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, LayoutOf, 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         match link_name {
 174             "__rust_maybe_catch_panic" => {
 175                 this.handle_catch_panic(args, dest, ret)?;
 176                 return Ok(None);
 177             }
 178
 179             _ => this.emulate_foreign_item_by_name(link_name, args, dest)?,
 180         };
 181
 182         this.dump_place(*dest);
 183         this.go_to_block(ret);
 184
 185         Ok(None)
 186     }
 187
 188     fn emulate_foreign_item_by_name(
 189         &mut self,
 190         link_name: &str,
 191         args: &[OpTy<'tcx, Tag>],
 192         dest: PlaceTy<'tcx, Tag>,
 193     ) -> InterpResult<'tcx> {
 194         let this = self.eval_context_mut();
 195         let tcx = &{ this.tcx.tcx };
 196
 197         match link_name {
 198             "malloc" => {
 199                 let size = this.read_scalar(args[0])?.to_machine_usize(this)?;
 200                 let res = this.malloc(size, /*zero_init:*/ false, MiriMemoryKind::C);
 201                 this.write_scalar(res, dest)?;
 202             }
 203             "calloc" => {
 204                 let items = this.read_scalar(args[0])?.to_machine_usize(this)?;
 205                 let len = this.read_scalar(args[1])?.to_machine_usize(this)?;
 206                 let size =
 207                     items.checked_mul(len).ok_or_else(|| err_ub_format!("overflow during calloc size computation"))?;
 208                 let res = this.malloc(size, /*zero_init:*/ true, MiriMemoryKind::C);
 209                 this.write_scalar(res, dest)?;
 210             }
 211             "free" => {
 212                 let ptr = this.read_scalar(args[0])?.not_undef()?;
 213                 this.free(ptr, MiriMemoryKind::C)?;
 214             }
 215             "realloc" => {
 216                 let old_ptr = this.read_scalar(args[0])?.not_undef()?;
 217                 let new_size = this.read_scalar(args[1])?.to_machine_usize(this)?;
 218                 let res = this.realloc(old_ptr, new_size, MiriMemoryKind::C)?;
 219                 this.write_scalar(res, dest)?;
 220             }
 221
 222             "__rust_alloc" => {
 223                 let size = this.read_scalar(args[0])?.to_machine_usize(this)?;
 224                 let align = this.read_scalar(args[1])?.to_machine_usize(this)?;
 225                 if size == 0 {
 226                     throw_unsup!(HeapAllocZeroBytes);
 227                 }
 228                 if !align.is_power_of_two() {
 229                     throw_unsup!(HeapAllocNonPowerOfTwoAlignment(align));
 230                 }
 231                 let ptr = this.memory.allocate(
 232                     Size::from_bytes(size),
 233                     Align::from_bytes(align).unwrap(),
 234                     MiriMemoryKind::Rust.into(),
 235                 );
 236                 this.write_scalar(ptr, dest)?;
 237             }
 238             "__rust_alloc_zeroed" => {
 239                 let size = this.read_scalar(args[0])?.to_machine_usize(this)?;
 240                 let align = this.read_scalar(args[1])?.to_machine_usize(this)?;
 241                 if size == 0 {
 242                     throw_unsup!(HeapAllocZeroBytes);
 243                 }
 244                 if !align.is_power_of_two() {
 245                     throw_unsup!(HeapAllocNonPowerOfTwoAlignment(align));
 246                 }
 247                 let ptr = this.memory.allocate(
 248                     Size::from_bytes(size),
 249                     Align::from_bytes(align).unwrap(),
 250                     MiriMemoryKind::Rust.into(),
 251                 );
 252                 // We just allocated this, the access is definitely in-bounds.
