src/shims/foreign_items.rs

   1 use std::{iter, convert::TryInto};
   2
   3 use rustc::mir;
   4 use rustc::ty::layout::{Align, LayoutOf, Size};
   5 use rustc::hir::def_id::DefId;
   6 use rustc_apfloat::Float;
   7 use rustc::ty;
   8 use syntax::attr;
   9 use syntax::symbol::sym;
  10
  11 use crate::*;
  12
  13 impl<'mir, 'tcx> EvalContextExt<'mir, 'tcx> for crate::MiriEvalContext<'mir, 'tcx> {}
  14 pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx> {
  15     /// Returns the minimum alignment for the target architecture for allocations of the given size.
  16     fn min_align(&self, size: u64, kind: MiriMemoryKind) -> Align {
  17         let this = self.eval_context_ref();
  18         // List taken from `libstd/sys_common/alloc.rs`.
  19         let min_align = match this.tcx.tcx.sess.target.target.arch.as_str() {
  20             "x86" | "arm" | "mips" | "powerpc" | "powerpc64" | "asmjs" | "wasm32" => 8,
  21             "x86_64" | "aarch64" | "mips64" | "s390x" | "sparc64" => 16,
  22             arch => bug!("Unsupported target architecture: {}", arch),
  23         };
  24         // Windows always aligns, even small allocations.
  25         // Source: <https://support.microsoft.com/en-us/help/286470/how-to-use-pageheap-exe-in-windows-xp-windows-2000-and-windows-server>
  26         // But jemalloc does not, so for the C heap we only align if the allocation is sufficiently big.
  27         if kind == MiriMemoryKind::WinHeap || size >= min_align {
  28             return Align::from_bytes(min_align).unwrap();
  29         }
  30         // We have `size < min_align`. Round `size` *down* to the next power of two and use that.
  31         fn prev_power_of_two(x: u64) -> u64 {
  32             let next_pow2 = x.next_power_of_two();
  33             if next_pow2 == x {
  34                 // x *is* a power of two, just use that.
  35                 x
  36             } else {
  37                 // x is between two powers, so next = 2*prev.
  38                 next_pow2 / 2
  39             }
  40         }
  41         Align::from_bytes(prev_power_of_two(size)).unwrap()
  42     }
  43
  44     fn malloc(&mut self, size: u64, zero_init: bool, kind: MiriMemoryKind) -> Scalar<Tag> {
  45         let this = self.eval_context_mut();
  46         if size == 0 {
  47             Scalar::from_int(0, this.pointer_size())
  48         } else {
  49             let align = this.min_align(size, kind);
  50             let ptr = this
  51                 .memory
  52                 .allocate(Size::from_bytes(size), align, kind.into());
  53             if zero_init {
  54                 // We just allocated this, the access is definitely in-bounds.
  55                 this.memory
  56                     .write_bytes(ptr.into(), iter::repeat(0u8).take(size as usize))
  57                     .unwrap();
  58             }
  59             Scalar::Ptr(ptr)
  60         }
  61     }
  62
  63     fn free(&mut self, ptr: Scalar<Tag>, kind: MiriMemoryKind) -> InterpResult<'tcx> {
  64         let this = self.eval_context_mut();
  65         if !this.is_null(ptr)? {
  66             let ptr = this.force_ptr(ptr)?;
  67             this.memory.deallocate(ptr, None, kind.into())?;
  68         }
  69         Ok(())
  70     }
  71
  72     fn realloc(
  73         &mut self,
  74         old_ptr: Scalar<Tag>,
  75         new_size: u64,
  76         kind: MiriMemoryKind,
  77     ) -> InterpResult<'tcx, Scalar<Tag>> {
  78         let this = self.eval_context_mut();
  79         let new_align = this.min_align(new_size, kind);
  80         if this.is_null(old_ptr)? {
  81             if new_size == 0 {
  82                 Ok(Scalar::from_int(0, this.pointer_size()))
  83             } else {
  84                 let new_ptr =
  85                     this.memory
  86                         .allocate(Size::from_bytes(new_size), new_align, kind.into());
  87                 Ok(Scalar::Ptr(new_ptr))
  88             }
  89         } else {
  90             let old_ptr = this.force_ptr(old_ptr)?;
  91             if new_size == 0 {
  92                 this.memory.deallocate(old_ptr, None, kind.into())?;
  93                 Ok(Scalar::from_int(0, this.pointer_size()))
  94             } else {
  95                 let new_ptr = this.memory.reallocate(
  96                     old_ptr,
  97                     None,
  98                     Size::from_bytes(new_size),
  99                     new_align,
 100                     kind.into(),
 101                 )?;
 102                 Ok(Scalar::Ptr(new_ptr))
 103             }
 104         }
 105     }
 106
 107     /// Emulates calling a foreign item, failing if the item is not supported.
 108     /// This function will handle `goto_block` if needed.
 109     /// Returns Ok(None) if the foreign item was completely handled
 110     /// by this function.
 111     /// Returns Ok(Some(body)) if processing the foreign item
 112     /// is delegated to another function.
