miri/shims/unix/
fd.rs

1//! General management of file descriptors, and support for
2//! standard file descriptors (stdin/stdout/stderr).
3
4use std::io;
5use std::io::ErrorKind;
6
7use rand::RngExt;
8use rustc_abi::{Align, Size};
9use rustc_target::spec::Os;
10
11use crate::shims::files::{DynFileDescriptionRef, FileDescription};
12use crate::shims::sig::check_min_vararg_count;
13use crate::shims::unix::linux_like::epoll::EpollReadiness;
14use crate::shims::unix::*;
15use crate::*;
16
17#[derive(Debug, Clone, Copy, Eq, PartialEq)]
18pub enum FlockOp {
19    SharedLock { nonblocking: bool },
20    ExclusiveLock { nonblocking: bool },
21    Unlock,
22}
23
24/// Represents unix-specific file descriptions.
25pub trait UnixFileDescription: FileDescription {
26    /// Reads as much as possible into the given buffer `ptr` from a given offset.
27    /// `len` indicates how many bytes we should try to read.
28    /// `dest` is where the return value should be stored: number of bytes read, or `-1` in case of error.
29    fn pread<'tcx>(
30        &self,
31        _communicate_allowed: bool,
32        _offset: u64,
33        _ptr: Pointer,
34        _len: usize,
35        _ecx: &mut MiriInterpCx<'tcx>,
36        _finish: DynMachineCallback<'tcx, Result<usize, IoError>>,
37    ) -> InterpResult<'tcx> {
38        throw_unsup_format!("cannot pread from {}", self.name());
39    }
40
41    /// Writes as much as possible from the given buffer `ptr` starting at a given offset.
42    /// `ptr` is the pointer to the user supplied read buffer.
43    /// `len` indicates how many bytes we should try to write.
44    /// `dest` is where the return value should be stored: number of bytes written, or `-1` in case of error.
45    fn pwrite<'tcx>(
46        &self,
47        _communicate_allowed: bool,
48        _ptr: Pointer,
49        _len: usize,
50        _offset: u64,
51        _ecx: &mut MiriInterpCx<'tcx>,
52        _finish: DynMachineCallback<'tcx, Result<usize, IoError>>,
53    ) -> InterpResult<'tcx> {
54        throw_unsup_format!("cannot pwrite to {}", self.name());
55    }
56
57    fn flock<'tcx>(
58        &self,
59        _communicate_allowed: bool,
60        _op: FlockOp,
61    ) -> InterpResult<'tcx, io::Result<()>> {
62        throw_unsup_format!("cannot flock {}", self.name());
63    }
64
65    /// Modifies device parameters.
66    /// `op` is the device-dependent operation code. It's either a `c_long` or `c_int`, depending on
67    /// the target and whether it uses glibc or musl.
68    /// `arg` is the optional third argument which exists depending on the operation code. It's either
69    /// an integer or a pointer.
70    fn ioctl<'tcx>(
71        &self,
72        _op: Scalar,
73        _arg: Option<&OpTy<'tcx>>,
74        _ecx: &mut MiriInterpCx<'tcx>,
75    ) -> InterpResult<'tcx, i32> {
76        throw_unsup_format!("cannot use ioctl on {}", self.name());
77    }
78
79    /// Return which epoll events are currently active.
80    fn epoll_active_events<'tcx>(&self) -> InterpResult<'tcx, EpollReadiness> {
81        throw_unsup_format!("{}: epoll does not support this file description", self.name());
82    }
83}
84
85impl<'tcx> EvalContextExt<'tcx> for crate::MiriInterpCx<'tcx> {}
86pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
87    fn dup(&mut self, old_fd_num: i32) -> InterpResult<'tcx, Scalar> {
88        let this = self.eval_context_mut();
89
90        let Some(fd) = this.machine.fds.get(old_fd_num) else {
91            return this.set_last_error_and_return_i32(LibcError("EBADF"));
92        };
93        interp_ok(Scalar::from_i32(this.machine.fds.insert(fd)))
94    }
95
96    fn dup2(&mut self, old_fd_num: i32, new_fd_num: i32) -> InterpResult<'tcx, Scalar> {
97        let this = self.eval_context_mut();
98
99        let Some(fd) = this.machine.fds.get(old_fd_num) else {
100            return this.set_last_error_and_return_i32(LibcError("EBADF"));
101        };
102        if new_fd_num != old_fd_num {
103            // Close new_fd if it is previously opened.
