[PATCH v9 14/27] vsprintf: add new `%pA` format specifier
From: Miguel Ojeda <ojeda@kernel.org>
Date: 2022-08-05 15:46:08
Also in:
linux-fsdevel, linux-patches, lkml, rust-for-linux
Subsystem:
documentation, library code, the rest, vsprintf · Maintainers:
Jonathan Corbet, Andrew Morton, Linus Torvalds, Petr Mladek, Steven Rostedt
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. Reviewed-by: Kees Cook <redacted> Acked-by: Petr Mladek <pmladek@suse.com> Co-developed-by: Alex Gaynor <redacted> Signed-off-by: Alex Gaynor <redacted> Co-developed-by: Wedson Almeida Filho <redacted> Signed-off-by: Wedson Almeida Filho <redacted> Signed-off-by: Gary Guo <gary@garyguo.net> Co-developed-by: Miguel Ojeda <ojeda@kernel.org> Signed-off-by: Miguel Ojeda <ojeda@kernel.org> --- Documentation/core-api/printk-formats.rst | 10 ++++++++++ lib/vsprintf.c | 13 +++++++++++++ 2 files changed, 23 insertions(+)
diff --git a/Documentation/core-api/printk-formats.rst b/Documentation/core-api/printk-formats.rst
index 5e89497ba314..dbe1aacc79d0 100644
--- a/Documentation/core-api/printk-formats.rst
+++ b/Documentation/core-api/printk-formats.rst@@ -625,6 +625,16 @@ Examples:: %p4cc Y10 little-endian (0x20303159) %p4cc NV12 big-endian (0xb231564e) +Rust +---- + +:: + + %pA + +Only intended to be used from Rust code to format ``core::fmt::Arguments``. +Do *not* use it from C. + Thanks ======
diff --git a/lib/vsprintf.c b/lib/vsprintf.c
index 3c1853a9d1c0..c414a8d9f1ea 100644
--- a/lib/vsprintf.c
+++ b/lib/vsprintf.c@@ -2246,6 +2246,9 @@ int __init no_hash_pointers_enable(char *str) } early_param("no_hash_pointers", no_hash_pointers_enable); +/* Used for Rust formatting ('%pA'). */ +char *rust_fmt_argument(char *buf, char *end, void *ptr); + /* * Show a '%p' thing. A kernel extension is that the '%p' is followed * by an extra set of alphanumeric characters that are extended format
@@ -2372,6 +2375,10 @@ 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,
@@ -2444,6 +2451,12 @@ 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': + if (!IS_ENABLED(CONFIG_RUST)) { + WARN_ONCE(1, "Please remove %%pA from non-Rust code\n"); + return error_string(buf, end, "(%pA?)", spec); + } + return rust_fmt_argument(buf, end, ptr); case 'x': return pointer_string(buf, end, ptr, spec); case 'e':
--
2.37.1