 113     fn emulate_foreign_item(
 114         &mut self,
 115         def_id: DefId,
 116         args: &[OpTy<'tcx, Tag>],
 117         dest: Option<PlaceTy<'tcx, Tag>>,
 118         ret: Option<mir::BasicBlock>,
 119         _unwind: Option<mir::BasicBlock>
 120     ) -> InterpResult<'tcx, Option<&'mir mir::Body<'tcx>>> {
 121         let this = self.eval_context_mut();
 122         let attrs = this.tcx.get_attrs(def_id);
 123         let link_name = match attr::first_attr_value_str_by_name(&attrs, sym::link_name) {
 124             Some(name) => name.as_str(),
 125             None => this.tcx.item_name(def_id).as_str(),
 126         };
 127         // Strip linker suffixes (seen on 32-bit macOS).
 128         let link_name = link_name.trim_end_matches("$UNIX2003");
 129         let tcx = &{ this.tcx.tcx };
 130
 131         // First: functions that diverge.
 132         match link_name {
 133             // Note that this matches calls to the *foreign* item `__rust_start_panic* -
 134             // that is, calls to `extern "Rust" { fn __rust_start_panic(...) }`.
 135             // We forward this to the underlying *implementation* in "libpanic_unwind".
 136             "__rust_start_panic" => {
 137                 let start_panic_instance = this.resolve_path(&["panic_unwind", "__rust_start_panic"])?;
 138                 return Ok(Some(this.load_mir(start_panic_instance.def, None)?));
 139             }
 140             // Similarly, we forward calls to the `panic_impl` foreign item to its implementation.
 141             // The implementation is provided by the function with the `#[panic_handler]` attribute.
 142             "panic_impl" => {
 143                 let panic_impl_id = this.tcx.lang_items().panic_impl().unwrap();
 144                 let panic_impl_instance = ty::Instance::mono(*this.tcx, panic_impl_id);
 145                 return Ok(Some(this.load_mir(panic_impl_instance.def, None)?));
 146             }
 147
 148             "exit" | "ExitProcess" => {
 149                 // it's really u32 for ExitProcess, but we have to put it into the `Exit` error variant anyway
 150                 let code = this.read_scalar(args[0])?.to_i32()?;
 151                 return Err(InterpError::Exit(code).into());
 152             }
 153             _ => {
 154                 if dest.is_none() {
 155                     throw_unsup_format!("can't call (diverging) foreign function: {}", link_name);
 156                 }
 157             }
 158         }
 159
 160         // Next: functions that assume a ret and dest.
 161         let dest = dest.expect("we already checked for a dest");
 162         let ret = ret.expect("dest is `Some` but ret is `None`");
 163         match link_name {
 164             "malloc" => {
 165                 let size = this.read_scalar(args[0])?.to_machine_usize(this)?;
 166                 let res = this.malloc(size, /*zero_init:*/ false, MiriMemoryKind::C);
 167                 this.write_scalar(res, dest)?;
 168             }
 169             "calloc" => {
 170                 let items = this.read_scalar(args[0])?.to_machine_usize(this)?;
 171                 let len = this.read_scalar(args[1])?.to_machine_usize(this)?;
 172                 let size = items
 173                     .checked_mul(len)
 174                     .ok_or_else(|| err_panic!(Overflow(mir::BinOp::Mul)))?;
 175                 let res = this.malloc(size, /*zero_init:*/ true, MiriMemoryKind::C);
 176                 this.write_scalar(res, dest)?;
 177             }
 178             "posix_memalign" => {
 179                 let ret = this.deref_operand(args[0])?;
 180                 let align = this.read_scalar(args[1])?.to_machine_usize(this)?;
 181                 let size = this.read_scalar(args[2])?.to_machine_usize(this)?;
 182                 // Align must be power of 2, and also at least ptr-sized (POSIX rules).
 183                 if !align.is_power_of_two() {
 184                     throw_unsup!(HeapAllocNonPowerOfTwoAlignment(align));
 185                 }
 186                 if align < this.pointer_size().bytes() {
 187                     throw_ub_format!(
 188                         "posix_memalign: alignment must be at least the size of a pointer, but is {}",
 189                         align,
 190                     );
 191                 }
 192
 193                 if size == 0 {
 194                     this.write_null(ret.into())?;
 195                 } else {
 196                     let ptr = this.memory.allocate(
 197                         Size::from_bytes(size),
 198                         Align::from_bytes(align).unwrap(),
 199                         MiriMemoryKind::C.into(),
 200                     );
 201                     this.write_scalar(Scalar::Ptr(ptr), ret.into())?;
 202                 }
 203                 this.write_null(dest)?;
 204             }
 205             "free" => {
 206                 let ptr = this.read_scalar(args[0])?.not_undef()?;
 207                 this.free(ptr, MiriMemoryKind::C)?;
 208             }
 209             "realloc" => {
 210                 let old_ptr = this.read_scalar(args[0])?.not_undef()?;
 211                 let new_size = this.read_scalar(args[1])?.to_machine_usize(this)?;
 212                 let res = this.realloc(old_ptr, new_size, MiriMemoryKind::C)?;
 213                 this.write_scalar(res, dest)?;
 214             }
 215
 216             "__rust_alloc" => {
 217                 let size = this.read_scalar(args[0])?.to_machine_usize(this)?;
 218                 let align = this.read_scalar(args[1])?.to_machine_usize(this)?;
 219                 if size == 0 {
 220                     throw_unsup!(HeapAllocZeroBytes);
 221                 }
 222                 if !align.is_power_of_two() {
 223                     throw_unsup!(HeapAllocNonPowerOfTwoAlignment(align));
 224                 }
 225                 let ptr = this.memory.allocate(
 226                     Size::from_bytes(size),
 227                     Align::from_bytes(align).unwrap(),
 228                     MiriMemoryKind::Rust.into(),
 229                 );
 230                 this.write_scalar(Scalar::Ptr(ptr), dest)?;
 231             }
 232             "__rust_alloc_zeroed" => {
 233                 let size = this.read_scalar(args[0])?.to_machine_usize(this)?;
 234                 let align = this.read_scalar(args[1])?.to_machine_usize(this)?;
 235                 if size == 0 {
 236                     throw_unsup!(HeapAllocZeroBytes);
 237                 }
 238                 if !align.is_power_of_two() {
 239                     throw_unsup!(HeapAllocNonPowerOfTwoAlignment(align));
 240                 }
 241                 let ptr = this.memory.allocate(
 242                     Size::from_bytes(size),
 243                     Align::from_bytes(align).unwrap(),
 244                     MiriMemoryKind::Rust.into(),
 245                 );
 246                 // We just allocated this, the access is definitely in-bounds.
