On Mon, Mar 31, 2025 at 07:26:33PM -0500, saman wrote:
> This change introduces initial support for tracing and logging in Rust-based
> QEMU code. As an example, tracing and logging have been implemented in the
> pl011 device, which is written in Rust.
>
> - Updated `rust/wrapper.h` to include the `qemu/log.h` and `hw/char/trace.h`
> header.
> - Added log.rs to wrap `qemu_log_mask` and `qemu_log_mask_and_addr`
> - Modified `tracetool` scripts to move C function implementation from
> header to .c
> - Added log and trace in rust version of PL011 device
>
> Future enhancements could include generating idiomatic Rust APIs for tracing
> using the tracetool scripts
>
> Signed-off-by: saman <sa...@enumclass.cc>
> ---
> include/qemu/log-for-trace.h | 5 +--
> rust/hw/char/pl011/src/device.rs | 34 +++++++++++++++---
> rust/hw/char/pl011/src/registers.rs | 20 +++++++++++
> rust/qemu-api/meson.build | 1 +
> rust/qemu-api/src/lib.rs | 1 +
> rust/qemu-api/src/log.rs | 54 +++++++++++++++++++++++++++++
> rust/wrapper.h | 2 ++
> scripts/tracetool/format/c.py | 16 +++++++++
> scripts/tracetool/format/h.py | 11 ++----
> util/log.c | 5 +++
> 10 files changed, 131 insertions(+), 18 deletions(-)
> create mode 100644 rust/qemu-api/src/log.rs
>
> diff --git a/include/qemu/log-for-trace.h b/include/qemu/log-for-trace.h
> index d47c9cd446..ad5cd0dd24 100644
> --- a/include/qemu/log-for-trace.h
> +++ b/include/qemu/log-for-trace.h
> @@ -24,10 +24,7 @@ extern int qemu_loglevel;
> #define LOG_TRACE (1 << 15)
>
> /* Returns true if a bit is set in the current loglevel mask */
> -static inline bool qemu_loglevel_mask(int mask)
> -{
> - return (qemu_loglevel & mask) != 0;
> -}
> +bool qemu_loglevel_mask(int mask);
>
> /* main logging function */
> void G_GNUC_PRINTF(1, 2) qemu_log(const char *fmt, ...);
> diff --git a/rust/hw/char/pl011/src/device.rs
> b/rust/hw/char/pl011/src/device.rs
> index bf88e0b00a..42385a7bf6 100644
> --- a/rust/hw/char/pl011/src/device.rs
> +++ b/rust/hw/char/pl011/src/device.rs
> @@ -2,15 +2,21 @@
> // Author(s): Manos Pitsidianakis <manos.pitsidiana...@linaro.org>
> // SPDX-License-Identifier: GPL-2.0-or-later
>
> -use std::{ffi::CStr, mem::size_of, ptr::addr_of_mut};
> +use std::{
> + ffi::{CStr, CString},
> + mem::size_of,
> + ptr::addr_of_mut,
> +};
>
> use qemu_api::{
> chardev::{CharBackend, Chardev, Event},
> impl_vmstate_forward,
> irq::{IRQState, InterruptSource},
> + log::Mask,
> memory::{hwaddr, MemoryRegion, MemoryRegionOps, MemoryRegionOpsBuilder},
> prelude::*,
> qdev::{Clock, ClockEvent, DeviceImpl, DeviceState, Property, ResetType,
> ResettablePhasesImpl},
> + qemu_log_mask,
> qom::{ObjectImpl, Owned, ParentField},
> static_assert,
> sysbus::{SysBusDevice, SysBusDeviceImpl},
> @@ -298,7 +304,7 @@ pub(self) fn write(
> DMACR => {
> self.dmacr = value;
> if value & 3 > 0 {
> - // qemu_log_mask(LOG_UNIMP, "pl011: DMA not
> implemented\n");
> + qemu_log_mask!(Mask::log_unimp, "pl011: DMA not
> implemented\n");
> eprintln!("pl011: DMA not implemented");
> }
> }
> @@ -535,11 +541,21 @@ fn read(&self, offset: hwaddr, _size: u32) -> u64 {
> u64::from(device_id[(offset - 0xfe0) >> 2])
> }
> Err(_) => {
> - // qemu_log_mask(LOG_GUEST_ERROR, "pl011_read: Bad offset
> 0x%x\n", (int)offset);
> + qemu_log_mask!(
> + Mask::log_guest_error,
> + "pl011_read: Bad offset 0x%x\n",
> + offset as i32
> + );
> 0
> }
> Ok(field) => {
> + let regname = field.as_str();
> let (update_irq, result) =
> self.regs.borrow_mut().read(field);
> + let c_string = CString::new(regname).expect("CString::new
> failed");
> + let name_ptr = c_string.as_ptr();
> + unsafe {
> + qemu_api::bindings::trace_pl011_read(offset as u32,
> result, name_ptr);
> + }I didn't look closely to see whether CString::new(field.as_str()) boils down to allocating a new string or just pointing to a NUL-terminated string constant in the .rodata section of the binary, but this looks suspicious. It has the pattern: ...do work to produce trace event arguments... trace_foo(arg1, arg2, arg3); Tracing is intended to be as low-overhead as possible when trace events are disabled but compiled in. The work to produce event arguments must be done only when the trace event is enabled.
signature.asc
Description: PGP signature
