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use crate::traphandlers::{tls, wasmtime_longjmp};
use std::io;
use windows_sys::Win32::Foundation::*;
use windows_sys::Win32::System::Diagnostics::Debug::*;
use windows_sys::Win32::System::Kernel::*;
/// Function which may handle custom signals while processing traps.
pub type SignalHandler<'a> = dyn Fn(*mut EXCEPTION_POINTERS) -> bool + Send + Sync + 'a;
pub unsafe fn platform_init() {
// our trap handler needs to go first, so that we can recover from
// wasm faults and continue execution, so pass `1` as a true value
// here.
if AddVectoredExceptionHandler(1, Some(exception_handler)).is_null() {
panic!(
"failed to add exception handler: {}",
io::Error::last_os_error()
);
}
}
unsafe extern "system" fn exception_handler(exception_info: *mut EXCEPTION_POINTERS) -> i32 {
// Check the kind of exception, since we only handle a subset within
// wasm code. If anything else happens we want to defer to whatever
// the rest of the system wants to do for this exception.
let record = &*(*exception_info).ExceptionRecord;
if record.ExceptionCode != EXCEPTION_ACCESS_VIOLATION
&& record.ExceptionCode != EXCEPTION_ILLEGAL_INSTRUCTION
&& record.ExceptionCode != EXCEPTION_INT_DIVIDE_BY_ZERO
&& record.ExceptionCode != EXCEPTION_INT_OVERFLOW
{
return ExceptionContinueSearch;
}
// FIXME: this is what the previous C++ did to make sure that TLS
// works by the time we execute this trap handling code. This isn't
// exactly super easy to call from Rust though and it's not clear we
// necessarily need to do so. Leaving this here in case we need this
// in the future, but for now we can probably wait until we see a
// strange fault before figuring out how to reimplement this in
// Rust.
//
// if (!NtCurrentTeb()->Reserved1[sThreadLocalArrayPointerIndex]) {
// return ExceptionContinueSearch;
// }
// This is basically the same as the unix version above, only with a
// few parameters tweaked here and there.
tls::with(|info| {
let info = match info {
Some(info) => info,
None => return ExceptionContinueSearch,
};
cfg_if::cfg_if! {
if #[cfg(target_arch = "x86_64")] {
let ip = (*(*exception_info).ContextRecord).Rip as *const u8;
let fp = (*(*exception_info).ContextRecord).Rbp as usize;
} else if #[cfg(target_arch = "aarch64")] {
let ip = (*(*exception_info).ContextRecord).Pc as *const u8;
let fp = (*(*exception_info).ContextRecord).Anonymous.Anonymous.Fp as usize;
} else {
compile_error!("unsupported platform");
}
}
// For access violations the first element in `ExceptionInformation` is
// an indicator as to whether the fault was a read/write. The second
// element is the address of the inaccessible data causing this
// violation.
let faulting_addr = if record.ExceptionCode == EXCEPTION_ACCESS_VIOLATION {
assert!(record.NumberParameters >= 2);
Some(record.ExceptionInformation[1])
} else {
None
};
let jmp_buf = info.take_jmp_buf_if_trap(ip, |handler| handler(exception_info));
if jmp_buf.is_null() {
ExceptionContinueSearch
} else if jmp_buf as usize == 1 {
ExceptionContinueExecution
} else {
info.set_jit_trap(ip, fp, faulting_addr);
wasmtime_longjmp(jmp_buf)
}
})
}
pub fn lazy_per_thread_init() {
// Unused on Windows
}