1 use std::{convert::{TryInto, TryFrom}, iter};
5 use rustc_hir::def_id::DefId;
7 use rustc_target::{abi::{Align, Size}, spec::PanicStrategy};
9 use rustc_apfloat::Float;
10 use rustc_span::symbol::sym;
13 use super::backtrace::EvalContextExt as _;
14 use helpers::check_arg_count;
16 impl<'mir, 'tcx: 'mir> EvalContextExt<'mir, 'tcx> for crate::MiriEvalContext<'mir, 'tcx> {}
17 pub trait EvalContextExt<'mir, 'tcx: 'mir>: crate::MiriEvalContextExt<'mir, 'tcx> {
18 /// Returns the minimum alignment for the target architecture for allocations of the given size.
19 fn min_align(&self, size: u64, kind: MiriMemoryKind) -> Align {
20 let this = self.eval_context_ref();
21 // List taken from `libstd/sys_common/alloc.rs`.
22 let min_align = match this.tcx.sess.target.arch.as_str() {
23 "x86" | "arm" | "mips" | "powerpc" | "powerpc64" | "asmjs" | "wasm32" => 8,
24 "x86_64" | "aarch64" | "mips64" | "s390x" | "sparc64" => 16,
25 arch => bug!("Unsupported target architecture: {}", arch),
27 // Windows always aligns, even small allocations.
28 // Source: <https://support.microsoft.com/en-us/help/286470/how-to-use-pageheap-exe-in-windows-xp-windows-2000-and-windows-server>
29 // But jemalloc does not, so for the C heap we only align if the allocation is sufficiently big.
30 if kind == MiriMemoryKind::WinHeap || size >= min_align {
31 return Align::from_bytes(min_align).unwrap();
33 // We have `size < min_align`. Round `size` *down* to the next power of two and use that.
34 fn prev_power_of_two(x: u64) -> u64 {
35 let next_pow2 = x.next_power_of_two();
37 // x *is* a power of two, just use that.
40 // x is between two powers, so next = 2*prev.
44 Align::from_bytes(prev_power_of_two(size)).unwrap()
47 fn malloc(&mut self, size: u64, zero_init: bool, kind: MiriMemoryKind) -> Scalar<Tag> {
48 let this = self.eval_context_mut();
50 Scalar::null_ptr(this)
52 let align = this.min_align(size, kind);
53 let ptr = this.memory.allocate(Size::from_bytes(size), align, kind.into());
55 // We just allocated this, the access is definitely in-bounds.
56 this.memory.write_bytes(ptr.into(), iter::repeat(0u8).take(size as usize)).unwrap();
62 fn free(&mut self, ptr: Scalar<Tag>, kind: MiriMemoryKind) -> InterpResult<'tcx> {
63 let this = self.eval_context_mut();
64 if !this.is_null(ptr)? {
65 let ptr = this.force_ptr(ptr)?;
66 this.memory.deallocate(ptr, None, kind.into())?;
76 ) -> InterpResult<'tcx, Scalar<Tag>> {
77 let this = self.eval_context_mut();
78 let new_align = this.min_align(new_size, kind);
79 if this.is_null(old_ptr)? {
81 Ok(Scalar::null_ptr(this))
84 this.memory.allocate(Size::from_bytes(new_size), new_align, kind.into());
85 Ok(Scalar::Ptr(new_ptr))
88 let old_ptr = this.force_ptr(old_ptr)?;
90 this.memory.deallocate(old_ptr, None, kind.into())?;
91 Ok(Scalar::null_ptr(this))
93 let new_ptr = this.memory.reallocate(
96 Size::from_bytes(new_size),
100 Ok(Scalar::Ptr(new_ptr))
105 /// Emulates calling a foreign item, failing if the item is not supported.
106 /// This function will handle `goto_block` if needed.
107 /// Returns Ok(None) if the foreign item was completely handled
108 /// by this function.
109 /// Returns Ok(Some(body)) if processing the foreign item
110 /// is delegated to another function.
112 fn emulate_foreign_item(
115 args: &[OpTy<'tcx, Tag>],
116 ret: Option<(PlaceTy<'tcx, Tag>, mir::BasicBlock)>,
117 unwind: Option<mir::BasicBlock>,
118 ) -> InterpResult<'tcx, Option<&'mir mir::Body<'tcx>>> {
119 let this = self.eval_context_mut();
120 let attrs = this.tcx.get_attrs(def_id);
121 let link_name = match this.tcx.sess.first_attr_value_str_by_name(&attrs, sym::link_name) {
122 Some(name) => name.as_str(),
123 None => this.tcx.item_name(def_id).as_str(),
125 // Strip linker suffixes (seen on 32-bit macOS).