104            // If old_fd and new_fd point to the same description, then `dup_fd` ensures we keep the underlying file description alive.
105            if let Some(old_new_fd) = this.machine.fds.fds.insert(new_fd_num, fd) {
106                // Ignore close error (not interpreter's) according to dup2() doc.
107                old_new_fd.close_ref(this.machine.communicate(), this)?.ok();
108            }
109        }
110        interp_ok(Scalar::from_i32(new_fd_num))
111    }
112
113    fn flock(&mut self, fd_num: i32, op: i32) -> InterpResult<'tcx, Scalar> {
114        let this = self.eval_context_mut();
115        let Some(fd) = this.machine.fds.get(fd_num) else {
116            return this.set_last_error_and_return_i32(LibcError("EBADF"));
117        };
118
119        // We need to check that there aren't unsupported options in `op`.
120        let lock_sh = this.eval_libc_i32("LOCK_SH");
121        let lock_ex = this.eval_libc_i32("LOCK_EX");
122        let lock_nb = this.eval_libc_i32("LOCK_NB");
123        let lock_un = this.eval_libc_i32("LOCK_UN");
124
125        use FlockOp::*;
126        let parsed_op = if op == lock_sh {
127            SharedLock { nonblocking: false }
128        } else if op == lock_sh | lock_nb {
129            SharedLock { nonblocking: true }
130        } else if op == lock_ex {
131            ExclusiveLock { nonblocking: false }
132        } else if op == lock_ex | lock_nb {
133            ExclusiveLock { nonblocking: true }
134        } else if op == lock_un {
135            Unlock
136        } else {
137            throw_unsup_format!("unsupported flags {:#x}", op);
138        };
139
140        let result = fd.as_unix(this).flock(this.machine.communicate(), parsed_op)?;
141        // return `0` if flock is successful
142        let result = result.map(|()| 0i32);
143        interp_ok(Scalar::from_i32(this.try_unwrap_io_result(result)?))
144    }
145
146    fn ioctl(
147        &mut self,
148        fd: &OpTy<'tcx>,
149        op: &OpTy<'tcx>,
150        varargs: &[OpTy<'tcx>],
151    ) -> InterpResult<'tcx, Scalar> {
152        let this = self.eval_context_mut();
153
154        let fd = this.read_scalar(fd)?.to_i32()?;
155        let op = this.read_scalar(op)?;
156        // There is at most one relevant variadic argument.
157        // It exists depending on the device and the opcode and thus we can't
158        // use `check_min_vararg_count` here.
159        let arg = varargs.first();
160
161        let Some(fd) = this.machine.fds.get(fd) else {
162            return this.set_last_error_and_return_i32(LibcError("EBADF"));
163        };
164
165        // Handle common opcodes.
166        let fioclex = this.eval_libc("FIOCLEX");
167        let fionclex = this.eval_libc("FIONCLEX");
168        if op == fioclex || op == fionclex {
169            // Since we don't support `exec`, those are NOPs.
170            return interp_ok(Scalar::from_i32(0));
171        }
172
173        // Since some ioctl operations use the return value as an output parameter, we cannot strictly use the convention of
174        // zero indicating success and -1 indicating an error.
