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-rw-r--r--rust/qemu-api/src/error.rs416
-rw-r--r--rust/qemu-api/src/lib.rs3
-rw-r--r--rust/qemu-api/src/qdev.rs12
3 files changed, 427 insertions, 4 deletions
diff --git a/rust/qemu-api/src/error.rs b/rust/qemu-api/src/error.rs
new file mode 100644
index 0000000..e114fc4
--- /dev/null
+++ b/rust/qemu-api/src/error.rs
@@ -0,0 +1,416 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+//! Error propagation for QEMU Rust code
+//!
+//! This module contains [`Error`], the bridge between Rust errors and
+//! [`Result`](std::result::Result)s and QEMU's C [`Error`](bindings::Error)
+//! struct.
+//!
+//! For FFI code, [`Error`] provides functions to simplify conversion between
+//! the Rust ([`Result<>`](std::result::Result)) and C (`Error**`) conventions:
+//!
+//! * [`ok_or_propagate`](crate::Error::ok_or_propagate),
+//! [`bool_or_propagate`](crate::Error::bool_or_propagate),
+//! [`ptr_or_propagate`](crate::Error::ptr_or_propagate) can be used to build
+//! a C return value while also propagating an error condition
+//!
+//! * [`err_or_else`](crate::Error::err_or_else) and
+//! [`err_or_unit`](crate::Error::err_or_unit) can be used to build a `Result`
+//!
+//! This module is most commonly used at the boundary between C and Rust code;
+//! other code will usually access it through the
+//! [`qemu_api::Result`](crate::Result) type alias, and will use the
+//! [`std::error::Error`] interface to let C errors participate in Rust's error
+//! handling functionality.
+//!
+//! Rust code can also create use this module to create an error object that
+//! will be passed up to C code, though in most cases this will be done
+//! transparently through the `?` operator. Errors can be constructed from a
+//! simple error string, from an [`anyhow::Error`] to pass any other Rust error
+//! type up to C code, or from a combination of the two.
+//!
+//! The third case, corresponding to [`Error::with_error`], is the only one that
+//! requires mentioning [`qemu_api::Error`](crate::Error) explicitly. Similar
+//! to how QEMU's C code handles errno values, the string and the
+//! `anyhow::Error` object will be concatenated with `:` as the separator.
+
+use std::{
+ borrow::Cow,
+ ffi::{c_char, c_int, c_void, CStr},
+ fmt::{self, Display},
+ panic, ptr,
+};
+
+use foreign::{prelude::*, OwnedPointer};
+
+use crate::bindings;
+
+pub type Result<T> = std::result::Result<T, Error>;
+
+#[derive(Debug)]
+pub struct Error {
+ msg: Option<Cow<'static, str>>,
+ /// Appends the print string of the error to the msg if not None
+ cause: Option<anyhow::Error>,
+ file: &'static str,
+ line: u32,
+}
+
+impl std::error::Error for Error {
+ fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
+ self.cause.as_ref().map(AsRef::as_ref)
+ }
+
+ #[allow(deprecated)]
+ fn description(&self) -> &str {
+ self.msg
+ .as_deref()
+ .or_else(|| self.cause.as_deref().map(std::error::Error::description))
+ .expect("no message nor cause?")
+ }
+}
+
+impl Display for Error {
+ fn fmt(&self, f: &mut fmt::Formatter) -> fmt::Result {
+ let mut prefix = "";
+ if let Some(ref msg) = self.msg {
+ write!(f, "{msg}")?;
+ prefix = ": ";
+ }
+ if let Some(ref cause) = self.cause {
+ write!(f, "{prefix}{cause}")?;
+ } else if prefix.is_empty() {
+ panic!("no message nor cause?");
+ }
+ Ok(())
+ }
+}
+
+impl From<String> for Error {
+ #[track_caller]
+ fn from(msg: String) -> Self {
+ let location = panic::Location::caller();
+ Error {
+ msg: Some(Cow::Owned(msg)),
+ cause: None,
+ file: location.file(),
+ line: location.line(),
+ }
+ }
+}
+
+impl From<&'static str> for Error {
+ #[track_caller]
+ fn from(msg: &'static str) -> Self {
+ let location = panic::Location::caller();
+ Error {
+ msg: Some(Cow::Borrowed(msg)),
+ cause: None,
+ file: location.file(),
+ line: location.line(),
+ }
+ }
+}
+
+impl From<anyhow::Error> for Error {
+ #[track_caller]
+ fn from(error: anyhow::Error) -> Self {
+ let location = panic::Location::caller();
+ Error {
+ msg: None,
+ cause: Some(error),
+ file: location.file(),
+ line: location.line(),
+ }
+ }
+}
+
+impl Error {
+ /// Create a new error, prepending `msg` to the
+ /// description of `cause`
+ #[track_caller]
+ pub fn with_error(msg: impl Into<Cow<'static, str>>, cause: impl Into<anyhow::Error>) -> Self {
+ let location = panic::Location::caller();
+ Error {
+ msg: Some(msg.into()),
+ cause: Some(cause.into()),
+ file: location.file(),
+ line: location.line(),
+ }
+ }
+
+ /// Consume a result, returning `false` if it is an error and
+ /// `true` if it is successful. The error is propagated into
+ /// `errp` like the C API `error_propagate` would do.
