src/shims/foreign_items.rs

   1 mod windows;
   2 mod posix;
   3
   4 use std::{convert::TryInto, iter};
   5
   6 use rustc_hir::def_id::DefId;
   7 use rustc::mir;
   8 use rustc::ty;
   9 use rustc::ty::layout::{Align, Size};
  10 use rustc_apfloat::Float;
  11 use rustc_span::symbol::sym;
  12 use syntax::attr;
  13
  14 use crate::*;
  15
  16 impl<'mir, 'tcx> EvalContextExt<'mir, 'tcx> for crate::MiriEvalContext<'mir, 'tcx> {}
  17 pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx> {
  18     /// Returns the minimum alignment for the target architecture for allocations of the given size.
  19     fn min_align(&self, size: u64, kind: MiriMemoryKind) -> Align {
  20         let this = self.eval_context_ref();
  21         // List taken from `libstd/sys_common/alloc.rs`.
  22         let min_align = match this.tcx.tcx.sess.target.target.arch.as_str() {
  23             "x86" | "arm" | "mips" | "powerpc" | "powerpc64" | "asmjs" | "wasm32" => 8,
  24             "x86_64" | "aarch64" | "mips64" | "s390x" | "sparc64" => 16,
  25             arch => bug!("Unsupported target architecture: {}", arch),
  26         };
  27         // Windows always aligns, even small allocations.
  28         // Source: <https://support.microsoft.com/en-us/help/286470/how-to-use-pageheap-exe-in-windows-xp-windows-2000-and-windows-server>
  29         // But jemalloc does not, so for the C heap we only align if the allocation is sufficiently big.
  30         if kind == MiriMemoryKind::WinHeap || size >= min_align {
  31             return Align::from_bytes(min_align).unwrap();
  32         }
  33         // We have `size < min_align`. Round `size` *down* to the next power of two and use that.
  34         fn prev_power_of_two(x: u64) -> u64 {
  35             let next_pow2 = x.next_power_of_two();
  36             if next_pow2 == x {
  37                 // x *is* a power of two, just use that.
  38                 x
  39             } else {
  40                 // x is between two powers, so next = 2*prev.
  41                 next_pow2 / 2
  42             }
  43         }
  44         Align::from_bytes(prev_power_of_two(size)).unwrap()
  45     }
  46
  47     fn malloc(&mut self, size: u64, zero_init: bool, kind: MiriMemoryKind) -> Scalar<Tag> {
  48         let this = self.eval_context_mut();
  49         if size == 0 {
  50             Scalar::from_int(0, this.pointer_size())
  51         } else {
  52             let align = this.min_align(size, kind);
  53             let ptr = this.memory.allocate(Size::from_bytes(size), align, kind.into());
  54             if zero_init {
  55                 // We just allocated this, the access is definitely in-bounds.
  56                 this.memory.write_bytes(ptr.into(), iter::repeat(0u8).take(size as usize)).unwrap();
  57             }
  58             Scalar::Ptr(ptr)
  59         }
  60     }
  61
  62     fn free(&mut self, ptr: Scalar<Tag>, kind: MiriMemoryKind) -> InterpResult<'tcx> {
  63         let this = self.eval_context_mut();
  64         if !this.is_null(ptr)? {
  65             let ptr = this.force_ptr(ptr)?;
  66             this.memory.deallocate(ptr, None, kind.into())?;
  67         }
  68         Ok(())
  69     }
  70
  71     fn realloc(
  72         &mut self,
  73         old_ptr: Scalar<Tag>,
  74         new_size: u64,
  75         kind: MiriMemoryKind,
  76     ) -> InterpResult<'tcx, Scalar<Tag>> {
  77         let this = self.eval_context_mut();
  78         let new_align = this.min_align(new_size, kind);
  79         if this.is_null(old_ptr)? {
  80             if new_size == 0 {
  81                 Ok(Scalar::from_int(0, this.pointer_size()))
  82             } else {
  83                 let new_ptr =
  84                     this.memory.allocate(Size::from_bytes(new_size), new_align, kind.into());
  85                 Ok(Scalar::Ptr(new_ptr))
  86             }
  87         } else {
  88             let old_ptr = this.force_ptr(old_ptr)?;
  89             if new_size == 0 {
  90                 this.memory.deallocate(old_ptr, None, kind.into())?;
  91                 Ok(Scalar::from_int(0, this.pointer_size()))
  92             } else {
  93                 let new_ptr = this.memory.reallocate(
  94                     old_ptr,
  95                     None,
  96                     Size::from_bytes(new_size),
  97                     new_align,
  98                     kind.into(),
  99                 )?;
 100                 Ok(Scalar::Ptr(new_ptr))
 101             }
 102         }
 103     }
 104
 105     /// Emulates calling a foreign item, failing if the item is not supported.