175        let return_value = fd.as_unix(this).ioctl(op, arg, this)?;
176        interp_ok(Scalar::from_i32(return_value))
177    }
178
179    fn fcntl(
180        &mut self,
181        fd_num: &OpTy<'tcx>,
182        cmd: &OpTy<'tcx>,
183        varargs: &[OpTy<'tcx>],
184    ) -> InterpResult<'tcx, Scalar> {
185        let this = self.eval_context_mut();
186
187        let fd_num = this.read_scalar(fd_num)?.to_i32()?;
188        let cmd = this.read_scalar(cmd)?.to_i32()?;
189
190        let f_getfd = this.eval_libc_i32("F_GETFD");
191        let f_dupfd = this.eval_libc_i32("F_DUPFD");
192        let f_dupfd_cloexec = this.eval_libc_i32("F_DUPFD_CLOEXEC");
193        let f_getfl = this.eval_libc_i32("F_GETFL");
194        let f_setfl = this.eval_libc_i32("F_SETFL");
195
196        // We only support getting the flags for a descriptor.
197        match cmd {
198            cmd if cmd == f_getfd => {
199                // Currently this is the only flag that `F_GETFD` returns. It is OK to just return the
200                // `FD_CLOEXEC` value without checking if the flag is set for the file because `std`
201                // always sets this flag when opening a file. However we still need to check that the
202                // file itself is open.
203                if !this.machine.fds.is_fd_num(fd_num) {
204                    this.set_last_error_and_return_i32(LibcError("EBADF"))
205                } else {
206                    interp_ok(this.eval_libc("FD_CLOEXEC"))
207                }
208            }
209            cmd if cmd == f_dupfd || cmd == f_dupfd_cloexec => {
210                // Note that we always assume the FD_CLOEXEC flag is set for every open file, in part
211                // because exec() isn't supported. The F_DUPFD and F_DUPFD_CLOEXEC commands only
212                // differ in whether the FD_CLOEXEC flag is pre-set on the new file descriptor,
213                // thus they can share the same implementation here.
214                let cmd_name = if cmd == f_dupfd {
215                    "fcntl(fd, F_DUPFD, ...)"
216                } else {
217                    "fcntl(fd, F_DUPFD_CLOEXEC, ...)"
218                };
219
220                let [start] = check_min_vararg_count(cmd_name, varargs)?;
221                let start = this.read_scalar(start)?.to_i32()?;
222
223                if let Some(fd) = this.machine.fds.get(fd_num) {
224                    interp_ok(Scalar::from_i32(this.machine.fds.insert_with_min_num(fd, start)))
225                } else {
226                    this.set_last_error_and_return_i32(LibcError("EBADF"))
227                }
228            }
229            cmd if cmd == f_getfl => {
230                // Check if this is a valid open file descriptor.
231                let Some(fd) = this.machine.fds.get(fd_num) else {
232                    return this.set_last_error_and_return_i32(LibcError("EBADF"));
233                };
234
235                fd.get_flags(this)
236            }
237            cmd if cmd == f_setfl => {
238                // Check if this is a valid open file descriptor.
239                let Some(fd) = this.machine.fds.get(fd_num) else {
240                    return this.set_last_error_and_return_i32(LibcError("EBADF"));
241                };
242
243                let [flag] = check_min_vararg_count("fcntl(fd, F_SETFL, ...)", varargs)?;
244                let flag = this.read_scalar(flag)?.to_i32()?;
245
246                // Ignore flags that never get stored by SETFL.
247                // "File access mode (O_RDONLY, O_WRONLY, O_RDWR) and file
248                // creation flags (i.e., O_CREAT, O_EXCL, O_NOCTTY, O_TRUNC)
249                // in arg are ignored."
250                let ignored_flags = this.eval_libc_i32("O_RDONLY")
251                    | this.eval_libc_i32("O_WRONLY")
252                    | this.eval_libc_i32("O_RDWR")
253                    | this.eval_libc_i32("O_CREAT")
254                    | this.eval_libc_i32("O_EXCL")
255                    | this.eval_libc_i32("O_NOCTTY")
256                    | this.eval_libc_i32("O_TRUNC");
257
258                fd.set_flags(flag & !ignored_flags, this)
259            }
260            cmd if this.tcx.sess.target.os == Os::MacOs
261                && cmd == this.eval_libc_i32("F_FULLFSYNC") =>
262            {
263                // Reject if isolation is enabled.
