rust/src/shims/fs.rs

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use std::collections::HashMap;
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use std::fs::{remove_file, File, OpenOptions};
use std::io::{Read, Write};
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use rustc::ty::layout::Size;
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use crate::stacked_borrows::Tag;
use crate::*;
#[derive(Debug)]
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pub struct FileHandle {
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file: File,
}
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pub struct FileHandler {
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handles: HashMap<i32, FileHandle>,
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low: i32,
}
impl Default for FileHandler {
fn default() -> Self {
FileHandler {
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handles: Default::default(),
// 0, 1 and 2 are reserved for stdin, stdout and stderr.
low: 3,
}
}
}
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impl<'mir, 'tcx> EvalContextExt<'mir, 'tcx> for crate::MiriEvalContext<'mir, 'tcx> {}
pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx> {
fn open(
&mut self,
path_op: OpTy<'tcx, Tag>,
flag_op: OpTy<'tcx, Tag>,
) -> InterpResult<'tcx, i32> {
let this = self.eval_context_mut();
this.check_no_isolation("open")?;
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let flag = this.read_scalar(flag_op)?.to_i32()?;
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let mut options = OpenOptions::new();
let o_rdonly = this.eval_libc_i32("O_RDONLY")?;
let o_wronly = this.eval_libc_i32("O_WRONLY")?;
let o_rdwr = this.eval_libc_i32("O_RDWR")?;
// The first two bits of the flag correspond to the access mode in linux, macOS and
// windows. We need to check that in fact the access mode flags for the current platform
// only use these two bits, otherwise we are in an unsupported platform and should error.
if (o_rdonly | o_wronly | o_rdwr) & !0b11 != 0 {
throw_unsup_format!("Access mode flags on this platform are unsupported");
}
// Now we check the access mode
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let access_mode = flag & 0b11;
if access_mode == o_rdonly {
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options.read(true);
} else if access_mode == o_wronly {
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options.write(true);
} else if access_mode == o_rdwr {
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options.read(true).write(true);
} else {
throw_unsup_format!("Unsupported access mode {:#x}", access_mode);
}
// We need to check that there aren't unsupported options in `flag`. For this we try to
// reproduce the content of `flag` in the `mirror` variable using only the supported
// options.
let mut mirror = access_mode;
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let o_append = this.eval_libc_i32("O_APPEND")?;
if flag & o_append != 0 {
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options.append(true);
mirror |= o_append;
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}
let o_trunc = this.eval_libc_i32("O_TRUNC")?;
if flag & o_trunc != 0 {
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options.truncate(true);
mirror |= o_trunc;
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}
let o_creat = this.eval_libc_i32("O_CREAT")?;
if flag & o_creat != 0 {
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options.create(true);
mirror |= o_creat;
}
let o_cloexec = this.eval_libc_i32("O_CLOEXEC")?;
if flag & o_cloexec != 0 {
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// We do not need to do anything for this flag because `std` already sets it.
// (Technically we do not support *not* setting this flag, but we ignore that.)
mirror |= o_cloexec;
}
// If `flag` is not equal to `mirror`, there is an unsupported option enabled in `flag`,
// then we throw an error.
if flag != mirror {
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throw_unsup_format!("unsupported flags {:#x}", flag & !mirror);
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}
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let path = this.read_os_string_from_c_string(this.read_scalar(path_op)?.not_undef()?)?;
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let fd = options.open(path).map(|file| {
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let mut fh = &mut this.machine.file_handler;
fh.low += 1;
fh.handles.insert(fh.low, FileHandle { file }).unwrap_none();
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fh.low
});
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this.try_unwrap_io_result(fd)
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}
fn fcntl(
&mut self,
fd_op: OpTy<'tcx, Tag>,
cmd_op: OpTy<'tcx, Tag>,
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_arg1_op: Option<OpTy<'tcx, Tag>>,
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) -> InterpResult<'tcx, i32> {
let this = self.eval_context_mut();
this.check_no_isolation("fcntl")?;
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let fd = this.read_scalar(fd_op)?.to_i32()?;
let cmd = this.read_scalar(cmd_op)?.to_i32()?;
// We only support getting the flags for a descriptor.