+ ///
+ /// # Safety
+ ///
+ /// `errp` must be a valid argument to `error_propagate`;
+ /// typically it is received from C code and need not be
+ /// checked further at the Rust↔C boundary.
+ pub unsafe fn bool_or_propagate(result: Result<()>, errp: *mut *mut bindings::Error) -> bool {
+ // SAFETY: caller guarantees errp is valid
+ unsafe { Self::ok_or_propagate(result, errp) }.is_some()
+ }
+
+ /// Consume a result, returning a `NULL` pointer if it is an error and
+ /// a C representation of the contents if it is successful. This is
+ /// similar to the C API `error_propagate`, but it panics if `*errp`
+ /// is not `NULL`.
+ ///
+ /// # Safety
+ ///
+ /// `errp` must be a valid argument to `error_propagate`;
+ /// typically it is received from C code and need not be
+ /// checked further at the Rust↔C boundary.
+ ///
+ /// See [`propagate`](Error::propagate) for more information.
+ #[must_use]
+ pub unsafe fn ptr_or_propagate<T: CloneToForeign>(
+ result: Result<T>,
+ errp: *mut *mut bindings::Error,
+ ) -> *mut T::Foreign {
+ // SAFETY: caller guarantees errp is valid
+ unsafe { Self::ok_or_propagate(result, errp) }.clone_to_foreign_ptr()
+ }
+
+ /// Consume a result in the same way as `self.ok()`, but also propagate
+ /// a possible error into `errp`. This is similar to the C API
+ /// `error_propagate`, but it panics if `*errp` is not `NULL`.
+ ///
+ /// # Safety
+ ///
+ /// `errp` must be a valid argument to `error_propagate`;
+ /// typically it is received from C code and need not be
+ /// checked further at the Rust↔C boundary.
+ ///
+ /// See [`propagate`](Error::propagate) for more information.
+ pub unsafe fn ok_or_propagate<T>(
+ result: Result<T>,
+ errp: *mut *mut bindings::Error,
+ ) -> Option<T> {
+ result.map_err(|err| unsafe { err.propagate(errp) }).ok()
+ }
+
+ /// Equivalent of the C function `error_propagate`. Fill `*errp`
+ /// with the information container in `self` if `errp` is not NULL;
+ /// then consume it.
+ ///
+ /// This is similar to the C API `error_propagate`, but it panics if
+ /// `*errp` is not `NULL`.
+ ///
+ /// # Safety
+ ///
+ /// `errp` must be a valid argument to `error_propagate`; it can be
+ /// `NULL` or it can point to any of:
+ /// * `error_abort`
+ /// * `error_fatal`
+ /// * a local variable of (C) type `Error *`
+ ///
+ /// Typically `errp` is received from C code and need not be
+ /// checked further at the Rust↔C boundary.
+ pub unsafe fn propagate(self, errp: *mut *mut bindings::Error) {
+ if errp.is_null() {
+ return;
+ }
+
+ // SAFETY: caller guarantees that errp and *errp are valid
+ unsafe {
+ assert_eq!(*errp, ptr::null_mut());
+ bindings::error_propagate(errp, self.clone_to_foreign_ptr());
+ }
+ }
+
+ /// Convert a C `Error*` into a Rust `Result`, using
+ /// `Ok(())` if `c_error` is NULL. Free the `Error*`.
+ ///
+ /// # Safety
+ ///
+ /// `c_error` must be `NULL` or valid; typically it was initialized
+ /// with `ptr::null_mut()` and passed by reference to a C function.
+ pub unsafe fn err_or_unit(c_error: *mut bindings::Error) -> Result<()> {
+ // SAFETY: caller guarantees c_error is valid
+ unsafe { Self::err_or_else(c_error, || ()) }
+ }
+
+ /// Convert a C `Error*` into a Rust `Result`, calling `f()` to
+ /// obtain an `Ok` value if `c_error` is NULL. Free the `Error*`.