264                if let IsolatedOp::Reject(reject_with) = this.machine.isolated_op {
265                    this.reject_in_isolation("`fcntl`", reject_with)?;
266                    return this.set_last_error_and_return_i32(ErrorKind::PermissionDenied);
267                }
268
269                this.ffullsync_fd(fd_num)
270            }
271            cmd => {
272                throw_unsup_format!("fcntl: unsupported command {cmd:#x}");
273            }
274        }
275    }
276
277    fn close(&mut self, fd_op: &OpTy<'tcx>) -> InterpResult<'tcx, Scalar> {
278        let this = self.eval_context_mut();
279
280        let fd_num = this.read_scalar(fd_op)?.to_i32()?;
281
282        let Some(fd) = this.machine.fds.remove(fd_num) else {
283            return this.set_last_error_and_return_i32(LibcError("EBADF"));
284        };
285        let result = fd.close_ref(this.machine.communicate(), this)?;
286        // return `0` if close is successful
287        let result = result.map(|()| 0i32);
288        interp_ok(Scalar::from_i32(this.try_unwrap_io_result(result)?))
289    }
290
291    /// Read data from `fd` into buffer specified by `buf` and `count`.
292    ///
293    /// If `offset` is `None`, reads data from current cursor position associated with `fd`
294    /// and updates cursor position on completion. Otherwise, reads from the specified offset
295    /// and keeps the cursor unchanged.
296    fn read(
297        &mut self,
298        fd_num: i32,
299        buf: Pointer,
300        count: u64,
301        offset: Option<i128>,
302        dest: &MPlaceTy<'tcx>,
303    ) -> InterpResult<'tcx> {
304        let this = self.eval_context_mut();
305
306        // Isolation check is done via `FileDescription` trait.
307
308        trace!("Reading from FD {}, size {}", fd_num, count);
309
310        // Check that the *entire* buffer is actually valid memory.
311        this.check_ptr_access(buf, Size::from_bytes(count), CheckInAllocMsg::MemoryAccess)?;
312
313        // We cap the number of read bytes to the largest value that we are able to fit in both the
314        // host's and target's `isize`. This saves us from having to handle overflows later.
315        let count = count
316            .min(u64::try_from(this.target_isize_max()).unwrap())
317            .min(u64::try_from(isize::MAX).unwrap());
318        let count = usize::try_from(count).unwrap(); // now it fits in a `usize`
319
320        // Get the FD.
321        let Some(fd) = this.machine.fds.get(fd_num) else {
322            trace!("read: FD not found");
323            return this.set_last_error_and_return(LibcError("EBADF"), dest);
324        };
325
326        trace!("read: FD mapped to {fd:?}");
327        // We want to read at most `count` bytes. We are sure that `count` is not negative
328        // because it was a target's `usize`. Also we are sure that it's smaller than
329        // `usize::MAX` because it is bounded by the host's `isize`.
330
331        let dest = dest.clone();
332        this.read_from_fd(
333            fd,
334            buf,
335            count,
336            offset,
337            callback!(
338                @capture<'tcx> {
339                    count: usize,
340                    dest: MPlaceTy<'tcx>,
341                }
342                |this, result: Result<usize, IoError>| {
343                    match result {
344                        Ok(read_size) => {
345                            assert!(read_size <= count);
346                            // This must fit since `count` fits.
347                            this.write_int(u64::try_from(read_size).unwrap(), &dest)
348                        }
349                        Err(e) => this.set_last_error_and_return(e, &dest)
350                }}
351            ),
352        )
353    }
354
355    fn write(
356        &mut self,
357        fd_num: i32,
358        buf: Pointer,
359        count: u64,
360        offset: Option<i128>,
361        dest: &MPlaceTy<'tcx>,
362    ) -> InterpResult<'tcx> {
363        let this = self.eval_context_mut();
364
365        // Isolation check is done via `FileDescription` trait.
