miri/shims/foreign_items.rs
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use std::collections::hash_map::Entry;
use std::io::Write;
use std::iter;
use std::path::Path;
use rustc_apfloat::Float;
use rustc_ast::expand::allocator::alloc_error_handler_name;
use rustc_hir::def::DefKind;
use rustc_hir::def_id::CrateNum;
use rustc_middle::middle::codegen_fn_attrs::CodegenFnAttrFlags;
use rustc_middle::{mir, ty};
use rustc_span::Symbol;
use rustc_target::abi::{Align, AlignFromBytesError, Size};
use rustc_target::spec::abi::Abi;
use self::helpers::{ToHost, ToSoft};
use super::alloc::EvalContextExt as _;
use super::backtrace::EvalContextExt as _;
use crate::*;
/// Type of dynamic symbols (for `dlsym` et al)
#[derive(Debug, Copy, Clone)]
pub struct DynSym(Symbol);
#[allow(clippy::should_implement_trait)]
impl DynSym {
pub fn from_str(name: &str) -> Self {
DynSym(Symbol::intern(name))
}
}
impl<'tcx> EvalContextExt<'tcx> for crate::MiriInterpCx<'tcx> {}
pub trait EvalContextExt<'tcx>: crate::MiriInterpCxExt<'tcx> {
/// Emulates calling a foreign item, failing if the item is not supported.
/// This function will handle `goto_block` if needed.
/// Returns Ok(None) if the foreign item was completely handled
/// by this function.
/// Returns Ok(Some(body)) if processing the foreign item
/// is delegated to another function.
fn emulate_foreign_item(
&mut self,
link_name: Symbol,
abi: Abi,
args: &[OpTy<'tcx>],
dest: &MPlaceTy<'tcx>,
ret: Option<mir::BasicBlock>,
unwind: mir::UnwindAction,
) -> InterpResult<'tcx, Option<(&'tcx mir::Body<'tcx>, ty::Instance<'tcx>)>> {
let this = self.eval_context_mut();
// Some shims forward to other MIR bodies.
match link_name.as_str() {
"__rust_alloc_error_handler" => {
// Forward to the right symbol that implements this function.
let Some(handler_kind) = this.tcx.alloc_error_handler_kind(()) else {
// in real code, this symbol does not exist without an allocator
throw_unsup_format!(
"`__rust_alloc_error_handler` cannot be called when no alloc error handler is set"
);
};
let name = alloc_error_handler_name(handler_kind);
let handler = this
.lookup_exported_symbol(Symbol::intern(name))?
.expect("missing alloc error handler symbol");
return interp_ok(Some(handler));
}
_ => {}
}
// The rest either implements the logic, or falls back to `lookup_exported_symbol`.
match this.emulate_foreign_item_inner(link_name, abi, args, dest)? {
EmulateItemResult::NeedsReturn => {
trace!("{:?}", this.dump_place(&dest.clone().into()));
this.return_to_block(ret)?;
}
EmulateItemResult::NeedsUnwind => {
// Jump to the unwind block to begin unwinding.
this.unwind_to_block(unwind)?;
}
EmulateItemResult::AlreadyJumped => (),
EmulateItemResult::NotSupported => {
if let Some(body) = this.lookup_exported_symbol(link_name)? {
return interp_ok(Some(body));
}
this.handle_unsupported_foreign_item(format!(
"can't call foreign function `{link_name}` on OS `{os}`",
os = this.tcx.sess.target.os,
))?;
return interp_ok(None);
}
}
interp_ok(None)
}
fn is_dyn_sym(&self, name: &str) -> bool {
let this = self.eval_context_ref();
match this.tcx.sess.target.os.as_ref() {
os if this.target_os_is_unix() => shims::unix::foreign_items::is_dyn_sym(name, os),
"wasi" => shims::wasi::foreign_items::is_dyn_sym(name),
"windows" => shims::windows::foreign_items::is_dyn_sym(name),
_ => false,
}
}
/// Emulates a call to a `DynSym`.
fn emulate_dyn_sym(
&mut self,
sym: DynSym,
abi: Abi,
args: &[OpTy<'tcx>],
dest: &MPlaceTy<'tcx>,
ret: Option<mir::BasicBlock>,
unwind: mir::UnwindAction,
) -> InterpResult<'tcx> {
let res = self.emulate_foreign_item(sym.0, abi, args, dest, ret, unwind)?;
assert!(res.is_none(), "DynSyms that delegate are not supported");
interp_ok(())
}
/// Lookup the body of a function that has `link_name` as the symbol name.
fn lookup_exported_symbol(
&mut self,
link_name: Symbol,
) -> InterpResult<'tcx, Option<(&'tcx mir::Body<'tcx>, ty::Instance<'tcx>)>> {
let this = self.eval_context_mut();
let tcx = this.tcx.tcx;
// If the result was cached, just return it.
