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| author | Stefan Hajnoczi <stefanha@redhat.com> | 2025-06-21 10:00:46 -0400 |
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| committer | Stefan Hajnoczi <stefanha@redhat.com> | 2025-06-21 10:00:46 -0400 |
| commit | 43ba160cb4bbb193560eb0d2d7decc4b5fc599fe (patch) | |
| tree | 2a12561d9da7a4bee1ad5279fe8dd10f4432d74a /rust/qemu-api/src/uninit.rs | |
| parent | 6e1571533fd92bec67e5ab9b1dd1e15032925757 (diff) | |
| parent | 40da501d8989913935660dc24953ece02c9e98b8 (diff) | |
| download | focaccia-qemu-43ba160cb4bbb193560eb0d2d7decc4b5fc599fe.tar.gz focaccia-qemu-43ba160cb4bbb193560eb0d2d7decc4b5fc599fe.zip | |
Merge tag 'for-upstream' of https://gitlab.com/bonzini/qemu into staging
* cleanups for distributed DTB files * scripts/meson-buildoptions: Sort coroutine_backend choices lexicographically * rust/qemu-api: Add initial logging support : rust: pl011: Implement logging * target/i386: fix Win98 * meson: cleanup win32 library detection * rust: safe(r) instance_init * rust: prepare for multiple bindgen invocations * rust: fix new warning * target/i386: Warn about why CPUID_EXT_PDCM is not available * target/i386: small TDX fixes and clarifications * target/i386: support for TDX quote generation # -----BEGIN PGP SIGNATURE----- # # iQFIBAABCgAyFiEE8TM4V0tmI4mGbHaCv/vSX3jHroMFAmhVRWsUHHBib256aW5p # QHJlZGhhdC5jb20ACgkQv/vSX3jHroOyDQf/YqX2jTZbC4jXdHZT6YiDlYPX9MPx # emFX0S+30X5zNuGYUQufKHEJWshMtklB1seUTQathOPaNeCFK13lY4m1CRbhbrMs # 3iG4ZQf5V+YTuB+JuE8KfclJeAPXDTnIc2uJbtXErIsPBeEGYZelFLnO5HLiMsY3 # iX9S2hSkjvjlikFv/m9ebg9SMP3+/ZunQMZxsDwgb7U3uqtuZagCJTWz0xTHHHxV # Ko5OPA0kIydm0NnlHs2DsF1mivmYSSIfBnxg4KXgmJxd3gNGd9SemBQOwYU68x0T # R3GzI6NLgdP/3mKOsxpM6hFiXBp84eT6zghpdqK5zQFidgz935EXP5WjvQ== # =ttQr # -----END PGP SIGNATURE----- # gpg: Signature made Fri 20 Jun 2025 07:26:35 EDT # gpg: using RSA key F13338574B662389866C7682BFFBD25F78C7AE83 # gpg: issuer "pbonzini@redhat.com" # gpg: Good signature from "Paolo Bonzini <bonzini@gnu.org>" [full] # gpg: aka "Paolo Bonzini <pbonzini@redhat.com>" [full] # Primary key fingerprint: 46F5 9FBD 57D6 12E7 BFD4 E2F7 7E15 100C CD36 69B1 # Subkey fingerprint: F133 3857 4B66 2389 866C 7682 BFFB D25F 78C7 AE83 * tag 'for-upstream' of https://gitlab.com/bonzini/qemu: (24 commits) i386/tdx: handle TDG.VP.VMCALL<GetQuote> i386/tdx: handle TDG.VP.VMCALL<GetTdVmCallInfo> update Linux headers to v6.16-rc3 i386/tdx: Clarify the error message of mrconfigid/mrowner/mrownerconfig i386/tdx: Fix the typo of the comment of struct TdxGuest i386/cpu: Rename enable_cpuid_0x1f to force_cpuid_0x1f i386/tdx: Error and exit when named cpu model is requested i386/cpu: Warn about why CPUID_EXT_PDCM is not available i386/cpu: Move adjustment of CPUID_EXT_PDCM before feature_dependencies[] check rust: hpet: fix new warning rust: pl011: Add missing logging to match C version rust: pl011: Implement logging rust/qemu-api: Add initial logging support based on C API rust: move rust.bindgen to qemu-api crate rust: prepare variable definitions for multiple bindgen invocations rust: qom: change instance_init to take a ParentInit<> rust: qom: make ParentInit lifetime-invariant rust: qom: introduce ParentInit rust: hpet: fully initialize object during instance_init rust: qemu_api: introduce MaybeUninit field projection ... Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>