366
367        // Check that the *entire* buffer is actually valid memory.
368        this.check_ptr_access(buf, Size::from_bytes(count), CheckInAllocMsg::MemoryAccess)?;
369
370        // We cap the number of written bytes to the largest value that we are able to fit in both the
371        // host's and target's `isize`. This saves us from having to handle overflows later.
372        let count = count
373            .min(u64::try_from(this.target_isize_max()).unwrap())
374            .min(u64::try_from(isize::MAX).unwrap());
375        let count = usize::try_from(count).unwrap(); // now it fits in a `usize`
376
377        // We temporarily dup the FD to be able to retain mutable access to `this`.
378        let Some(fd) = this.machine.fds.get(fd_num) else {
379            return this.set_last_error_and_return(LibcError("EBADF"), dest);
380        };
381
382        let dest = dest.clone();
383        this.write_to_fd(
384            fd,
385            buf,
386            count,
387            offset,
388            callback!(
389                @capture<'tcx> {
390                    count: usize,
391                    dest: MPlaceTy<'tcx>,
392                }
393                |this, result: Result<usize, IoError>| {
394                    match result {
395                        Ok(write_size) => {
396                            assert!(write_size <= count);
397                            // This must fit since `count` fits.
398                            this.write_int(u64::try_from(write_size).unwrap(), &dest)
399                        }
400                        Err(e) => this.set_last_error_and_return(e, &dest)
401
402                }}
403            ),
404        )
405    }
406
407    /// Vectored reads are implemented by first reading bytes from `fd`
408    /// into a temporary buffer which has the combined size of all buffers in
409    /// `iov`. After that we split the bytes of the combined buffer into the
410    /// buffers of `iov`. This ensures that the vectored read occurs atomically.
411    fn readv(
412        &mut self,
413        fd: &OpTy<'tcx>,
414        iov: &OpTy<'tcx>,
415        iovcnt: &OpTy<'tcx>,
416        offset: Option<&OpTy<'tcx>>,
417        dest: &MPlaceTy<'tcx>,
418    ) -> InterpResult<'tcx> {
419        let this = self.eval_context_mut();
420
421        let fd = this.read_scalar(fd)?.to_i32()?;
422        let iov_ptr = this.read_pointer(iov)?;
423        let iovcnt: u64 = this.read_scalar(iovcnt)?.to_i32()?.try_into().unwrap();
424        // `readv` is the same as `preadv` without an offset.
425        let offset = if let Some(offset) = offset {
426            if matches!(this.tcx.sess.target.os, Os::Solaris) {
427                throw_unsup_format!(
428                    "preadv: vectored reads with offsets aren't supported on Solaris"
429                )
430            }
431            Some(this.read_scalar(offset)?.to_int(offset.layout.size)?)
432        } else {
433            None
434        };
435
436        // Check that the FD exists.
437        let Some(fd) = this.machine.fds.get(fd) else {
438            return this.set_last_error_and_return(LibcError("EBADF"), dest);
439        };
440
441        let iovec_layout = this.libc_array_ty_layout("iovec", iovcnt);
442        let iov_ptr_mplace = this.ptr_to_mplace(iov_ptr, iovec_layout);
443
444        // Read list of buffers from `iov`.
445        let mut buffers = Vec::new();
446
447        let mut array = this.project_array_fields(&iov_ptr_mplace)?;
448        while let Some((_idx, iovec)) = array.next(this)? {
449            let iov_len_field = this.project_field_named(&iovec, "iov_len")?;
450            let iov_len: u64 = this
451                .read_scalar(&iov_len_field)?
452                .to_int(iov_len_field.layout.size)?