// (Cannot use `or_insert` since the code below might have to throw an error.)
let entry = this.machine.exported_symbols_cache.entry(link_name);
let instance = *match entry {
Entry::Occupied(e) => e.into_mut(),
Entry::Vacant(e) => {
// Find it if it was not cached.
let mut instance_and_crate: Option<(ty::Instance<'_>, CrateNum)> = None;
helpers::iter_exported_symbols(tcx, |cnum, def_id| {
let attrs = tcx.codegen_fn_attrs(def_id);
let symbol_name = if let Some(export_name) = attrs.export_name {
export_name
} else if attrs.flags.contains(CodegenFnAttrFlags::NO_MANGLE) {
tcx.item_name(def_id)
} else {
// Skip over items without an explicitly defined symbol name.
return interp_ok(());
};
if symbol_name == link_name {
if let Some((original_instance, original_cnum)) = instance_and_crate {
// Make sure we are consistent wrt what is 'first' and 'second'.
let original_span = tcx.def_span(original_instance.def_id()).data();
let span = tcx.def_span(def_id).data();
if original_span < span {
throw_machine_stop!(TerminationInfo::MultipleSymbolDefinitions {
link_name,
first: original_span,
first_crate: tcx.crate_name(original_cnum),
second: span,
second_crate: tcx.crate_name(cnum),
});
} else {
throw_machine_stop!(TerminationInfo::MultipleSymbolDefinitions {
link_name,
first: span,
first_crate: tcx.crate_name(cnum),
second: original_span,
second_crate: tcx.crate_name(original_cnum),
});
}
}
if !matches!(tcx.def_kind(def_id), DefKind::Fn | DefKind::AssocFn) {
throw_ub_format!(
"attempt to call an exported symbol that is not defined as a function"
);
}
instance_and_crate = Some((ty::Instance::mono(tcx, def_id), cnum));
}
interp_ok(())
})?;
e.insert(instance_and_crate.map(|ic| ic.0))
}
};
match instance {
None => interp_ok(None), // no symbol with this name
Some(instance) => interp_ok(Some((this.load_mir(instance.def, None)?, instance))),
}
}
}
impl<'tcx> EvalContextExtPriv<'tcx> for crate::MiriInterpCx<'tcx> {}
trait EvalContextExtPriv<'tcx>: crate::MiriInterpCxExt<'tcx> {
/// Check some basic requirements for this allocation request:
/// non-zero size, power-of-two alignment.
fn check_rustc_alloc_request(&self, size: u64, align: u64) -> InterpResult<'tcx> {
let this = self.eval_context_ref();
if size == 0 {
throw_ub_format!("creating allocation with size 0");
}
if size > this.max_size_of_val().bytes() {
throw_ub_format!("creating an allocation larger than half the address space");
}
if let Err(e) = Align::from_bytes(align) {
match e {
AlignFromBytesError::TooLarge(_) => {
throw_unsup_format!(
"creating allocation with alignment {align} exceeding rustc's maximum \
supported value"
);
}
AlignFromBytesError::NotPowerOfTwo(_) => {
throw_ub_format!("creating allocation with non-power-of-two alignment {align}");
}
}
}
interp_ok(())
}
fn emulate_foreign_item_inner(
&mut self,
link_name: Symbol,
abi: Abi,
args: &[OpTy<'tcx>],
dest: &MPlaceTy<'tcx>,
) -> InterpResult<'tcx, EmulateItemResult> {
let this = self.eval_context_mut();
// First deal with any external C functions in linked .so file.
#[cfg(unix)]
if this.machine.native_lib.as_ref().is_some() {
use crate::shims::native_lib::EvalContextExt as _;
// An Ok(false) here means that the function being called was not exported
// by the specified `.so` file; we should continue and check if it corresponds to
// a provided shim.
if this.call_native_fn(link_name, dest, args)? {
return interp_ok(EmulateItemResult::NeedsReturn);
}
}
// When adding a new shim, you should follow the following pattern:
// ```
// "shim_name" => {
// let [arg1, arg2, arg3] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
// let result = this.shim_name(arg1, arg2, arg3)?;
// this.write_scalar(result, dest)?;
// }
// ```
// and then define `shim_name` as a helper function in an extension trait in a suitable file
// (see e.g. `unix/fs.rs`):
// ```
// fn shim_name(
// &mut self,
// arg1: &OpTy<'tcx>,
// arg2: &OpTy<'tcx>,
// arg3: &OpTy<'tcx>,
// arg4: &OpTy<'tcx>)
// -> InterpResult<'tcx, Scalar> {
// let this = self.eval_context_mut();
//
// // First thing: load all the arguments. Details depend on the shim.
