tracetool/syslog: add Rust support

The syslog backend needs the syslog function from libc and the LOG_INFO enum
value; they are re-exported as "::trace::syslog" and "::trace::LOG_INFO"
so that device crates do not all have to add the libc dependency, but
otherwise there is nothing special.

Signed-off-by: Tanish Desai <tanishdesai37@gmail.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20250929154938.594389-17-pbonzini@redhat.com>
Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com>

rust/Cargo.lock

@@ -262,6 +262,9 @@ dependencies = [
 [[package]]
 name = "trace"
 version = "0.1.0"
+dependencies = [
+ "libc",
+]
 
 [[package]]
 name = "unicode-ident"

rust/trace/Cargo.toml

@@ -12,5 +12,8 @@ license.workspace = true
 repository.workspace = true
 rust-version.workspace = true
 
+[dependencies]
+libc = { workspace = true }
+
 [lints]
 workspace = true

rust/trace/src/lib.rs

@@ -3,6 +3,10 @@
 //! This crate provides macros that aid in using QEMU's tracepoint
 //! functionality.
 
+#[doc(hidden)]
+/// Re-exported item to avoid adding libc as a dependency everywhere.
+pub use libc::{syslog, LOG_INFO};
+
 #[macro_export]
 /// Define the trace-points from the named directory (which should have slashes
 /// replaced by underscore characters) as functions in a module called `trace`.