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if cmd == this.eval_libc_i32("F_GETFD")? {
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// Currently this is the only flag that `F_GETFD` returns. It is OK to just return the
// `FD_CLOEXEC` value without checking if the flag is set for the file because `std`
// always sets this flag when opening a file. However we still need to check that the
// file itself is open.
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if this.machine.file_handler.handles.contains_key(&fd) {
Ok(this.eval_libc_i32("FD_CLOEXEC")?)
} else {
this.handle_not_found()
}
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} else {
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throw_unsup_format!("The {:#x} command is not supported for `fcntl`)", cmd);
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}
}
fn close(&mut self, fd_op: OpTy<'tcx, Tag>) -> InterpResult<'tcx, i32> {
let this = self.eval_context_mut();
this.check_no_isolation("close")?;
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let fd = this.read_scalar(fd_op)?.to_i32()?;
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if let Some(handle) = this.machine.file_handler.handles.remove(&fd) {
// `File::sync_all` does the checks that are done when closing a file. We do this to
// to handle possible errors correctly.
let result = this.try_unwrap_io_result(handle.file.sync_all().map(|_| 0i32));
// Now we actually drop the handle.
drop(handle);
// And return the result.
result
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} else {
this.handle_not_found()
}
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}
fn read(
&mut self,
fd_op: OpTy<'tcx, Tag>,
buf_op: OpTy<'tcx, Tag>,
count_op: OpTy<'tcx, Tag>,
) -> InterpResult<'tcx, i64> {
let this = self.eval_context_mut();
this.check_no_isolation("read")?;
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let count = this.read_scalar(count_op)?.to_usize(&*this.tcx)?;
// Reading zero bytes should not change `buf`.
if count == 0 {
return Ok(0);
}
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let fd = this.read_scalar(fd_op)?.to_i32()?;
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let buf = this.read_scalar(buf_op)?.not_undef()?;
if let Some(handle) = this.machine.file_handler.handles.get_mut(&fd) {
// We want to read at most `count` bytes
let mut bytes = vec![0; count as usize];
let result = handle.file.read(&mut bytes).map(|c| c as i64);
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// If reading to `bytes` did not fail, we write those bytes to the buffer.
if result.is_ok() {
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this.memory.write_bytes(buf, bytes)?;
}
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this.try_unwrap_io_result(result)
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} else {
this.handle_not_found()
}
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}
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fn write(
&mut self,
fd_op: OpTy<'tcx, Tag>,
buf_op: OpTy<'tcx, Tag>,
count_op: OpTy<'tcx, Tag>,
) -> InterpResult<'tcx, i64> {
let this = self.eval_context_mut();
this.check_no_isolation("write")?;
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let count = this.read_scalar(count_op)?.to_usize(&*this.tcx)?;
// Writing zero bytes should not change `buf`.
if count == 0 {
return Ok(0);
}
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let fd = this.read_scalar(fd_op)?.to_i32()?;
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let buf = this.read_scalar(buf_op)?.not_undef()?;
if let Some(handle) = this.machine.file_handler.handles.get_mut(&fd) {
let bytes = this.memory.read_bytes(buf, Size::from_bytes(count))?;
let result = handle.file.write(&bytes).map(|c| c as i64);
this.try_unwrap_io_result(result)
} else {
this.handle_not_found()
}
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}
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fn unlink(&mut self, path_op: OpTy<'tcx, Tag>) -> InterpResult<'tcx, i32> {
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let this = self.eval_context_mut();
this.check_no_isolation("unlink")?;
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let path = this.read_os_string_from_c_string(this.read_scalar(path_op)?.not_undef()?)?;
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let result = remove_file(path).map(|_| 0);
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this.try_unwrap_io_result(result)
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}
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/// Function used when a handle is not found inside `FileHandler`. It returns `Ok(-1)`and sets
/// the last OS error to `libc::EBADF` (invalid file descriptor). This function uses
/// `T: From<i32>` instead of `i32` directly because some fs functions return different integer
/// types (like `read`, that returns an `i64`).
fn handle_not_found<T: From<i32>>(&mut self) -> InterpResult<'tcx, T> {
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let this = self.eval_context_mut();
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let ebadf = this.eval_libc("EBADF")?;
this.set_last_error(ebadf)?;
Ok((-1).into())
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}
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}