1 files changed, 142 insertions, 0 deletions
diff --git a/vendor/stacker/src/backends/windows.rs b/vendor/stacker/src/backends/windows.rs
new file mode 100644
index 00000000..69c76133
--- /dev/null
+++ b/vendor/stacker/src/backends/windows.rs
@@ -0,0 +1,142 @@
+use libc::c_void;
+use std::io;
+use std::ptr;
+use windows_sys::Win32::Foundation::BOOL;
+use windows_sys::Win32::System::Memory::VirtualQuery;
+use windows_sys::Win32::System::Threading::{
+    ConvertFiberToThread, ConvertThreadToFiber, CreateFiber, DeleteFiber, IsThreadAFiber,
+    SetThreadStackGuarantee, SwitchToFiber,
+};
+
+// Make sure the libstacker.a (implemented in C) is linked.
+// See https://github.com/rust-lang/rust/issues/65610
+#[link(name = "stacker")]
+extern "C" {
+    fn __stacker_get_current_fiber() -> *mut c_void;
+}
+
+struct FiberInfo<F> {
+    callback: std::mem::MaybeUninit<F>,
+    panic: Option<Box<dyn std::any::Any + Send + 'static>>,
+    parent_fiber: *mut c_void,
+}
+
+unsafe extern "system" fn fiber_proc<F: FnOnce()>(data: *mut c_void) {
+    // This function is the entry point to our inner fiber, and as argument we get an
+    // instance of `FiberInfo`. We will set-up the "runtime" for the callback and execute
+    // it.
+    let data = &mut *(data as *mut FiberInfo<F>);
+    let old_stack_limit = crate::get_stack_limit();
+    crate::set_stack_limit(guess_os_stack_limit());
+    let callback = data.callback.as_ptr();
+    data.panic = std::panic::catch_unwind(std::panic::AssertUnwindSafe(callback.read())).err();
+
+    // Restore to the previous Fiber
+    crate::set_stack_limit(old_stack_limit);
+    SwitchToFiber(data.parent_fiber);
+}
+
+pub fn _grow(stack_size: usize, callback: &mut dyn FnMut()) {
+    // Fibers (or stackful coroutines) is the only official way to create new stacks on the
+    // same thread on Windows. So in order to extend the stack we create fiber and switch
+    // to it so we can use it's stack. After running `callback` within our fiber, we switch
+    // back to the current stack and destroy the fiber and its associated stack.
+    unsafe {
+        let was_fiber = IsThreadAFiber() == 1 as BOOL;
+        let mut data = FiberInfo {
+            callback: std::mem::MaybeUninit::new(callback),
+            panic: None,
+            parent_fiber: {
+                if was_fiber {
+                    // Get a handle to the current fiber. We need to use a C implementation
+                    // for this as GetCurrentFiber is an header only function.
+                    __stacker_get_current_fiber()
+                } else {
+                    // Convert the current thread to a fiber, so we are able to switch back
+                    // to the current stack. Threads coverted to fibers still act like
+                    // regular threads, but they have associated fiber data. We later
+                    // convert it back to a regular thread and free the fiber data.
+                    ConvertThreadToFiber(ptr::null_mut())
+                }
+            },
+        };
+
+        if data.parent_fiber.is_null() {
+            panic!(
+                "unable to convert thread to fiber: {}",
+                io::Error::last_os_error()
+            );
+        }
+
+        let fiber = CreateFiber(
+            stack_size as usize,
+            Some(fiber_proc::<&mut dyn FnMut()>),
+            &mut data as *mut FiberInfo<&mut dyn FnMut()> as *mut _,
+        );
+        if fiber.is_null() {
+            panic!("unable to allocate fiber: {}", io::Error::last_os_error());
+        }
+
+        // Switch to the fiber we created. This changes stacks and starts executing
+        // fiber_proc on it. fiber_proc will run `callback` and then switch back to run the
+        // next statement.
+        SwitchToFiber(fiber);
+        DeleteFiber(fiber);
+
+        // Clean-up.
+        if !was_fiber && ConvertFiberToThread() == 0 {
+            // FIXME: Perhaps should not panic here?
+            panic!(
+                "unable to convert back to thread: {}",
+                io::Error::last_os_error()
+            );
+        }
+
+        if let Some(p) = data.panic {
+            std::panic::resume_unwind(p);
+        }
+    }
+}
+
+#[inline(always)]
+fn get_thread_stack_guarantee() -> Option<usize> {
+    let min_guarantee = if cfg!(target_pointer_width = "32") {
+        0x1000
+    } else {
+        0x2000
+    };
+    let mut stack_guarantee = 0;
+    unsafe {
+        // Read the current thread stack guarantee
+        // This is the stack reserved for stack overflow
+        // exception handling.
+        // This doesn't return the true value so we need
+        // some further logic to calculate the real stack
+        // guarantee. This logic is what is used on x86-32 and
+        // x86-64 Windows 10. Other versions and platforms may differ
+        let ret = SetThreadStackGuarantee(&mut stack_guarantee);
+        if ret == 0 {
+            return None;
+        }
+    };
+    Some(std::cmp::max(stack_guarantee, min_guarantee) as usize + 0x1000)
+}
+
+#[inline(always)]
+pub unsafe fn guess_os_stack_limit() -> Option<usize> {
+    // Query the allocation which contains our stack pointer in order
+    // to discover the size of the stack
+    //
+    // FIXME: we could read stack base from the TIB, specifically the 3rd element of it.
+    type QueryT = windows_sys::Win32::System::Memory::MEMORY_BASIC_INFORMATION;
+    let mut mi = std::mem::MaybeUninit::<QueryT>::uninit();
+    let res = VirtualQuery(
+        psm::stack_pointer() as *const _,
+        mi.as_mut_ptr(),
+        std::mem::size_of::<QueryT>() as usize,
+    );
+    if res == 0 {
+        return None;
+    }
+    Some(mi.assume_init().AllocationBase as usize + get_thread_stack_guarantee()? + 0x1000)
+}