 247                 this.memory
 248                     .write_bytes(ptr.into(), iter::repeat(0u8).take(size as usize))
 249                     .unwrap();
 250                 this.write_scalar(Scalar::Ptr(ptr), dest)?;
 251             }
 252             "__rust_dealloc" => {
 253                 let ptr = this.read_scalar(args[0])?.not_undef()?;
 254                 let old_size = this.read_scalar(args[1])?.to_machine_usize(this)?;
 255                 let align = this.read_scalar(args[2])?.to_machine_usize(this)?;
 256                 if old_size == 0 {
 257                     throw_unsup!(HeapAllocZeroBytes);
 258                 }
 259                 if !align.is_power_of_two() {
 260                     throw_unsup!(HeapAllocNonPowerOfTwoAlignment(align));
 261                 }
 262                 let ptr = this.force_ptr(ptr)?;
 263                 this.memory.deallocate(
 264                     ptr,
 265                     Some((
 266                         Size::from_bytes(old_size),
 267                         Align::from_bytes(align).unwrap(),
 268                     )),
 269                     MiriMemoryKind::Rust.into(),
 270                 )?;
 271             }
 272             "__rust_realloc" => {
 273                 let ptr = this.read_scalar(args[0])?.to_ptr()?;
 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 align = Align::from_bytes(align).unwrap();
 284                 let new_ptr = this.memory.reallocate(
 285                     ptr,
 286                     Some((Size::from_bytes(old_size), align)),
 287                     Size::from_bytes(new_size),
 288                     align,
 289                     MiriMemoryKind::Rust.into(),
 290                 )?;
 291                 this.write_scalar(Scalar::Ptr(new_ptr), dest)?;
 292             }
 293
 294             "syscall" => {
 295                 let sys_getrandom = this
 296                     .eval_path_scalar(&["libc", "SYS_getrandom"])?
 297                     .expect("Failed to get libc::SYS_getrandom")
 298                     .to_machine_usize(this)?;
 299
 300                 // `libc::syscall(NR_GETRANDOM, buf.as_mut_ptr(), buf.len(), GRND_NONBLOCK)`
 301                 // is called if a `HashMap` is created the regular way (e.g. HashMap<K, V>).
 302                 match this.read_scalar(args[0])?.to_machine_usize(this)? {
 303                     id if id == sys_getrandom => {
 304                         // The first argument is the syscall id,
 305                         // so skip over it.
 306                         linux_getrandom(this, &args[1..], dest)?;
 307                     }
 308                     id => throw_unsup_format!("miri does not support syscall ID {}", id),
 309                 }
 310             }
 311
 312             "getrandom" => {
 313                 linux_getrandom(this, args, dest)?;
 314             }
 315
 316             "dlsym" => {
 317                 let _handle = this.read_scalar(args[0])?;
 318                 let symbol = this.read_scalar(args[1])?.not_undef()?;
 319                 let symbol_name = this.memory.read_c_str(symbol)?;
 320                 let err = format!("bad c unicode symbol: {:?}", symbol_name);
 321                 let symbol_name = ::std::str::from_utf8(symbol_name).unwrap_or(&err);
 322                 if let Some(dlsym) = Dlsym::from_str(symbol_name)? {
 323                     let ptr = this.memory.create_fn_alloc(FnVal::Other(dlsym));
 324                     this.write_scalar(Scalar::from(ptr), dest)?;
 325                 } else {
 326                     this.write_null(dest)?;
 327                 }
 328             }
 329
 330             "__rust_maybe_catch_panic" => {
 331                 this.handle_catch_panic(args, dest, ret)?;
 332                 return Ok(None)
 333             }
 334
 335             "memcmp" => {
 336                 let left = this.read_scalar(args[0])?.not_undef()?;
 337                 let right = this.read_scalar(args[1])?.not_undef()?;
 338                 let n = Size::from_bytes(this.read_scalar(args[2])?.to_machine_usize(this)?);
 339
 340                 let result = {
 341                     let left_bytes = this.memory.read_bytes(left, n)?;
 342                     let right_bytes = this.memory.read_bytes(right, n)?;
 343
 344                     use std::cmp::Ordering::*;
 345                     match left_bytes.cmp(right_bytes) {
 346                         Less => -1i32,
 347                         Equal => 0,
 348                         Greater => 1,
 349                     }
 350                 };
 351
 352                 this.write_scalar(Scalar::from_int(result, Size::from_bits(32)), dest)?;
 353             }
 354
 355             "memrchr" => {
 356                 let ptr = this.read_scalar(args[0])?.not_undef()?;
 357                 let val = this.read_scalar(args[1])?.to_i32()? as u8;
 358                 let num = this.read_scalar(args[2])?.to_machine_usize(this)?;
 359                 if let Some(idx) = this
 360                     .memory
 361                     .read_bytes(ptr, Size::from_bytes(num))?
