src/shims/posix/foreign_items.rs

   1 use log::trace;
   2
   3 use rustc_middle::mir;
   4 use rustc_span::Symbol;
   5 use rustc_target::abi::{Align, LayoutOf, Size};
   6 use rustc_target::spec::abi::Abi;
   7
   8 use crate::*;
   9 use shims::foreign_items::EmulateByNameResult;
  10 use shims::posix::fs::EvalContextExt as _;
  11 use shims::posix::sync::EvalContextExt as _;
  12 use shims::posix::thread::EvalContextExt as _;
  13
  14 impl<'mir, 'tcx: 'mir> EvalContextExt<'mir, 'tcx> for crate::MiriEvalContext<'mir, 'tcx> {}
  15 pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx> {
  16     fn emulate_foreign_item_by_name(
  17         &mut self,
  18         link_name: Symbol,
  19         abi: Abi,
  20         args: &[OpTy<'tcx, Tag>],
  21         dest: &PlaceTy<'tcx, Tag>,
  22         ret: mir::BasicBlock,
  23     ) -> InterpResult<'tcx, EmulateByNameResult> {
  24         let this = self.eval_context_mut();
  25
  26         match &*link_name.as_str() {
  27             // Environment related shims
  28             "getenv" => {
  29                 let &[ref name] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
  30                 let result = this.getenv(name)?;
  31                 this.write_scalar(result, dest)?;
  32             }
  33             "unsetenv" => {
  34                 let &[ref name] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
  35                 let result = this.unsetenv(name)?;
  36                 this.write_scalar(Scalar::from_i32(result), dest)?;
  37             }
  38             "setenv" => {
  39                 let &[ref name, ref value, ref overwrite] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
  40                 this.read_scalar(overwrite)?.to_i32()?;
  41                 let result = this.setenv(name, value)?;
  42                 this.write_scalar(Scalar::from_i32(result), dest)?;
  43             }
  44             "getcwd" => {
  45                 let &[ref buf, ref size] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
  46                 let result = this.getcwd(buf, size)?;
  47                 this.write_scalar(result, dest)?;
  48             }
  49             "chdir" => {
  50                 let &[ref path] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
  51                 let result = this.chdir(path)?;
  52                 this.write_scalar(Scalar::from_i32(result), dest)?;
  53             }
  54
  55             // File related shims
  56             "open" | "open64" => {
  57                 let &[ref path, ref flag, ref mode] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
  58                 let result = this.open(path, flag, mode)?;
  59                 this.write_scalar(Scalar::from_i32(result), dest)?;
  60             }
  61             "fcntl" => {
  62                 // `fcntl` is variadic. The argument count is checked based on the first argument
  63                 // in `this.fcntl()`, so we do not use `check_shim` here.
  64                 this.check_abi_and_shim_symbol_clash(abi, Abi::C { unwind: false }, link_name)?;
  65                 let result = this.fcntl(args)?;
  66                 this.write_scalar(Scalar::from_i32(result), dest)?;
  67             }
  68             "read" => {
  69                 let &[ref fd, ref buf, ref count] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
  70                 let fd = this.read_scalar(fd)?.to_i32()?;
  71                 let buf = this.read_scalar(buf)?.check_init()?;
  72                 let count = this.read_scalar(count)?.to_machine_usize(this)?;
  73                 let result = this.read(fd, buf, count)?;
  74                 this.write_scalar(Scalar::from_machine_isize(result, this), dest)?;
  75             }
  76             "write" => {
  77                 let &[ref fd, ref buf, ref n] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
  78                 let fd = this.read_scalar(fd)?.to_i32()?;
  79                 let buf = this.read_scalar(buf)?.check_init()?;
  80                 let count = this.read_scalar(n)?.to_machine_usize(this)?;
  81                 trace!("Called write({:?}, {:?}, {:?})", fd, buf, count);
  82                 let result = this.write(fd, buf, count)?;
  83                 // Now, `result` is the value we return back to the program.
