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//! Implements calling functions from a native library.
use libffi::{high::call as ffi, low::CodePtr};
use std::ops::Deref;
use rustc_middle::ty::{self as ty, IntTy, UintTy};
use rustc_span::Symbol;
use rustc_target::abi::{Abi, HasDataLayout};
use crate::*;
impl<'tcx> EvalContextExtPriv<'tcx> for crate::MiriInterpCx<'tcx> {}
trait EvalContextExtPriv<'tcx>: crate::MiriInterpCxExt<'tcx> {
/// Call native host function and return the output as an immediate.
fn call_native_with_args<'a>(
&mut self,
link_name: Symbol,
dest: &MPlaceTy<'tcx>,
ptr: CodePtr,
libffi_args: Vec<libffi::high::Arg<'a>>,
) -> InterpResult<'tcx, ImmTy<'tcx>> {
let this = self.eval_context_mut();
// Call the function (`ptr`) with arguments `libffi_args`, and obtain the return value
// as the specified primitive integer type
let scalar = match dest.layout.ty.kind() {
// ints
ty::Int(IntTy::I8) => {
// Unsafe because of the call to native 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.
let x = unsafe { ffi::call::<i8>(ptr, libffi_args.as_slice()) };
Scalar::from_i8(x)
}
ty::Int(IntTy::I16) => {
let x = unsafe { ffi::call::<i16>(ptr, libffi_args.as_slice()) };
Scalar::from_i16(x)
}
ty::Int(IntTy::I32) => {
let x = unsafe { ffi::call::<i32>(ptr, libffi_args.as_slice()) };
Scalar::from_i32(x)
}
ty::Int(IntTy::I64) => {
let x = unsafe { ffi::call::<i64>(ptr, libffi_args.as_slice()) };
Scalar::from_i64(x)
}
ty::Int(IntTy::Isize) => {
let x = unsafe { ffi::call::<isize>(ptr, libffi_args.as_slice()) };
Scalar::from_target_isize(x.try_into().unwrap(), this)
}
// uints
ty::Uint(UintTy::U8) => {
let x = unsafe { ffi::call::<u8>(ptr, libffi_args.as_slice()) };
Scalar::from_u8(x)
}
ty::Uint(UintTy::U16) => {
let x = unsafe { ffi::call::<u16>(ptr, libffi_args.as_slice()) };
Scalar::from_u16(x)
}
ty::Uint(UintTy::U32) => {
let x = unsafe { ffi::call::<u32>(ptr, libffi_args.as_slice()) };
Scalar::from_u32(x)
}
ty::Uint(UintTy::U64) => {
let x = unsafe { ffi::call::<u64>(ptr, libffi_args.as_slice()) };
Scalar::from_u64(x)
}
ty::Uint(UintTy::Usize) => {
let x = unsafe { ffi::call::<usize>(ptr, libffi_args.as_slice()) };
Scalar::from_target_usize(x.try_into().unwrap(), this)
}
// 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 => {
unsafe { ffi::call::<()>(ptr, libffi_args.as_slice()) };
return Ok(ImmTy::uninit(dest.layout));
}
_ => throw_unsup_format!("unsupported return type for native call: {:?}", link_name),
};
Ok(ImmTy::from_scalar(scalar, dest.layout))
}
/// 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.native_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.
let mut info = std::mem::MaybeUninit::<libc::Dl_info>::uninit();
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 _))
}
}
impl<'tcx> EvalContextExt<'tcx> for crate::MiriInterpCx<'tcx> {}
pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
/// Call the native host function, with supplied arguments.
/// Needs to convert all the arguments from their Miri representations to
/// a native form (through `libffi` call).
/// Then, convert the return value from the native form into something that
/// can be stored in Miri's internal memory.
fn call_native_fn(
&mut self,
link_name: Symbol,
dest: &MPlaceTy<'tcx>,
args: &[OpTy<'tcx>],
) -> InterpResult<'tcx, bool> {
let this = self.eval_context_mut();
// Get the pointer to the function in the shared object file if it exists.
let code_ptr = match this.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);
}
};
// Get the function arguments, and convert them to `libffi`-compatible form.
let mut libffi_args = Vec::<CArg>::with_capacity(args.len());
for arg in args.iter() {
if !matches!(arg.layout.abi, Abi::Scalar(_)) {
throw_unsup_format!("only scalar argument types are support for native calls")
}
libffi_args.push(imm_to_carg(this.read_immediate(arg)?, this)?);
}
// Convert them to `libffi::high::Arg` type.
let libffi_args = libffi_args
.iter()
.map(|arg| arg.arg_downcast())
.collect::<Vec<libffi::high::Arg<'_>>>();
// Call the function and store output, depending on return type in the function signature.
let ret = this.call_native_with_args(link_name, dest, code_ptr, libffi_args)?;
this.write_immediate(*ret, dest)?;
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.
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),
/// Raw pointer, stored as C's `void*`.
RawPtr(*mut std::ffi::c_void),
}
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),
CArg::RawPtr(i) => ffi::arg(i),
}
}
}
/// Extract the scalar value from the result of reading a scalar from the machine,
/// and convert it to a `CArg`.
fn imm_to_carg<'tcx>(v: ImmTy<'tcx>, cx: &impl HasDataLayout) -> InterpResult<'tcx, CArg> {
Ok(match v.layout.ty.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) => CArg::Int8(v.to_scalar().to_i8()?),
ty::Int(IntTy::I16) => CArg::Int16(v.to_scalar().to_i16()?),
ty::Int(IntTy::I32) => CArg::Int32(v.to_scalar().to_i32()?),
ty::Int(IntTy::I64) => CArg::Int64(v.to_scalar().to_i64()?),
ty::Int(IntTy::Isize) =>
CArg::ISize(v.to_scalar().to_target_isize(cx)?.try_into().unwrap()),
// the uints
ty::Uint(UintTy::U8) => CArg::UInt8(v.to_scalar().to_u8()?),
ty::Uint(UintTy::U16) => CArg::UInt16(v.to_scalar().to_u16()?),
ty::Uint(UintTy::U32) => CArg::UInt32(v.to_scalar().to_u32()?),
ty::Uint(UintTy::U64) => CArg::UInt64(v.to_scalar().to_u64()?),
ty::Uint(UintTy::Usize) =>
CArg::USize(v.to_scalar().to_target_usize(cx)?.try_into().unwrap()),
ty::RawPtr(_, mutability) => {
// Arbitrary mutable pointer accesses are not currently supported in Miri.
if mutability.is_mut() {
throw_unsup_format!("unsupported mutable pointer type for native call: {}", v.layout.ty);
} else {
let s = v.to_scalar().to_pointer(cx)?.addr();
// This relies on the `expose_provenance` in `addr_from_alloc_id`.
CArg::RawPtr(std::ptr::with_exposed_provenance_mut(s.bytes_usize()))
}
},
_ => throw_unsup_format!("unsupported argument type for native call: {}", v.layout.ty),
})
}