 362                     .iter()
 363                     .rev()
 364                     .position(|&c| c == val)
 365                 {
 366                     let new_ptr = ptr.ptr_offset(Size::from_bytes(num - idx as u64 - 1), this)?;
 367                     this.write_scalar(new_ptr, dest)?;
 368                 } else {
 369                     this.write_null(dest)?;
 370                 }
 371             }
 372
 373             "memchr" => {
 374                 let ptr = this.read_scalar(args[0])?.not_undef()?;
 375                 let val = this.read_scalar(args[1])?.to_i32()? as u8;
 376                 let num = this.read_scalar(args[2])?.to_machine_usize(this)?;
 377                 let idx = this
 378                     .memory
 379                     .read_bytes(ptr, Size::from_bytes(num))?
 380                     .iter()
 381                     .position(|&c| c == val);
 382                 if let Some(idx) = idx {
 383                     let new_ptr = ptr.ptr_offset(Size::from_bytes(idx as u64), this)?;
 384                     this.write_scalar(new_ptr, dest)?;
 385                 } else {
 386                     this.write_null(dest)?;
 387                 }
 388             }
 389
 390             "__errno_location" | "__error" => {
 391                 let errno_place = this.machine.last_error.unwrap();
 392                 this.write_scalar(errno_place.to_ref().to_scalar()?, dest)?;
 393             }
 394
 395             "getenv" => {
 396                 let result = this.getenv(args[0])?;
 397                 this.write_scalar(result, dest)?;
 398             }
 399
 400             "unsetenv" => {
 401                 let result = this.unsetenv(args[0])?;
 402                 this.write_scalar(Scalar::from_int(result, dest.layout.size), dest)?;
 403             }
 404
 405             "setenv" => {
 406                 let result = this.setenv(args[0], args[1])?;
 407                 this.write_scalar(Scalar::from_int(result, dest.layout.size), dest)?;
 408             }
 409
 410             "getcwd" => {
 411                 let result = this.getcwd(args[0], args[1])?;
 412                 this.write_scalar(result, dest)?;
 413             }
 414
 415             "chdir" => {
 416                 let result = this.chdir(args[0])?;
 417                 this.write_scalar(Scalar::from_int(result, dest.layout.size), dest)?;
 418             }
 419
 420             "open" | "open64" => {
 421                 let result = this.open(args[0], args[1])?;
 422                 this.write_scalar(Scalar::from_int(result, dest.layout.size), dest)?;
 423             }
 424
 425             "fcntl" => {
 426                 let result = this.fcntl(args[0], args[1], args.get(2).cloned())?;
 427                 this.write_scalar(Scalar::from_int(result, dest.layout.size), dest)?;
 428             }
 429
 430             "close" | "close$NOCANCEL" => {
 431                 let result = this.close(args[0])?;
 432                 this.write_scalar(Scalar::from_int(result, dest.layout.size), dest)?;
 433             }
 434
 435             "read" => {
 436                 let result = this.read(args[0], args[1], args[2])?;
 437                 this.write_scalar(Scalar::from_int(result, dest.layout.size), dest)?;
 438             }
 439
 440             "write" => {
 441                 let fd = this.read_scalar(args[0])?.to_i32()?;
 442                 let buf = this.read_scalar(args[1])?.not_undef()?;
 443                 let n = this.read_scalar(args[2])?.to_machine_usize(tcx)?;
 444                 trace!("Called write({:?}, {:?}, {:?})", fd, buf, n);
 445                 let result = if fd == 1 || fd == 2 {
 446                     // stdout/stderr
 447                     use std::io::{self, Write};
 448
 449                     let buf_cont = this.memory.read_bytes(buf, Size::from_bytes(n))?;
 450                     // We need to flush to make sure this actually appears on the screen
 451                     let res = if fd == 1 {
 452                         // Stdout is buffered, flush to make sure it appears on the screen.
 453                         // This is the write() syscall of the interpreted program, we want it
 454                         // to correspond to a write() syscall on the host -- there is no good
 455                         // in adding extra buffering here.
 456                         let res = io::stdout().write(buf_cont);
 457                         io::stdout().flush().unwrap();
 458                         res
 459                     } else {
 460                         // No need to flush, stderr is not buffered.
 461                         io::stderr().write(buf_cont)
 462                     };
 463                     match res {
 464                         Ok(n) => n as i64,
 465                         Err(_) => -1,
 466                     }
 467                 } else {
 468                     this.write(args[0], args[1], args[2])?
 469                 };
 470                 // Now, `result` is the value we return back to the program.
