Re: [PATCH v1 03/28] rust: print: add `pr_cont!` macro

["Sergio González Collado" <sergio.collado@gmail.com>]

On Thu, 10 Nov 2022 at 11:43, Miguel Ojeda <ojeda@kernel.org> wrote:
>
> 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>
> Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
> ---
>  rust/kernel/print.rs | 72 ++++++++++++++++++++++++++++++++++++++------
>  1 file changed, 63 insertions(+), 9 deletions(-)
>
> diff --git a/rust/kernel/print.rs b/rust/kernel/print.rs
> index 694f51c6da5c..29bf9c2e8aee 100644
> --- a/rust/kernel/print.rs
> +++ b/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)*)
> +    )
> +);
> --
> 2.38.1
>
Reviewed-by: Sergio González Collado <sergio.collado@gmail.com>