src/shims/foreign_items.rs

   1 mod windows;
   2 mod posix;
   3
   4 use std::{convert::{TryInto, TryFrom}, 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 rustc_ast::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 ret {
 131             None => match link_name {
 132                 // This matches calls to the foreign item `panic_impl`.
 133                 // The implementation is provided by the function with the `#[panic_handler]` attribute.
 134                 "panic_impl" => {
 135                     let panic_impl_id = this.tcx.lang_items().panic_impl().unwrap();
 136                     let panic_impl_instance = ty::Instance::mono(*this.tcx, panic_impl_id);
 137                     return Ok(Some(&*this.load_mir(panic_impl_instance.def, None)?));
 138                 }
 139                 | "exit"
 140                 | "ExitProcess"
 141                 => {
 142                     // it's really u32 for ExitProcess, but we have to put it into the `Exit` variant anyway
 143                     let code = this.read_scalar(args[0])?.to_i32()?;
 144                     throw_machine_stop!(TerminationInfo::Exit(code.into()));
 145                 }
 146                 _ => throw_unsup_format!("can't call (diverging) foreign function: {}", link_name),
 147             },
 148             Some(p) => p,
 149         };
 150
 151         // Second: some functions that we forward to MIR implementations.
 152         match link_name {
 153             // This matches calls to the foreign item `__rust_start_panic`, that is,
 154             // calls to `extern "Rust" { fn __rust_start_panic(...) }`
 155             // (and `__rust_panic_cleanup`, respectively).
 156             // We forward this to the underlying *implementation* in the panic runtime crate.
 157             // Normally, this will be either `libpanic_unwind` or `libpanic_abort`, but it could
 158             // also be a custom user-provided implementation via `#![feature(panic_runtime)]`
 159             "__rust_start_panic" | "__rust_panic_cleanup"=> {
 160                 // FIXME we might want to cache this... but it's not really performance-critical.
 161                 let panic_runtime = tcx
 162                     .crates()
 163                     .iter()
 164                     .find(|cnum| tcx.is_panic_runtime(**cnum))
 165                     .expect("No panic runtime found!");
 166                 let panic_runtime = tcx.crate_name(*panic_runtime);
 167                 let start_panic_instance =
 168                     this.resolve_path(&[&*panic_runtime.as_str(), link_name])?;
 169                 return Ok(Some(&*this.load_mir(start_panic_instance.def, None)?));
 170             }
 171             _ => {}
 172         }
 173
 174         // Third: functions that return.
 175         if this.emulate_foreign_item_by_name(link_name, args, dest, ret)? {
 176             this.dump_place(*dest);
 177             this.go_to_block(ret);
 178         }
 179
 180         Ok(None)
 181     }
 182
 183     /// Emulates calling a foreign item using its name, failing if the item is not supported.
 184     /// Returns `true` if the caller is expected to jump to the return block, and `false` if
 185     /// jumping has already been taken care of.
 186     fn emulate_foreign_item_by_name(
 187         &mut self,
 188         link_name: &str,
 189         args: &[OpTy<'tcx, Tag>],
 190         dest: PlaceTy<'tcx, Tag>,
 191         ret: mir::BasicBlock,
 192     ) -> InterpResult<'tcx, bool> {
 193         let this = self.eval_context_mut();
 194
 195         // Here we dispatch all the shims for foreign functions. If you have a platform specific
 196         // shim, add it to the corresponding submodule.
 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                 Self::check_alloc_request(size, align)?;
 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                 Self::check_alloc_request(size, align)?;
 237                 let ptr = this.memory.allocate(
 238                     Size::from_bytes(size),
 239                     Align::from_bytes(align).unwrap(),
 240                     MiriMemoryKind::Rust.into(),
 241                 );
 242                 // We just allocated this, the access is definitely in-bounds.
 243                 this.memory.write_bytes(ptr.into(), iter::repeat(0u8).take(usize::try_from(size).unwrap())).unwrap();
 244                 this.write_scalar(ptr, dest)?;
 245             }
 246             "__rust_dealloc" => {
 247                 let ptr = this.read_scalar(args[0])?.not_undef()?;
 248                 let old_size = this.read_scalar(args[1])?.to_machine_usize(this)?;
 249                 let align = this.read_scalar(args[2])?.to_machine_usize(this)?;
 250                 // No need to check old_size/align; we anyway check that they match the allocation.
