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use libffi::{high::call as ffi, low::CodePtr};
use std::ops::Deref;
use rustc_middle::ty::{self as ty, IntTy, Ty, UintTy};
use rustc_span::Symbol;
use rustc_target::abi::HasDataLayout;
use crate::*;
impl<'mir, 'tcx: 'mir> EvalContextExt<'mir, 'tcx> for crate::MiriEvalContext<'mir, 'tcx> {}
pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx> {
/// Extract the scalar value from the result of reading a scalar from the machine,
/// and convert it to a `CArg`.
fn scalar_to_carg(
k: Scalar<Provenance>,
arg_type: Ty<'tcx>,
cx: &impl HasDataLayout,
) -> InterpResult<'tcx, CArg> {
match arg_type.kind() {
// If the primitive provided can be converted to a type matching the type pattern
// then create a `CArg` of this primitive value with the corresponding `CArg` constructor.
// the ints
ty::Int(IntTy::I8) => {
return Ok(CArg::Int8(k.to_i8()?));
}
ty::Int(IntTy::I16) => {
return Ok(CArg::Int16(k.to_i16()?));
}
ty::Int(IntTy::I32) => {
return Ok(CArg::Int32(k.to_i32()?));
}
ty::Int(IntTy::I64) => {
return Ok(CArg::Int64(k.to_i64()?));
}
ty::Int(IntTy::Isize) => {
// This will fail if host != target, but then the entire FFI thing probably won't work well
// in that situation.
return Ok(CArg::ISize(k.to_machine_isize(cx)?.try_into().unwrap()));
}
// the uints
ty::Uint(UintTy::U8) => {
return Ok(CArg::UInt8(k.to_u8()?));
}
ty::Uint(UintTy::U16) => {
return Ok(CArg::UInt16(k.to_u16()?));
}
ty::Uint(UintTy::U32) => {
return Ok(CArg::UInt32(k.to_u32()?));
}
ty::Uint(UintTy::U64) => {
return Ok(CArg::UInt64(k.to_u64()?));
}
ty::Uint(UintTy::Usize) => {
// This will fail if host != target, but then the entire FFI thing probably won't work well
// in that situation.
return Ok(CArg::USize(k.to_machine_usize(cx)?.try_into().unwrap()));
}
_ => {}
}
// If no primitives were returned then we have an unsupported type.
throw_unsup_format!(
"unsupported scalar argument type to external C function: {:?}",
arg_type
);
}
/// Call external C function and
/// store output, depending on return type in the function signature.
fn call_external_c_and_store_return<'a>(
&mut self,
link_name: Symbol,
dest: &PlaceTy<'tcx, Provenance>,
ptr: CodePtr,
libffi_args: Vec<libffi::high::Arg<'a>>,
) -> InterpResult<'tcx, ()> {
let this = self.eval_context_mut();
// Unsafe because of the call to external C code.
// Because this is calling a C function it is not necessarily sound,
// but there is no way around this and we've checked as much as we can.
unsafe {
// If the return type of a function is a primitive integer type,
// then call the function (`ptr`) with arguments `libffi_args`, store the return value as the specified
// primitive integer type, and then write this value out to the miri memory as an integer.
match dest.layout.ty.kind() {
// ints
ty::Int(IntTy::I8) => {
let x = ffi::call::<i8>(ptr, libffi_args.as_slice());
this.write_int(x, dest)?;
return Ok(());
}
ty::Int(IntTy::I16) => {
let x = ffi::call::<i16>(ptr, libffi_args.as_slice());
this.write_int(x, dest)?;
return Ok(());
}
ty::Int(IntTy::I32) => {
let x = ffi::call::<i32>(ptr, libffi_args.as_slice());
this.write_int(x, dest)?;
return Ok(());
}
ty::Int(IntTy::I64) => {
let x = ffi::call::<i64>(ptr, libffi_args.as_slice());
this.write_int(x, dest)?;
return Ok(());
}
ty::Int(IntTy::Isize) => {
let x = ffi::call::<isize>(ptr, libffi_args.as_slice());
// `isize` doesn't `impl Into<i128>`, so convert manually.
// Convert to `i64` since this covers both 32- and 64-bit machines.
this.write_int(i64::try_from(x).unwrap(), dest)?;
return Ok(());
}
// uints
ty::Uint(UintTy::U8) => {
let x = ffi::call::<u8>(ptr, libffi_args.as_slice());
this.write_int(x, dest)?;
return Ok(());
}
ty::Uint(UintTy::U16) => {
let x = ffi::call::<u16>(ptr, libffi_args.as_slice());
this.write_int(x, dest)?;
return Ok(());
}
ty::Uint(UintTy::U32) => {
let x = ffi::call::<u32>(ptr, libffi_args.as_slice());
this.write_int(x, dest)?;
return Ok(());
}
ty::Uint(UintTy::U64) => {
let x = ffi::call::<u64>(ptr, libffi_args.as_slice());
this.write_int(x, dest)?;
return Ok(());
}
ty::Uint(UintTy::Usize) => {
let x = ffi::call::<usize>(ptr, libffi_args.as_slice());
// `usize` doesn't `impl Into<i128>`, so convert manually.
