wasmtime/runtime/vm/sys/unix/
signals.rs

1//! Trap handling on Unix based on POSIX signals.
2
3use crate::prelude::*;
4use crate::runtime::vm::traphandlers::{TrapRegisters, TrapTest, tls};
5use std::cell::RefCell;
6use std::io;
7use std::mem;
8use std::ptr::{self, null_mut};
9use wasmtime_unwinder::Handler;
10
11/// Function which may handle custom signals while processing traps.
12pub type SignalHandler =
13    Box<dyn Fn(libc::c_int, *const libc::siginfo_t, *const libc::c_void) -> bool + Send + Sync>;
14
15const UNINIT_SIGACTION: libc::sigaction = unsafe { mem::zeroed() };
16static mut PREV_SIGSEGV: libc::sigaction = UNINIT_SIGACTION;
17static mut PREV_SIGBUS: libc::sigaction = UNINIT_SIGACTION;
18static mut PREV_SIGILL: libc::sigaction = UNINIT_SIGACTION;
19static mut PREV_SIGFPE: libc::sigaction = UNINIT_SIGACTION;
20
21pub struct TrapHandler;
22
23impl TrapHandler {
24    /// Installs all trap handlers.
25    ///
26    /// # Unsafety
27    ///
28    /// This function is unsafe because it's not safe to call concurrently and
29    /// it's not safe to call if the trap handlers have already been initialized
30    /// for this process.
31    pub unsafe fn new(macos_use_mach_ports: bool) -> TrapHandler {
32        // Either mach ports shouldn't be in use or we shouldn't be on macOS,
33        // otherwise the `machports.rs` module should be used instead.
34        assert!(!macos_use_mach_ports || !cfg!(target_vendor = "apple"));
35
36        foreach_handler(|slot, signal| {
37            let mut handler: libc::sigaction = unsafe { mem::zeroed() };
38            // The flags here are relatively careful, and they are...
39            //
40            // SA_SIGINFO gives us access to information like the program
41            // counter from where the fault happened.
42            //
43            // SA_ONSTACK allows us to handle signals on an alternate stack,
44            // so that the handler can run in response to running out of
45            // stack space on the main stack. Rust installs an alternate
46            // stack with sigaltstack, so we rely on that.
47            //
48            // SA_NODEFER allows us to reenter the signal handler if we
49            // crash while handling the signal, and fall through to the
50            // Breakpad handler by testing handlingSegFault.
51            handler.sa_flags = libc::SA_SIGINFO | libc::SA_NODEFER | libc::SA_ONSTACK;
52            handler.sa_sigaction = (trap_handler as *const ()).addr();
53            unsafe {
54                libc::sigemptyset(&mut handler.sa_mask);
55                if libc::sigaction(signal, &handler, slot) != 0 {
56                    panic!(
57                        "unable to install signal handler: {}",
58                        io::Error::last_os_error(),
59                    );
60                }
61            }
62        });
63
64        TrapHandler
65    }
66
67    pub fn validate_config(&self, macos_use_mach_ports: bool) {
68        assert!(!macos_use_mach_ports || !cfg!(target_vendor = "apple"));
69    }
70}
71
72fn foreach_handler(mut f: impl FnMut(*mut libc::sigaction, i32)) {
73    // Allow handling OOB with signals on all architectures
74    f(&raw mut PREV_SIGSEGV, libc::SIGSEGV);
75
76    // Handle `unreachable` instructions which execute `ud2` right now
77    f(&raw mut PREV_SIGILL, libc::SIGILL);
78
79    // x86 and s390x use SIGFPE to report division by zero
80    if cfg!(target_arch = "x86_64") || cfg!(target_arch = "s390x") {
81        f(&raw mut PREV_SIGFPE, libc::SIGFPE);
82    }
83
84    // Sometimes we need to handle SIGBUS too:
85    // - On Darwin, guard page accesses are raised as SIGBUS.
86    if cfg!(target_vendor = "apple") || cfg!(target_os = "freebsd") {
87        f(&raw mut PREV_SIGBUS, libc::SIGBUS);
88    }
89
90    // TODO(#1980): x86-32, if we support it, will also need a SIGFPE handler.
91    // TODO(#1173): ARM32, if we support it, will also need a SIGBUS handler.
92}
93
94impl Drop for TrapHandler {
95    fn drop(&mut self) {
96        unsafe {
97            foreach_handler(|slot, signal| {
98                let mut prev: libc::sigaction = mem::zeroed();
99
100                // Restore the previous handler that this signal had.