 251                 let ptr = this.force_ptr(ptr)?;
 252                 this.memory.deallocate(
 253                     ptr,
 254                     Some((Size::from_bytes(old_size), Align::from_bytes(align).unwrap())),
 255                     MiriMemoryKind::Rust.into(),
 256                 )?;
 257             }
 258             "__rust_realloc" => {
 259                 let old_size = this.read_scalar(args[1])?.to_machine_usize(this)?;
 260                 let align = this.read_scalar(args[2])?.to_machine_usize(this)?;
 261                 let new_size = this.read_scalar(args[3])?.to_machine_usize(this)?;
 262                 Self::check_alloc_request(new_size, align)?;
 263                 // No need to check old_size; we anyway check that they match the allocation.
 264                 let ptr = this.force_ptr(this.read_scalar(args[0])?.not_undef()?)?;
 265                 let align = Align::from_bytes(align).unwrap();
 266                 let new_ptr = this.memory.reallocate(
 267                     ptr,
 268                     Some((Size::from_bytes(old_size), align)),
 269                     Size::from_bytes(new_size),
 270                     align,
 271                     MiriMemoryKind::Rust.into(),
 272                 )?;
 273                 this.write_scalar(new_ptr, dest)?;
 274             }
 275
 276             "memcmp" => {
 277                 let left = this.read_scalar(args[0])?.not_undef()?;
 278                 let right = this.read_scalar(args[1])?.not_undef()?;
 279                 let n = Size::from_bytes(this.read_scalar(args[2])?.to_machine_usize(this)?);
 280
 281                 let result = {
 282                     let left_bytes = this.memory.read_bytes(left, n)?;
 283                     let right_bytes = this.memory.read_bytes(right, n)?;
 284
 285                     use std::cmp::Ordering::*;
 286                     match left_bytes.cmp(right_bytes) {
 287                         Less => -1i32,
 288                         Equal => 0,
 289                         Greater => 1,
 290                     }
 291                 };
 292
 293                 this.write_scalar(Scalar::from_int(result, Size::from_bits(32)), dest)?;
 294             }
 295
 296             "memrchr" => {
 297                 let ptr = this.read_scalar(args[0])?.not_undef()?;
 298                 let val = this.read_scalar(args[1])?.to_i32()? as u8;
 299                 let num = this.read_scalar(args[2])?.to_machine_usize(this)?;
 300                 if let Some(idx) = this
 301                     .memory
 302                     .read_bytes(ptr, Size::from_bytes(num))?
 303                     .iter()
 304                     .rev()
 305                     .position(|&c| c == val)
 306                 {
 307                     let new_ptr = ptr.ptr_offset(Size::from_bytes(num - idx as u64 - 1), this)?;
 308                     this.write_scalar(new_ptr, dest)?;
 309                 } else {
 310                     this.write_null(dest)?;
 311                 }
 312             }
 313
 314             "memchr" => {
 315                 let ptr = this.read_scalar(args[0])?.not_undef()?;
 316                 let val = this.read_scalar(args[1])?.to_i32()? as u8;
 317                 let num = this.read_scalar(args[2])?.to_machine_usize(this)?;
 318                 let idx = this
 319                     .memory
 320                     .read_bytes(ptr, Size::from_bytes(num))?
 321                     .iter()
 322                     .position(|&c| c == val);
 323                 if let Some(idx) = idx {
 324                     let new_ptr = ptr.ptr_offset(Size::from_bytes(idx as u64), this)?;
 325                     this.write_scalar(new_ptr, dest)?;
 326                 } else {
 327                     this.write_null(dest)?;
 328                 }
 329             }
 330
 331             "strlen" => {
 332                 let ptr = this.read_scalar(args[0])?.not_undef()?;
 333                 let n = this.memory.read_c_str(ptr)?.len();
 334                 this.write_scalar(Scalar::from_uint(u64::try_from(n).unwrap(), dest.layout.size), dest)?;
 335             }
 336
 337             // math functions
 338             | "cbrtf"
 339             | "coshf"
 340             | "sinhf"
 341             | "tanf"
 342             | "acosf"
 343             | "asinf"
 344             | "atanf"
 345             => {
 346                 // FIXME: Using host floats.
 347                 let f = f32::from_bits(this.read_scalar(args[0])?.to_u32()?);
 348                 let f = match link_name {
 349                     "cbrtf" => f.cbrt(),
 350                     "coshf" => f.cosh(),
 351                     "sinhf" => f.sinh(),
 352                     "tanf" => f.tan(),
 353                     "acosf" => f.acos(),
 354                     "asinf" => f.asin(),
 355                     "atanf" => f.atan(),
 356                     _ => bug!(),
 357                 };
 358                 this.write_scalar(Scalar::from_u32(f.to_bits()), dest)?;
 359             }
 360             // underscore case for windows
 361             | "_hypotf"
 362             | "hypotf"
 363             | "atan2f"
 364             => {
 365                 // FIXME: Using host floats.