// let arg1 = this.read_scalar(arg1)?.to_u32()?;
// let arg2 = this.read_pointer(arg2)?; // when you need to work with the pointer directly
// let arg3 = this.deref_pointer_as(arg3, this.libc_ty_layout("some_libc_struct"))?; // when you want to load/store
// // through the pointer and supply the type information yourself
// let arg4 = this.deref_pointer(arg4)?; // when you want to load/store through the pointer and trust
// // the user-given type (which you shouldn't usually do)
//
// // ...
//
// interp_ok(Scalar::from_u32(42))
// }
// ```
// You might find existing shims not following this pattern, most
// likely because they predate it or because for some reason they cannot be made to fit.
// Here we dispatch all the shims for foreign functions. If you have a platform specific
// shim, add it to the corresponding submodule.
match link_name.as_str() {
// Miri-specific extern functions
"miri_start_unwind" => {
let [payload] = this.check_shim(abi, Abi::Rust, link_name, args)?;
this.handle_miri_start_unwind(payload)?;
return interp_ok(EmulateItemResult::NeedsUnwind);
}
"miri_run_provenance_gc" => {
let [] = this.check_shim(abi, Abi::Rust, link_name, args)?;
this.run_provenance_gc();
}
"miri_get_alloc_id" => {
let [ptr] = this.check_shim(abi, Abi::Rust, link_name, args)?;
let ptr = this.read_pointer(ptr)?;
let (alloc_id, _, _) = this.ptr_get_alloc_id(ptr, 0).map_err(|_e| {
err_machine_stop!(TerminationInfo::Abort(format!(
"pointer passed to `miri_get_alloc_id` must not be dangling, got {ptr:?}"
)))
.into()
})?;
this.write_scalar(Scalar::from_u64(alloc_id.0.get()), dest)?;
}
"miri_print_borrow_state" => {
let [id, show_unnamed] = this.check_shim(abi, Abi::Rust, link_name, args)?;
let id = this.read_scalar(id)?.to_u64()?;
let show_unnamed = this.read_scalar(show_unnamed)?.to_bool()?;
if let Some(id) = std::num::NonZero::new(id).map(AllocId)
&& this.get_alloc_info(id).2 == AllocKind::LiveData
{
this.print_borrow_state(id, show_unnamed)?;
} else {
eprintln!("{id} is not the ID of a live data allocation");
}
}
"miri_pointer_name" => {
// This associates a name to a tag. Very useful for debugging, and also makes
// tests more strict.
let [ptr, nth_parent, name] = this.check_shim(abi, Abi::Rust, link_name, args)?;
let ptr = this.read_pointer(ptr)?;
let nth_parent = this.read_scalar(nth_parent)?.to_u8()?;
let name = this.read_immediate(name)?;
let name = this.read_byte_slice(&name)?;
// We must make `name` owned because we need to
// end the shared borrow from `read_byte_slice` before we can
// start the mutable borrow for `give_pointer_debug_name`.
let name = String::from_utf8_lossy(name).into_owned();
this.give_pointer_debug_name(ptr, nth_parent, &name)?;
}
"miri_static_root" => {
let [ptr] = this.check_shim(abi, Abi::Rust, link_name, args)?;
let ptr = this.read_pointer(ptr)?;
let (alloc_id, offset, _) = this.ptr_get_alloc_id(ptr, 0)?;
if offset != Size::ZERO {
throw_unsup_format!(
"pointer passed to `miri_static_root` must point to beginning of an allocated block"
);
}
this.machine.static_roots.push(alloc_id);
}
"miri_host_to_target_path" => {
let [ptr, out, out_size] = this.check_shim(abi, Abi::Rust, link_name, args)?;
let ptr = this.read_pointer(ptr)?;
let out = this.read_pointer(out)?;
let out_size = this.read_scalar(out_size)?.to_target_usize(this)?;
// The host affects program behavior here, so this requires isolation to be disabled.
this.check_no_isolation("`miri_host_to_target_path`")?;
// We read this as a plain OsStr and write it as a path, which will convert it to the target.
let path = this.read_os_str_from_c_str(ptr)?.to_owned();
let (success, needed_size) =
this.write_path_to_c_str(Path::new(&path), out, out_size)?;
// Return value: 0 on success, otherwise the size it would have needed.
this.write_int(if success { 0 } else { needed_size }, dest)?;
}
// Obtains the size of a Miri backtrace. See the README for details.