101                if libc::sigaction(signal, slot, &mut prev) != 0 {
102                    eprintln!(
103                        "unable to reinstall signal handler: {}",
104                        io::Error::last_os_error(),
105                    );
106                    libc::abort();
107                }
108
109                // If our trap handler wasn't currently listed for this process
110                // then that's a problem because we have just corrupted the
111                // signal handler state and don't know how to remove ourselves
112                // from the signal handling state. Inform the user of this and
113                // abort the process.
114                if prev.sa_sigaction != (trap_handler as *const ()).addr() {
115                    eprintln!(
116                        "
117Wasmtime's signal handler was not the last signal handler to be installed
118in the process so it's not certain how to unload signal handlers. In this
119situation the Engine::unload_process_handlers API is not applicable and requires
120perhaps initializing libraries in a different order. The process will be aborted
121now.
122"
123                    );
124                    libc::abort();
125                }
126            });
127        }
128    }
129}
130
131unsafe extern "C" fn trap_handler(
132    signum: libc::c_int,
133    siginfo: *mut libc::siginfo_t,
134    context: *mut libc::c_void,
135) {
136    let previous = match signum {
137        libc::SIGSEGV => &raw const PREV_SIGSEGV,
138        libc::SIGBUS => &raw const PREV_SIGBUS,
139        libc::SIGFPE => &raw const PREV_SIGFPE,
140        libc::SIGILL => &raw const PREV_SIGILL,
141        _ => panic!("unknown signal: {signum}"),
142    };
143    let handled = tls::with(|info| {
144        // If no wasm code is executing, we don't handle this as a wasm
145        // trap.
146        let info = match info {
147            Some(info) => info,
148            None => return false,
149        };
150
151        // If we hit an exception while handling a previous trap, that's
152        // quite bad, so bail out and let the system handle this
153        // recursive segfault.
154        //
155        // Otherwise flag ourselves as handling a trap, do the trap
156        // handling, and reset our trap handling flag. Then we figure
157        // out what to do based on the result of the trap handling.
158        let faulting_addr = match signum {
159            libc::SIGSEGV | libc::SIGBUS => unsafe { Some((*siginfo).si_addr() as usize) },
160            _ => None,
161        };
162        let regs = unsafe { get_trap_registers(context, signum) };
163        let test = info.test_if_trap(regs, faulting_addr, |handler| {
164            handler(signum, siginfo, context)
165        });
166
167        // Figure out what to do based on the result of this handling of
168        // the trap. Note that our sentinel value of 1 means that the
169        // exception was handled by a custom exception handler, so we
170        // keep executing.
171        match test {
172            TrapTest::NotWasm => {
173                if let Some(faulting_addr) = faulting_addr {
174                    let range = unsafe { &info.vm_store_context.as_ref().async_guard_range };
175                    if range.start.addr() <= faulting_addr && faulting_addr < range.end.addr() {
176                        abort_stack_overflow();
177                    }
178                }
179                false
180            }
181            TrapTest::HandledByEmbedder => true,
182            TrapTest::Trap(handler) => {
183                unsafe {
184                    store_handler_in_ucontext(context, &handler);
185                }
186                true
187            }
188        }
189    });
190
191    if handled {
192        return;
193    }
194
195    unsafe { delegate_signal_to_previous_handler(previous, signum, siginfo, context) }
196}
197
198pub unsafe fn delegate_signal_to_previous_handler(
199    previous: *const libc::sigaction,
200    signum: libc::c_int,
201    siginfo: *mut libc::siginfo_t,
202    context: *mut libc::c_void,
203) {
204    // This signal is not for any compiled wasm code we expect, so we
205    // need to forward the signal to the next handler. If there is no
206    // next handler (SIG_IGN or SIG_DFL), then it's time to crash. To do
207    // this, we set the signal back to its original disposition and
208    // return. This will cause the faulting op to be re-executed which
209    // will crash in the normal way. If there is a next handler, call
210    // it. It will either crash synchronously, fix up the instruction
211    // so that execution can continue and return, or trigger a crash by
212    // returning the signal to it's original disposition and returning.