126 let link_name = link_name.trim_end_matches("$UNIX2003");
127 let tcx = this.tcx.tcx;
129 // First: functions that diverge.
130 let (dest, ret) = match ret {
131 None => match link_name {
132 "miri_start_panic" => {
133 this.handle_miri_start_panic(args, unwind)?;
136 // This matches calls to the foreign item `panic_impl`.
137 // The implementation is provided by the function with the `#[panic_handler]` attribute.
139 let panic_impl_id = tcx.lang_items().panic_impl().unwrap();
140 let panic_impl_instance = ty::Instance::mono(tcx, panic_impl_id);
141 return Ok(Some(&*this.load_mir(panic_impl_instance.def, None)?));
146 let &[code] = check_arg_count(args)?;
147 // it's really u32 for ExitProcess, but we have to put it into the `Exit` variant anyway
148 let code = this.read_scalar(code)?.to_i32()?;
149 throw_machine_stop!(TerminationInfo::Exit(code.into()));
152 throw_machine_stop!(TerminationInfo::Abort("the program aborted execution".to_owned()))
154 _ => throw_unsup_format!("can't call (diverging) foreign function: {}", link_name),
159 // Second: some functions that we forward to MIR implementations.
161 // This matches calls to the foreign item `__rust_start_panic`, that is,
162 // calls to `extern "Rust" { fn __rust_start_panic(...) }`
163 // (and `__rust_panic_cleanup`, respectively).
164 // We forward this to the underlying *implementation* in the panic runtime crate.
165 // Normally, this will be either `libpanic_unwind` or `libpanic_abort`, but it could
166 // also be a custom user-provided implementation via `#![feature(panic_runtime)]`
167 "__rust_start_panic" | "__rust_panic_cleanup" => {
168 // This replicates some of the logic in `inject_panic_runtime`.
169 // FIXME: is there a way to reuse that logic?
170 let panic_runtime = match this.tcx.sess.panic_strategy() {
171 PanicStrategy::Unwind => sym::panic_unwind,
172 PanicStrategy::Abort => sym::panic_abort,
174 let start_panic_instance =
175 this.resolve_path(&[&*panic_runtime.as_str(), link_name]);
176 return Ok(Some(&*this.load_mir(start_panic_instance.def, None)?));
181 // Third: functions that return.
182 if this.emulate_foreign_item_by_name(link_name, args, dest, ret)? {
183 trace!("{:?}", this.dump_place(*dest));
184 this.go_to_block(ret);
190 /// Emulates calling a foreign item using its name, failing if the item is not supported.
191 /// Returns `true` if the caller is expected to jump to the return block, and `false` if
192 /// jumping has already been taken care of.
193 fn emulate_foreign_item_by_name(
196 args: &[OpTy<'tcx, Tag>],
197 dest: PlaceTy<'tcx, Tag>,
198 ret: mir::BasicBlock,
199 ) -> InterpResult<'tcx, bool> {
200 let this = self.eval_context_mut();
202 // Here we dispatch all the shims for foreign functions. If you have a platform specific
203 // shim, add it to the corresponding submodule.
205 // Miri-specific extern functions
206 "miri_static_root" => {
207 let &[ptr] = check_arg_count(args)?;
208 let ptr = this.read_scalar(ptr)?.check_init()?;
209 let ptr = this.force_ptr(ptr)?;
210 if ptr.offset != Size::ZERO {
211 throw_unsup_format!("pointer passed to miri_static_root must point to beginning of an allocated block");
213 this.machine.static_roots.push(ptr.alloc_id);
216 // Obtains a Miri backtrace. See the README for details.
217 "miri_get_backtrace" => {
218 this.handle_miri_get_backtrace(args, dest)?;
221 // Resolves a Miri backtrace frame. See the README for details.