+ ///
+ /// # Safety
+ ///
+ /// `c_error` must be `NULL` or point to a valid C [`struct
+ /// Error`](bindings::Error); typically it was initialized with
+ /// `ptr::null_mut()` and passed by reference to a C function.
+ pub unsafe fn err_or_else<T, F: FnOnce() -> T>(
+ c_error: *mut bindings::Error,
+ f: F,
+ ) -> Result<T> {
+ // SAFETY: caller guarantees c_error is valid
+ let err = unsafe { Option::<Self>::from_foreign(c_error) };
+ match err {
+ None => Ok(f()),
+ Some(err) => Err(err),
+ }
+ }
+}
+
+impl FreeForeign for Error {
+ type Foreign = bindings::Error;
+
+ unsafe fn free_foreign(p: *mut bindings::Error) {
+ // SAFETY: caller guarantees p is valid
+ unsafe {
+ bindings::error_free(p);
+ }
+ }
+}
+
+impl CloneToForeign for Error {
+ fn clone_to_foreign(&self) -> OwnedPointer<Self> {
+ // SAFETY: all arguments are controlled by this function
+ unsafe {
+ let err: *mut c_void = libc::malloc(std::mem::size_of::<bindings::Error>());
+ let err: &mut bindings::Error = &mut *err.cast();
+ *err = bindings::Error {
+ msg: format!("{self}").clone_to_foreign_ptr(),
+ err_class: bindings::ERROR_CLASS_GENERIC_ERROR,
+ src_len: self.file.len() as c_int,
+ src: self.file.as_ptr().cast::<c_char>(),
+ line: self.line as c_int,
+ func: ptr::null_mut(),
+ hint: ptr::null_mut(),
+ };
+ OwnedPointer::new(err)
+ }
+ }
+}
+
+impl FromForeign for Error {
+ unsafe fn cloned_from_foreign(c_error: *const bindings::Error) -> Self {
+ // SAFETY: caller guarantees c_error is valid
+ unsafe {
+ let error = &*c_error;
+ let file = if error.src_len < 0 {
+ // NUL-terminated
+ CStr::from_ptr(error.src).to_str()
+ } else {
+ // Can become str::from_utf8 with Rust 1.87.0
+ std::str::from_utf8(std::slice::from_raw_parts(
+ &*error.src.cast::<u8>(),
+ error.src_len as usize,
+ ))
+ };
+
+ Error {
+ msg: FromForeign::cloned_from_foreign(error.msg),
+ cause: None,
+ file: file.unwrap(),
+ line: error.line as u32,
+ }
+ }
+ }
+}
+
+#[cfg(test)]
+mod tests {
+ use std::ffi::CStr;
+
+ use anyhow::anyhow;
+ use foreign::OwnedPointer;
+
+ use super::*;
+ use crate::{assert_match, bindings};
+
+ #[track_caller]
+ fn error_for_test(msg: &CStr) -> OwnedPointer<Error> {
+ // SAFETY: all arguments are controlled by this function
+ let location = panic::Location::caller();
+ unsafe {
+ let err: *mut c_void = libc::malloc(std::mem::size_of::<bindings::Error>());
+ let err: &mut bindings::Error = &mut *err.cast();
+ *err = bindings::Error {
+ msg: msg.clone_to_foreign_ptr(),
+ err_class: bindings::ERROR_CLASS_GENERIC_ERROR,
+ src_len: location.file().len() as c_int,
+ src: location.file().as_ptr().cast::<c_char>(),
+ line: location.line() as c_int,
+ func: ptr::null_mut(),
+ hint: ptr::null_mut(),
+ };
+ OwnedPointer::new(err)
+ }
+ }
+
+ unsafe fn error_get_pretty<'a>(local_err: *mut bindings::Error) -> &'a CStr {
+ unsafe { CStr::from_ptr(bindings::error_get_pretty(local_err)) }
+ }
+
+ #[test]
+ #[allow(deprecated)]
+ fn test_description() {
+ use std::error::Error;
+
+ assert_eq!(super::Error::from("msg").description(), "msg");
+ assert_eq!(super::Error::from("msg".to_owned()).description(), "msg");
+ }
+
+ #[test]
+ fn test_display() {
+ assert_eq!(&*format!("{}", Error::from("msg")), "msg");
+ assert_eq!(&*format!("{}", Error::from("msg".to_owned())), "msg");
+ assert_eq!(&*format!("{}", Error::from(anyhow!("msg"))), "msg");
+
+ assert_eq!(
+ &*format!("{}", Error::with_error("msg", anyhow!("cause"))),
+ "msg: cause"