  84                 this.write_scalar(Scalar::from_machine_isize(result, this), dest)?;
  85             }
  86             "unlink" => {
  87                 let &[ref path] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
  88                 let result = this.unlink(path)?;
  89                 this.write_scalar(Scalar::from_i32(result), dest)?;
  90             }
  91             "symlink" => {
  92                 let &[ref target, ref linkpath] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
  93                 let result = this.symlink(target, linkpath)?;
  94                 this.write_scalar(Scalar::from_i32(result), dest)?;
  95             }
  96             "rename" => {
  97                 let &[ref oldpath, ref newpath] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
  98                 let result = this.rename(oldpath, newpath)?;
  99                 this.write_scalar(Scalar::from_i32(result), dest)?;
 100             }
 101             "mkdir" => {
 102                 let &[ref path, ref mode] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 103                 let result = this.mkdir(path, mode)?;
 104                 this.write_scalar(Scalar::from_i32(result), dest)?;
 105             }
 106             "rmdir" => {
 107                 let &[ref path] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 108                 let result = this.rmdir(path)?;
 109                 this.write_scalar(Scalar::from_i32(result), dest)?;
 110             }
 111             "closedir" => {
 112                 let &[ref dirp] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 113                 let result = this.closedir(dirp)?;
 114                 this.write_scalar(Scalar::from_i32(result), dest)?;
 115             }
 116             "lseek" | "lseek64" => {
 117                 let &[ref fd, ref offset, ref whence] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 118                 let result = this.lseek64(fd, offset, whence)?;
 119                 // "lseek" is only used on macOS which is 64bit-only, so `i64` always works.
 120                 this.write_scalar(Scalar::from_i64(result), dest)?;
 121             }
 122             "fsync" => {
 123                 let &[ref fd] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 124                 let result = this.fsync(fd)?;
 125                 this.write_scalar(Scalar::from_i32(result), dest)?;
 126             }
 127             "fdatasync" => {
 128                 let &[ref fd] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 129                 let result = this.fdatasync(fd)?;
 130                 this.write_scalar(Scalar::from_i32(result), dest)?;
 131             }
 132             "readlink" => {
 133                 let &[ref pathname, ref buf, ref bufsize] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 134                 let result = this.readlink(pathname, buf, bufsize)?;
 135                 this.write_scalar(Scalar::from_machine_isize(result, this), dest)?;
 136             }
 137
 138             // Allocation
 139             "posix_memalign" => {
 140                 let &[ref ret, ref align, ref size] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 141                 let ret = this.deref_operand(ret)?;
 142                 let align = this.read_scalar(align)?.to_machine_usize(this)?;
 143                 let size = this.read_scalar(size)?.to_machine_usize(this)?;
 144                 // Align must be power of 2, and also at least ptr-sized (POSIX rules).
 145                 if !align.is_power_of_two() {
 146                     throw_ub_format!("posix_memalign: alignment must be a power of two, but is {}", align);
 147                 }
 148                 if align < this.pointer_size().bytes() {
 149                     throw_ub_format!(
 150                         "posix_memalign: alignment must be at least the size of a pointer, but is {}",
 151                         align,
 152                     );
 153                 }
 154
 155                 if size == 0 {
 156                     this.write_null(&ret.into())?;
 157                 } else {
 158                     let ptr = this.memory.allocate(
 159                         Size::from_bytes(size),
 160                         Align::from_bytes(align).unwrap(),
 161                         MiriMemoryKind::C.into(),
 162                     );
 163                     this.write_scalar(ptr, &ret.into())?;
 164                 }
 165                 this.write_null(dest)?;
 166             }
 167
 168             // Dynamic symbol loading
 169             "dlsym" => {
 170                 let &[ref handle, ref symbol] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 171                 this.read_scalar(handle)?.to_machine_usize(this)?;
 172                 let symbol = this.read_scalar(symbol)?.check_init()?;
 173                 let symbol_name = this.read_c_str(symbol)?;
 174                 if let Some(dlsym) = Dlsym::from_str(symbol_name, &this.tcx.sess.target.os)? {
 175                     let ptr = this.memory.create_fn_alloc(FnVal::Other(dlsym));
 176                     this.write_scalar(Scalar::from(ptr), dest)?;
 177                 } else {
 178                     this.write_null(dest)?;
 179                 }
 180             }
 181
 182             // Querying system information
 183             "sysconf" => {
 184                 let &[ref name] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 185                 let name = this.read_scalar(name)?.to_i32()?;
 186
 187                 let sysconfs = &[
 188                     ("_SC_PAGESIZE", Scalar::from_int(PAGE_SIZE, this.pointer_size())),
 189                     ("_SC_NPROCESSORS_CONF", Scalar::from_int(NUM_CPUS, this.pointer_size())),
 190                     ("_SC_NPROCESSORS_ONLN", Scalar::from_int(NUM_CPUS, this.pointer_size())),
 191                 ];
 192                 let mut result = None;
 193                 for &(sysconf_name, value) in sysconfs {
 194                     let sysconf_name = this.eval_libc_i32(sysconf_name)?;
 195                     if sysconf_name == name {
 196                         result = Some(value);
 197                         break;
 198                     }
 199                 }
 200                 if let Some(result) = result {
 201                     this.write_scalar(result, dest)?;
 202                 } else {
 203                     throw_unsup_format!("unimplemented sysconf name: {}", name)
 204                 }
 205             }
 206
 207             // Thread-local storage
 208             "pthread_key_create" => {
 209                 let &[ref key, ref dtor] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 210                 let key_place = this.deref_operand(key)?;
 211                 let dtor = this.read_scalar(dtor)?.check_init()?;
 212
 213                 // Extract the function type out of the signature (that seems easier than constructing it ourselves).