"miri_backtrace_size" => {
this.handle_miri_backtrace_size(abi, link_name, args, dest)?;
}
// Obtains a Miri backtrace. See the README for details.
"miri_get_backtrace" => {
// `check_shim` happens inside `handle_miri_get_backtrace`.
this.handle_miri_get_backtrace(abi, link_name, args, dest)?;
}
// Resolves a Miri backtrace frame. See the README for details.
"miri_resolve_frame" => {
// `check_shim` happens inside `handle_miri_resolve_frame`.
this.handle_miri_resolve_frame(abi, link_name, args, dest)?;
}
// Writes the function and file names of a Miri backtrace frame into a user provided buffer. See the README for details.
"miri_resolve_frame_names" => {
this.handle_miri_resolve_frame_names(abi, link_name, args)?;
}
// Writes some bytes to the interpreter's stdout/stderr. See the
// README for details.
"miri_write_to_stdout" | "miri_write_to_stderr" => {
let [msg] = this.check_shim(abi, Abi::Rust, link_name, args)?;
let msg = this.read_immediate(msg)?;
let msg = this.read_byte_slice(&msg)?;
// Note: we're ignoring errors writing to host stdout/stderr.
let _ignore = match link_name.as_str() {
"miri_write_to_stdout" => std::io::stdout().write_all(msg),
"miri_write_to_stderr" => std::io::stderr().write_all(msg),
_ => unreachable!(),
};
}
// Promises that a pointer has a given symbolic alignment.
"miri_promise_symbolic_alignment" => {
use rustc_target::abi::AlignFromBytesError;
let [ptr, align] = this.check_shim(abi, Abi::Rust, link_name, args)?;
let ptr = this.read_pointer(ptr)?;
let align = this.read_target_usize(align)?;
if !align.is_power_of_two() {
throw_unsup_format!(
"`miri_promise_symbolic_alignment`: alignment must be a power of 2, got {align}"
);
}
let align = Align::from_bytes(align).unwrap_or_else(|err| {
match err {
AlignFromBytesError::NotPowerOfTwo(_) => unreachable!(),
// When the alignment is a power of 2 but too big, clamp it to MAX.
AlignFromBytesError::TooLarge(_) => Align::MAX,
}
});
let (_, addr) = ptr.into_parts(); // we know the offset is absolute
// Cannot panic since `align` is a power of 2 and hence non-zero.
if addr.bytes().strict_rem(align.bytes()) != 0 {
throw_unsup_format!(
"`miri_promise_symbolic_alignment`: pointer is not actually aligned"
);
}
if let Ok((alloc_id, offset, ..)) = this.ptr_try_get_alloc_id(ptr, 0) {
let (_size, alloc_align, _kind) = this.get_alloc_info(alloc_id);
// If the newly promised alignment is bigger than the native alignment of this
// allocation, and bigger than the previously promised alignment, then set it.
if align > alloc_align
&& this
.machine
.symbolic_alignment
.get_mut()
.get(&alloc_id)
.is_none_or(|&(_, old_align)| align > old_align)
{
this.machine.symbolic_alignment.get_mut().insert(alloc_id, (offset, align));
}
}
}
// Aborting the process.
"exit" => {
let [code] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
let code = this.read_scalar(code)?.to_i32()?;
throw_machine_stop!(TerminationInfo::Exit { code: code.into(), leak_check: false });
}
"abort" => {
let [] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
throw_machine_stop!(TerminationInfo::Abort(
"the program aborted execution".to_owned()
))
}
// Standard C allocation
"malloc" => {
let [size] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
let size = this.read_target_usize(size)?;
if size <= this.max_size_of_val().bytes() {
let res = this.malloc(size, /*zero_init:*/ false)?;
this.write_pointer(res, dest)?;
} else {
// If this does not fit in an isize, return null and, on Unix, set errno.
if this.target_os_is_unix() {
let einval = this.eval_libc("ENOMEM");
this.set_last_error(einval)?;
}
this.write_null(dest)?;
}
}
"calloc" => {
let [items, elem_size] =
this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
let items = this.read_target_usize(items)?;
let elem_size = this.read_target_usize(elem_size)?;
if let Some(size) = this.compute_size_in_bytes(Size::from_bytes(elem_size), items) {
let res = this.malloc(size.bytes(), /*zero_init:*/ true)?;
this.write_pointer(res, dest)?;
} else {
// On size overflow, return null and, on Unix, set errno.