+ );
+ }
+
+ #[test]
+ fn test_bool_or_propagate() {
+ unsafe {
+ let mut local_err: *mut bindings::Error = ptr::null_mut();
+
+ assert!(Error::bool_or_propagate(Ok(()), &mut local_err));
+ assert_eq!(local_err, ptr::null_mut());
+
+ let my_err = Error::from("msg");
+ assert!(!Error::bool_or_propagate(Err(my_err), &mut local_err));
+ assert_ne!(local_err, ptr::null_mut());
+ assert_eq!(error_get_pretty(local_err), c"msg");
+ bindings::error_free(local_err);
+ }
+ }
+
+ #[test]
+ fn test_ptr_or_propagate() {
+ unsafe {
+ let mut local_err: *mut bindings::Error = ptr::null_mut();
+
+ let ret = Error::ptr_or_propagate(Ok("abc".to_owned()), &mut local_err);
+ assert_eq!(String::from_foreign(ret), "abc");
+ assert_eq!(local_err, ptr::null_mut());
+
+ let my_err = Error::from("msg");
+ assert_eq!(
+ Error::ptr_or_propagate(Err::<String, _>(my_err), &mut local_err),
+ ptr::null_mut()
+ );
+ assert_ne!(local_err, ptr::null_mut());
+ assert_eq!(error_get_pretty(local_err), c"msg");
+ bindings::error_free(local_err);
+ }
+ }
+
+ #[test]
+ fn test_err_or_unit() {
+ unsafe {
+ let result = Error::err_or_unit(ptr::null_mut());
+ assert_match!(result, Ok(()));
+
+ let err = error_for_test(c"msg");
+ let err = Error::err_or_unit(err.into_inner()).unwrap_err();
+ assert_eq!(&*format!("{err}"), "msg");
+ }
+ }
+}
diff --git a/rust/qemu-api/src/lib.rs b/rust/qemu-api/src/lib.rs
index 234a94e..93902fc 100644
--- a/rust/qemu-api/src/lib.rs
+++ b/rust/qemu-api/src/lib.rs
@@ -19,6 +19,7 @@ pub mod callbacks;
pub mod cell;
pub mod chardev;
pub mod errno;
+pub mod error;
pub mod irq;
pub mod memory;
pub mod module;
@@ -34,6 +35,8 @@ use std::{
ffi::c_void,
};
+pub use error::{Error, Result};
+
#[cfg(HAVE_GLIB_WITH_ALIGNED_ALLOC)]
extern "C" {
fn g_aligned_alloc0(
diff --git a/rust/qemu-api/src/qdev.rs b/rust/qemu-api/src/qdev.rs
index 1279d7a..0610959 100644
--- a/rust/qemu-api/src/qdev.rs
+++ b/rust/qemu-api/src/qdev.rs
@@ -12,10 +12,11 @@ use std::{
pub use bindings::{ClockEvent, DeviceClass, Property, ResetType};
use crate::{
- bindings::{self, qdev_init_gpio_in, qdev_init_gpio_out, Error, ResettableClass},
+ bindings::{self, qdev_init_gpio_in, qdev_init_gpio_out, ResettableClass},
callbacks::FnCall,
cell::{bql_locked, Opaque},
chardev::Chardev,
+ error::{Error, Result},
irq::InterruptSource,
prelude::*,
qom::{ObjectClass, ObjectImpl, Owned},
@@ -108,7 +109,7 @@ pub trait DeviceImpl: ObjectImpl + ResettablePhasesImpl + IsA<DeviceState> {
///
/// If not `None`, the parent class's `realize` method is overridden
/// with the function pointed to by `REALIZE`.
- const REALIZE: Option<fn(&Self)> = None;
+ const REALIZE: Option<fn(&Self) -> Result<()>> = None;
/// An array providing the properties that the user can set on the
/// device. Not a `const` because referencing statics in constants
@@ -134,10 +135,13 @@ pub trait DeviceImpl: ObjectImpl + ResettablePhasesImpl + IsA<DeviceState> {
/// readable/writeable from one thread at any time.
unsafe extern "C" fn rust_realize_fn<T: DeviceImpl>(
dev: *mut bindings::DeviceState,
- _errp: *mut *mut Error,
+ errp: *mut *mut bindings::Error,
) {
let state = NonNull::new(dev).unwrap().cast::<T>();
- T::REALIZE.unwrap()(unsafe { state.as_ref() });
+ let result = T::REALIZE.unwrap()(unsafe { state.as_ref() });
+ unsafe {
+ Error::ok_or_propagate(result, errp);
+ }
}
unsafe impl InterfaceType for ResettableClass {
generated by cgit v1.1 at 2025-06-07 10:51:34 +0000