rust: add crate to expose bindings and interfaces

Add rust/qemu-api, which exposes rust-bindgen generated FFI bindings and
provides some declaration macros for symbols visible to the rest of
QEMU.

Co-authored-by: Junjie Mao <junjie.mao@intel.com>
Co-authored-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Junjie Mao <junjie.mao@intel.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
Link: https://lore.kernel.org/r/0fb23fbe211761b263aacec03deaf85c0cc39995.1727961605.git.manos.pitsidianakis@linaro.org
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

rust/qemu-api/src/lib.rs

@@ -0,0 +1,166 @@
+// Copyright 2024, Linaro Limited
+// Author(s): Manos Pitsidianakis <manos.pitsidianakis@linaro.org>
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#![cfg_attr(not(MESON), doc = include_str!("../README.md"))]
+
+#[allow(
+    dead_code,
+    improper_ctypes_definitions,
+    improper_ctypes,
+    non_camel_case_types,
+    non_snake_case,
+    non_upper_case_globals,
+    unsafe_op_in_unsafe_fn,
+    clippy::missing_const_for_fn,
+    clippy::too_many_arguments,
+    clippy::approx_constant,
+    clippy::use_self,
+    clippy::useless_transmute,
+    clippy::missing_safety_doc,
+)]
+#[rustfmt::skip]
+pub mod bindings;
+
+unsafe impl Send for bindings::Property {}
+unsafe impl Sync for bindings::Property {}
+unsafe impl Sync for bindings::TypeInfo {}
+unsafe impl Sync for bindings::VMStateDescription {}
+
+pub mod definitions;
+pub mod device_class;
+
+#[cfg(test)]
+mod tests;
+
+use std::alloc::{GlobalAlloc, Layout};
+
+#[cfg(HAVE_GLIB_WITH_ALIGNED_ALLOC)]
+extern "C" {
+    fn g_aligned_alloc0(
+        n_blocks: bindings::gsize,
+        n_block_bytes: bindings::gsize,
+        alignment: bindings::gsize,
+    ) -> bindings::gpointer;
+    fn g_aligned_free(mem: bindings::gpointer);
+}
+
+#[cfg(not(HAVE_GLIB_WITH_ALIGNED_ALLOC))]
+extern "C" {
+    fn qemu_memalign(alignment: usize, size: usize) -> *mut ::core::ffi::c_void;
+    fn qemu_vfree(ptr: *mut ::core::ffi::c_void);
+}
+
+extern "C" {
+    fn g_malloc0(n_bytes: bindings::gsize) -> bindings::gpointer;
+    fn g_free(mem: bindings::gpointer);
+}
+
+/// An allocator that uses the same allocator as QEMU in C.
+///
+/// It is enabled by default with the `allocator` feature.
+///
+/// To set it up manually as a global allocator in your crate:
+///
+/// ```ignore
+/// use qemu_api::QemuAllocator;
+///
+/// #[global_allocator]
+/// static GLOBAL: QemuAllocator = QemuAllocator::new();
+/// ```
+#[derive(Clone, Copy, Debug)]
+#[repr(C)]
+pub struct QemuAllocator {
+    _unused: [u8; 0],
+}
+
+#[cfg_attr(all(feature = "allocator", not(test)), global_allocator)]
+pub static GLOBAL: QemuAllocator = QemuAllocator::new();
+
+impl QemuAllocator {
+    // From the glibc documentation, on GNU systems, malloc guarantees 16-byte
+    // alignment on 64-bit systems and 8-byte alignment on 32-bit systems. See
+    // https://www.gnu.org/software/libc/manual/html_node/Malloc-Examples.html.
+    // This alignment guarantee also applies to Windows and Android. On Darwin
+    // and OpenBSD, the alignment is 16 bytes on both 64-bit and 32-bit systems.
+    #[cfg(all(
+        target_pointer_width = "32",
+        not(any(target_os = "macos", target_os = "openbsd"))
+    ))]
+    pub const DEFAULT_ALIGNMENT_BYTES: Option<usize> = Some(8);
+    #[cfg(all(
+        target_pointer_width = "64",
+        not(any(target_os = "macos", target_os = "openbsd"))
+    ))]
+    pub const DEFAULT_ALIGNMENT_BYTES: Option<usize> = Some(16);
+    #[cfg(all(
+        any(target_pointer_width = "32", target_pointer_width = "64"),
+        any(target_os = "macos", target_os = "openbsd")
+    ))]
+    pub const DEFAULT_ALIGNMENT_BYTES: Option<usize> = Some(16);
+    #[cfg(not(any(target_pointer_width = "32", target_pointer_width = "64")))]
+    pub const DEFAULT_ALIGNMENT_BYTES: Option<usize> = None;
+
+    pub const fn new() -> Self {
+        Self { _unused: [] }
+    }
+}
+
+impl Default for QemuAllocator {
+    fn default() -> Self {
+        Self::new()
+    }
+}
+
+// Sanity check.
+const _: [(); 8] = [(); ::core::mem::size_of::<*mut ::core::ffi::c_void>()];
+
+unsafe impl GlobalAlloc for QemuAllocator {
+    unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
+        if matches!(Self::DEFAULT_ALIGNMENT_BYTES, Some(default) if default.checked_rem(layout.align()) == Some(0))
+        {
+            // SAFETY: g_malloc0() is safe to call.
+            unsafe { g_malloc0(layout.size().try_into().unwrap()).cast::<u8>() }
+        } else {
+            #[cfg(HAVE_GLIB_WITH_ALIGNED_ALLOC)]
+            {
+                // SAFETY: g_aligned_alloc0() is safe to call.
+                unsafe {
+                    g_aligned_alloc0(
+                        layout.size().try_into().unwrap(),
+                        1,
+                        layout.align().try_into().unwrap(),
+                    )
+                    .cast::<u8>()
+                }
+            }
+            #[cfg(not(HAVE_GLIB_WITH_ALIGNED_ALLOC))]
+            {
+                // SAFETY: qemu_memalign() is safe to call.
+                unsafe { qemu_memalign(layout.align(), layout.size()).cast::<u8>() }
+            }
+        }
+    }
+
+    unsafe fn dealloc(&self, ptr: *mut u8, layout: Layout) {
+        if matches!(Self::DEFAULT_ALIGNMENT_BYTES, Some(default) if default.checked_rem(layout.align()) == Some(0))
+        {
+            // SAFETY: `ptr` must have been allocated by Self::alloc thus a valid
+            // glib-allocated pointer, so `g_free`ing is safe.
+            unsafe { g_free(ptr.cast::<_>()) }
+        } else {
+            #[cfg(HAVE_GLIB_WITH_ALIGNED_ALLOC)]
+            {
+                // SAFETY: `ptr` must have been allocated by Self::alloc thus a valid aligned
+                // glib-allocated pointer, so `g_aligned_free`ing is safe.
+                unsafe { g_aligned_free(ptr.cast::<_>()) }
+            }
+            #[cfg(not(HAVE_GLIB_WITH_ALIGNED_ALLOC))]
+            {
+                // SAFETY: `ptr` must have been allocated by Self::alloc thus a valid aligned
+                // glib-allocated pointer, so `qemu_vfree`ing is safe.
+                unsafe { qemu_vfree(ptr.cast::<_>()) }
+            }
+        }
+    }
+}