if this.target_os_is_unix() {
let einval = this.eval_libc("ENOMEM");
this.set_last_error(einval)?;
}
this.write_null(dest)?;
}
}
"free" => {
let [ptr] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
let ptr = this.read_pointer(ptr)?;
this.free(ptr)?;
}
"realloc" => {
let [old_ptr, new_size] =
this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
let old_ptr = this.read_pointer(old_ptr)?;
let new_size = this.read_target_usize(new_size)?;
if new_size <= this.max_size_of_val().bytes() {
let res = this.realloc(old_ptr, new_size)?;
this.write_pointer(res, dest)?;
} else {
// If this does not fit in an isize, return null and, on Unix, set errno.
if this.target_os_is_unix() {
let einval = this.eval_libc("ENOMEM");
this.set_last_error(einval)?;
}
this.write_null(dest)?;
}
}
// Rust allocation
"__rust_alloc" | "miri_alloc" => {
let default = |this: &mut MiriInterpCx<'tcx>| {
// Only call `check_shim` when `#[global_allocator]` isn't used. When that
// macro is used, we act like no shim exists, so that the exported function can run.
let [size, align] = this.check_shim(abi, Abi::Rust, link_name, args)?;
let size = this.read_target_usize(size)?;
let align = this.read_target_usize(align)?;
this.check_rustc_alloc_request(size, align)?;
let memory_kind = match link_name.as_str() {
"__rust_alloc" => MiriMemoryKind::Rust,
"miri_alloc" => MiriMemoryKind::Miri,
_ => unreachable!(),
};
let ptr = this.allocate_ptr(
Size::from_bytes(size),
Align::from_bytes(align).unwrap(),
memory_kind.into(),
)?;
this.write_pointer(ptr, dest)
};
match link_name.as_str() {
"__rust_alloc" => return this.emulate_allocator(default),
"miri_alloc" => {
default(this)?;
return interp_ok(EmulateItemResult::NeedsReturn);
}
_ => unreachable!(),
}
}
"__rust_alloc_zeroed" => {
return this.emulate_allocator(|this| {
// See the comment for `__rust_alloc` why `check_shim` is only called in the
// default case.
let [size, align] = this.check_shim(abi, Abi::Rust, link_name, args)?;
let size = this.read_target_usize(size)?;
let align = this.read_target_usize(align)?;
this.check_rustc_alloc_request(size, align)?;
let ptr = this.allocate_ptr(
Size::from_bytes(size),
Align::from_bytes(align).unwrap(),
MiriMemoryKind::Rust.into(),
)?;
// We just allocated this, the access is definitely in-bounds.
this.write_bytes_ptr(
ptr.into(),
iter::repeat(0u8).take(usize::try_from(size).unwrap()),
)
.unwrap();
this.write_pointer(ptr, dest)
});
}
"__rust_dealloc" | "miri_dealloc" => {
let default = |this: &mut MiriInterpCx<'tcx>| {
// See the comment for `__rust_alloc` why `check_shim` is only called in the
// default case.
let [ptr, old_size, align] =
this.check_shim(abi, Abi::Rust, link_name, args)?;
let ptr = this.read_pointer(ptr)?;
let old_size = this.read_target_usize(old_size)?;
let align = this.read_target_usize(align)?;
let memory_kind = match link_name.as_str() {
"__rust_dealloc" => MiriMemoryKind::Rust,
"miri_dealloc" => MiriMemoryKind::Miri,
_ => unreachable!(),
};
// No need to check old_size/align; we anyway check that they match the allocation.
this.deallocate_ptr(
ptr,
Some((Size::from_bytes(old_size), Align::from_bytes(align).unwrap())),
memory_kind.into(),
)
};
match link_name.as_str() {
"__rust_dealloc" => {
return this.emulate_allocator(default);
}
"miri_dealloc" => {
default(this)?;
return interp_ok(EmulateItemResult::NeedsReturn);
}
_ => unreachable!(),
}
}
"__rust_realloc" => {
return this.emulate_allocator(|this| {
// See the comment for `__rust_alloc` why `check_shim` is only called in the
// default case.
let [ptr, old_size, align, new_size] =
this.check_shim(abi, Abi::Rust, link_name, args)?;
let ptr = this.read_pointer(ptr)?;
let old_size = this.read_target_usize(old_size)?;
let align = this.read_target_usize(align)?;
let new_size = this.read_target_usize(new_size)?;
// No need to check old_size; we anyway check that they match the allocation.
this.check_rustc_alloc_request(new_size, align)?;
let align = Align::from_bytes(align).unwrap();
let new_ptr = this.reallocate_ptr(
ptr,
Some((Size::from_bytes(old_size), align)),
Size::from_bytes(new_size),
align,
MiriMemoryKind::Rust.into(),
)?;
this.write_pointer(new_ptr, dest)
});
}
// C memory handling functions
"memcmp" => {
let [left, right, n] =
this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
let left = this.read_pointer(left)?;
let right = this.read_pointer(right)?;
let n = Size::from_bytes(this.read_target_usize(n)?);
// C requires that this must always be a valid pointer (C18 §7.1.4).