 214                 let dtor = match this.test_null(dtor)? {
 215                     Some(dtor_ptr) => Some(this.memory.get_fn(dtor_ptr)?.as_instance()?),
 216                     None => None,
 217                 };
 218
 219                 // Figure out how large a pthread TLS key actually is.
 220                 // To this end, deref the argument type. This is `libc::pthread_key_t`.
 221                 let key_type = key.layout.ty
 222                     .builtin_deref(true)
 223                     .ok_or_else(|| err_ub_format!(
 224                         "wrong signature used for `pthread_key_create`: first argument must be a raw pointer."
 225                     ))?
 226                     .ty;
 227                 let key_layout = this.layout_of(key_type)?;
 228
 229                 // Create key and write it into the memory where `key_ptr` wants it.
 230                 let key = this.machine.tls.create_tls_key(dtor, key_layout.size)?;
 231                 this.write_scalar(Scalar::from_uint(key, key_layout.size), &key_place.into())?;
 232
 233                 // Return success (`0`).
 234                 this.write_null(dest)?;
 235             }
 236             "pthread_key_delete" => {
 237                 let &[ref key] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 238                 let key = this.force_bits(this.read_scalar(key)?.check_init()?, key.layout.size)?;
 239                 this.machine.tls.delete_tls_key(key)?;
 240                 // Return success (0)
 241                 this.write_null(dest)?;
 242             }
 243             "pthread_getspecific" => {
 244                 let &[ref key] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 245                 let key = this.force_bits(this.read_scalar(key)?.check_init()?, key.layout.size)?;
 246                 let active_thread = this.get_active_thread();
 247                 let ptr = this.machine.tls.load_tls(key, active_thread, this)?;
 248                 this.write_scalar(ptr, dest)?;
 249             }
 250             "pthread_setspecific" => {
 251                 let &[ref key, ref new_ptr] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 252                 let key = this.force_bits(this.read_scalar(key)?.check_init()?, key.layout.size)?;
 253                 let active_thread = this.get_active_thread();
 254                 let new_ptr = this.read_scalar(new_ptr)?.check_init()?;
 255                 this.machine.tls.store_tls(key, active_thread, this.test_null(new_ptr)?)?;
 256
 257                 // Return success (`0`).
