From dab63b8a710c2c489276d60d51e21e82b91a92f5 Mon Sep 17 00:00:00 2001 From: Manos Pitsidianakis Date: Thu, 3 Jul 2025 17:20:22 +0300 Subject: rust/bindings: allow unnecessary_transmutes (1.88) This is a new lint introduced in Rust 1.88. It does not affect compilation when using a previous version or our MSRV, 1.77. But with 1.88 compilation fails because we deny all warnings: error: unnecessary transmute --> rust/qemu-api/libqemu_api.rlib.p/structured/bindings.inc.rs:729:18 | 729 | unsafe { ::std::mem::transmute(self._bitfield_1.get(0usize, 24u8) as u32) } | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ help: replace this with: `u32::cast_signed(self._bitfield_1.get(0usize, 24u8) as u32)` | = note: `-D unnecessary-transmutes` implied by `-D warnings` = help: to override `-D warnings` add `#[allow(unnecessary_transmutes)]` Allow this lint, which even though it does not exist in previous versions, it works because we allow for `unknown_lints` in rust/Cargo.toml. Signed-off-by: Manos Pitsidianakis Link: https://lore.kernel.org/r/20250703-rust_bindings_allow_unnecessary_transmutes-v1-1-692ca210d331@linaro.org Signed-off-by: Paolo Bonzini --- rust/qemu-api/src/bindings.rs | 1 + 1 file changed, 1 insertion(+) (limited to 'rust/qemu-api/src') diff --git a/rust/qemu-api/src/bindings.rs b/rust/qemu-api/src/bindings.rs index 057de4b..3cdad0f 100644 --- a/rust/qemu-api/src/bindings.rs +++ b/rust/qemu-api/src/bindings.rs @@ -6,6 +6,7 @@ non_camel_case_types, non_snake_case, non_upper_case_globals, + unnecessary_transmutes, unsafe_op_in_unsafe_fn, clippy::pedantic, clippy::restriction, -- cgit v1.1 From ed7f6da282e263403badb507b2532f51f8ed31cf Mon Sep 17 00:00:00 2001 From: Paolo Bonzini Date: Wed, 11 Jun 2025 10:16:10 +0200 Subject: rust/qemu-api: log: implement io::Write This makes it possible to lock the log file; it also makes log_mask_ln! not allocate memory when logging a constant string. Reviewed-by: Zhao Liu Reviewed-by: Manos Pitsidianakis Signed-off-by: Paolo Bonzini --- rust/qemu-api/src/log.rs | 92 +++++++++++++++++++++++++++++++++++++++++++----- 1 file changed, 84 insertions(+), 8 deletions(-) (limited to 'rust/qemu-api/src') diff --git a/rust/qemu-api/src/log.rs b/rust/qemu-api/src/log.rs index d6c3d6c..a441b8c 100644 --- a/rust/qemu-api/src/log.rs +++ b/rust/qemu-api/src/log.rs @@ -3,6 +3,13 @@ //! Bindings for QEMU's logging infrastructure +use std::{ + io::{self, Write}, + ptr::NonNull, +}; + +use crate::{bindings, errno}; + #[repr(u32)] /// Represents specific error categories within QEMU's logging system. /// @@ -11,11 +18,82 @@ pub enum Log { /// Log invalid access caused by the guest. /// Corresponds to `LOG_GUEST_ERROR` in the C implementation. - GuestError = crate::bindings::LOG_GUEST_ERROR, + GuestError = bindings::LOG_GUEST_ERROR, /// Log guest access of unimplemented functionality. /// Corresponds to `LOG_UNIMP` in the C implementation. - Unimp = crate::bindings::LOG_UNIMP, + Unimp = bindings::LOG_UNIMP, +} + +/// A RAII guard for QEMU's logging infrastructure. Creating the guard +/// locks the log file, and dropping it (letting it go out of scope) unlocks +/// the file. +/// +/// As long as the guard lives, it can be written to using [`std::io::Write`]. +/// +/// The locking is recursive, therefore owning a guard does not prevent +/// using [`log_mask_ln!()`](crate::log_mask_ln). +pub struct LogGuard(NonNull); + +impl LogGuard { + /// Return a RAII guard that writes to QEMU's logging infrastructure. + /// The log file is locked while the guard exists, ensuring that there + /// is no tearing of the messages. + /// + /// Return `None` if the log file is closed and could not be opened. + /// Do *not* use `unwrap()` on the result; failure can be handled simply + /// by not logging anything. + /// + /// # Examples + /// + /// ``` + /// # use qemu_api::log::LogGuard; + /// # use std::io::Write; + /// if let Some(mut log) = LogGuard::new() { + /// writeln!(log, "test"); + /// } + /// ``` + pub fn new() -> Option { + let f = unsafe { bindings::qemu_log_trylock() }.cast(); + NonNull::new(f).map(Self) + } + + /// Writes a formatted string into the log, returning any error encountered. + /// + /// This method is primarily used by the + /// [`log_mask_ln!()`](crate::log_mask_ln) macro, and it is rare for it + /// to be called explicitly. It is public because it is the only way to + /// examine the error, which `log_mask_ln!()` ignores + /// + /// Unlike `log_mask_ln!()`, it does *not* append a newline at the end. + pub fn log_fmt(args: std::fmt::Arguments) -> io::Result<()> { + if let Some(mut log) = Self::new() { + log.write_fmt(args)?; + } + Ok(()) + } +} + +impl Write for LogGuard { + fn write(&mut self, bytes: &[u8]) -> io::Result { + let ret = unsafe { + bindings::rust_fwrite(bytes.as_ptr().cast(), 1, bytes.len(), self.0.as_ptr()) + }; + errno::into_io_result(ret) + } + + fn flush(&mut self) -> io::Result<()> { + // Do nothing, dropping the guard takes care of flushing + Ok(()) + } +} + +impl Drop for LogGuard { + fn drop(&mut self) { + unsafe { + bindings::qemu_log_unlock(self.0.as_ptr()); + } + } } /// A macro to log messages conditionally based on a provided mask. @@ -24,6 +102,8 @@ pub enum Log { /// log level and, if so, formats and logs the message. It is the Rust /// counterpart of the `qemu_log_mask()` macro in the C implementation. /// +/// Errors from writing to the log are ignored. +/// /// # Parameters /// /// - `$mask`: A log level mask. This should be a variant of the `Log` enum. @@ -62,12 +142,8 @@ macro_rules! log_mask_ln { if unsafe { (::qemu_api::bindings::qemu_loglevel & ($mask as std::os::raw::c_int)) != 0 } { - let formatted_string = format!("{}\n", format_args!($fmt $($args)*)); - let c_string = std::ffi::CString::new(formatted_string).unwrap(); - - unsafe { - ::qemu_api::bindings::qemu_log(c_string.as_ptr()); - } + _ = ::qemu_api::log::LogGuard::log_fmt( + format_args!("{}\n", format_args!($fmt $($args)*))); } }}; } -- cgit v1.1