this.ptr_get_alloc_id(left, 0)?;
this.ptr_get_alloc_id(right, 0)?;
let result = {
let left_bytes = this.read_bytes_ptr_strip_provenance(left, n)?;
let right_bytes = this.read_bytes_ptr_strip_provenance(right, n)?;
use std::cmp::Ordering::*;
match left_bytes.cmp(right_bytes) {
Less => -1i32,
Equal => 0,
Greater => 1,
}
};
this.write_scalar(Scalar::from_i32(result), dest)?;
}
"memrchr" => {
let [ptr, val, num] =
this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
let ptr = this.read_pointer(ptr)?;
let val = this.read_scalar(val)?.to_i32()?;
let num = this.read_target_usize(num)?;
// The docs say val is "interpreted as unsigned char".
#[allow(clippy::cast_sign_loss, clippy::cast_possible_truncation)]
let val = val as u8;
// C requires that this must always be a valid pointer (C18 §7.1.4).
this.ptr_get_alloc_id(ptr, 0)?;
if let Some(idx) = this
.read_bytes_ptr_strip_provenance(ptr, Size::from_bytes(num))?
.iter()
.rev()
.position(|&c| c == val)
{
let idx = u64::try_from(idx).unwrap();
#[allow(clippy::arithmetic_side_effects)] // idx < num, so this never wraps
let new_ptr = ptr.wrapping_offset(Size::from_bytes(num - idx - 1), this);
this.write_pointer(new_ptr, dest)?;
} else {
this.write_null(dest)?;
}
}
"memchr" => {
let [ptr, val, num] =
this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
let ptr = this.read_pointer(ptr)?;
let val = this.read_scalar(val)?.to_i32()?;
let num = this.read_target_usize(num)?;
// The docs say val is "interpreted as unsigned char".
#[allow(clippy::cast_sign_loss, clippy::cast_possible_truncation)]
let val = val as u8;
// C requires that this must always be a valid pointer (C18 §7.1.4).
this.ptr_get_alloc_id(ptr, 0)?;
let idx = this
.read_bytes_ptr_strip_provenance(ptr, Size::from_bytes(num))?
.iter()
.position(|&c| c == val);
if let Some(idx) = idx {
let new_ptr = ptr.wrapping_offset(Size::from_bytes(idx as u64), this);
this.write_pointer(new_ptr, dest)?;
} else {
this.write_null(dest)?;
}
}
"strlen" => {
let [ptr] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
let ptr = this.read_pointer(ptr)?;
// This reads at least 1 byte, so we are already enforcing that this is a valid pointer.
let n = this.read_c_str(ptr)?.len();
this.write_scalar(
Scalar::from_target_usize(u64::try_from(n).unwrap(), this),
dest,
)?;
}
"wcslen" => {
let [ptr] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
let ptr = this.read_pointer(ptr)?;
// This reads at least 1 byte, so we are already enforcing that this is a valid pointer.
let n = this.read_wchar_t_str(ptr)?.len();
this.write_scalar(
Scalar::from_target_usize(u64::try_from(n).unwrap(), this),
dest,
)?;
}
"memcpy" => {
let [ptr_dest, ptr_src, n] =
this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
let ptr_dest = this.read_pointer(ptr_dest)?;
let ptr_src = this.read_pointer(ptr_src)?;
let n = this.read_target_usize(n)?;
// C requires that this must always be a valid pointer, even if `n` is zero, so we better check that.
// (This is more than Rust requires, so `mem_copy` is not sufficient.)
this.ptr_get_alloc_id(ptr_dest, 0)?;
this.ptr_get_alloc_id(ptr_src, 0)?;
this.mem_copy(ptr_src, ptr_dest, Size::from_bytes(n), true)?;
this.write_pointer(ptr_dest, dest)?;
}
"strcpy" => {
let [ptr_dest, ptr_src] =
this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
let ptr_dest = this.read_pointer(ptr_dest)?;
let ptr_src = this.read_pointer(ptr_src)?;
// We use `read_c_str` to determine the amount of data to copy,
// and then use `mem_copy` for the actual copy. This means
// pointer provenance is preserved by this implementation of `strcpy`.
// That is probably overly cautious, but there also is no fundamental
// reason to have `strcpy` destroy pointer provenance.
