Rust: Add pr_*_ratelimited

This commit adds equivalent pr_*_ratelimited to kernel crate.
They are macros that define a static local `ratelimit_state` and
uses Atomic and CAS to guard its initialization.
That `ratelimit_state` will be used later
by `___ratelimit()` to decide if to suppress the `printk` or not.

Because we use Atomic & CAS to help initialize `ratelimit_state`,
in concurrent situation some thread may reach `__ratelimit()`
before `ratelimit_state` is initialized. If that happens, we
call `printk` anyway.

This commit does not implement pr_debug_ratelimited since it's
special and way more complicated and deserves another dedicated
commit.

`printk_ratelimit` is also implemented in this commit

Signed-off-by: Fox Chen <[email protected]>

Author: foxhlchen

rust/helpers.c

@@ -12,6 +12,7 @@
 #include <linux/platform_device.h>
 #include <linux/security.h>
 #include <asm/io.h>
+#include <linux/printk.h>
 
 __noreturn void rust_helper_BUG(void)
 {
@@ -278,6 +279,13 @@ void *rust_helper_dev_get_drvdata(struct device *dev)
 }
 EXPORT_SYMBOL_GPL(rust_helper_dev_get_drvdata);
 
+void rust_helper_ratelimit_state_init(struct ratelimit_state *rs)
+{
+	static DEFINE_RATELIMIT_STATE(rs_tmpl, DEFAULT_RATELIMIT_INTERVAL, DEFAULT_RATELIMIT_BURST);
+	*rs = rs_tmpl;
+}
+EXPORT_SYMBOL_GPL(rust_helper_ratelimit_state_init);
+
 /* We use bindgen's --size_t-is-usize option to bind the C size_t type
  * as the Rust usize type, so we can use it in contexts where Rust
  * expects a usize like slice (array) indices. usize is defined to be

rust/kernel/prelude.rs

@@ -19,7 +19,11 @@ pub use macros::{module, module_misc_device};
 
 pub use super::build_assert;
 
-pub use super::{dbg, pr_alert, pr_crit, pr_debug, pr_emerg, pr_err, pr_info, pr_notice, pr_warn};
+pub use super::{
+    dbg, pr_alert, pr_alert_ratelimited, pr_crit, pr_crit_ratelimited, pr_debug, pr_emerg,
+    pr_emerg_ratelimited, pr_err, pr_err_ratelimited, pr_info, pr_info_ratelimited, pr_notice,
+    pr_notice_ratelimited, pr_warn, pr_warn_ratelimited, printk_ratelimit,
+};
 
 pub use super::static_assert;