222 "miri_resolve_frame" => {
223 this.handle_miri_resolve_frame(args, dest)?;
227 // Standard C allocation
229 let &[size] = check_arg_count(args)?;
230 let size = this.read_scalar(size)?.to_machine_usize(this)?;
231 let res = this.malloc(size, /*zero_init:*/ false, MiriMemoryKind::C);
232 this.write_scalar(res, dest)?;
235 let &[items, len] = check_arg_count(args)?;
236 let items = this.read_scalar(items)?.to_machine_usize(this)?;
237 let len = this.read_scalar(len)?.to_machine_usize(this)?;
239 items.checked_mul(len).ok_or_else(|| err_ub_format!("overflow during calloc size computation"))?;
240 let res = this.malloc(size, /*zero_init:*/ true, MiriMemoryKind::C);
241 this.write_scalar(res, dest)?;
244 let &[ptr] = check_arg_count(args)?;
245 let ptr = this.read_scalar(ptr)?.check_init()?;
246 this.free(ptr, MiriMemoryKind::C)?;
249 let &[old_ptr, new_size] = check_arg_count(args)?;
250 let old_ptr = this.read_scalar(old_ptr)?.check_init()?;
251 let new_size = this.read_scalar(new_size)?.to_machine_usize(this)?;
252 let res = this.realloc(old_ptr, new_size, MiriMemoryKind::C)?;
253 this.write_scalar(res, dest)?;
257 // (Usually these would be forwarded to to `#[global_allocator]`; we instead implement a generic
258 // allocation that also checks that all conditions are met, such as not permitting zero-sized allocations.)
260 let &[size, align] = check_arg_count(args)?;
261 let size = this.read_scalar(size)?.to_machine_usize(this)?;
262 let align = this.read_scalar(align)?.to_machine_usize(this)?;
263 Self::check_alloc_request(size, align)?;
264 let ptr = this.memory.allocate(
265 Size::from_bytes(size),
266 Align::from_bytes(align).unwrap(),
267 MiriMemoryKind::Rust.into(),
269 this.write_scalar(ptr, dest)?;
271 "__rust_alloc_zeroed" => {
272 let &[size, align] = check_arg_count(args)?;
273 let size = this.read_scalar(size)?.to_machine_usize(this)?;
274 let align = this.read_scalar(align)?.to_machine_usize(this)?;
275 Self::check_alloc_request(size, align)?;
276 let ptr = this.memory.allocate(
277 Size::from_bytes(size),
278 Align::from_bytes(align).unwrap(),
279 MiriMemoryKind::Rust.into(),
281 // We just allocated this, the access is definitely in-bounds.
282 this.memory.write_bytes(ptr.into(), iter::repeat(0u8).take(usize::try_from(size).unwrap())).unwrap();
283 this.write_scalar(ptr, dest)?;
285 "__rust_dealloc" => {
286 let &[ptr, old_size, align] = check_arg_count(args)?;
287 let ptr = this.read_scalar(ptr)?.check_init()?;
288 let old_size = this.read_scalar(old_size)?.to_machine_usize(this)?;
289 let align = this.read_scalar(align)?.to_machine_usize(this)?;
290 // No need to check old_size/align; we anyway check that they match the allocation.
291 let ptr = this.force_ptr(ptr)?;
292 this.memory.deallocate(
294 Some((Size::from_bytes(old_size), Align::from_bytes(align).unwrap())),
295 MiriMemoryKind::Rust.into(),
298 "__rust_realloc" => {
299 let &[ptr, old_size, align, new_size] = check_arg_count(args)?;
300 let ptr = this.force_ptr(this.read_scalar(ptr)?.check_init()?)?;
301 let old_size = this.read_scalar(old_size)?.to_machine_usize(this)?;
302 let align = this.read_scalar(align)?.to_machine_usize(this)?;
303 let new_size = this.read_scalar(new_size)?.to_machine_usize(this)?;
304 Self::check_alloc_request(new_size, align)?;
305 // No need to check old_size; we anyway check that they match the allocation.
306 let align = Align::from_bytes(align).unwrap();
307 let new_ptr = this.memory.reallocate(
309 Some((Size::from_bytes(old_size), align)),
310 Size::from_bytes(new_size),
312 MiriMemoryKind::Rust.into(),
314 this.write_scalar(new_ptr, dest)?;
317 // C memory handling functions
319 let &[left, right, n] = check_arg_count(args)?;
320 let left = this.read_scalar(left)?.check_init()?;
321 let right = this.read_scalar(right)?.check_init()?;
322 let n = Size::from_bytes(this.read_scalar(n)?.to_machine_usize(this)?);
325 let left_bytes = this.memory.read_bytes(left, n)?;
326 let right_bytes = this.memory.read_bytes(right, n)?;
328 use std::cmp::Ordering::*;
329 match left_bytes.cmp(right_bytes) {
336 this.write_scalar(Scalar::from_i32(result), dest)?;
339 let &[ptr, val, num] = check_arg_count(args)?;
340 let ptr = this.read_scalar(ptr)?.check_init()?;
341 let val = this.read_scalar(val)?.to_i32()? as u8;
342 let num = this.read_scalar(num)?.to_machine_usize(this)?;
343 if let Some(idx) = this
345 .read_bytes(ptr, Size::from_bytes(num))?