 106     /// This function will handle `goto_block` if needed.
 107     /// Returns Ok(None) if the foreign item was completely handled
 108     /// by this function.
 109     /// Returns Ok(Some(body)) if processing the foreign item
 110     /// is delegated to another function.
 111     #[rustfmt::skip]
 112     fn emulate_foreign_item(
 113         &mut self,
 114         def_id: DefId,
 115         args: &[OpTy<'tcx, Tag>],
 116         ret: Option<(PlaceTy<'tcx, Tag>, mir::BasicBlock)>,
 117         _unwind: Option<mir::BasicBlock>,
 118     ) -> InterpResult<'tcx, Option<&'mir mir::Body<'tcx>>> {
 119         let this = self.eval_context_mut();
 120         let attrs = this.tcx.get_attrs(def_id);
 121         let link_name = match attr::first_attr_value_str_by_name(&attrs, sym::link_name) {
 122             Some(name) => name.as_str(),
 123             None => this.tcx.item_name(def_id).as_str(),
 124         };
 125         // Strip linker suffixes (seen on 32-bit macOS).
 126         let link_name = link_name.trim_end_matches("$UNIX2003");
 127         let tcx = &{ this.tcx.tcx };
 128
 129         // First: functions that diverge.
 130         let (dest, ret) = match link_name {
 131             // Note that this matches calls to the *foreign* item `__rust_start_panic* -
 132             // that is, calls to `extern "Rust" { fn __rust_start_panic(...) }`.
 133             // We forward this to the underlying *implementation* in the panic runtime crate.
 134             // Normally, this will be either `libpanic_unwind` or `libpanic_abort`, but it could
 135             // also be a custom user-provided implementation via `#![feature(panic_runtime)]`
 136             "__rust_start_panic" => {
 137                 // FIXME we might want to cache this... but it's not really performance-critical.
 138                 let panic_runtime = tcx
 139                     .crates()
 140                     .iter()
 141                     .find(|cnum| tcx.is_panic_runtime(**cnum))
 142                     .expect("No panic runtime found!");
 143                 let panic_runtime = tcx.crate_name(*panic_runtime);
 144                 let start_panic_instance =
 145                     this.resolve_path(&[&*panic_runtime.as_str(), "__rust_start_panic"])?;
 146                 return Ok(Some(&*this.load_mir(start_panic_instance.def, None)?));
 147             }
 148             // Similarly, we forward calls to the `panic_impl` foreign item to its implementation.
 149             // The implementation is provided by the function with the `#[panic_handler]` attribute.
 150             "panic_impl" => {
 151                 let panic_impl_id = this.tcx.lang_items().panic_impl().unwrap();
 152                 let panic_impl_instance = ty::Instance::mono(*this.tcx, panic_impl_id);
 153                 return Ok(Some(&*this.load_mir(panic_impl_instance.def, None)?));
 154             }
 155
 156             | "exit"
 157             | "ExitProcess"
 158             => {
 159                 // it's really u32 for ExitProcess, but we have to put it into the `Exit` variant anyway
 160                 let code = this.read_scalar(args[0])?.to_i32()?;
 161                 throw_machine_stop!(TerminationInfo::Exit(code.into()));
 162             }
 163             _ => {
 164                 if let Some(p) = ret {
 165                     p
 166                 } else {
 167                     throw_unsup_format!("can't call (diverging) foreign function: {}", link_name);
 168                 }
 169             }
 170         };
 171
 172         // Next: functions that return.