213    unsafe {
214        let previous = *previous;
215        if previous.sa_flags & libc::SA_SIGINFO != 0 {
216            mem::transmute::<
217                usize,
218                extern "C" fn(libc::c_int, *mut libc::siginfo_t, *mut libc::c_void),
219            >(previous.sa_sigaction)(signum, siginfo, context)
220        } else if previous.sa_sigaction == libc::SIG_DFL || previous.sa_sigaction == libc::SIG_IGN {
221            libc::sigaction(signum, &previous as *const _, ptr::null_mut());
222        } else {
223            mem::transmute::<usize, extern "C" fn(libc::c_int)>(previous.sa_sigaction)(signum)
224        }
225    }
226}
227
228pub fn abort_stack_overflow() -> ! {
229    unsafe {
230        let msg = "execution on async fiber has overflowed its stack";
231        libc::write(libc::STDERR_FILENO, msg.as_ptr().cast(), msg.len());
232        libc::abort();
233    }
234}
235
236#[allow(
237    clippy::cast_possible_truncation,
238    reason = "too fiddly to handle and wouldn't help much anyway"
239)]
240unsafe fn get_trap_registers(cx: *mut libc::c_void, _signum: libc::c_int) -> TrapRegisters {
241    cfg_if::cfg_if! {
242        if #[cfg(all(any(target_os = "linux", target_os = "android", target_os = "illumos"), target_arch = "x86_64"))] {
243            let cx = unsafe { &*(cx as *const libc::ucontext_t) };
244            TrapRegisters {
245                pc: cx.uc_mcontext.gregs[libc::REG_RIP as usize] as usize,
246                fp: cx.uc_mcontext.gregs[libc::REG_RBP as usize] as usize,
247            }
248        } else if #[cfg(all(target_os = "linux", target_arch = "x86"))] {
249            let cx = unsafe { &*(cx as *const libc::ucontext_t) };
250            TrapRegisters {
251                pc: cx.uc_mcontext.gregs[libc::REG_EIP as usize] as usize,
252                fp: cx.uc_mcontext.gregs[libc::REG_EBP as usize] as usize,
253            }
254        } else if #[cfg(all(any(target_os = "linux", target_os = "android"), target_arch = "aarch64"))] {
255            let cx = unsafe { &*(cx as *const libc::ucontext_t) };
256            TrapRegisters {
257                pc: cx.uc_mcontext.pc as usize,
258                fp: cx.uc_mcontext.regs[29] as usize,
259            }
260        } else if #[cfg(all(target_os = "linux", target_arch = "s390x"))] {
261            // On s390x, SIGILL and SIGFPE are delivered with the PSW address
262            // pointing *after* the faulting instruction, while SIGSEGV and
263            // SIGBUS are delivered with the PSW address pointing *to* the
264            // faulting instruction.  To handle this, the code generator registers
265            // any trap that results in one of "late" signals on the last byte
266            // of the instruction, and any trap that results in one of the "early"
267            // signals on the first byte of the instruction (as usual).  This
268            // means we simply need to decrement the reported PSW address by
269            // one in the case of a "late" signal here to ensure we always
270            // correctly find the associated trap handler.
271            let trap_offset = match _signum {
272                libc::SIGILL | libc::SIGFPE => 1,
273                _ => 0,
274            };
275            unsafe {
276                let cx = &*(cx as *const libc::ucontext_t);
277                TrapRegisters {
278                    pc: (cx.uc_mcontext.psw.addr - trap_offset) as usize,
279                    fp: *(cx.uc_mcontext.gregs[15] as *const usize),
280                }
281            }
282        } else if #[cfg(all(target_vendor = "apple", target_arch = "x86_64"))] {
283            unsafe {
284                let cx = &*(cx as *const libc::ucontext_t);
285                TrapRegisters {
286                    pc: (*cx.uc_mcontext).__ss.__rip as usize,
287                    fp: (*cx.uc_mcontext).__ss.__rbp as usize,
288                }
289            }
290        } else if #[cfg(all(target_vendor = "apple", target_arch = "aarch64"))] {
291            unsafe {
292                let cx = &*(cx as *const libc::ucontext_t);
293                TrapRegisters {
294                    pc: (*cx.uc_mcontext).__ss.__pc as usize,
295                    fp: (*cx.uc_mcontext).__ss.__fp as usize,
296                }
297            }