 471                 this.write_scalar(Scalar::from_int(result, dest.layout.size), dest)?;
 472             }
 473
 474             "unlink" => {
 475                 let result = this.unlink(args[0])?;
 476                 this.write_scalar(Scalar::from_int(result, dest.layout.size), dest)?;
 477             }
 478
 479             "clock_gettime" => {
 480                 let result = this.clock_gettime(args[0], args[1])?;
 481                 this.write_scalar(Scalar::from_int(result, dest.layout.size), dest)?;
 482             }
 483
 484             "gettimeofday" => {
 485                 let result = this.gettimeofday(args[0], args[1])?;
 486                 this.write_scalar(Scalar::from_int(result, dest.layout.size), dest)?;
 487             }
 488
 489             "strlen" => {
 490                 let ptr = this.read_scalar(args[0])?.not_undef()?;
 491                 let n = this.memory.read_c_str(ptr)?.len();
 492                 this.write_scalar(Scalar::from_uint(n as u64, dest.layout.size), dest)?;
 493             }
 494
 495             // math functions
 496             "cbrtf" | "coshf" | "sinhf" | "tanf" => {
 497                 // FIXME: Using host floats.
 498                 let f = f32::from_bits(this.read_scalar(args[0])?.to_u32()?);
 499                 let f = match link_name {
 500                     "cbrtf" => f.cbrt(),
 501                     "coshf" => f.cosh(),
 502                     "sinhf" => f.sinh(),
 503                     "tanf" => f.tan(),
 504                     _ => bug!(),
 505                 };
 506                 this.write_scalar(Scalar::from_u32(f.to_bits()), dest)?;
 507             }
 508             // underscore case for windows
 509             "_hypotf" | "hypotf" | "atan2f" => {
 510                 // FIXME: Using host floats.
 511                 let f1 = f32::from_bits(this.read_scalar(args[0])?.to_u32()?);
 512                 let f2 = f32::from_bits(this.read_scalar(args[1])?.to_u32()?);
 513                 let n = match link_name {
 514                     "_hypotf" | "hypotf" => f1.hypot(f2),
 515                     "atan2f" => f1.atan2(f2),
 516                     _ => bug!(),
 517                 };
 518                 this.write_scalar(Scalar::from_u32(n.to_bits()), dest)?;
 519             }
 520
 521             "cbrt" | "cosh" | "sinh" | "tan" => {
 522                 // FIXME: Using host floats.
 523                 let f = f64::from_bits(this.read_scalar(args[0])?.to_u64()?);
 524                 let f = match link_name {
 525                     "cbrt" => f.cbrt(),
 526                     "cosh" => f.cosh(),
 527                     "sinh" => f.sinh(),
 528                     "tan" => f.tan(),
 529                     _ => bug!(),
 530                 };
 531                 this.write_scalar(Scalar::from_u64(f.to_bits()), dest)?;
 532             }
 533             // underscore case for windows, here and below
 534             // (see https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/floating-point-primitives?view=vs-2019)
 535             "_hypot" | "hypot" | "atan2" => {
 536                 // FIXME: Using host floats.
 537                 let f1 = f64::from_bits(this.read_scalar(args[0])?.to_u64()?);
 538                 let f2 = f64::from_bits(this.read_scalar(args[1])?.to_u64()?);
 539                 let n = match link_name {
 540                     "_hypot" | "hypot" => f1.hypot(f2),
 541                     "atan2" => f1.atan2(f2),
 542                     _ => bug!(),
 543                 };
 544                 this.write_scalar(Scalar::from_u64(n.to_bits()), dest)?;
 545             }
 546             // For radix-2 (binary) systems, `ldexp` and `scalbn` are the same.
 547             "_ldexp" | "ldexp" | "scalbn" => {
 548                 let x = this.read_scalar(args[0])?.to_f64()?;
 549                 let exp = this.read_scalar(args[1])?.to_i32()?;
 550
 551                 // Saturating cast to i16. Even those are outside the valid exponent range to
 552                 // `scalbn` below will do its over/underflow handling.
 553                 let exp = if exp > i16::max_value() as i32 {
 554                     i16::max_value()
 555                 } else if exp < i16::min_value() as i32 {
 556                     i16::min_value()
 557                 } else {
 558                     exp.try_into().unwrap()
 559                 };
 560
 561                 let res = x.scalbn(exp);
 562                 this.write_scalar(Scalar::from_f64(res), dest)?;
 563             }
 564
 565             // Some things needed for `sys::thread` initialization to go through.
 566             "signal" | "sigaction" | "sigaltstack" => {
 567                 this.write_scalar(Scalar::from_int(0, dest.layout.size), dest)?;
 568             }
 569
 570             "sysconf" => {
 571                 let name = this.read_scalar(args[0])?.to_i32()?;
 572
 573                 trace!("sysconf() called with name {}", name);
 574                 // TODO: Cache the sysconf integers via Miri's global cache.
 575                 let paths = &[
 576                     (
 577                         &["libc", "_SC_PAGESIZE"],
 578                         Scalar::from_int(PAGE_SIZE, dest.layout.size),
 579                     ),
 580                     (
 581                         &["libc", "_SC_GETPW_R_SIZE_MAX"],
 582                         Scalar::from_int(-1, dest.layout.size),
 583                     ),
 584                     (
 585                         &["libc", "_SC_NPROCESSORS_ONLN"],
 586                         Scalar::from_int(NUM_CPUS, dest.layout.size),
 587                     ),
 588                 ];
 589                 let mut result = None;
 590                 for &(path, path_value) in paths {
 591                     if let Some(val) = this.eval_path_scalar(path)? {
 592                         let val = val.to_i32()?;
 593                         if val == name {
 594                             result = Some(path_value);
 595                             break;
 596                         }
 597                     }
 598                 }
 599                 if let Some(result) = result {
 600                     this.write_scalar(result, dest)?;
 601                 } else {
 602                     throw_unsup_format!("Unimplemented sysconf name: {}", name)
 603                 }
 604             }
 605
 606             "sched_getaffinity" => {
 607                 // Return an error; `num_cpus` then falls back to `sysconf`.