348 .position(|&c| c == val)
350 let new_ptr = ptr.ptr_offset(Size::from_bytes(num - idx as u64 - 1), this)?;
351 this.write_scalar(new_ptr, dest)?;
353 this.write_null(dest)?;
357 let &[ptr, val, num] = check_arg_count(args)?;
358 let ptr = this.read_scalar(ptr)?.check_init()?;
359 let val = this.read_scalar(val)?.to_i32()? as u8;
360 let num = this.read_scalar(num)?.to_machine_usize(this)?;
363 .read_bytes(ptr, Size::from_bytes(num))?
365 .position(|&c| c == val);
366 if let Some(idx) = idx {
367 let new_ptr = ptr.ptr_offset(Size::from_bytes(idx as u64), this)?;
368 this.write_scalar(new_ptr, dest)?;
370 this.write_null(dest)?;
374 let &[ptr] = check_arg_count(args)?;
375 let ptr = this.read_scalar(ptr)?.check_init()?;
376 let n = this.memory.read_c_str(ptr)?.len();
377 this.write_scalar(Scalar::from_machine_usize(u64::try_from(n).unwrap(), this), dest)?;
389 let &[f] = check_arg_count(args)?;
390 // FIXME: Using host floats.
391 let f = f32::from_bits(this.read_scalar(f)?.to_u32()?);
392 let f = match link_name {
402 this.write_scalar(Scalar::from_u32(f.to_bits()), dest)?;
408 let &[f1, f2] = check_arg_count(args)?;
409 // underscore case for windows, here and below
410 // (see https://docs.microsoft.com/en-us/cpp/c-runtime-library/reference/floating-point-primitives?view=vs-2019)
411 // FIXME: Using host floats.
412 let f1 = f32::from_bits(this.read_scalar(f1)?.to_u32()?);
413 let f2 = f32::from_bits(this.read_scalar(f2)?.to_u32()?);
414 let n = match link_name {
415 "_hypotf" | "hypotf" => f1.hypot(f2),
416 "atan2f" => f1.atan2(f2),
419 this.write_scalar(Scalar::from_u32(n.to_bits()), dest)?;
429 let &[f] = check_arg_count(args)?;
430 // FIXME: Using host floats.
431 let f = f64::from_bits(this.read_scalar(f)?.to_u64()?);
432 let f = match link_name {
442 this.write_scalar(Scalar::from_u64(f.to_bits()), dest)?;
448 let &[f1, f2] = check_arg_count(args)?;
449 // FIXME: Using host floats.
450 let f1 = f64::from_bits(this.read_scalar(f1)?.to_u64()?);
451 let f2 = f64::from_bits(this.read_scalar(f2)?.to_u64()?);
452 let n = match link_name {
453 "_hypot" | "hypot" => f1.hypot(f2),
454 "atan2" => f1.atan2(f2),
457 this.write_scalar(Scalar::from_u64(n.to_bits()), dest)?;
463 let &[x, exp] = check_arg_count(args)?;
464 // For radix-2 (binary) systems, `ldexp` and `scalbn` are the same.
465 let x = this.read_scalar(x)?.to_f64()?;
466 let exp = this.read_scalar(exp)?.to_i32()?;
468 // Saturating cast to i16. Even those are outside the valid exponent range to
469 // `scalbn` below will do its over/underflow handling.
470 let exp = if exp > i32::from(i16::MAX) {
472 } else if exp < i32::from(i16::MIN) {
475 exp.try_into().unwrap()
478 let res = x.scalbn(exp);
479 this.write_scalar(Scalar::from_f64(res), dest)?;
482 // Architecture-specific shims
483 "llvm.x86.sse2.pause" if this.tcx.sess.target.arch == "x86" || this.tcx.sess.target.arch == "x86_64" => {
484 let &[] = check_arg_count(args)?;
485 this.yield_active_thread();
488 // Platform-specific shims
489 _ => match this.tcx.sess.target.os.as_str() {
490 "linux" | "macos" => return shims::posix::foreign_items::EvalContextExt::emulate_foreign_item_by_name(this, link_name, args, dest, ret),
491 "windows" => return shims::windows::foreign_items::EvalContextExt::emulate_foreign_item_by_name(this, link_name, args, dest, ret),
492 target => throw_unsup_format!("the target `{}` is not supported", target),
499 /// Check some basic requirements for this allocation request:
500 /// non-zero size, power-of-two alignment.
501 fn check_alloc_request(size: u64, align: u64) -> InterpResult<'tcx> {
503 throw_ub_format!("creating allocation with size 0");
505 if !align.is_power_of_two() {
506 throw_ub_format!("creating allocation with non-power-of-two alignment {}", align);