298        } else if #[cfg(all(target_os = "freebsd", target_arch = "x86_64"))] {
299            let cx = unsafe { &*(cx as *const libc::ucontext_t) };
300            TrapRegisters {
301                pc: cx.uc_mcontext.mc_rip as usize,
302                fp: cx.uc_mcontext.mc_rbp as usize,
303            }
304        } else if #[cfg(all(target_os = "linux", target_arch = "riscv64"))] {
305            let cx = unsafe { &*(cx as *const libc::ucontext_t) };
306            TrapRegisters {
307                pc: cx.uc_mcontext.__gregs[libc::REG_PC] as usize,
308                fp: cx.uc_mcontext.__gregs[libc::REG_S0] as usize,
309            }
310        } else if #[cfg(all(target_os = "freebsd", target_arch = "aarch64"))] {
311            let cx = unsafe { &*(cx as *const libc::mcontext_t) };
312            TrapRegisters {
313                pc: cx.mc_gpregs.gp_elr as usize,
314                fp: cx.mc_gpregs.gp_x[29] as usize,
315            }
316        } else if #[cfg(all(target_os = "openbsd", target_arch = "x86_64"))] {
317            let cx = unsafe { &*(cx as *const libc::ucontext_t) };
318            TrapRegisters {
319                pc: cx.sc_rip as usize,
320                fp: cx.sc_rbp as usize,
321            }
322        } else if #[cfg(all(target_os = "linux", target_arch = "arm"))] {
323            let cx = unsafe { &*(cx as *const libc::ucontext_t) };
324            TrapRegisters {
325                pc: cx.uc_mcontext.arm_pc as usize,
326                fp: cx.uc_mcontext.arm_fp as usize,
327            }
328        } else {
329            compile_error!("unsupported platform");
330            panic!();
331        }
332    }
333}
334
335/// Updates the siginfo context stored in `cx` to resume to `handler` up on
336/// resumption while returning from the signal handler.
337unsafe fn store_handler_in_ucontext(cx: *mut libc::c_void, handler: &Handler) {
338    cfg_if::cfg_if! {
339        if #[cfg(all(any(target_os = "linux", target_os = "android", target_os = "illumos"), target_arch = "x86_64"))] {
340            let cx = unsafe { cx.cast::<libc::ucontext_t>().as_mut().unwrap() };
341            cx.uc_mcontext.gregs[libc::REG_RIP as usize] = handler.pc as _;
342            cx.uc_mcontext.gregs[libc::REG_RSP as usize] = handler.sp as _;
343            cx.uc_mcontext.gregs[libc::REG_RBP as usize] = handler.fp as _;
344            cx.uc_mcontext.gregs[libc::REG_RAX as usize] = 0;
345            cx.uc_mcontext.gregs[libc::REG_RDX as usize] = 0;
346        } else if #[cfg(all(any(target_os = "linux", target_os = "android"), target_arch = "aarch64"))] {
347            let cx = unsafe { cx.cast::<libc::ucontext_t>().as_mut().unwrap() };
348            cx.uc_mcontext.pc = handler.pc as _;
349            cx.uc_mcontext.sp = handler.sp as _;
350            cx.uc_mcontext.regs[29] = handler.fp as _;
351            cx.uc_mcontext.regs[0] = 0;
352            cx.uc_mcontext.regs[1] = 0;
353        } else if #[cfg(all(target_os = "linux", target_arch = "s390x"))] {
354            let cx = unsafe { cx.cast::<libc::ucontext_t>().as_mut().unwrap() };
355            cx.uc_mcontext.psw.addr = handler.pc as _;
356            cx.uc_mcontext.gregs[15] = handler.sp as _;
357            cx.uc_mcontext.gregs[6] = 0;
358            cx.uc_mcontext.gregs[7] = 0;
359        } else if #[cfg(all(target_vendor = "apple", target_arch = "x86_64"))] {
360            unsafe {
361                let cx = cx.cast::<libc::ucontext_t>().as_mut().unwrap();
362                let cx = cx.uc_mcontext.as_mut().unwrap();
363                cx.__ss.__rip = handler.pc as _;
364                cx.__ss.__rsp = handler.sp as _;
365                cx.__ss.__rbp = handler.fp as _;
366                cx.__ss.__rax = 0;
367                cx.__ss.__rdx = 0;
368            }
369        } else if #[cfg(all(target_vendor = "apple", target_arch = "aarch64"))] {
370            unsafe {
371                let cx = cx.cast::<libc::ucontext_t>().as_mut().unwrap();
372                let cx = cx.uc_mcontext.as_mut().unwrap();
373                cx.__ss.__pc = handler.pc as _;
374                cx.__ss.__sp = handler.sp as _;
375                cx.__ss.__fp = handler.fp as _;
376                cx.__ss.__x[0] = 0;
377                cx.__ss.__x[1] = 0;
378            }
379        } else if #[cfg(all(target_os = "freebsd", target_arch = "x86_64"))] {
