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