 608                 this.write_scalar(Scalar::from_int(-1, dest.layout.size), dest)?;
 609             }
 610
 611             "isatty" => {
 612                 this.write_null(dest)?;
 613             }
 614
 615             // Hook pthread calls that go to the thread-local storage memory subsystem.
 616             "pthread_key_create" => {
 617                 let key_place = this.deref_operand(args[0])?;
 618
 619                 // Extract the function type out of the signature (that seems easier than constructing it ourselves).
 620                 let dtor = match this.test_null(this.read_scalar(args[1])?.not_undef()?)? {
 621                     Some(dtor_ptr) => Some(this.memory.get_fn(dtor_ptr)?.as_instance()?),
 622                     None => None,
 623                 };
 624
 625                 // Figure out how large a pthread TLS key actually is.
 626                 // This is `libc::pthread_key_t`.
 627                 let key_type = args[0].layout.ty
 628                     .builtin_deref(true)
 629                     .ok_or_else(|| err_ub_format!(
 630                         "wrong signature used for `pthread_key_create`: first argument must be a raw pointer."
 631                     ))?
 632                     .ty;
 633                 let key_layout = this.layout_of(key_type)?;
 634
 635                 // Create key and write it into the memory where `key_ptr` wants it.
 636                 let key = this.machine.tls.create_tls_key(dtor) as u128;
 637                 if key_layout.size.bits() < 128 && key >= (1u128 << key_layout.size.bits() as u128)
 638                 {
 639                     throw_unsup!(OutOfTls);
 640                 }
 641
 642                 this.write_scalar(Scalar::from_uint(key, key_layout.size), key_place.into())?;
 643
 644                 // Return success (`0`).
 645                 this.write_null(dest)?;
 646             }
 647             "pthread_key_delete" => {
 648                 let key = this.read_scalar(args[0])?.to_bits(args[0].layout.size)?;
 649                 this.machine.tls.delete_tls_key(key)?;
 650                 // Return success (0)
 651                 this.write_null(dest)?;
 652             }
 653             "pthread_getspecific" => {
 654                 let key = this.read_scalar(args[0])?.to_bits(args[0].layout.size)?;
 655                 let ptr = this.machine.tls.load_tls(key, tcx)?;
 656                 this.write_scalar(ptr, dest)?;
 657             }
 658             "pthread_setspecific" => {
 659                 let key = this.read_scalar(args[0])?.to_bits(args[0].layout.size)?;
 660                 let new_ptr = this.read_scalar(args[1])?.not_undef()?;
 661                 this.machine.tls.store_tls(key, this.test_null(new_ptr)?)?;
 662
 663                 // Return success (`0`).
 664                 this.write_null(dest)?;
 665             }
 666
 667             // Stack size/address stuff.
 668             "pthread_attr_init"
 669             | "pthread_attr_destroy"
 670             | "pthread_self"
 671             | "pthread_attr_setstacksize" => {
 672                 this.write_null(dest)?;
 673             }
 674             "pthread_attr_getstack" => {
 675                 let addr_place = this.deref_operand(args[1])?;
 676                 let size_place = this.deref_operand(args[2])?;
 677
 678                 this.write_scalar(
 679                     Scalar::from_uint(STACK_ADDR, addr_place.layout.size),
 680                     addr_place.into(),
 681                 )?;
 682                 this.write_scalar(
 683                     Scalar::from_uint(STACK_SIZE, size_place.layout.size),
 684                     size_place.into(),
 685                 )?;
 686
 687                 // Return success (`0`).
 688                 this.write_null(dest)?;
 689             }
 690
 691             // We don't support threading. (Also for Windows.)
 692             "pthread_create" | "CreateThread" => {
 693                 throw_unsup_format!("Miri does not support threading");
 694             }
 695
 696             // Stub out calls for condvar, mutex and rwlock, to just return `0`.
 697             "pthread_mutexattr_init"
 698             | "pthread_mutexattr_settype"
 699             | "pthread_mutex_init"
 700             | "pthread_mutexattr_destroy"
 701             | "pthread_mutex_lock"
 702             | "pthread_mutex_unlock"
 703             | "pthread_mutex_destroy"
 704             | "pthread_rwlock_rdlock"
 705             | "pthread_rwlock_unlock"
 706             | "pthread_rwlock_wrlock"
 707             | "pthread_rwlock_destroy"
 708             | "pthread_condattr_init"
 709             | "pthread_condattr_setclock"
 710             | "pthread_cond_init"
 711             | "pthread_condattr_destroy"
 712             | "pthread_cond_destroy" => {
 713                 this.write_null(dest)?;
 714             }
 715
 716             // We don't support fork so we don't have to do anything for atfork.
 717             "pthread_atfork" => {
 718                 this.write_null(dest)?;
 719             }
 720
 721             "mmap" => {
 722                 // 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.
 723                 let addr = this.read_scalar(args[0])?.not_undef()?;
 724                 this.write_scalar(addr, dest)?;
 725             }
 726             "mprotect" => {
 727                 this.write_null(dest)?;
 728             }
 729
 730             // macOS API stubs.
