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From: Miguel Ojeda <ojeda@kernel.org>
To: Linus Torvalds <torvalds@linux-foundation.org>,
	Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Cc: rust-for-linux@vger.kernel.org, linux-kbuild@vger.kernel.org,
	linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org,
	Miguel Ojeda <ojeda@kernel.org>, Gary Guo <gary@garyguo.net>,
	Alex Gaynor <alex.gaynor@gmail.com>,
	Wedson Almeida Filho <wedsonaf@google.com>
Subject: [PATCH v3 11/19] vsprintf: add new `%pA` format specifier
Date: Mon, 17 Jan 2022 06:33:41 +0100	[thread overview]
Message-ID: <20220117053349.6804-12-ojeda@kernel.org> (raw)
In-Reply-To: <20220117053349.6804-1-ojeda@kernel.org>

From: Gary Guo <gary@garyguo.net>

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@gmail.com>
Signed-off-by: Alex Gaynor <alex.gaynor@gmail.com>
Co-developed-by: Wedson Almeida Filho <wedsonaf@google.com>
Signed-off-by: Wedson Almeida Filho <wedsonaf@google.com>
Signed-off-by: Gary Guo <gary@garyguo.net>
Co-developed-by: Miguel Ojeda <ojeda@kernel.org>
Signed-off-by: Miguel Ojeda <ojeda@kernel.org>
---
 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


  parent reply	other threads:[~2022-01-17  5:35 UTC|newest]

Thread overview: 19+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2022-01-17  5:33 [PATCH v3 00/19] Rust support Miguel Ojeda
2022-01-17  5:33 ` [PATCH v3 01/19] kallsyms: support "big" kernel symbols Miguel Ojeda
2022-01-17  5:33 ` [PATCH v3 02/19] kallsyms: increase maximum kernel symbol length to 512 Miguel Ojeda
2022-01-17  5:33 ` [PATCH v3 03/19] kallsyms: use the correct buffer size for symbols Miguel Ojeda
2022-01-17  5:33 ` [PATCH v3 04/19] rust: add C helpers Miguel Ojeda
2022-01-17  5:33 ` [PATCH v3 05/19] rust: add `compiler_builtins` crate Miguel Ojeda
2022-01-17  5:33 ` [PATCH v3 07/19] rust: add `build_error` crate Miguel Ojeda
2022-01-17  5:33 ` [PATCH v3 08/19] rust: add `macros` crate Miguel Ojeda
2022-01-17  5:33 ` [PATCH v3 10/19] rust: export generated symbols Miguel Ojeda
2022-01-17  5:33 ` Miguel Ojeda [this message]
2022-01-17  5:33 ` [PATCH v3 12/19] scripts: add `generate_rust_analyzer.py` Miguel Ojeda
2022-01-17  5:33 ` [PATCH v3 13/19] scripts: decode_stacktrace: demangle Rust symbols Miguel Ojeda
2022-01-17  5:33 ` [PATCH v3 14/19] docs: add Rust documentation Miguel Ojeda
2022-01-18 22:33   ` Jonathan Corbet
2022-01-19 13:58     ` Miguel Ojeda
2022-01-17  5:33 ` [PATCH v3 15/19] Kbuild: add Rust support Miguel Ojeda
2022-01-17  5:33 ` [PATCH v3 16/19] samples: add Rust examples Miguel Ojeda
2022-01-17  5:33 ` [PATCH v3 17/19] MAINTAINERS: Rust Miguel Ojeda
2022-01-17  5:33 ` [RFC PATCH v3 18/19] drivers: gpio: PrimeCell PL061 in Rust Miguel Ojeda

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