 253                 this.memory.write_bytes(ptr.into(), iter::repeat(0u8).take(size as usize)).unwrap();
 254                 this.write_scalar(ptr, dest)?;
 255             }
 256             "__rust_dealloc" => {
 257                 let ptr = this.read_scalar(args[0])?.not_undef()?;
 258                 let old_size = this.read_scalar(args[1])?.to_machine_usize(this)?;
 259                 let align = this.read_scalar(args[2])?.to_machine_usize(this)?;
 260                 if old_size == 0 {
 261                     throw_unsup!(HeapAllocZeroBytes);
 262                 }
 263                 if !align.is_power_of_two() {
 264                     throw_unsup!(HeapAllocNonPowerOfTwoAlignment(align));
 265                 }
 266                 let ptr = this.force_ptr(ptr)?;
 267                 this.memory.deallocate(
 268                     ptr,
 269                     Some((Size::from_bytes(old_size), Align::from_bytes(align).unwrap())),
 270                     MiriMemoryKind::Rust.into(),
 271                 )?;
 272             }
 273             "__rust_realloc" => {
 274                 let old_size = this.read_scalar(args[1])?.to_machine_usize(this)?;
 275                 let align = this.read_scalar(args[2])?.to_machine_usize(this)?;
 276                 let new_size = this.read_scalar(args[3])?.to_machine_usize(this)?;
 277                 if old_size == 0 || new_size == 0 {
 278                     throw_unsup!(HeapAllocZeroBytes);
 279                 }
 280                 if !align.is_power_of_two() {
 281                     throw_unsup!(HeapAllocNonPowerOfTwoAlignment(align));
 282                 }
 283                 let ptr = this.force_ptr(this.read_scalar(args[0])?.not_undef()?)?;
 284                 let align = Align::from_bytes(align).unwrap();
 285                 let new_ptr = this.memory.reallocate(
 286                     ptr,
 287                     Some((Size::from_bytes(old_size), align)),
 288                     Size::from_bytes(new_size),
 289                     align,
 290                     MiriMemoryKind::Rust.into(),
 291                 )?;
 292                 this.write_scalar(new_ptr, dest)?;
 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
 333             "rename" => {
 334                 let result = this.rename(args[0], args[1])?;
 335                 this.write_scalar(Scalar::from_int(result, dest.layout.size), dest)?;
 336             }
 337
 338             "strlen" => {
 339                 let ptr = this.read_scalar(args[0])?.not_undef()?;
 340                 let n = this.memory.read_c_str(ptr)?.len();
 341                 this.write_scalar(Scalar::from_uint(n as u64, dest.layout.size), dest)?;
 342             }
 343
 344             // math functions
 345             | "cbrtf"
 346             | "coshf"
 347             | "sinhf"
 348             | "tanf"
 349             | "acosf"
 350             | "asinf"
 351             | "atanf"
 352             => {
 353                 // FIXME: Using host floats.
 354                 let f = f32::from_bits(this.read_scalar(args[0])?.to_u32()?);
 355                 let f = match link_name {
 356                     "cbrtf" => f.cbrt(),
 357                     "coshf" => f.cosh(),
 358                     "sinhf" => f.sinh(),
 359                     "tanf" => f.tan(),
 360                     "acosf" => f.acos(),
 361                     "asinf" => f.asin(),
 362                     "atanf" => f.atan(),
 363                     _ => bug!(),
 364                 };
 365                 this.write_scalar(Scalar::from_u32(f.to_bits()), dest)?;
 366             }
 367             // underscore case for windows
 368             | "_hypotf"
 369             | "hypotf"
 370             | "atan2f"
 371             => {
 372                 // FIXME: Using host floats.
 373                 let f1 = f32::from_bits(this.read_scalar(args[0])?.to_u32()?);
 374                 let f2 = f32::from_bits(this.read_scalar(args[1])?.to_u32()?);
 375                 let n = match link_name {
 376                     "_hypotf" | "hypotf" => f1.hypot(f2),
 377                     "atan2f" => f1.atan2(f2),
 378                     _ => bug!(),
 379                 };
 380                 this.write_scalar(Scalar::from_u32(n.to_bits()), dest)?;
 381             }
 382
 383             | "cbrt"
 384             | "cosh"
 385             | "sinh"
 386             | "tan"
 387             | "acos"
 388             | "asin"
 389             | "atan"
 390             => {
 391                 // FIXME: Using host floats.
 392                 let f = f64::from_bits(this.read_scalar(args[0])?.to_u64()?);
 393                 let f = match link_name {
 394                     "cbrt" => f.cbrt(),
 395                     "cosh" => f.cosh(),
 396                     "sinh" => f.sinh(),
 397                     "tan" => f.tan(),
 398                     "acos" => f.acos(),
 399                     "asin" => f.asin(),
 400                     "atan" => f.atan(),
 401                     _ => bug!(),
 402                 };
 403                 this.write_scalar(Scalar::from_u64(f.to_bits()), dest)?;
 404             }
 405             // underscore case for windows, here and below
 406             // (see https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/floating-point-primitives?view=vs-2019)
 407             | "_hypot"
 408             | "hypot"
 409             | "atan2"
 410             => {
 411                 // FIXME: Using host floats.
 412                 let f1 = f64::from_bits(this.read_scalar(args[0])?.to_u64()?);
 413                 let f2 = f64::from_bits(this.read_scalar(args[1])?.to_u64()?);
 414                 let n = match link_name {
 415                     "_hypot" | "hypot" => f1.hypot(f2),
 416                     "atan2" => f1.atan2(f2),
 417                     _ => bug!(),
 418                 };
 419                 this.write_scalar(Scalar::from_u64(n.to_bits()), dest)?;
 420             }
 421             // For radix-2 (binary) systems, `ldexp` and `scalbn` are the same.