453                .try_into()
454                .unwrap();
455
456            let iov_base_field = this.project_field_named(&iovec, "iov_base")?;
457            let iov_base_ptr = this.read_pointer(&iov_base_field)?;
458
459            buffers.push((iov_base_ptr, iov_len));
460        }
461
462        let total_bytes = buffers.iter().map(|(_, len)| len).sum::<u64>();
463
464        // Allocate a temporary buffer which has the combined size of all buffers provided in `iov`.
465        let tmp_ptr: Pointer = this
466            .allocate_ptr(
467                Size::from_bytes(total_bytes),
468                Align::ONE,
469                MemoryKind::Stack,
470                AllocInit::Uninit,
471            )?
472            .into();
473
474        let dest = dest.clone();
475        this.read_from_fd(
476            fd,
477            tmp_ptr,
478            usize::try_from(total_bytes).unwrap(),
479            offset,
480            callback!(
481                @capture<'tcx> {
482                    tmp_ptr: Pointer,
483                    buffers: Vec<(Pointer, u64)>,
484                    dest: MPlaceTy<'tcx>
485                } |this, result: Result<usize, IoError>| {
486                    let bytes_read = match result {
487                        Ok(size) => {
488                            this.write_scalar(Scalar::from_target_isize(size.try_into().unwrap(), this), &dest)?;
489                            u64::try_from(size).unwrap()
490                        },
491                        Err(e) => return this.set_last_error_and_return(e, &dest)
492                    };
493                    let mut remaining_bytes = bytes_read;
494
495                    // Split the bytes from the temporary buffer into the buffers provided in `iov`.
496                    // We start at the first buffer and fill them in order, until we reach the end of the
497                    // initialized bytes in the temporary buffer.
498                    for (buffer_ptr, buffer_len) in buffers {
499                        // Offset temporary buffer by the amount of bytes we already copied into previous buffers.
500                        let tmp_ptr_with_offset =
501                            this.ptr_offset_inbounds(tmp_ptr, i64::try_from(bytes_read.strict_sub(remaining_bytes)).unwrap())?;
502
503                        // Copy at most as many bytes as the buffer fits but without reading
504                        // any uninitialized bytes from the temporary buffer.
505                        let copy_amount = buffer_len.min(remaining_bytes);
506                        this.mem_copy(
507                            tmp_ptr_with_offset,
508                            buffer_ptr,
509                            Size::from_bytes(copy_amount),
510                            // The buffers are guaranteed to not overlap because we just newly allocated
511                            // the `tmp_ptr`, and `tmp_ptr_with_offset` is guaranteed to be
512                            // within those boundaries.
513                            true,
514                        )?;
515
516                        remaining_bytes = remaining_bytes.strict_sub(copy_amount);
517                        if remaining_bytes == 0 {
518                            // We don't have anything left to copy; exit the loop.
519                            break;
520                        }
521                    }
522
523                    this.deallocate_ptr(tmp_ptr, None, MemoryKind::Stack)
524                }),
525        )
526    }
527
528    /// Vectored writes are implemented by first writing the bytes from all
529    /// buffers of `iov` into a combined temporary buffer and then writing this
530    /// combined buffer into `fd`. This ensures that the vectored write occurs atomically.
531    fn writev(
532        &mut self,
533        fd: &OpTy<'tcx>,
534        iov: &OpTy<'tcx>,
535        iovcnt: &OpTy<'tcx>,
536        offset: Option<&OpTy<'tcx>>,
537        dest: &MPlaceTy<'tcx>,
538    ) -> InterpResult<'tcx> {
539        let this = self.eval_context_mut();
540
541        let fd = this.read_scalar(fd)?.to_i32()?;
542        let iov_ptr = this.read_pointer(iov)?;
543        let iovcnt: u64 = this.read_scalar(iovcnt)?.to_i32()?.try_into().unwrap();
544        // `writev` is the same as `pwritev` without an offset.