// This reads at least 1 byte, so we are already enforcing that this is a valid pointer.
let n = this.read_c_str(ptr_src)?.len().strict_add(1);
this.mem_copy(ptr_src, ptr_dest, Size::from_bytes(n), true)?;
this.write_pointer(ptr_dest, dest)?;
}
// math functions (note that there are also intrinsics for some other functions)
#[rustfmt::skip]
| "cbrtf"
| "coshf"
| "sinhf"
| "tanf"
| "tanhf"
| "acosf"
| "asinf"
| "atanf"
| "log1pf"
| "expm1f"
| "tgammaf"
=> {
let [f] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
let f = this.read_scalar(f)?.to_f32()?;
// Using host floats (but it's fine, these operations do not have guaranteed precision).
let f_host = f.to_host();
let res = match link_name.as_str() {
"cbrtf" => f_host.cbrt(),
"coshf" => f_host.cosh(),
"sinhf" => f_host.sinh(),
"tanf" => f_host.tan(),
"tanhf" => f_host.tanh(),
"acosf" => f_host.acos(),
"asinf" => f_host.asin(),
"atanf" => f_host.atan(),
"log1pf" => f_host.ln_1p(),
"expm1f" => f_host.exp_m1(),
"tgammaf" => f_host.gamma(),
_ => bug!(),
};
let res = res.to_soft();
let res = this.adjust_nan(res, &[f]);
this.write_scalar(res, dest)?;
}
#[rustfmt::skip]
| "_hypotf"
| "hypotf"
| "atan2f"
| "fdimf"
=> {
let [f1, f2] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
let f1 = this.read_scalar(f1)?.to_f32()?;
let f2 = this.read_scalar(f2)?.to_f32()?;
// underscore case for windows, here and below
// (see https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/floating-point-primitives?view=vs-2019)
// Using host floats (but it's fine, these operations do not have guaranteed precision).
let res = match link_name.as_str() {
"_hypotf" | "hypotf" => f1.to_host().hypot(f2.to_host()).to_soft(),
"atan2f" => f1.to_host().atan2(f2.to_host()).to_soft(),
#[allow(deprecated)]
"fdimf" => f1.to_host().abs_sub(f2.to_host()).to_soft(),
_ => bug!(),
};
let res = this.adjust_nan(res, &[f1, f2]);
this.write_scalar(res, dest)?;
}
#[rustfmt::skip]
| "cbrt"
| "cosh"
| "sinh"
| "tan"
| "tanh"
| "acos"
| "asin"
| "atan"
| "log1p"
| "expm1"
| "tgamma"
=> {
let [f] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
let f = this.read_scalar(f)?.to_f64()?;
// Using host floats (but it's fine, these operations do not have guaranteed precision).
let f_host = f.to_host();
let res = match link_name.as_str() {
"cbrt" => f_host.cbrt(),
"cosh" => f_host.cosh(),
"sinh" => f_host.sinh(),
"tan" => f_host.tan(),
"tanh" => f_host.tanh(),
"acos" => f_host.acos(),
"asin" => f_host.asin(),
"atan" => f_host.atan(),
"log1p" => f_host.ln_1p(),
"expm1" => f_host.exp_m1(),
"tgamma" => f_host.gamma(),
_ => bug!(),
};
let res = res.to_soft();
let res = this.adjust_nan(res, &[f]);
this.write_scalar(res, dest)?;
}
#[rustfmt::skip]
| "_hypot"
| "hypot"
| "atan2"
| "fdim"
=> {
let [f1, f2] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
let f1 = this.read_scalar(f1)?.to_f64()?;
let f2 = this.read_scalar(f2)?.to_f64()?;
// underscore case for windows, here and below
// (see https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/floating-point-primitives?view=vs-2019)
// Using host floats (but it's fine, these operations do not have guaranteed precision).
let res = match link_name.as_str() {
"_hypot" | "hypot" => f1.to_host().hypot(f2.to_host()).to_soft(),
"atan2" => f1.to_host().atan2(f2.to_host()).to_soft(),
#[allow(deprecated)]
"fdim" => f1.to_host().abs_sub(f2.to_host()).to_soft(),
_ => bug!(),
};
let res = this.adjust_nan(res, &[f1, f2]);
this.write_scalar(res, dest)?;
}
#[rustfmt::skip]
| "_ldexp"
| "ldexp"
| "scalbn"
=> {
let [x, exp] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
// For radix-2 (binary) systems, `ldexp` and `scalbn` are the same.
let x = this.read_scalar(x)?.to_f64()?;
let exp = this.read_scalar(exp)?.to_i32()?;
let res = x.scalbn(exp);
let res = this.adjust_nan(res, &[x]);
this.write_scalar(res, dest)?;
}
"lgammaf_r" => {
let [x, signp] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
let x = this.read_scalar(x)?.to_f32()?;
let signp = this.deref_pointer(signp)?;
// Using host floats (but it's fine, these operations do not have guaranteed precision).