 731             "pthread_attr_get_np" | "pthread_getattr_np" => {
 732                 this.write_null(dest)?;
 733             }
 734             "pthread_get_stackaddr_np" => {
 735                 let stack_addr = Scalar::from_uint(STACK_ADDR, dest.layout.size);
 736                 this.write_scalar(stack_addr, dest)?;
 737             }
 738             "pthread_get_stacksize_np" => {
 739                 let stack_size = Scalar::from_uint(STACK_SIZE, dest.layout.size);
 740                 this.write_scalar(stack_size, dest)?;
 741             }
 742             "_tlv_atexit" => {
 743                 // FIXME: register the destructor.
 744             }
 745             "_NSGetArgc" => {
 746                 this.write_scalar(this.machine.argc.expect("machine must be initialized"), dest)?;
 747             }
 748             "_NSGetArgv" => {
 749                 this.write_scalar(this.machine.argv.expect("machine must be initialized"), dest)?;
 750             }
 751             "SecRandomCopyBytes" => {
 752                 let len = this.read_scalar(args[1])?.to_machine_usize(this)?;
 753                 let ptr = this.read_scalar(args[2])?.not_undef()?;
 754                 this.gen_random(ptr, len as usize)?;
 755                 this.write_null(dest)?;
 756             }
 757
 758             // Windows API stubs.
 759             // HANDLE = isize
 760             // DWORD = ULONG = u32
 761             // BOOL = i32
 762             "GetProcessHeap" => {
 763                 // Just fake a HANDLE
 764                 this.write_scalar(Scalar::from_int(1, this.pointer_size()), dest)?;
 765             }
 766             "HeapAlloc" => {
 767                 let _handle = this.read_scalar(args[0])?.to_machine_isize(this)?;
 768                 let flags = this.read_scalar(args[1])?.to_u32()?;
 769                 let size = this.read_scalar(args[2])?.to_machine_usize(this)?;
 770                 let zero_init = (flags & 0x00000008) != 0; // HEAP_ZERO_MEMORY
 771                 let res = this.malloc(size, zero_init, MiriMemoryKind::WinHeap);
 772                 this.write_scalar(res, dest)?;
 773             }
 774             "HeapFree" => {
 775                 let _handle = this.read_scalar(args[0])?.to_machine_isize(this)?;
 776                 let _flags = this.read_scalar(args[1])?.to_u32()?;
 777                 let ptr = this.read_scalar(args[2])?.not_undef()?;
 778                 this.free(ptr, MiriMemoryKind::WinHeap)?;
 779                 this.write_scalar(Scalar::from_int(1, Size::from_bytes(4)), dest)?;
 780             }
 781             "HeapReAlloc" => {
 782                 let _handle = this.read_scalar(args[0])?.to_machine_isize(this)?;
 783                 let _flags = this.read_scalar(args[1])?.to_u32()?;
 784                 let ptr = this.read_scalar(args[2])?.not_undef()?;
 785                 let size = this.read_scalar(args[3])?.to_machine_usize(this)?;
 786                 let res = this.realloc(ptr, size, MiriMemoryKind::WinHeap)?;
 787                 this.write_scalar(res, dest)?;
 788             }
 789
 790             "SetLastError" => {
 791                 this.set_last_error(this.read_scalar(args[0])?.not_undef()?)?;
 792             }
 793             "GetLastError" => {
 794                 let last_error = this.get_last_error()?;
 795                 this.write_scalar(last_error, dest)?;
 796             }
 797
 798             "AddVectoredExceptionHandler" => {
 799                 // Any non zero value works for the stdlib. This is just used for stack overflows anyway.
 800                 this.write_scalar(Scalar::from_int(1, dest.layout.size), dest)?;
 801             }
 802             "InitializeCriticalSection"
 803             | "EnterCriticalSection"
 804             | "LeaveCriticalSection"
 805             | "DeleteCriticalSection" => {
 806                 // Nothing to do, not even a return value.
 807             }
 808             "GetModuleHandleW"
 809             | "GetProcAddress"
 810             | "TryEnterCriticalSection"
 811             | "GetConsoleScreenBufferInfo"
 812             | "SetConsoleTextAttribute" => {
 813                 // Pretend these do not exist / nothing happened, by returning zero.
 814                 this.write_null(dest)?;
 815             }
 816             "GetSystemInfo" => {
 817                 let system_info = this.deref_operand(args[0])?;
 818                 // Initialize with `0`.
 819                 this.memory
 820                     .write_bytes(system_info.ptr, iter::repeat(0u8).take(system_info.layout.size.bytes() as usize))?;
 821                 // Set number of processors.
 822                 let dword_size = Size::from_bytes(4);
 823                 let num_cpus = this.mplace_field(system_info, 6)?;
 824                 this.write_scalar(
 825                     Scalar::from_int(NUM_CPUS, dword_size),
 826                     num_cpus.into(),
 827                 )?;
 828             }
 829
 830             "TlsAlloc" => {
 831                 // This just creates a key; Windows does not natively support TLS destructors.
 832
 833                 // Create key and return it.
 834                 let key = this.machine.tls.create_tls_key(None) as u128;
 835
 836                 // Figure out how large a TLS key actually is. This is `c::DWORD`.