 422             | "_ldexp"
 423             | "ldexp"
 424             | "scalbn"
 425             => {
 426                 let x = this.read_scalar(args[0])?.to_f64()?;
 427                 let exp = this.read_scalar(args[1])?.to_i32()?;
 428
 429                 // Saturating cast to i16. Even those are outside the valid exponent range to
 430                 // `scalbn` below will do its over/underflow handling.
 431                 let exp = if exp > i16::max_value() as i32 {
 432                     i16::max_value()
 433                 } else if exp < i16::min_value() as i32 {
 434                     i16::min_value()
 435                 } else {
 436                     exp.try_into().unwrap()
 437                 };
 438
 439                 let res = x.scalbn(exp);
 440                 this.write_scalar(Scalar::from_f64(res), dest)?;
 441             }
 442
 443             // Some things needed for `sys::thread` initialization to go through.
 444             | "signal"
 445             | "sigaction"
 446             | "sigaltstack"
 447             => {
 448                 this.write_scalar(Scalar::from_int(0, dest.layout.size), dest)?;
 449             }
 450
 451             "sysconf" => {
 452                 let name = this.read_scalar(args[0])?.to_i32()?;
 453
 454                 trace!("sysconf() called with name {}", name);
 455                 // TODO: Cache the sysconf integers via Miri's global cache.
 456                 let paths = &[
 457                     (&["libc", "_SC_PAGESIZE"], Scalar::from_int(PAGE_SIZE, dest.layout.size)),
 458                     (&["libc", "_SC_GETPW_R_SIZE_MAX"], Scalar::from_int(-1, dest.layout.size)),
 459                     (
 460                         &["libc", "_SC_NPROCESSORS_ONLN"],
 461                         Scalar::from_int(NUM_CPUS, dest.layout.size),
 462                     ),
 463                 ];
 464                 let mut result = None;
 465                 for &(path, path_value) in paths {
 466                     if let Some(val) = this.eval_path_scalar(path)? {
 467                         let val = val.to_i32()?;
 468                         if val == name {
 469                             result = Some(path_value);
 470                             break;
 471                         }
 472                     }
 473                 }
 474                 if let Some(result) = result {
 475                     this.write_scalar(result, dest)?;
 476                 } else {
 477                     throw_unsup_format!("Unimplemented sysconf name: {}", name)
 478                 }
 479             }
 480
 481             "sched_getaffinity" => {
 482                 // Return an error; `num_cpus` then falls back to `sysconf`.
 483                 this.write_scalar(Scalar::from_int(-1, dest.layout.size), dest)?;
 484             }
 485
 486             "isatty" => {
 487                 this.write_null(dest)?;
 488             }
 489
 490             // Hook pthread calls that go to the thread-local storage memory subsystem.
 491             "pthread_key_create" => {
 492                 let key_place = this.deref_operand(args[0])?;
 493
 494                 // Extract the function type out of the signature (that seems easier than constructing it ourselves).
 495                 let dtor = match this.test_null(this.read_scalar(args[1])?.not_undef()?)? {
 496                     Some(dtor_ptr) => Some(this.memory.get_fn(dtor_ptr)?.as_instance()?),
 497                     None => None,
 498                 };
 499
 500                 // Figure out how large a pthread TLS key actually is.
 501                 // This is `libc::pthread_key_t`.
 502                 let key_type = args[0].layout.ty
 503                     .builtin_deref(true)
 504                     .ok_or_else(|| err_ub_format!(
 505                         "wrong signature used for `pthread_key_create`: first argument must be a raw pointer."
 506                     ))?
 507                     .ty;
 508                 let key_layout = this.layout_of(key_type)?;
 509
 510                 // Create key and write it into the memory where `key_ptr` wants it.
 511                 let key = this.machine.tls.create_tls_key(dtor) as u128;
 512                 if key_layout.size.bits() < 128 && key >= (1u128 << key_layout.size.bits() as u128)
 513                 {
 514                     throw_unsup!(OutOfTls);
 515                 }
 516
 517                 this.write_scalar(Scalar::from_uint(key, key_layout.size), key_place.into())?;
 518
 519                 // Return success (`0`).