 173         if this.emulate_foreign_item_by_name(link_name, args, dest, ret)? {
 174             this.dump_place(*dest);
 175             this.go_to_block(ret);
 176         }
 177
 178         Ok(None)
 179     }
 180
 181     fn emulate_foreign_item_by_name(
 182         &mut self,
 183         link_name: &str,
 184         args: &[OpTy<'tcx, Tag>],
 185         dest: PlaceTy<'tcx, Tag>,
 186         ret: mir::BasicBlock,
 187     ) -> InterpResult<'tcx, bool> {
 188         let this = self.eval_context_mut();
 189
 190         // Here we dispatch all the shims for foreign functions. If you have a platform specific
 191         // shim, add it to the corresponding submodule.
 192         match link_name {
 193             "malloc" => {
 194                 let size = this.read_scalar(args[0])?.to_machine_usize(this)?;
 195                 let res = this.malloc(size, /*zero_init:*/ false, MiriMemoryKind::C);
 196                 this.write_scalar(res, dest)?;
 197             }
 198             "calloc" => {
 199                 let items = this.read_scalar(args[0])?.to_machine_usize(this)?;
 200                 let len = this.read_scalar(args[1])?.to_machine_usize(this)?;
 201                 let size =
 202                     items.checked_mul(len).ok_or_else(|| err_ub_format!("overflow during calloc size computation"))?;
 203                 let res = this.malloc(size, /*zero_init:*/ true, MiriMemoryKind::C);
 204                 this.write_scalar(res, dest)?;
 205             }
 206             "free" => {
 207                 let ptr = this.read_scalar(args[0])?.not_undef()?;
 208                 this.free(ptr, MiriMemoryKind::C)?;
 209             }
 210             "realloc" => {
 211                 let old_ptr = this.read_scalar(args[0])?.not_undef()?;
 212                 let new_size = this.read_scalar(args[1])?.to_machine_usize(this)?;
 213                 let res = this.realloc(old_ptr, new_size, MiriMemoryKind::C)?;
 214                 this.write_scalar(res, dest)?;
 215             }
 216
 217             "__rust_alloc" => {
 218                 let size = this.read_scalar(args[0])?.to_machine_usize(this)?;
 219                 let align = this.read_scalar(args[1])?.to_machine_usize(this)?;
 220                 if size == 0 {
 221                     throw_unsup!(HeapAllocZeroBytes);
 222                 }
 223                 if !align.is_power_of_two() {
 224                     throw_unsup!(HeapAllocNonPowerOfTwoAlignment(align));
 225                 }
 226                 let ptr = this.memory.allocate(
 227                     Size::from_bytes(size),
 228                     Align::from_bytes(align).unwrap(),
 229                     MiriMemoryKind::Rust.into(),
 230                 );
 231                 this.write_scalar(ptr, dest)?;
 232             }
 233             "__rust_alloc_zeroed" => {
 234                 let size = this.read_scalar(args[0])?.to_machine_usize(this)?;
 235                 let align = this.read_scalar(args[1])?.to_machine_usize(this)?;
 236                 if size == 0 {
 237                     throw_unsup!(HeapAllocZeroBytes);
 238                 }
 239                 if !align.is_power_of_two() {
 240                     throw_unsup!(HeapAllocNonPowerOfTwoAlignment(align));
 241                 }
 242                 let ptr = this.memory.allocate(
 243                     Size::from_bytes(size),
 244                     Align::from_bytes(align).unwrap(),
 245                     MiriMemoryKind::Rust.into(),
 246                 );
 247                 // We just allocated this, the access is definitely in-bounds.
