Add shims for env var emulation in Windows

README.md

@@ -166,7 +166,7 @@ Several `-Z` flags are relevant for Miri:
 * `-Zmiri-disable-stacked-borrows` disables checking the experimental
  [Stacked Borrows] aliasing rules. This can make Miri run faster, but it also
  means no aliasing violations will be detected.
-* `-Zmiri-disable-isolation` disables host host isolation. As a consequence,
+* `-Zmiri-disable-isolation` disables host isolation. As a consequence,
  the program has access to host resources such as environment variables, file
  systems, and randomness.
 * `-Zmiri-ignore-leaks` disables the memory leak checker.

src/shims/env.rs

@@ -23,10 +23,16 @@ pub struct EnvVars<'tcx> {
 impl<'tcx> EnvVars<'tcx> {
  pub(crate) fn init<'mir>(
  ecx: &mut InterpCx<'mir, 'tcx, Evaluator<'tcx>>,
- excluded_env_vars: Vec<String>,
+ mut excluded_env_vars: Vec<String>,
  ) -> InterpResult<'tcx> {
+ let target_os = ecx.tcx.sess.target.target.target_os.as_str();
+ if target_os == "windows" {
+ // Temporary hack: Exclude `TERM` var to avoid terminfo trying to open the termcap file.
+ // Can be removed once Issue#1013(Implement file system access for Windows) is resolved.
+ excluded_env_vars.push("TERM".to_owned());
+ }
+
  if ecx.machine.communicate {
- let target_os = ecx.tcx.sess.target.target.target_os.as_str();
  for (name, value) in env::vars() {
  if !excluded_env_vars.contains(&name) {
  let var_ptr = match target_os {
@@ -82,6 +88,86 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
  })
  }
 
+ #[allow(non_snake_case)]
+ fn GetEnvironmentVariableW(
+ &mut self,
+ name_op: OpTy<'tcx, Tag>, // LPCWSTR
+ buf_op: OpTy<'tcx, Tag>, // LPWSTR
+ size_op: OpTy<'tcx, Tag>, // DWORD
+ ) -> InterpResult<'tcx, u64> {
+ let this = self.eval_context_mut();
+ this.assert_target_os("windows", "GetEnvironmentVariableW");
+
+ let name_ptr = this.read_scalar(name_op)?.not_undef()?;
+ let name = this.read_os_str_from_wide_str(name_ptr)?;
+ Ok(match this.machine.env_vars.map.get(&name) {
+ Some(var_ptr) => {
+ // The offset is used to strip the "{name}=" part of the string.
+ let name_offset_bytes =
+ u64::try_from(name.len()).unwrap().checked_add(1).unwrap().checked_mul(2).unwrap();
+ let var_ptr = Scalar::from(var_ptr.offset(Size::from_bytes(name_offset_bytes), this)?);
+ let var = this.read_os_str_from_wide_str(var_ptr)?;
+
+ let buf_ptr = this.read_scalar(buf_op)?.not_undef()?;
+ // `buf_size` represents the size in characters.
+ let buf_size = u64::try_from(this.read_scalar(size_op)?.to_u32()?).unwrap();
+ let (success, len) = this.write_os_str_to_wide_str(&var, buf_ptr, buf_size)?;
+
+ if success {
+ // If the function succeeds, the return value is the number of characters stored in the buffer pointed to by lpBuffer,
+ // not including the terminating null character.
+ len
+ } else {
+ // If lpBuffer is not large enough to hold the data, the return value is the buffer size, in characters,
+ // required to hold the string and its terminating null character and the contents of lpBuffer are undefined.
+ len + 1
+ }
+ }
+ None => {
+ let envvar_not_found = this.eval_path_scalar(&["std", "sys", "windows", "c", "ERROR_ENVVAR_NOT_FOUND"])?;
+ this.set_last_error(envvar_not_found.not_undef()?)?;
+ 0 // return zero upon failure
+ }
+ })
+ }
+
+ #[allow(non_snake_case)]
+ fn GetEnvironmentStringsW(&mut self) -> InterpResult<'tcx, Scalar<Tag>> {
+ let this = self.eval_context_mut();
+ this.assert_target_os("windows", "GetEnvironmentStringsW");
+
+ // Info on layout of environment blocks in Windows: 
+ // https://docs.microsoft.com/en-us/windows/win32/procthread/environment-variables
+ let mut env_vars = std::ffi::OsString::new();
+ for &item in this.machine.env_vars.map.values() {
+ let env_var = this.read_os_str_from_wide_str(Scalar::from(item))?;
+ env_vars.push(env_var);
+ env_vars.push("\0");
+ }
+ // Allocate environment block & Store environment variables to environment block.
+ // Final null terminator(block terminator) is added by `alloc_os_str_to_wide_str`.
+ // FIXME: MemoryKind should be `MiMemoryKind::Machine`,
+ // but using it results in a Stacked Borrows error when running MIRI on 'tests/run-pass/env.rs'
+ // For now, use `MiriMemoryKind::WinHeap` instead.
+ let envblock_ptr = this.alloc_os_str_as_wide_str(&env_vars, MiriMemoryKind::WinHeap.into());
+ // If the function succeeds, the return value is a pointer to the environment block of the current process.
+ Ok(envblock_ptr.into())
+ }
+
+ #[allow(non_snake_case)]
+ fn FreeEnvironmentStringsW(&mut self, env_block_op: OpTy<'tcx, Tag>) -> InterpResult<'tcx, i32> {
+ let this = self.eval_context_mut();
+ this.assert_target_os("windows", "FreeEnvironmentStringsW");
+
+ let env_block_ptr = this.read_scalar(env_block_op)?.not_undef()?;
+ // FIXME: MemoryKind should be `MiMemoryKind::Machine`,
+ // but using it results in a Stacked Borrows error when running MIRI on 'tests/run-pass/env.rs'
+ // For now, use `MiriMemoryKind::WinHeap` instead.
+ let result = this.memory.deallocate(this.force_ptr(env_block_ptr)?, None, MiriMemoryKind::WinHeap.into());
+ // If the function succeeds, the return value is nonzero.
+ Ok(result.is_ok() as i32)
+ }
+
  fn setenv(
  &mut self,
  name_op: OpTy<'tcx, Tag>,
@@ -118,6 +204,47 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
  }
  }
 