 520                 this.write_null(dest)?;
 521             }
 522             "pthread_key_delete" => {
 523                 let key = this.read_scalar(args[0])?.to_bits(args[0].layout.size)?;
 524                 this.machine.tls.delete_tls_key(key)?;
 525                 // Return success (0)
 526                 this.write_null(dest)?;
 527             }
 528             "pthread_getspecific" => {
 529                 let key = this.read_scalar(args[0])?.to_bits(args[0].layout.size)?;
 530                 let ptr = this.machine.tls.load_tls(key, tcx)?;
 531                 this.write_scalar(ptr, dest)?;
 532             }
 533             "pthread_setspecific" => {
 534                 let key = this.read_scalar(args[0])?.to_bits(args[0].layout.size)?;
 535                 let new_ptr = this.read_scalar(args[1])?.not_undef()?;
 536                 this.machine.tls.store_tls(key, this.test_null(new_ptr)?)?;
 537
 538                 // Return success (`0`).
 539                 this.write_null(dest)?;
 540             }
 541
 542             // Stack size/address stuff.
 543             | "pthread_attr_init"
 544             | "pthread_attr_destroy"
 545             | "pthread_self"
 546             | "pthread_attr_setstacksize" => {
 547                 this.write_null(dest)?;
 548             }
 549             "pthread_attr_getstack" => {
 550                 let addr_place = this.deref_operand(args[1])?;
 551                 let size_place = this.deref_operand(args[2])?;
 552
 553                 this.write_scalar(
 554                     Scalar::from_uint(STACK_ADDR, addr_place.layout.size),
 555                     addr_place.into(),
 556                 )?;
 557                 this.write_scalar(
 558                     Scalar::from_uint(STACK_SIZE, size_place.layout.size),
 559                     size_place.into(),
 560                 )?;
 561
 562                 // Return success (`0`).
 563                 this.write_null(dest)?;
 564             }
 565
 566             // We don't support threading. (Also for Windows.)
 567             | "pthread_create"
 568             | "CreateThread"
 569             => {
 570                 throw_unsup_format!("Miri does not support threading");
 571             }
 572
 573             // Stub out calls for condvar, mutex and rwlock, to just return `0`.
 574             | "pthread_mutexattr_init"
 575             | "pthread_mutexattr_settype"
 576             | "pthread_mutex_init"
 577             | "pthread_mutexattr_destroy"
 578             | "pthread_mutex_lock"
 579             | "pthread_mutex_unlock"
 580             | "pthread_mutex_destroy"
 581             | "pthread_rwlock_rdlock"
 582             | "pthread_rwlock_unlock"
 583             | "pthread_rwlock_wrlock"
 584             | "pthread_rwlock_destroy"
 585             | "pthread_condattr_init"
 586             | "pthread_condattr_setclock"
 587             | "pthread_cond_init"
 588             | "pthread_condattr_destroy"
 589             | "pthread_cond_destroy"
 590             => {
 591                 this.write_null(dest)?;
 592             }
 593
 594             // We don't support fork so we don't have to do anything for atfork.
 595             "pthread_atfork" => {
 596                 this.write_null(dest)?;
 597             }
 598
 599             "posix_fadvise" => {
 600                 // fadvise is only informational, we can ignore it.
 601                 this.write_null(dest)?;
 602             }
 603
 604             "mmap" => {
 605                 // This is a horrible hack, but since the guard page mechanism calls mmap and expects a particular return value, we just give it that value.
 606                 let addr = this.read_scalar(args[0])?.not_undef()?;
 607                 this.write_scalar(addr, dest)?;
 608             }
 609             "mprotect" => {
 610                 this.write_null(dest)?;
 611             }
 612
 613             _ => match this.tcx.sess.target.target.target_os.to_lowercase().as_str() {
 614                 "linux" | "macos" => posix::EvalContextExt::emulate_foreign_item_by_name(this, link_name, args, dest)?,
 615                 "windows" => windows::EvalContextExt::emulate_foreign_item_by_name(this, link_name, args, dest)?,
 616                 target => throw_unsup_format!("The {} target platform is not supported", target),
 617             }
 618         };
 619
 620         Ok(())
 621     }
 622
 623     /// Evaluates the scalar at the specified path. Returns Some(val)
 624     /// if the path could be resolved, and None otherwise
 625     fn eval_path_scalar(
 626         &mut self,
 627         path: &[&str],
 628     ) -> InterpResult<'tcx, Option<ScalarMaybeUndef<Tag>>> {
 629         let this = self.eval_context_mut();
 630         if let Ok(instance) = this.resolve_path(path) {
 631             let cid = GlobalId { instance, promoted: None };
 632             let const_val = this.const_eval_raw(cid)?;
 633             let const_val = this.read_scalar(const_val.into())?;
 634             return Ok(Some(const_val));
 635         }
 636         return Ok(None);
 637     }
 638 }