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From: Gary Guo <gary@garyguo.net> maillist inclusion category: feature bugzilla: https://gitee.com/openeuler/kernel/issues/I5J75G CVE: NA Reference: https://lore.kernel.org/rust-for-linux/CANiq72nDcJLSB3pLhkdqGdLitfmqqCUVVfkY... -------------------------------- 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 <keescook@chromium.org> Acked-by: Petr Mladek <pmladek@suse.com> 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> Signed-off-by: Weilong Chen <chenweilong@huawei.com> --- 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 dd7ea06eda03..e069098bf99f 100644 --- a/Documentation/core-api/printk-formats.rst +++ b/Documentation/core-api/printk-formats.rst @@ -589,6 +589,16 @@ For printing netdev_features_t. Passed by reference. +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 e5751a33dfa0..cbab9e427357 100644 --- a/lib/vsprintf.c +++ b/lib/vsprintf.c @@ -2201,6 +2201,9 @@ 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 @@ -2324,6 +2327,10 @@ 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, @@ -2394,6 +2401,12 @@ 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': -- 2.20.1