rust/src/shims/env.rs

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use std::collections::HashMap;
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use std::env;
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use std::path::Path;
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use crate::stacked_borrows::Tag;
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use crate::*;
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use rustc::ty::layout::Size;
use rustc_mir::interpret::{Memory, Pointer};
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#[derive(Default)]
pub struct EnvVars {
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/// Stores pointers to the environment variables. These variables must be stored as
/// null-terminated C strings with the `"{name}={value}"` format.
map: HashMap<Vec<u8>, Pointer<Tag>>,
}
impl EnvVars {
pub(crate) fn init<'mir, 'tcx>(
ecx: &mut InterpCx<'mir, 'tcx, Evaluator<'tcx>>,
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mut excluded_env_vars: Vec<String>,
) {
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// Exclude `TERM` var to avoid terminfo trying to open the termcap file.
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excluded_env_vars.push("TERM".to_owned());
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if ecx.machine.communicate {
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for (name, value) in env::vars() {
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if !excluded_env_vars.contains(&name) {
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let var_ptr =
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alloc_env_var(name.as_bytes(), value.as_bytes(), &mut ecx.memory);
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ecx.machine.env_vars.map.insert(name.into_bytes(), var_ptr);
}
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}
}
}
}
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fn alloc_env_var<'mir, 'tcx>(
name: &[u8],
value: &[u8],
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memory: &mut Memory<'mir, 'tcx, Evaluator<'tcx>>,
) -> Pointer<Tag> {
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let mut bytes = name.to_vec();
bytes.push(b'=');
bytes.extend_from_slice(value);
bytes.push(0);
memory.allocate_static_bytes(bytes.as_slice(), MiriMemoryKind::Env.into())
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}
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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> {
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fn getenv(&mut self, name_op: OpTy<'tcx, Tag>) -> InterpResult<'tcx, Scalar<Tag>> {
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let this = self.eval_context_mut();
let name_ptr = this.read_scalar(name_op)?.not_undef()?;
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let name = this.memory.read_c_str(name_ptr)?;
Ok(match this.machine.env_vars.map.get(name) {
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// The offset is used to strip the "{name}=" part of the string.
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Some(var_ptr) => {
Scalar::Ptr(var_ptr.offset(Size::from_bytes(name.len() as u64 + 1), this)?)
}
None => Scalar::ptr_null(&*this.tcx),
})
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}
fn setenv(
&mut self,
name_op: OpTy<'tcx, Tag>,
value_op: OpTy<'tcx, Tag>,
) -> InterpResult<'tcx, i32> {
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let this = self.eval_context_mut();
let name_ptr = this.read_scalar(name_op)?.not_undef()?;
let value_ptr = this.read_scalar(value_op)?.not_undef()?;
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let value = this.memory.read_c_str(value_ptr)?;
let mut new = None;
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if !this.is_null(name_ptr)? {
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let name = this.memory.read_c_str(name_ptr)?;
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if !name.is_empty() && !name.contains(&b'=') {
new = Some((name.to_owned(), value.to_owned()));
}
}
if let Some((name, value)) = new {
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let var_ptr = alloc_env_var(&name, &value, &mut this.memory);
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if let Some(var) = this.machine.env_vars.map.insert(name.to_owned(), var_ptr) {
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this.memory
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.deallocate(var, None, MiriMemoryKind::Env.into())?;
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}
Ok(0)
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} else {
Ok(-1)
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}
}
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fn unsetenv(&mut self, name_op: OpTy<'tcx, Tag>) -> InterpResult<'tcx, i32> {
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let this = self.eval_context_mut();
let name_ptr = this.read_scalar(name_op)?.not_undef()?;
let mut success = None;
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if !this.is_null(name_ptr)? {
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let name = this.memory.read_c_str(name_ptr)?.to_owned();
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if !name.is_empty() && !name.contains(&b'=') {
success = Some(this.machine.env_vars.map.remove(&name));
}
}
if let Some(old) = success {
if let Some(var) = old {
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this.memory
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.deallocate(var, None, MiriMemoryKind::Env.into())?;
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}
Ok(0)
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} else {
Ok(-1)
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}
}
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fn getcwd(
&mut self,
buf_op: OpTy<'tcx, Tag>,
size_op: OpTy<'tcx, Tag>,
) -> InterpResult<'tcx, Scalar<Tag>> {
let this = self.eval_context_mut();
this.check_no_isolation("getcwd")?;
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let buf = this.force_ptr(this.read_scalar(buf_op)?.not_undef()?)?;
let size = this.read_scalar(size_op)?.to_usize(&*this.tcx)?;
// If we cannot get the current directory, we return null
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match env::current_dir() {
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Ok(cwd) => {
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// It is not clear what happens with non-utf8 paths here
let mut bytes = cwd.display().to_string().into_bytes();
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// If `size` is smaller or equal than the `bytes.len()`, writing `bytes` plus the
// required null terminator to memory using the `buf` pointer would cause an
// overflow. The desired behavior in this case is to return null.
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if (bytes.len() as u64) < size {
// We add a `/0` terminator
bytes.push(0);
// This is ok because the buffer was strictly larger than `bytes`, so after
// adding the null terminator, the buffer size is larger or equal to
// `bytes.len()`, meaning that `bytes` actually fit inside tbe buffer.
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this.memory
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.get_mut(buf.alloc_id)?
.write_bytes(&*this.tcx, buf, &bytes)?;
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return Ok(Scalar::Ptr(buf));
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}
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let erange = this.eval_libc("ERANGE")?;
this.set_last_error(erange)?;
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}
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Err(e) => this.set_last_error_from_io_error(e)?,
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}
Ok(Scalar::ptr_null(&*this.tcx))
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}
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fn chdir(&mut self, path_op: OpTy<'tcx, Tag>) -> InterpResult<'tcx, i32> {
let this = self.eval_context_mut();
this.check_no_isolation("chdir")?;
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let path_bytes = this
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.memory
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.read_c_str(this.read_scalar(path_op)?.not_undef()?)?;
let path = Path::new(
std::str::from_utf8(path_bytes)
.map_err(|_| err_unsup_format!("{:?} is not a valid utf-8 string", path_bytes))?,
);
match env::set_current_dir(path) {
Ok(()) => Ok(0),
Err(e) => {
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this.set_last_error_from_io_error(e)?;
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Ok(-1)
}
}
}
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}