 248                 this.memory.write_bytes(ptr.into(), iter::repeat(0u8).take(size as usize)).unwrap();
 249                 this.write_scalar(ptr, dest)?;
 250             }
 251             "__rust_dealloc" => {
 252                 let ptr = this.read_scalar(args[0])?.not_undef()?;
 253                 let old_size = this.read_scalar(args[1])?.to_machine_usize(this)?;
 254                 let align = this.read_scalar(args[2])?.to_machine_usize(this)?;
 255                 if old_size == 0 {
 256                     throw_unsup!(HeapAllocZeroBytes);
 257                 }
 258                 if !align.is_power_of_two() {
 259                     throw_unsup!(HeapAllocNonPowerOfTwoAlignment(align));
 260                 }
 261                 let ptr = this.force_ptr(ptr)?;
 262                 this.memory.deallocate(
 263                     ptr,
 264                     Some((Size::from_bytes(old_size), Align::from_bytes(align).unwrap())),
 265                     MiriMemoryKind::Rust.into(),
 266                 )?;
 267             }
 268             "__rust_realloc" => {
 269                 let old_size = this.read_scalar(args[1])?.to_machine_usize(this)?;
 270                 let align = this.read_scalar(args[2])?.to_machine_usize(this)?;
 271                 let new_size = this.read_scalar(args[3])?.to_machine_usize(this)?;
 272                 if old_size == 0 || new_size == 0 {
 273                     throw_unsup!(HeapAllocZeroBytes);
 274                 }
 275                 if !align.is_power_of_two() {
 276                     throw_unsup!(HeapAllocNonPowerOfTwoAlignment(align));
 277                 }
 278                 let ptr = this.force_ptr(this.read_scalar(args[0])?.not_undef()?)?;
 279                 let align = Align::from_bytes(align).unwrap();
 280                 let new_ptr = this.memory.reallocate(
 281                     ptr,
 282                     Some((Size::from_bytes(old_size), align)),
 283                     Size::from_bytes(new_size),
 284                     align,
 285                     MiriMemoryKind::Rust.into(),
 286                 )?;
 287                 this.write_scalar(new_ptr, dest)?;
 288             }
 289
 290             "__rust_maybe_catch_panic" => {
 291                 this.handle_catch_panic(args, dest, ret)?;
 292                 return Ok(false);
 293             }
 294
 295             "memcmp" => {
 296                 let left = this.read_scalar(args[0])?.not_undef()?;
 297                 let right = this.read_scalar(args[1])?.not_undef()?;
 298                 let n = Size::from_bytes(this.read_scalar(args[2])?.to_machine_usize(this)?);
 299
 300                 let result = {
 301                     let left_bytes = this.memory.read_bytes(left, n)?;
 302                     let right_bytes = this.memory.read_bytes(right, n)?;
 303
 304                     use std::cmp::Ordering::*;
 305                     match left_bytes.cmp(right_bytes) {
 306                         Less => -1i32,
 307                         Equal => 0,
 308                         Greater => 1,
 309                     }
 310                 };
 311
 312                 this.write_scalar(Scalar::from_int(result, Size::from_bits(32)), dest)?;
 313             }
 314
 315             "memchr" => {
 316                 let ptr = this.read_scalar(args[0])?.not_undef()?;
 317                 let val = this.read_scalar(args[1])?.to_i32()? as u8;
 318                 let num = this.read_scalar(args[2])?.to_machine_usize(this)?;
 319                 let idx = this
 320                     .memory
 321                     .read_bytes(ptr, Size::from_bytes(num))?
 322                     .iter()
 323                     .position(|&c| c == val);
 324                 if let Some(idx) = idx {
 325                     let new_ptr = ptr.ptr_offset(Size::from_bytes(idx as u64), this)?;
 326                     this.write_scalar(new_ptr, dest)?;
 327                 } else {
 328                     this.write_null(dest)?;
 329                 }
 330             }
 331
 332             "strlen" => {
 333                 let ptr = this.read_scalar(args[0])?.not_undef()?;
 334                 let n = this.memory.read_c_str(ptr)?.len();
 335                 this.write_scalar(Scalar::from_uint(n as u64, dest.layout.size), dest)?;
 336             }
 337
 338             // math functions
 339             | "cbrtf"
 340             | "coshf"
 341             | "sinhf"
 342             | "tanf"
 343             | "acosf"
 344             | "asinf"
 345             | "atanf"
 346             => {
 347                 // FIXME: Using host floats.
 348                 let f = f32::from_bits(this.read_scalar(args[0])?.to_u32()?);
 349                 let f = match link_name {
 350                     "cbrtf" => f.cbrt(),
 351                     "coshf" => f.cosh(),
 352                     "sinhf" => f.sinh(),
 353                     "tanf" => f.tan(),
 354                     "acosf" => f.acos(),
 355                     "asinf" => f.asin(),
 356                     "atanf" => f.atan(),
 357                     _ => bug!(),
 358                 };
 359                 this.write_scalar(Scalar::from_u32(f.to_bits()), dest)?;
 360             }
 361             // underscore case for windows
 362             | "_hypotf"
 363             | "hypotf"
 364             | "atan2f"
 365             => {
 366                 // FIXME: Using host floats.
