Initial reorg.

This is largely the same as #305, but updated for the current tree.

crates/jit/src/function_table.rs

@@ -0,0 +1,134 @@
+//! Runtime function table.
+//!
+//! This module is primarily used to track JIT functions on Windows for stack walking and unwind.
+
+/// Represents a runtime function table.
+///
+/// The runtime function table is not implemented for non-Windows target platforms.
+#[cfg(not(target_os = "windows"))]
+pub(crate) struct FunctionTable;
+
+#[cfg(not(target_os = "windows"))]
+impl FunctionTable {
+    /// Creates a new function table.
+    pub fn new() -> Self {
+        Self
+    }
+
+    /// Returns the number of functions in the table, also referred to as its 'length'.
+    ///
+    /// For non-Windows platforms, the table will always be empty.
+    pub fn len(&self) -> usize {
+        0
+    }
+
+    /// Adds a function to the table based off of the start offset, end offset, and unwind offset.
+    ///
+    /// The offsets are from the "module base", which is provided when the table is published.
+    ///
+    /// For non-Windows platforms, this is a no-op.
+    pub fn add_function(&mut self, _start: u32, _end: u32, _unwind: u32) {}
+
+    /// Publishes the function table using the given base address.
+    ///
+    /// A published function table will automatically be deleted when it is dropped.
+    ///
+    /// For non-Windows platforms, this is a no-op.
+    pub fn publish(&mut self, _base_address: u64) -> Result<(), String> {
+        Ok(())
+    }
+}
+
+/// Represents a runtime function table.
+///
+/// This is used to register JIT code with the operating system to enable stack walking and unwinding.
+#[cfg(all(target_os = "windows", target_arch = "x86_64"))]
+pub(crate) struct FunctionTable {
+    functions: Vec<winapi::um::winnt::RUNTIME_FUNCTION>,
+    published: bool,
+}
+
+#[cfg(all(target_os = "windows", target_arch = "x86_64"))]
+impl FunctionTable {
+    /// Creates a new function table.
+    pub fn new() -> Self {
+        Self {
+            functions: Vec::new(),
+            published: false,
+        }
+    }
+
+    /// Returns the number of functions in the table, also referred to as its 'length'.
+    pub fn len(&self) -> usize {
+        self.functions.len()
+    }
+
+    /// Adds a function to the table based off of the start offset, end offset, and unwind offset.
+    ///
+    /// The offsets are from the "module base", which is provided when the table is published.
+    pub fn add_function(&mut self, start: u32, end: u32, unwind: u32) {
+        use winapi::um::winnt;
+
+        assert!(!self.published, "table has already been published");
+
+        let mut entry = winnt::RUNTIME_FUNCTION::default();
+
+        entry.BeginAddress = start;
+        entry.EndAddress = end;
+
+        unsafe {
+            *entry.u.UnwindInfoAddress_mut() = unwind;
+        }
+
+        self.functions.push(entry);
+    }
+
+    /// Publishes the function table using the given base address.
+    ///
+    /// A published function table will automatically be deleted when it is dropped.
+    pub fn publish(&mut self, base_address: u64) -> Result<(), String> {
+        use winapi::um::winnt;
+
+        if self.published {
+            return Err("function table was already published".into());
+        }
+
+        self.published = true;
+
+        if self.functions.is_empty() {
+            return Ok(());
+        }
+
+        unsafe {
+            // Windows heap allocations are 32-bit aligned, but assert just in case
+            assert!(
+                (self.functions.as_mut_ptr() as u64) % 4 == 0,
+                "function table allocation was not aligned"
+            );
+
+            if winnt::RtlAddFunctionTable(
+                self.functions.as_mut_ptr(),
+                self.functions.len() as u32,
+                base_address,
+            ) == 0
+            {
+                return Err("failed to add function table".into());
+            }
+        }
+
+        Ok(())
+    }
+}
+
+#[cfg(target_os = "windows")]
+impl Drop for FunctionTable {
+    fn drop(&mut self) {
+        use winapi::um::winnt;
+
+        if self.published {
+            unsafe {
+                winnt::RtlDeleteFunctionTable(self.functions.as_mut_ptr());
+            }
+        }
+    }
+}