545        let offset = if let Some(offset) = offset {
546            if matches!(this.tcx.sess.target.os, Os::Solaris) {
547                throw_unsup_format!(
548                    "pwritev: vectored writes with offsets aren't supported on Solaris"
549                )
550            }
551            Some(this.read_scalar(offset)?.to_int(offset.layout.size)?)
552        } else {
553            None
554        };
555
556        // Check that the FD exists.
557        let Some(fd) = this.machine.fds.get(fd) else {
558            return this.set_last_error_and_return(LibcError("EBADF"), dest);
559        };
560
561        let iovec_layout = this.libc_array_ty_layout("iovec", iovcnt);
562        let iov_ptr_mplace = this.ptr_to_mplace(iov_ptr, iovec_layout);
563
564        // Read list of buffers from `iov`.
565        let mut buffers = Vec::new();
566
567        let mut array = this.project_array_fields(&iov_ptr_mplace)?;
568        while let Some((_idx, iovec)) = array.next(this)? {
569            let iov_len_field = this.project_field_named(&iovec, "iov_len")?;
570            let iov_len: u64 = this
571                .read_scalar(&iov_len_field)?
572                .to_int(iov_len_field.layout.size)?
573                .try_into()
574                .unwrap();
575
576            let iov_base_field = this.project_field_named(&iovec, "iov_base")?;
577            let iov_base_ptr = this.read_pointer(&iov_base_field)?;
578
579            buffers.push((iov_base_ptr, iov_len));
580        }
581
582        let total_bytes = buffers.iter().map(|(_, len)| len).sum::<u64>();
583
584        // Allocate a temporary buffer which has the combined size of all buffers provided in `iov`.
585        let tmp_ptr: Pointer = this
586            .allocate_ptr(
587                Size::from_bytes(total_bytes),
588                Align::ONE,
589                MemoryKind::Stack,
590                AllocInit::Uninit,
591            )?
592            .into();
593
594        // Copy the bytes from all buffers provided in `iov` into the temporary buffer.
595        // We start at the first buffer and then continue buffer by buffer.
596        let mut bytes_copied: u64 = 0;
597        for (buffer_ptr, buffer_len) in buffers {
598            // Offset temporary buffer by the amount of bytes we already copied from previous buffers.
599            let tmp_ptr_with_offset =
600                this.ptr_offset_inbounds(tmp_ptr, i64::try_from(bytes_copied).unwrap())?;
601
602            this.mem_copy(
603                buffer_ptr,
604                tmp_ptr_with_offset,
605                Size::from_bytes(buffer_len),
606                // The buffers are guaranteed to not overlap because we just newly allocated
607                // the `tmp_ptr`, and `tmp_ptr_with_offset` is guaranteed to be
608                // within those boundaries.
609                true,
610            )?;
611
612            bytes_copied = bytes_copied.strict_add(buffer_len);
613        }
614
615        let dest = dest.clone();
616        // Write bytes from the temporary buffer. This ensures the write is atomic.
617        this.write_to_fd(
618            fd,
619            tmp_ptr,
620            usize::try_from(total_bytes).unwrap(),
621            offset,
622            callback!(
623                @capture<'tcx> {
624                    tmp_ptr: Pointer,
625                    dest: MPlaceTy<'tcx>,
626                }
627                |this, result: Result<usize, IoError>| {
628                    this.deallocate_ptr(tmp_ptr, None, MemoryKind::Stack)?;
629                    match result {
630                        Ok(size) => this.write_scalar(Scalar::from_target_isize(size.try_into().unwrap(), this), &dest),
631                        Err(e) => this.set_last_error_and_return(e, &dest)
632                    }
633            }),
634        )
635    }
636}
637
638impl<'tcx> EvalContextPrivExt<'tcx> for crate::MiriInterpCx<'tcx> {}
639trait EvalContextPrivExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
640    /// Read `len` bytes from the `fd` file description at `offset` into the buffer
641    /// pointed to by `ptr`.
642    /// If `offset` is [`Some`], the read occurs at the given absolute position rather
643    /// than the current file position (`read_at` semantics rather than `read`).