 367                 let f1 = f32::from_bits(this.read_scalar(args[0])?.to_u32()?);
 368                 let f2 = f32::from_bits(this.read_scalar(args[1])?.to_u32()?);
 369                 let n = match link_name {
 370                     "_hypotf" | "hypotf" => f1.hypot(f2),
 371                     "atan2f" => f1.atan2(f2),
 372                     _ => bug!(),
 373                 };
 374                 this.write_scalar(Scalar::from_u32(n.to_bits()), dest)?;
 375             }
 376
 377             | "cbrt"
 378             | "cosh"
 379             | "sinh"
 380             | "tan"
 381             | "acos"
 382             | "asin"
 383             | "atan"
 384             => {
 385                 // FIXME: Using host floats.
 386                 let f = f64::from_bits(this.read_scalar(args[0])?.to_u64()?);
 387                 let f = match link_name {
 388                     "cbrt" => f.cbrt(),
 389                     "cosh" => f.cosh(),
 390                     "sinh" => f.sinh(),
 391                     "tan" => f.tan(),
 392                     "acos" => f.acos(),
 393                     "asin" => f.asin(),
 394                     "atan" => f.atan(),
 395                     _ => bug!(),
 396                 };
 397                 this.write_scalar(Scalar::from_u64(f.to_bits()), dest)?;
 398             }
 399             // underscore case for windows, here and below
 400             // (see https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/floating-point-primitives?view=vs-2019)
 401             | "_hypot"
 402             | "hypot"
 403             | "atan2"
 404             => {
 405                 // FIXME: Using host floats.
 406                 let f1 = f64::from_bits(this.read_scalar(args[0])?.to_u64()?);
 407                 let f2 = f64::from_bits(this.read_scalar(args[1])?.to_u64()?);
 408                 let n = match link_name {
 409                     "_hypot" | "hypot" => f1.hypot(f2),
 410                     "atan2" => f1.atan2(f2),
 411                     _ => bug!(),
 412                 };
 413                 this.write_scalar(Scalar::from_u64(n.to_bits()), dest)?;
 414             }
 415             // For radix-2 (binary) systems, `ldexp` and `scalbn` are the same.
 416             | "_ldexp"
 417             | "ldexp"
 418             | "scalbn"
 419             => {
 420                 let x = this.read_scalar(args[0])?.to_f64()?;
 421                 let exp = this.read_scalar(args[1])?.to_i32()?;
 422
 423                 // Saturating cast to i16. Even those are outside the valid exponent range to
 424                 // `scalbn` below will do its over/underflow handling.
 425                 let exp = if exp > i16::max_value() as i32 {
 426                     i16::max_value()
 427                 } else if exp < i16::min_value() as i32 {
 428                     i16::min_value()
 429                 } else {
 430                     exp.try_into().unwrap()
 431                 };
 432
 433                 let res = x.scalbn(exp);
 434                 this.write_scalar(Scalar::from_f64(res), dest)?;
 435             }
 436
 437             _ => match this.tcx.sess.target.target.target_os.to_lowercase().as_str() {
 438                 "linux" | "macos" => return posix::EvalContextExt::emulate_foreign_item_by_name(this, link_name, args, dest, ret),
 439                 "windows" => return windows::EvalContextExt::emulate_foreign_item_by_name(this, link_name, args, dest, ret),
 440                 target => throw_unsup_format!("The {} target platform is not supported", target),
 441             }
 442         };
 443
 444         Ok(true)
 445     }
 446
 447     /// Evaluates the scalar at the specified path. Returns Some(val)
 448     /// if the path could be resolved, and None otherwise
 449     fn eval_path_scalar(
 450         &mut self,
 451         path: &[&str],
 452     ) -> InterpResult<'tcx, Option<ScalarMaybeUndef<Tag>>> {
 453         let this = self.eval_context_mut();
 454         if let Ok(instance) = this.resolve_path(path) {
 455             let cid = GlobalId { instance, promoted: None };
 456             let const_val = this.const_eval_raw(cid)?;
 457             let const_val = this.read_scalar(const_val.into())?;
 458             return Ok(Some(const_val));
 459         }
 460         return Ok(None);
 461     }
 462 }