+ #[allow(non_snake_case)]
+ fn SetEnvironmentVariableW(
+ &mut self,
+ name_op: OpTy<'tcx, Tag>, // LPCWSTR
+ value_op: OpTy<'tcx, Tag>, // LPCWSTR
+ ) -> InterpResult<'tcx, i32> {
+ let mut this = self.eval_context_mut();
+ this.assert_target_os("windows", "SetEnvironmentVariableW");
+
+ let name_ptr = this.read_scalar(name_op)?.not_undef()?;
+ let value_ptr = this.read_scalar(value_op)?.not_undef()?;
+
+ if this.is_null(name_ptr)? {
+ // ERROR CODE is not clearly explained in docs.. For now, throw UB instead.
+ throw_ub_format!("pointer to environment variable name is NULL");
+ }
+
+ let name = this.read_os_str_from_wide_str(name_ptr)?;
+ if name.is_empty() {
+ throw_unsup_format!("environment variable name is an empty string");
+ } else if name.to_string_lossy().contains('=') {
+ throw_unsup_format!("environment variable name contains '='");
+ } else if this.is_null(value_ptr)? {
+ // Delete environment variable `{name}`
+ if let Some(var) = this.machine.env_vars.map.remove(&name) {
+ this.memory.deallocate(var, None, MiriMemoryKind::Machine.into())?;
+ this.update_environ()?;
+ }
+ Ok(1) // return non-zero on success
+ } else {
+ let value = this.read_os_str_from_wide_str(value_ptr)?;
+ let var_ptr = alloc_env_var_as_wide_str(&name, &value, &mut this)?;
+ if let Some(var) = this.machine.env_vars.map.insert(name, var_ptr) {
+ this.memory
+ .deallocate(var, None, MiriMemoryKind::Machine.into())?;
+ }
+ this.update_environ()?;
+ Ok(1) // return non-zero on success
+ }
+ }
+
  fn unsetenv(&mut self, name_op: OpTy<'tcx, Tag>) -> InterpResult<'tcx, i32> {
  let this = self.eval_context_mut();
  let target_os = &this.tcx.sess.target.target.target_os;

src/shims/foreign_items/windows.rs

@@ -23,22 +23,23 @@ pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx
 
  // Environment related shims
  "GetEnvironmentVariableW" => {
- // args[0] : LPCWSTR lpName (32-bit ptr to a const string of 16-bit Unicode chars)
- // args[1] : LPWSTR lpBuffer (32-bit pointer to a string of 16-bit Unicode chars)
- // lpBuffer : ptr to buffer that receives contents of the env_var as a null-terminated string.
- // Return `# of chars` stored in the buffer pointed to by lpBuffer, excluding null-terminator.
- // Return 0 upon failure.
-
- // This is not the env var you are looking for.
- this.set_last_error(Scalar::from_u32(203))?; // ERROR_ENVVAR_NOT_FOUND
- this.write_null(dest)?;
+ let result = this.GetEnvironmentVariableW(args[0], args[1], args[2])?;
+ this.write_scalar(Scalar::from_uint(result, dest.layout.size), dest)?;
  }
 
  "SetEnvironmentVariableW" => {
- // args[0] : LPCWSTR lpName (32-bit ptr to a const string of 16-bit Unicode chars)
- // args[1] : LPCWSTR lpValue (32-bit ptr to a const string of 16-bit Unicode chars)
- // Return nonzero if success, else return 0.
- throw_unsup_format!("can't set environment variable on Windows");
+ let result = this.SetEnvironmentVariableW(args[0], args[1])?;
+ this.write_scalar(Scalar::from_int(result, dest.layout.size), dest)?;
+ }
+
+ "GetEnvironmentStringsW" => {
+ let result = this.GetEnvironmentStringsW()?;
+ this.write_scalar(result, dest)?;
+ }
+
+ "FreeEnvironmentStringsW" => {
+ let result = this.FreeEnvironmentStringsW(args[0])?;
+ this.write_scalar(Scalar::from_i32(result), dest)?;
  }
 
  // File related shims

tests/run-pass/env.rs

@@ -1,5 +1,3 @@
-//ignore-windows: TODO env var emulation stubbed out on Windows
-
 use std::env;
 
 fn main() {