380            let cx = unsafe { cx.cast::<libc::ucontext_t>().as_mut().unwrap() };
381            cx.uc_mcontext.mc_rip = handler.pc as _;
382            cx.uc_mcontext.mc_rbp = handler.fp as _;
383            cx.uc_mcontext.mc_rsp = handler.sp as _;
384            cx.uc_mcontext.mc_rax = 0;
385            cx.uc_mcontext.mc_rdx = 0;
386        } else if #[cfg(all(target_os = "openbsd", target_arch = "x86_64"))] {
387            let cx = unsafe { cx.cast::<libc::ucontext_t>().as_mut().unwrap() };
388            cx.sc_rip = handler.pc as _;
389            cx.sc_rbp = handler.fp as _;
390            cx.sc_rsp = handler.sp as _;
391            cx.sc_rax = 0;
392            cx.sc_rdx = 0;
393        } else if #[cfg(all(target_os = "linux", target_arch = "riscv64"))] {
394            let cx = unsafe { cx.cast::<libc::ucontext_t>().as_mut().unwrap() };
395            cx.uc_mcontext.__gregs[libc::REG_PC] = handler.pc as _;
396            cx.uc_mcontext.__gregs[libc::REG_S0] = handler.fp as _;
397            cx.uc_mcontext.__gregs[libc::REG_SP] = handler.sp as _;
398            cx.uc_mcontext.__gregs[libc::REG_A0] = 0;
399            cx.uc_mcontext.__gregs[libc::REG_A0 + 1] = 0;
400        } else {
401            compile_error!("unsupported platform");
402            panic!();
403        }
404    }
405}
406
407/// A function for registering a custom alternate signal stack (sigaltstack).
408///
409/// Rust's libstd installs an alternate stack with size `SIGSTKSZ`, which is not
410/// always large enough for our signal handling code. Override it by creating
411/// and registering our own alternate stack that is large enough and has a guard
412/// page.
413///
414/// Note that one might reasonably ask why do this at all? Why not remove
415/// `SA_ONSTACK` from our signal handlers entirely? The basic reason for that is
416/// because we want to print a message on stack overflow. The Rust standard
417/// library will print this message by default and by us overriding the
418/// `SIGSEGV` handler above we're now sharing responsibility for that as well.
419/// We must have `SA_ONSTACK` to even attempt to being able to printing this
420/// message, and so we leave it turned on. Wasmtime will determine a stack
421/// overflow fault isn't caused by wasm and then forward to libstd's signal
422/// handler which will actually print-and-abort.
423///
424/// Another reasonable question might be why we need to increase the size of the
425/// sigaltstack at all? This is something which we may want to reconsider in the
426/// future. For now it helps keep debug builds working which consume more stack
427/// when handling normal wasm out-of-bounds and faults. Perhaps in the future we
428/// could optimize this more or maybe even do something clever like lazily
429/// allocate the sigaltstack on the fault itself. (e.g. trampoline from a tiny
430/// stack to the "big stack" during a wasm fault or something like that)
431#[cold]
432pub fn lazy_per_thread_init() {
433    // This is a load-bearing requirement to keep address-sanitizer working and
434    // prevent crashes during fuzzing. The general idea here is that we skip the
435    // sigaltstack setup below entirely on asan builds, aka fuzzing. The exact
436    // reason for this is not entirely known, but the closest guess we have at
437    // this time is something like:
438    //
439    // * ASAN builds intercept mmap/munmap to keep track of what's going on.
440    // * The sigaltstack below registers a TLS destructor for when the current
441    //   thread exits to deallocate the stack.
442    // * ASAN looks to also have TLS destructors for its own internal state.
443    // * The current assumption is that the order of these TLS destructors can
444    //   cause corruption in ASAN state where if we run after asan's destructor
445    //   it may intercept munmap and then asan doesn't know it's been
446    //   de-initialized yet.
447    //
448    // The reproduction of this involved a standalone project built with
449    // `-Zsanitizer=address` where internally it would spawn two threads. Each
450    // thread would build a "hello world" module and then one of the threads
451    // would execute a noop exported function. If this was run thousands of
452    // times in a loop in the same process it would eventually crash under asan.