let (res, sign) = x.to_host().ln_gamma();
this.write_int(sign, &signp)?;
let res = this.adjust_nan(res.to_soft(), &[x]);
this.write_scalar(res, dest)?;
}
"lgamma_r" => {
let [x, signp] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
let x = this.read_scalar(x)?.to_f64()?;
let signp = this.deref_pointer(signp)?;
// Using host floats (but it's fine, these operations do not have guaranteed precision).
let (res, sign) = x.to_host().ln_gamma();
this.write_int(sign, &signp)?;
let res = this.adjust_nan(res.to_soft(), &[x]);
this.write_scalar(res, dest)?;
}
// LLVM intrinsics
"llvm.prefetch" => {
let [p, rw, loc, ty] =
this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
let _ = this.read_pointer(p)?;
let rw = this.read_scalar(rw)?.to_i32()?;
let loc = this.read_scalar(loc)?.to_i32()?;
let ty = this.read_scalar(ty)?.to_i32()?;
if ty == 1 {
// Data cache prefetch.
// Notably, we do not have to check the pointer, this operation is never UB!
if !matches!(rw, 0 | 1) {
throw_unsup_format!("invalid `rw` value passed to `llvm.prefetch`: {}", rw);
}
if !matches!(loc, 0..=3) {
throw_unsup_format!(
"invalid `loc` value passed to `llvm.prefetch`: {}",
loc
);
}
} else {
throw_unsup_format!("unsupported `llvm.prefetch` type argument: {}", ty);
}
}
// Used to implement the x86 `_mm{,256,512}_popcnt_epi{8,16,32,64}` and wasm
// `{i,u}8x16_popcnt` functions.
name if name.starts_with("llvm.ctpop.v") => {
let [op] = this.check_shim(abi, Abi::C { unwind: false }, link_name, args)?;
let (op, op_len) = this.project_to_simd(op)?;
let (dest, dest_len) = this.project_to_simd(dest)?;
assert_eq!(dest_len, op_len);
for i in 0..dest_len {
let op = this.read_immediate(&this.project_index(&op, i)?)?;
// Use `to_uint` to get a zero-extended `u128`. Those
// extra zeros will not affect `count_ones`.
let res = op.to_scalar().to_uint(op.layout.size)?.count_ones();
this.write_scalar(
Scalar::from_uint(res, op.layout.size),
&this.project_index(&dest, i)?,
)?;
}
}
// Target-specific shims
name if name.starts_with("llvm.x86.")
&& (this.tcx.sess.target.arch == "x86"
|| this.tcx.sess.target.arch == "x86_64") =>
{
return shims::x86::EvalContextExt::emulate_x86_intrinsic(
this, link_name, abi, args, dest,
);
}
// FIXME: Move these to an `arm` submodule.
"llvm.aarch64.isb" if this.tcx.sess.target.arch == "aarch64" => {
let [arg] = this.check_shim(abi, Abi::Unadjusted, link_name, args)?;
let arg = this.read_scalar(arg)?.to_i32()?;
match arg {
// SY ("full system scope")
15 => {
this.yield_active_thread();
}
_ => {
throw_unsup_format!("unsupported llvm.aarch64.isb argument {}", arg);
}
}
}
"llvm.arm.hint" if this.tcx.sess.target.arch == "arm" => {
let [arg] = this.check_shim(abi, Abi::Unadjusted, link_name, args)?;
let arg = this.read_scalar(arg)?.to_i32()?;
// Note that different arguments might have different target feature requirements.
match arg {
// YIELD
1 => {
this.expect_target_feature_for_intrinsic(link_name, "v6")?;
this.yield_active_thread();
}
_ => {
throw_unsup_format!("unsupported llvm.arm.hint argument {}", arg);
}
}
}
// Platform-specific shims
_ =>
return match this.tcx.sess.target.os.as_ref() {
_ if this.target_os_is_unix() =>
shims::unix::foreign_items::EvalContextExt::emulate_foreign_item_inner(
this, link_name, abi, args, dest,
),
"wasi" =>
shims::wasi::foreign_items::EvalContextExt::emulate_foreign_item_inner(
this, link_name, abi, args, dest,
),
"windows" =>
shims::windows::foreign_items::EvalContextExt::emulate_foreign_item_inner(
this, link_name, abi, args, dest,
),
_ => interp_ok(EmulateItemResult::NotSupported),
},
};
// We only fall through to here if we did *not* hit the `_` arm above,
// i.e., if we actually emulated the function with one of the shims.
interp_ok(EmulateItemResult::NeedsReturn)
}
}