From: Gary Guo <gary@xxxxxxxxxxx>
This patch adds a format specifier `%pA` to `vsprintf` which formats
a pointer as `core::fmt::Arguments`. Doing so allows us to directly
format to the internal buffer of `printf`, so we do not have to use
a temporary buffer on the stack to pre-assemble the message on
the Rust side.
This specifier is intended only to be used from Rust and not for C, so
`checkpatch.pl` is intentionally unchanged to catch any misuse.
Co-developed-by: Alex Gaynor <alex.gaynor@xxxxxxxxx>
Signed-off-by: Alex Gaynor <alex.gaynor@xxxxxxxxx>
Co-developed-by: Wedson Almeida Filho <wedsonaf@xxxxxxxxxx>
Signed-off-by: Wedson Almeida Filho <wedsonaf@xxxxxxxxxx>
Signed-off-by: Gary Guo <gary@xxxxxxxxxxx>
Co-developed-by: Miguel Ojeda <ojeda@xxxxxxxxxx>
Signed-off-by: Miguel Ojeda <ojeda@xxxxxxxxxx>
---
lib/rust.h | 14 ++++++++++++++
lib/vsprintf.c | 7 +++++++
2 files changed, 21 insertions(+)
create mode 100644 lib/rust.h
diff --git a/lib/rust.h b/lib/rust.h
new file mode 100644
index 000000000000..9cf0b102b496
--- /dev/null
+++ b/lib/rust.h
@@ -0,0 +1,14 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+#ifndef _LIB_RUST_H
+#define _LIB_RUST_H
+
+#ifdef CONFIG_RUST
+char *rust_fmt_argument(char* buf, char* end, void *ptr);
+#else
+static inline char *rust_fmt_argument(char* buf, char* end, void *ptr)
+{
+ return NULL;
+}
+#endif
+
+#endif /* _LIB_RUST_H */
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 58d5e567f836..84a1c9496e6e 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c
@@ -52,6 +52,7 @@
#include <linux/string_helpers.h>
#include "kstrtox.h"
+#include "rust.h"
static noinline unsigned long long simple_strntoull(const char *startp, size_t max_chars, char **endp, unsigned int base)
{
@@ -2388,6 +2389,10 @@ early_param("no_hash_pointers", no_hash_pointers_enable);
*
* Note: The default behaviour (unadorned %p) is to hash the address,
* rendering it useful as a unique identifier.
+ *
+ * There is also a '%pA' format specifier, but it is only intended to be used
+ * from Rust code to format core::fmt::Arguments. Do *not* use it from C.
+ * See rust/kernel/print.rs for details.
*/
static noinline_for_stack
char *pointer(const char *fmt, char *buf, char *end, void *ptr,
@@ -2460,6 +2465,8 @@ char *pointer(const char *fmt, char *buf, char *end, void *ptr,
return device_node_string(buf, end, ptr, spec, fmt + 1);
case 'f':
return fwnode_string(buf, end, ptr, spec, fmt + 1);
+ case 'A':
+ return rust_fmt_argument(buf, end, ptr);
case 'x':
return pointer_string(buf, end, ptr, spec);
case 'e':
--
2.34.1