453    //
454    // It's notably not quite so simple as frobbing TLS destructors. There's
455    // clearly something else going on with ASAN state internally which we don't
456    // fully understand at this time. An attempt to make a standalone C++
457    // reproduction, for example, was not successful. In lieu of that the best
458    // we have for now is to disable our custom and larger sigaltstack in asan
459    // builds.
460    //
461    // The exact source was
462    // https://gist.github.com/alexcrichton/6815a5d57a3c5ca94a8d816a9fcc91af for
463    // future reference if necessary.
464    if cfg!(asan) {
465        return;
466    }
467
468    // This thread local is purely used to register a `Stack` to get deallocated
469    // when the thread exists. Otherwise this function is only ever called at
470    // most once per-thread.
471    std::thread_local! {
472        static STACK: RefCell<Option<Stack>> = const { RefCell::new(None) };
473    }
474
475    /// The size of the sigaltstack (not including the guard, which will be
476    /// added). Make this large enough to run our signal handlers.
477    ///
478    /// The main current requirement of the signal handler in terms of stack
479    /// space is that `malloc`/`realloc` are called to create a `Backtrace` of
480    /// wasm frames.
481    ///
482    /// Historically this was 16k. Turns out jemalloc requires more than 16k of
483    /// stack space in debug mode, so this was bumped to 64k.
484    const MIN_STACK_SIZE: usize = 64 * 4096;
485
486    struct Stack {
487        mmap_ptr: *mut libc::c_void,
488        mmap_size: usize,
489    }
490
491    return STACK.with(|s| {
492        *s.borrow_mut() = unsafe { allocate_sigaltstack() };
493    });
494
495    unsafe fn allocate_sigaltstack() -> Option<Stack> {
496        // Check to see if the existing sigaltstack, if it exists, is big
497        // enough. If so we don't need to allocate our own.
498        let mut old_stack = unsafe { mem::zeroed() };
499        let r = unsafe { libc::sigaltstack(ptr::null(), &mut old_stack) };
500        assert_eq!(
501            r,
502            0,
503            "learning about sigaltstack failed: {}",
504            io::Error::last_os_error()
505        );
506        if old_stack.ss_flags & libc::SS_DISABLE == 0 && old_stack.ss_size >= MIN_STACK_SIZE {
507            return None;
508        }
509
510        // ... but failing that we need to allocate our own, so do all that
511        // here.
512        let page_size = crate::runtime::vm::host_page_size();
513        let guard_size = page_size;
514        let alloc_size = guard_size + MIN_STACK_SIZE;
515
516        let ptr = unsafe {
517            rustix::mm::mmap_anonymous(
518                null_mut(),
519                alloc_size,
520                rustix::mm::ProtFlags::empty(),
521                rustix::mm::MapFlags::PRIVATE,
522            )
523            .expect("failed to allocate memory for sigaltstack")
524        };
525
526        // Prepare the stack with readable/writable memory and then register it
527        // with `sigaltstack`.
528        let stack_ptr = (ptr as usize + guard_size) as *mut std::ffi::c_void;
529        unsafe {
530            rustix::mm::mprotect(
531                stack_ptr,
532                MIN_STACK_SIZE,
533                rustix::mm::MprotectFlags::READ | rustix::mm::MprotectFlags::WRITE,
534            )
535            .expect("mprotect to configure memory for sigaltstack failed");
536        }
537        let new_stack = libc::stack_t {
538            ss_sp: stack_ptr,
539            ss_flags: 0,
540            ss_size: MIN_STACK_SIZE,
541        };
542        let r = unsafe { libc::sigaltstack(&new_stack, ptr::null_mut()) };
543        assert_eq!(
544            r,
545            0,
546            "registering new sigaltstack failed: {}",
547            io::Error::last_os_error()
548        );
549
550        Some(Stack {
551            mmap_ptr: ptr,
552            mmap_size: alloc_size,
553        })
554    }
555
556    impl Drop for Stack {
557        fn drop(&mut self) {
558            unsafe {
559                // Deallocate the stack memory.
560                let r = rustix::mm::munmap(self.mmap_ptr, self.mmap_size);
561                debug_assert!(r.is_ok(), "munmap failed during thread shutdown");
562            }
563        }
564    }
565}
wasmtime/runtime/vm/sys/unix/signals.rs

wasmtime/runtime/vm/sys/unix/
signals.rs