 258                 this.write_null(dest)?;
 259             }
 260
 261             // Synchronization primitives
 262             "pthread_mutexattr_init" => {
 263                 let &[ref attr] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 264                 let result = this.pthread_mutexattr_init(attr)?;
 265                 this.write_scalar(Scalar::from_i32(result), dest)?;
 266             }
 267             "pthread_mutexattr_settype" => {
 268                 let &[ref attr, ref kind] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 269                 let result = this.pthread_mutexattr_settype(attr, kind)?;
 270                 this.write_scalar(Scalar::from_i32(result), dest)?;
 271             }
 272             "pthread_mutexattr_destroy" => {
 273                 let &[ref attr] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 274                 let result = this.pthread_mutexattr_destroy(attr)?;
 275                 this.write_scalar(Scalar::from_i32(result), dest)?;
 276             }
 277             "pthread_mutex_init" => {
 278                 let &[ref mutex, ref attr] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 279                 let result = this.pthread_mutex_init(mutex, attr)?;
 280                 this.write_scalar(Scalar::from_i32(result), dest)?;
 281             }
 282             "pthread_mutex_lock" => {
 283                 let &[ref mutex] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 284                 let result = this.pthread_mutex_lock(mutex)?;
 285                 this.write_scalar(Scalar::from_i32(result), dest)?;
 286             }
 287             "pthread_mutex_trylock" => {
 288                 let &[ref mutex] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 289                 let result = this.pthread_mutex_trylock(mutex)?;
 290                 this.write_scalar(Scalar::from_i32(result), dest)?;
 291             }
 292             "pthread_mutex_unlock" => {
 293                 let &[ref mutex] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 294                 let result = this.pthread_mutex_unlock(mutex)?;
 295                 this.write_scalar(Scalar::from_i32(result), dest)?;
 296             }
 297             "pthread_mutex_destroy" => {
 298                 let &[ref mutex] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 299                 let result = this.pthread_mutex_destroy(mutex)?;
 300                 this.write_scalar(Scalar::from_i32(result), dest)?;
 301             }
 302             "pthread_rwlock_rdlock" => {
 303                 let &[ref rwlock] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 304                 let result = this.pthread_rwlock_rdlock(rwlock)?;
 305                 this.write_scalar(Scalar::from_i32(result), dest)?;
 306             }
 307             "pthread_rwlock_tryrdlock" => {
 308                 let &[ref rwlock] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 309                 let result = this.pthread_rwlock_tryrdlock(rwlock)?;
 310                 this.write_scalar(Scalar::from_i32(result), dest)?;
 311             }
 312             "pthread_rwlock_wrlock" => {
 313                 let &[ref rwlock] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 314                 let result = this.pthread_rwlock_wrlock(rwlock)?;
 315                 this.write_scalar(Scalar::from_i32(result), dest)?;
 316             }
 317             "pthread_rwlock_trywrlock" => {
 318                 let &[ref rwlock] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 319                 let result = this.pthread_rwlock_trywrlock(rwlock)?;
 320                 this.write_scalar(Scalar::from_i32(result), dest)?;
 321             }
 322             "pthread_rwlock_unlock" => {
 323                 let &[ref rwlock] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 324                 let result = this.pthread_rwlock_unlock(rwlock)?;
 325                 this.write_scalar(Scalar::from_i32(result), dest)?;
 326             }
 327             "pthread_rwlock_destroy" => {
 328                 let &[ref rwlock] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 329                 let result = this.pthread_rwlock_destroy(rwlock)?;
 330                 this.write_scalar(Scalar::from_i32(result), dest)?;
 331             }
 332             "pthread_condattr_init" => {
 333                 let &[ref attr] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 334                 let result = this.pthread_condattr_init(attr)?;
 335                 this.write_scalar(Scalar::from_i32(result), dest)?;
 336             }
 337             "pthread_condattr_destroy" => {
 338                 let &[ref attr] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 339                 let result = this.pthread_condattr_destroy(attr)?;
 340                 this.write_scalar(Scalar::from_i32(result), dest)?;
 341             }
 342             "pthread_cond_init" => {
 343                 let &[ref cond, ref attr] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 344                 let result = this.pthread_cond_init(cond, attr)?;
 345                 this.write_scalar(Scalar::from_i32(result), dest)?;
 346             }
 347             "pthread_cond_signal" => {
 348                 let &[ref cond] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 349                 let result = this.pthread_cond_signal(cond)?;
 350                 this.write_scalar(Scalar::from_i32(result), dest)?;
 351             }
 352             "pthread_cond_broadcast" => {
 353                 let &[ref cond] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 354                 let result = this.pthread_cond_broadcast(cond)?;
 355                 this.write_scalar(Scalar::from_i32(result), dest)?;
 356             }
 357             "pthread_cond_wait" => {
 358                 let &[ref cond, ref mutex] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 359                 let result = this.pthread_cond_wait(cond, mutex)?;
