rust: print: add `pr_cont!` macro

This level is a bit different from the rest since it does not
pass the module name to the `_printk()` call.

Thus add a new parameter to the general `print_macro!` to
handle it differently.
Co-developed-by: Adam Bratschi-Kaye <ark.email@gmail.com>
Signed-off-by: Adam Bratschi-Kaye <ark.email@gmail.com>
Co-developed-by: Wedson Almeida Filho <wedsonaf@gmail.com>
Signed-off-by: Wedson Almeida Filho <wedsonaf@gmail.com>
Co-developed-by: Gary Guo <gary@garyguo.net>
Signed-off-by: Gary Guo <gary@garyguo.net>
Reviewed-by: Wei Liu <wei.liu@kernel.org>
Reviewed-by: Sergio González Collado <sergio.collado@gmail.com>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

rust/kernel/print.rs

@@ -81,6 +81,7 @@ pub mod format_strings {
     pub static NOTICE: [u8; LENGTH] = generate(false, bindings::KERN_NOTICE);
     pub static INFO: [u8; LENGTH] = generate(false, bindings::KERN_INFO);
     pub static DEBUG: [u8; LENGTH] = generate(false, bindings::KERN_DEBUG);
+    pub static CONT: [u8; LENGTH] = generate(true, bindings::KERN_CONT);
 }
 
 /// Prints a message via the kernel's [`_printk`].
@@ -111,6 +112,26 @@ pub unsafe fn call_printk(
     }
 }
 
+/// Prints a message via the kernel's [`_printk`] for the `CONT` level.
+///
+/// Public but hidden since it should only be used from public macros.
+///
+/// [`_printk`]: ../../../../include/linux/printk.h
+#[doc(hidden)]
+#[cfg_attr(not(CONFIG_PRINTK), allow(unused_variables))]
+pub fn call_printk_cont(args: fmt::Arguments<'_>) {
+    // `_printk` does not seem to fail in any path.
+    //
+    // SAFETY: The format string is fixed.
+    #[cfg(CONFIG_PRINTK)]
+    unsafe {
+        bindings::_printk(
+            format_strings::CONT.as_ptr() as _,
+            &args as *const _ as *const c_void,
+        );
+    }
+}
+
 /// Performs formatting and forwards the string to [`call_printk`].
 ///
 /// Public but hidden since it should only be used from public macros.
@@ -120,7 +141,7 @@ pub unsafe fn call_printk(
 #[allow(clippy::crate_in_macro_def)]
 macro_rules! print_macro (
     // The non-continuation cases (most of them, e.g. `INFO`).
-    ($format_string:path, $($arg:tt)+) => (
+    ($format_string:path, false, $($arg:tt)+) => (
         // SAFETY: This hidden macro should only be called by the documented
         // printing macros which ensure the format string is one of the fixed
         // ones. All `__LOG_PREFIX`s are null-terminated as they are generated
@@ -134,6 +155,13 @@ macro_rules! print_macro (
             );
         }
     );
+
+    // The `CONT` case.
+    ($format_string:path, true, $($arg:tt)+) => (
+        $crate::print::call_printk_cont(
+            format_args!($($arg)+),
+        );
+    );
 );
 
 /// Stub for doctests
@@ -174,7 +202,7 @@ macro_rules! print_macro (
 #[macro_export]
 macro_rules! pr_emerg (
     ($($arg:tt)*) => (
-        $crate::print_macro!($crate::print::format_strings::EMERG, $($arg)*)
+        $crate::print_macro!($crate::print::format_strings::EMERG, false, $($arg)*)
     )
 );
 
@@ -198,7 +226,7 @@ macro_rules! pr_emerg (
 #[macro_export]
 macro_rules! pr_alert (
     ($($arg:tt)*) => (
-        $crate::print_macro!($crate::print::format_strings::ALERT, $($arg)*)
+        $crate::print_macro!($crate::print::format_strings::ALERT, false, $($arg)*)
     )
 );
 
@@ -222,7 +250,7 @@ macro_rules! pr_alert (
 #[macro_export]
 macro_rules! pr_crit (
     ($($arg:tt)*) => (
-        $crate::print_macro!($crate::print::format_strings::CRIT, $($arg)*)
+        $crate::print_macro!($crate::print::format_strings::CRIT, false, $($arg)*)
     )
 );
 
@@ -246,7 +274,7 @@ macro_rules! pr_crit (
 #[macro_export]
 macro_rules! pr_err (
     ($($arg:tt)*) => (
-        $crate::print_macro!($crate::print::format_strings::ERR, $($arg)*)
+        $crate::print_macro!($crate::print::format_strings::ERR, false, $($arg)*)
     )
 );
 
@@ -270,7 +298,7 @@ macro_rules! pr_err (
 #[macro_export]
 macro_rules! pr_warn (
     ($($arg:tt)*) => (
-        $crate::print_macro!($crate::print::format_strings::WARNING, $($arg)*)
+        $crate::print_macro!($crate::print::format_strings::WARNING, false, $($arg)*)
     )
 );
 
@@ -294,7 +322,7 @@ macro_rules! pr_warn (
 #[macro_export]
 macro_rules! pr_notice (
     ($($arg:tt)*) => (
-        $crate::print_macro!($crate::print::format_strings::NOTICE, $($arg)*)
+        $crate::print_macro!($crate::print::format_strings::NOTICE, false, $($arg)*)
     )
 );
 
@@ -319,7 +347,7 @@ macro_rules! pr_notice (
 #[doc(alias = "print")]
 macro_rules! pr_info (
     ($($arg:tt)*) => (
-        $crate::print_macro!($crate::print::format_strings::INFO, $($arg)*)
+        $crate::print_macro!($crate::print::format_strings::INFO, false, $($arg)*)
     )
 );
 
@@ -346,7 +374,33 @@ macro_rules! pr_info (
 macro_rules! pr_debug (
     ($($arg:tt)*) => (
         if cfg!(debug_assertions) {
-            $crate::print_macro!($crate::print::format_strings::DEBUG, $($arg)*)
+            $crate::print_macro!($crate::print::format_strings::DEBUG, false, $($arg)*)
         }
     )
 );
+
+/// Continues a previous log message in the same line.
+///
+/// Use only when continuing a previous `pr_*!` macro (e.g. [`pr_info!`]).
+///
+/// Equivalent to the kernel's [`pr_cont`] macro.
+///
+/// Mimics the interface of [`std::print!`]. See [`core::fmt`] and
+/// `alloc::format!` for information about the formatting syntax.
+///
+/// [`pr_cont`]: https://www.kernel.org/doc/html/latest/core-api/printk-basics.html#c.pr_cont
+/// [`std::print!`]: https://doc.rust-lang.org/std/macro.print.html
+///
+/// # Examples
+///
+/// ```
+/// # use kernel::pr_cont;
+/// pr_info!("hello");
+/// pr_cont!(" {}\n", "there");
+/// ```
+#[macro_export]
+macro_rules! pr_cont (
+    ($($arg:tt)*) => (
+        $crate::print_macro!($crate::print::format_strings::CONT, true, $($arg)*)
+    )
+);