fn drop_in_place(
 421         &mut self,
 422         place: PlaceTy<'tcx, M::PointerTag>,
 423         instance: ty::Instance<'tcx>,
 424         target: mir::BasicBlock,
 425         unwind: Option<mir::BasicBlock>,
 426     ) -> InterpResult<'tcx> {
 427         trace!("drop_in_place: {:?},\n  {:?}, {:?}", *place, place.layout.ty, instance);
 428         // We take the address of the object.  This may well be unaligned, which is fine
 429         // for us here.  However, unaligned accesses will probably make the actual drop
 430         // implementation fail -- a problem shared by rustc.
 431         let place = self.force_allocation(place)?;
 432
 433         let (instance, place) = match place.layout.ty.kind {
 434             ty::Dynamic(..) => {
 435                 // Dropping a trait object.
 436                 self.unpack_dyn_trait(place)?
 437             }
 438             _ => (instance, place),
 439         };
 440
 441         let arg = ImmTy::from_immediate(
 442             place.to_ref(),
 443             self.layout_of(self.tcx.mk_mut_ptr(place.layout.ty))?,
 444         );
 445
 446         let ty = self.tcx.mk_unit(); // return type is ()
 447         let dest = MPlaceTy::dangling(self.layout_of(ty)?, self);
 448
 449         self.eval_fn_call(
 450             FnVal::Instance(instance),
 451             Abi::Rust,
 452             &[arg.into()],
 453             Some((dest.into(), target)),
 454             unwind,
 455         )
 456     }
 457 }