644    /// `finish` will be invoked when the read is done (which might be way after
645    /// this function returns as the read may block).
646    fn read_from_fd(
647        &mut self,
648        fd: DynFileDescriptionRef,
649        ptr: Pointer,
650        len: usize,
651        offset: Option<i128>,
652        finish: DynMachineCallback<'tcx, Result<usize, IoError>>,
653    ) -> InterpResult<'tcx> {
654        let this = self.eval_context_mut();
655
656        // Handle the zero-sized case. The man page says:
657        // > If count is zero, read() may detect the errors described below.  In the absence of any
658        // > errors, or if read() does not check for errors, a read() with a count of 0 returns zero
659        // > and has no other effects.
660        if len == 0 {
661            return finish.call(this, Ok(0));
662        }
663
664        // Non-deterministically decide to further reduce the length, simulating a partial read (but
665        // never to 0, that would indicate EOF).
666        let len = if this.machine.short_fd_operations
667            && fd.short_fd_operations()
668            && len >= 2
669            && this.machine.rng.get_mut().random()
670        {
671            len / 2 // since `len` is at least 2, the result is still at least 1
672        } else {
673            len
674        };
675
676        match offset {
677            None => fd.read(this.machine.communicate(), ptr, len, this, finish)?,
678            Some(offset) => {
679                let Ok(offset) = u64::try_from(offset) else {
680                    return finish.call(this, Err(LibcError("EINVAL")));
681                };
682                fd.as_unix(this).pread(
683                    this.machine.communicate(),
684                    offset,
685                    ptr,
686                    len,
687                    this,
688                    finish,
689                )?
690            }
691        };
692        interp_ok(())
693    }
694
695    /// Write `len` bytes at `offset` from the buffer pointed to by `ptr` into the `fd`
696    /// file description.
697    /// If `offset` is [`Some`], the write occurs at the given absolute position rather
698    /// than the current file position (`write_at` semantics rather than `write`).
699    /// `finish` will be invoked when the write is done (which might be way after
700    /// this function returns as the write may block).
701    fn write_to_fd(
702        &mut self,
703        fd: DynFileDescriptionRef,
704        ptr: Pointer,
705        len: usize,
706        offset: Option<i128>,
707        finish: DynMachineCallback<'tcx, Result<usize, IoError>>,
708    ) -> InterpResult<'tcx> {
709        let this = self.eval_context_mut();
710
711        // Handle the zero-sized case. The man page says:
712        // > If count is zero and fd refers to a regular file, then write() may return a failure
713        // > status if one of the errors below is detected.  If no errors are detected, or error
714        // > detection is not performed, 0 is returned without causing any other effect.   If  count
715        // > is  zero  and  fd refers to a file other than a regular file, the results are not
716        // > specified.
717        if len == 0 {
718            // For now let's not open the can of worms of what exactly "not specified" could mean...
719            return finish.call(this, Ok(0));
720        }
721
722        // Non-deterministically decide to further reduce the length, simulating a partial write.
723        // We avoid reducing the write size to 0: the docs seem to be entirely fine with that,
724        // but the standard library is not (https://github.com/rust-lang/rust/issues/145959).
725        let len = if this.machine.short_fd_operations
726            && fd.short_fd_operations()
727            && len >= 2
728            && this.machine.rng.get_mut().random()
729        {
730            len / 2
731        } else {
732            len
733        };
734
735        match offset {
736            None => fd.write(this.machine.communicate(), ptr, len, this, finish)?,
737            Some(offset) => {
738                let Ok(offset) = u64::try_from(offset) else {
739                    return finish.call(this, Err(LibcError("EINVAL")));
740                };
741                fd.as_unix(this).pwrite(
742                    this.machine.communicate(),
743                    ptr,
744                    len,
745                    offset,
746                    this,
747                    finish,
748                )?
749            }
750        };
751        interp_ok(())
752    }
753}
miri/shims/unix/fd.rs

miri/shims/unix/
fd.rs