// Convert to `u64` since this covers both 32- and 64-bit machines.
this.write_int(u64::try_from(x).unwrap(), dest)?;
return Ok(());
}
// Functions with no declared return type (i.e., the default return)
// have the output_type `Tuple([])`.
ty::Tuple(t_list) =>
if t_list.len() == 0 {
ffi::call::<()>(ptr, libffi_args.as_slice());
return Ok(());
},
_ => {}
}
// FIXME ellen! deal with all the other return types
throw_unsup_format!("unsupported return type to external C function: {:?}", link_name);
}
}
/// Get the pointer to the function of the specified name in the shared object file,
/// if it exists. The function must be in the shared object file specified: we do *not*
/// return pointers to functions in dependencies of the library.
fn get_func_ptr_explicitly_from_lib(&mut self, link_name: Symbol) -> Option<CodePtr> {
let this = self.eval_context_mut();
// Try getting the function from the shared library.
// On windows `_lib_path` will be unused, hence the name starting with `_`.
let (lib, _lib_path) = this.machine.external_so_lib.as_ref().unwrap();
let func: libloading::Symbol<'_, unsafe extern "C" fn()> = unsafe {
match lib.get(link_name.as_str().as_bytes()) {
Ok(x) => x,
Err(_) => {
return None;
}
}
};
// FIXME: this is a hack!
// The `libloading` crate will automatically load system libraries like `libc`.
// On linux `libloading` is based on `dlsym`: https://docs.rs/libloading/0.7.3/src/libloading/os/unix/mod.rs.html#202
// and `dlsym`(https://linux.die.net/man/3/dlsym) looks through the dependency tree of the
// library if it can't find the symbol in the library itself.
// So, in order to check if the function was actually found in the specified
// `machine.external_so_lib` we need to check its `dli_fname` and compare it to
// the specified SO file path.
// This code is a reimplementation of the mechanism for getting `dli_fname` in `libloading`,
// from: https://docs.rs/libloading/0.7.3/src/libloading/os/unix/mod.rs.html#411
// using the `libc` crate where this interface is public.
// No `libc::dladdr` on windows.
#[cfg(unix)]
let mut info = std::mem::MaybeUninit::<libc::Dl_info>::uninit();
#[cfg(unix)]
unsafe {
if libc::dladdr(*func.deref() as *const _, info.as_mut_ptr()) != 0 {
if std::ffi::CStr::from_ptr(info.assume_init().dli_fname).to_str().unwrap()
!= _lib_path.to_str().unwrap()
{
return None;
}
}
}
// Return a pointer to the function.
Some(CodePtr(*func.deref() as *mut _))
}
/// Call specified external C function, with supplied arguments.
/// Need to convert all the arguments from their hir representations to
/// a form compatible with C (through `libffi` call).
/// Then, convert return from the C call into a corresponding form that
/// can be stored in Miri internal memory.
fn call_external_c_fct(
&mut self,
link_name: Symbol,
dest: &PlaceTy<'tcx, Provenance>,
args: &[OpTy<'tcx, Provenance>],
) -> InterpResult<'tcx, bool> {
// Get the pointer to the function in the shared object file if it exists.
let code_ptr = match self.get_func_ptr_explicitly_from_lib(link_name) {
Some(ptr) => ptr,
None => {
// Shared object file does not export this function -- try the shims next.
return Ok(false);
}
};
let this = self.eval_context_mut();
// Get the function arguments, and convert them to `libffi`-compatible form.
let mut libffi_args = Vec::<CArg>::with_capacity(args.len());
for cur_arg in args.iter() {
libffi_args.push(Self::scalar_to_carg(
this.read_scalar(cur_arg)?,
cur_arg.layout.ty,
this,
)?);
}
// Convert them to `libffi::high::Arg` type.
let libffi_args = libffi_args
.iter()
.map(|cur_arg| cur_arg.arg_downcast())
.collect::<Vec<libffi::high::Arg<'_>>>();
// Call the function and store output, depending on return type in the function signature.
self.call_external_c_and_store_return(link_name, dest, code_ptr, libffi_args)?;
Ok(true)
}
}
#[derive(Debug, Clone)]
/// Enum of supported arguments to external C functions.
// We introduce this enum instead of just calling `ffi::arg` and storing a list
// of `libffi::high::Arg` directly, because the `libffi::high::Arg` just wraps a reference
// to the value it represents: https://docs.rs/libffi/latest/libffi/high/call/struct.Arg.html
// and we need to store a copy of the value, and pass a reference to this copy to C instead.
pub enum CArg {
/// 8-bit signed integer.
Int8(i8),
/// 16-bit signed integer.
Int16(i16),
/// 32-bit signed integer.
Int32(i32),
/// 64-bit signed integer.
Int64(i64),
/// isize.
ISize(isize),
/// 8-bit unsigned integer.
UInt8(u8),
/// 16-bit unsigned integer.
UInt16(u16),
/// 32-bit unsigned integer.
UInt32(u32),
/// 64-bit unsigned integer.
UInt64(u64),
/// usize.
USize(usize),
}
impl<'a> CArg {
/// Convert a `CArg` to a `libffi` argument type.
fn arg_downcast(&'a self) -> libffi::high::Arg<'a> {
match self {
CArg::Int8(i) => ffi::arg(i),
CArg::Int16(i) => ffi::arg(i),
CArg::Int32(i) => ffi::arg(i),
CArg::Int64(i) => ffi::arg(i),
CArg::ISize(i) => ffi::arg(i),
CArg::UInt8(i) => ffi::arg(i),
CArg::UInt16(i) => ffi::arg(i),
CArg::UInt32(i) => ffi::arg(i),
CArg::UInt64(i) => ffi::arg(i),
CArg::USize(i) => ffi::arg(i),
}
}
}