 366                 let f1 = f32::from_bits(this.read_scalar(args[0])?.to_u32()?);
 367                 let f2 = f32::from_bits(this.read_scalar(args[1])?.to_u32()?);
 368                 let n = match link_name {
 369                     "_hypotf" | "hypotf" => f1.hypot(f2),
 370                     "atan2f" => f1.atan2(f2),
 371                     _ => bug!(),
 372                 };
 373                 this.write_scalar(Scalar::from_u32(n.to_bits()), dest)?;
 374             }
 375
 376             | "cbrt"
 377             | "cosh"
 378             | "sinh"
 379             | "tan"
 380             | "acos"
 381             | "asin"
 382             | "atan"
 383             => {
 384                 // FIXME: Using host floats.
 385                 let f = f64::from_bits(this.read_scalar(args[0])?.to_u64()?);
 386                 let f = match link_name {
 387                     "cbrt" => f.cbrt(),
 388                     "cosh" => f.cosh(),
 389                     "sinh" => f.sinh(),
 390                     "tan" => f.tan(),
 391                     "acos" => f.acos(),
 392                     "asin" => f.asin(),
 393                     "atan" => f.atan(),
 394                     _ => bug!(),
 395                 };
 396                 this.write_scalar(Scalar::from_u64(f.to_bits()), dest)?;
 397             }
 398             // underscore case for windows, here and below
 399             // (see https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/floating-point-primitives?view=vs-2019)
 400             | "_hypot"
 401             | "hypot"
 402             | "atan2"
 403             => {
 404                 // FIXME: Using host floats.
 405                 let f1 = f64::from_bits(this.read_scalar(args[0])?.to_u64()?);
 406                 let f2 = f64::from_bits(this.read_scalar(args[1])?.to_u64()?);
 407                 let n = match link_name {
 408                     "_hypot" | "hypot" => f1.hypot(f2),
 409                     "atan2" => f1.atan2(f2),
 410                     _ => bug!(),
 411                 };
 412                 this.write_scalar(Scalar::from_u64(n.to_bits()), dest)?;
 413             }
 414             // For radix-2 (binary) systems, `ldexp` and `scalbn` are the same.
 415             | "_ldexp"
 416             | "ldexp"
 417             | "scalbn"
 418             => {
 419                 let x = this.read_scalar(args[0])?.to_f64()?;
 420                 let exp = this.read_scalar(args[1])?.to_i32()?;
 421
 422                 // Saturating cast to i16. Even those are outside the valid exponent range to
 423                 // `scalbn` below will do its over/underflow handling.
 424                 let exp = if exp > i32::from(i16::MAX) {
 425                     i16::MAX
 426                 } else if exp < i32::from(i16::MIN) {
 427                     i16::MIN
 428                 } else {
 429                     exp.try_into().unwrap()
 430                 };
 431
 432                 let res = x.scalbn(exp);
 433                 this.write_scalar(Scalar::from_f64(res), dest)?;
 434             }
 435
 436             _ => match this.tcx.sess.target.target.target_os.as_str() {
 437                 "linux" | "macos" => return posix::EvalContextExt::emulate_foreign_item_by_name(this, link_name, args, dest, ret),
 438                 "windows" => return windows::EvalContextExt::emulate_foreign_item_by_name(this, link_name, args, dest, ret),
 439                 target => throw_unsup_format!("the {} target platform is not supported", target),
 440             }
 441         };
 442
 443         Ok(true)
 444     }
 445
 446     /// Check some basic requirements for this allocation request:
 447     /// non-zero size, power-of-two alignment.
 448     fn check_alloc_request(size: u64, align: u64) -> InterpResult<'tcx> {
 449         if size == 0 {
 450             throw_ub_format!("creating allocation with size 0");
 451         }
 452         if !align.is_power_of_two() {
 453             throw_ub_format!("creating allocation with non-power-of-two alignment {}", align);
 454         }
 455         Ok(())
 456     }
 457
 458     /// Evaluates the scalar at the specified path. Returns Some(val)
 459     /// if the path could be resolved, and None otherwise
 460     fn eval_path_scalar(
 461         &mut self,
 462         path: &[&str],
 463     ) -> InterpResult<'tcx, Option<ScalarMaybeUndef<Tag>>> {
 464         let this = self.eval_context_mut();
 465         if let Ok(instance) = this.resolve_path(path) {
 466             let cid = GlobalId { instance, promoted: None };
 467             let const_val = this.const_eval_raw(cid)?;
 468             let const_val = this.read_scalar(const_val.into())?;
 469             return Ok(Some(const_val));
 470         }
 471         return Ok(None);
 472     }
 473 }