rust: error: `impl Debug` for `Error` with `errname()` integration

Integrate the `Error` type with `errname()` by providing a new
`name()` method.

Then, implement `Debug` for the type using the new method.

[ Miguel: under `CONFIG_SYMBOLIC_ERRNAME=n`, `errname()` is a
  `static inline`, so added a helper to support that case,
  like we had in the `rust` branch. Also moved `#include` up
  and reworded commit message for clarity. ]

Co-developed-by: Wedson Almeida Filho <walmeida@microsoft.com>
Signed-off-by: Wedson Almeida Filho <walmeida@microsoft.com>
Co-developed-by: Sven Van Asbroeck <thesven73@gmail.com>
Signed-off-by: Sven Van Asbroeck <thesven73@gmail.com>
Signed-off-by: Gary Guo <gary@garyguo.net>
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Reviewed-by: Martin Rodriguez Reboredo <yakoyoku@gmail.com>
Link: https://lore.kernel.org/r/20230531174450.3733220-1-aliceryhl@google.com
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>

1 files changed, 7 insertions, 0 deletions

diff --git a/rust/helpers.c b/rust/helpers.c
index 81e80261d597..bb594da56137 100644
--- a/rust/helpers.c
+++ b/rust/helpers.c
@@ -21,6 +21,7 @@
 #include <linux/bug.h>
 #include <linux/build_bug.h>
 #include <linux/err.h>
+#include <linux/errname.h>
 #include <linux/refcount.h>
 #include <linux/mutex.h>
 #include <linux/spinlock.h>
@@ -110,6 +111,12 @@ long rust_helper_PTR_ERR(__force const void *ptr)
 }
 EXPORT_SYMBOL_GPL(rust_helper_PTR_ERR);
 
+const char *rust_helper_errname(int err)
+{
+	return errname(err);
+}
+EXPORT_SYMBOL_GPL(rust_helper_errname);
+
 struct task_struct *rust_helper_get_current(void)
 {
 	return current;