Re: [PATCH v8 6/8] rust: add crate to expose bindings and interfaces

[Junjie Mao <junjie.mao@intel.com>]

On 8/23/2024 4:11 PM, Manos Pitsidianakis wrote:
> 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>
> ---
>   MAINTAINERS                       |   6 ++
>   rust/meson.build                  |   1 +
>   rust/qemu-api/.gitignore          |   2 +
>   rust/qemu-api/Cargo.lock          |   7 +++
>   rust/qemu-api/Cargo.toml          |  26 ++++++++
>   rust/qemu-api/README.md           |  17 +++++
>   rust/qemu-api/build.rs            |  14 +++++
>   rust/qemu-api/meson.build         |  20 ++++++
>   rust/qemu-api/rustfmt.toml        |   1 +
>   rust/qemu-api/src/definitions.rs  | 109 ++++++++++++++++++++++++++++++++
>   rust/qemu-api/src/device_class.rs | 128 ++++++++++++++++++++++++++++++++++++++
>   rust/qemu-api/src/lib.rs          | 102 ++++++++++++++++++++++++++++++
>   rust/qemu-api/src/tests.rs        |  49 +++++++++++++++
>   rust/rustfmt.toml                 |   7 +++
>   14 files changed, 489 insertions(+)
[snip]
> diff --git a/rust/qemu-api/src/lib.rs b/rust/qemu-api/src/lib.rs
> new file mode 100644
> index 0000000000..ab95d0d5f7
> --- /dev/null
> +++ b/rust/qemu-api/src/lib.rs
> @@ -0,0 +1,102 @@
> +// 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,
> +    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};
> +
> +extern "C" {
> +    pub fn g_aligned_alloc0(
> +        n_blocks: bindings::gsize,
> +        n_block_bytes: bindings::gsize,
> +        alignment: bindings::gsize,
> +    ) -> bindings::gpointer;
> +    pub fn g_aligned_free(mem: bindings::gpointer);
> +    pub fn g_malloc0(n_bytes: bindings::gsize) -> bindings::gpointer;
> +    pub 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(feature = "allocator", global_allocator)]
> +pub static GLOBAL: QemuAllocator = QemuAllocator::new();
> +
> +impl QemuAllocator {
> +    pub const fn new() -> Self {
> +        Self { _unused: [] }
> +    }
> +}
> +
> +impl Default for QemuAllocator {
> +    fn default() -> Self {
> +        Self::new()
> +    }
> +}
> +
> +unsafe impl GlobalAlloc for QemuAllocator {
> +    unsafe fn alloc(&self, layout: Layout) -> *mut u8 {
> +        if layout.align() == 0 {
> +            g_malloc0(layout.size().try_into().unwrap()).cast::<u8>()
> +        } else {
> +            g_aligned_alloc0(

One more thing: g_aligned_alloc0() was introduced in glib 2.72 [1] but the 
current glib version check in meson is >= 2.66.0.

Glib 2.72 still supports Win 7+, so no increase to _WIN32_WINNT is needed for 
this version bumping.

[1] https://docs.gtk.org/glib/func.aligned_alloc0.html
[2] https://gitlab.gnome.org/GNOME/glib/-/blob/2.72.0/meson.build?ref_type=tags#L509

---
Best Regards
Junjie Mao

> +                layout.size().try_into().unwrap(),
> +                1,
> +                layout.align().try_into().unwrap(),
> +            )
> +            .cast::<u8>()
> +        }
> +    }
> +
> +    unsafe fn dealloc(&self, ptr: *mut u8, layout: Layout) {
> +        if layout.align() == 0 {
> +            g_free(ptr.cast::<_>())
> +        } else {
> +            g_aligned_free(ptr.cast::<_>())
> +        }
> +    }
> +}