Diffstat (limited to 'rust/qemu-api/src/uninit.rs')
| -rw-r--r-- | rust/qemu-api/src/uninit.rs | 85 |
1 files changed, 85 insertions, 0 deletions
diff --git a/rust/qemu-api/src/uninit.rs b/rust/qemu-api/src/uninit.rs new file mode 100644 index 0000000000..04123b4ae9 --- /dev/null +++ b/rust/qemu-api/src/uninit.rs @@ -0,0 +1,85 @@ +//! Access fields of a [`MaybeUninit`] + +use std::{ + mem::MaybeUninit, + ops::{Deref, DerefMut}, +}; + +pub struct MaybeUninitField<'a, T, U> { + parent: &'a mut MaybeUninit<T>, + child: *mut U, +} + +impl<'a, T, U> MaybeUninitField<'a, T, U> { + #[doc(hidden)] + pub fn new(parent: &'a mut MaybeUninit<T>, child: *mut U) -> Self { + MaybeUninitField { parent, child } + } + + /// Return a constant pointer to the containing object of the field. + /// + /// Because the `MaybeUninitField` remembers the containing object, + /// it is possible to use it in foreign APIs that initialize the + /// child. + pub fn parent(f: &Self) -> *const T { + f.parent.as_ptr() + } + + /// Return a mutable pointer to the containing object. + /// + /// Because the `MaybeUninitField` remembers the containing object, + /// it is possible to use it in foreign APIs that initialize the + /// child. + pub fn parent_mut(f: &mut Self) -> *mut T { + f.parent.as_mut_ptr() + } +} + +impl<'a, T, U> Deref for MaybeUninitField<'a, T, U> { + type Target = MaybeUninit<U>; + + fn deref(&self) -> &MaybeUninit<U> { + // SAFETY: self.child was obtained by dereferencing a valid mutable + // reference; the content of the memory may be invalid or uninitialized + // but MaybeUninit<_> makes no assumption on it + unsafe { &*(self.child.cast()) } + } +} + +impl<'a, T, U> DerefMut for MaybeUninitField<'a, T, U> { + fn deref_mut(&mut self) -> &mut MaybeUninit<U> { + // SAFETY: self.child was obtained by dereferencing a valid mutable + // reference; the content of the memory may be invalid or uninitialized + // but MaybeUninit<_> makes no assumption on it + unsafe { &mut *(self.child.cast()) } + } +} + +/// ``` +/// #[derive(Debug)] +/// struct S { +/// x: u32, +/// y: u32, +/// } +/// +/// # use std::mem::MaybeUninit; +/// # use qemu_api::{assert_match, uninit_field_mut}; +/// +/// let mut s: MaybeUninit<S> = MaybeUninit::zeroed(); +/// uninit_field_mut!(s, x).write(5); +/// let s = unsafe { s.assume_init() }; +/// assert_match!(s, S { x: 5, y: 0 }); +/// ``` +#[macro_export] +macro_rules! uninit_field_mut { + ($container:expr, $($field:tt)+) => {{ + let container__: &mut ::std::mem::MaybeUninit<_> = &mut $container; + let container_ptr__ = container__.as_mut_ptr(); + + // SAFETY: the container is not used directly, only through a MaybeUninit<>, + // so the safety is delegated to the caller and to final invocation of + // assume_init() + let target__ = unsafe { std::ptr::addr_of_mut!((*container_ptr__).$($field)+) }; + $crate::uninit::MaybeUninitField::new(container__, target__) + }}; +} |