 360                 this.write_scalar(Scalar::from_i32(result), dest)?;
 361             }
 362             "pthread_cond_timedwait" => {
 363                 let &[ref cond, ref mutex, ref abstime] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 364                 this.pthread_cond_timedwait(cond, mutex, abstime, dest)?;
 365             }
 366             "pthread_cond_destroy" => {
 367                 let &[ref cond] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 368                 let result = this.pthread_cond_destroy(cond)?;
 369                 this.write_scalar(Scalar::from_i32(result), dest)?;
 370             }
 371
 372             // Threading
 373             "pthread_create" => {
 374                 let &[ref thread, ref attr, ref start, ref arg] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 375                 let result = this.pthread_create(thread, attr, start, arg)?;
 376                 this.write_scalar(Scalar::from_i32(result), dest)?;
 377             }
 378             "pthread_join" => {
 379                 let &[ref thread, ref retval] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 380                 let result = this.pthread_join(thread, retval)?;
 381                 this.write_scalar(Scalar::from_i32(result), dest)?;
 382             }
 383             "pthread_detach" => {
 384                 let &[ref thread] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 385                 let result = this.pthread_detach(thread)?;
 386                 this.write_scalar(Scalar::from_i32(result), dest)?;
 387             }
 388             "pthread_self" => {
 389                 let &[] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 390                 this.pthread_self(dest)?;
 391             }
 392             "sched_yield" => {
 393                 let &[] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 394                 let result = this.sched_yield()?;
 395                 this.write_scalar(Scalar::from_i32(result), dest)?;
 396             }
 397             "nanosleep" => {
 398                 let &[ref req, ref rem] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 399                 let result = this.nanosleep(req, rem)?;
 400                 this.write_scalar(Scalar::from_i32(result), dest)?;
 401             }
 402
 403             // Miscellaneous
 404             "isatty" => {
 405                 let &[ref fd] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 406                 this.read_scalar(fd)?.to_i32()?;
 407                 // "returns 1 if fd is an open file descriptor referring to a terminal; otherwise 0 is returned, and errno is set to indicate the error"
 408                 // FIXME: we just say nothing is a terminal.
 409                 let enotty = this.eval_libc("ENOTTY")?;
 410                 this.set_last_error(enotty)?;
 411                 this.write_null(dest)?;
 412             }
 413             "pthread_atfork" => {
 414                 let &[ref prepare, ref parent, ref child] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 415                 this.force_bits(this.read_scalar(prepare)?.check_init()?, this.memory.pointer_size())?;
 416                 this.force_bits(this.read_scalar(parent)?.check_init()?, this.memory.pointer_size())?;
 417                 this.force_bits(this.read_scalar(child)?.check_init()?, this.memory.pointer_size())?;
 418                 // We do not support forking, so there is nothing to do here.
 419                 this.write_null(dest)?;
 420             }
 421
 422             // Incomplete shims that we "stub out" just to get pre-main initialization code to work.
 423             // These shims are enabled only when the caller is in the standard library.
 424             "pthread_attr_getguardsize"
 425             if this.frame_in_std() => {
 426                 let &[ref _attr, ref guard_size] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 427                 let guard_size = this.deref_operand(guard_size)?;
 428                 let guard_size_layout = this.libc_ty_layout("size_t")?;
 429                 this.write_scalar(Scalar::from_uint(crate::PAGE_SIZE, guard_size_layout.size), &guard_size.into())?;
 430
 431                 // Return success (`0`).
 432                 this.write_null(dest)?;
 433             }
 434
 435             | "pthread_attr_init"
 436             | "pthread_attr_destroy"
 437             if this.frame_in_std() => {
 438                 let &[_] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 439                 this.write_null(dest)?;
 440             }
 441             | "pthread_attr_setstacksize"
 442             if this.frame_in_std() => {
 443                 let &[_, _] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 444                 this.write_null(dest)?;
 445             }
 446
 447             | "signal"
 448             | "sigaltstack"
 449             if this.frame_in_std() => {
 450                 let &[_, _] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 451                 this.write_null(dest)?;
 452             }
 453             | "sigaction"
 454             | "mprotect"
 455             if this.frame_in_std() => {
 456                 let &[_, _, _] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
 457                 this.write_null(dest)?;
 458             }
 459
 460             // Platform-specific shims
 461             _ => {
 462                 match this.tcx.sess.target.os.as_str() {
 463                     "linux" => return shims::posix::linux::foreign_items::EvalContextExt::emulate_foreign_item_by_name(this, link_name, abi, args, dest, ret),
 464                     "macos" => return shims::posix::macos::foreign_items::EvalContextExt::emulate_foreign_item_by_name(this, link_name, abi, args, dest, ret),
 465                     _ => unreachable!(),
 466                 }
 467             }
 468         };
 469
 470         Ok(EmulateByNameResult::NeedsJumping)
 471     }
 472 }