 837                 if dest.layout.size.bits() < 128
 838                     && key >= (1u128 << dest.layout.size.bits() as u128)
 839                 {
 840                     throw_unsup!(OutOfTls);
 841                 }
 842                 this.write_scalar(Scalar::from_uint(key, dest.layout.size), dest)?;
 843             }
 844             "TlsGetValue" => {
 845                 let key = this.read_scalar(args[0])?.to_u32()? as u128;
 846                 let ptr = this.machine.tls.load_tls(key, tcx)?;
 847                 this.write_scalar(ptr, dest)?;
 848             }
 849             "TlsSetValue" => {
 850                 let key = this.read_scalar(args[0])?.to_u32()? as u128;
 851                 let new_ptr = this.read_scalar(args[1])?.not_undef()?;
 852                 this.machine.tls.store_tls(key, this.test_null(new_ptr)?)?;
 853
 854                 // Return success (`1`).
 855                 this.write_scalar(Scalar::from_int(1, dest.layout.size), dest)?;
 856             }
 857             "GetStdHandle" => {
 858                 let which = this.read_scalar(args[0])?.to_i32()?;
 859                 // We just make this the identity function, so we know later in `WriteFile`
 860                 // which one it is.
 861                 this.write_scalar(Scalar::from_int(which, this.pointer_size()), dest)?;
 862             }
 863             "WriteFile" => {
 864                 let handle = this.read_scalar(args[0])?.to_machine_isize(this)?;
 865                 let buf = this.read_scalar(args[1])?.not_undef()?;
 866                 let n = this.read_scalar(args[2])?.to_u32()?;
 867                 let written_place = this.deref_operand(args[3])?;
 868                 // Spec says to always write `0` first.
 869                 this.write_null(written_place.into())?;
 870                 let written = if handle == -11 || handle == -12 {
 871                     // stdout/stderr
 872                     use std::io::{self, Write};
 873
 874                     let buf_cont = this
 875                         .memory
 876                         .read_bytes(buf, Size::from_bytes(u64::from(n)))?;
 877                     let res = if handle == -11 {
 878                         io::stdout().write(buf_cont)
 879                     } else {
 880                         io::stderr().write(buf_cont)
 881                     };
 882                     res.ok().map(|n| n as u32)
 883                 } else {
 884                     eprintln!("Miri: Ignored output to handle {}", handle);
 885                     // Pretend it all went well.
 886                     Some(n)
 887                 };
 888                 // If there was no error, write back how much was written.
 889                 if let Some(n) = written {
 890                     this.write_scalar(Scalar::from_u32(n), written_place.into())?;
 891                 }
 892                 // Return whether this was a success.
 893                 this.write_scalar(
 894                     Scalar::from_int(if written.is_some() { 1 } else { 0 }, dest.layout.size),
 895                     dest,
 896                 )?;
 897             }
 898             "GetConsoleMode" => {
 899                 // Everything is a pipe.
 900                 this.write_null(dest)?;
 901             }
 902             "GetEnvironmentVariableW" => {
 903                 // This is not the env var you are looking for.
 904                 this.set_last_error(Scalar::from_u32(203))?; // ERROR_ENVVAR_NOT_FOUND
 905                 this.write_null(dest)?;
 906             }
 907             "GetCommandLineW" => {
 908                 this.write_scalar(this.machine.cmd_line.expect("machine must be initialized"), dest)?;
 909             }
 910             // The actual name of 'RtlGenRandom'
 911             "SystemFunction036" => {
 912                 let ptr = this.read_scalar(args[0])?.not_undef()?;
 913                 let len = this.read_scalar(args[1])?.to_u32()?;
 914                 this.gen_random(ptr, len as usize)?;
 915                 this.write_scalar(Scalar::from_bool(true), dest)?;
 916             }
 917
 918             // We can't execute anything else.
 919             _ => throw_unsup_format!("can't call foreign function: {}", link_name),
 920         }
 921
 922         this.goto_block(Some(ret))?;
 923         this.dump_place(*dest);
 924         Ok(None)
 925     }
 926
 927     /// Evaluates the scalar at the specified path. Returns Some(val)
 928     /// if the path could be resolved, and None otherwise
 929     fn eval_path_scalar(
 930         &mut self,
 931         path: &[&str],
 932     ) -> InterpResult<'tcx, Option<ScalarMaybeUndef<Tag>>> {
 933         let this = self.eval_context_mut();
 934         if let Ok(instance) = this.resolve_path(path) {
 935             let cid = GlobalId {
 936                 instance,
 937                 promoted: None,
 938             };
 939             let const_val = this.const_eval_raw(cid)?;
 940             let const_val = this.read_scalar(const_val.into())?;
 941             return Ok(Some(const_val));
 942         }
 943         return Ok(None);
 944     }
 945 }
 946
 947 // Shims the linux 'getrandom()' syscall.
 948 fn linux_getrandom<'tcx>(
 949     this: &mut MiriEvalContext<'_, 'tcx>,
 950     args: &[OpTy<'tcx, Tag>],
 951     dest: PlaceTy<'tcx, Tag>,
 952 ) -> InterpResult<'tcx> {
 953     let ptr = this.read_scalar(args[0])?.not_undef()?;
 954     let len = this.read_scalar(args[1])?.to_machine_usize(this)?;
 955
 956     // The only supported flags are GRND_RANDOM and GRND_NONBLOCK,
 957     // neither of which have any effect on our current PRNG.
 958     let _flags = this.read_scalar(args[2])?.to_i32()?;
 959
 960     this.gen_random(ptr, len as usize)?;
 961     this.write_scalar(Scalar::from_uint(len, dest.layout.size), dest)?;
 962     Ok(())
 963 }