From nobody Sat Feb 7 07:10:24 2026 Received: from mail-wr1-f73.google.com (mail-wr1-f73.google.com [209.85.221.73]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 3CEFF27AC48 for ; Sat, 18 Oct 2025 18:03:30 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.221.73 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760810614; cv=none; b=Rjhs+wv/bMelsIeoC7RJ9UIOJXe5g7NZIldNrcJmeEZ5URP9t7Vgu8ZpOWgGK8kpbYIAVDYnG7Okgglg3RKdGIgkhkcyv9EUJg/YmHAm6us/xOKQ9cLKuk2pZEZ2e09fDGj756Wl6UheO3OoRPnnIFLD0gCqGshB+svW7kR9iW4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1760810614; c=relaxed/simple; bh=sGhtag8qWZn35dcfXoa8gr9jZ+96UIwtNQKYHPYg/UQ=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=Ni66XJrvkgE6SHVK+j+09Jc3H6hjGuECi6ze6YG+WwNPLt3HCx/NIFG46kU3Hb4nITWaq6APRIICCMb1SsC2RRLgk5J4aI5EK7rNxUB6K+IGjKNH00su/x1HuGu2i7GwKHS6Gke4Y5ajiI2Wt1SvAWe8g899QHMeJezCa5VXAWA= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--aliceryhl.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=yZiDWGvg; arc=none smtp.client-ip=209.85.221.73 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=flex--aliceryhl.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="yZiDWGvg" Received: by mail-wr1-f73.google.com with SMTP id ffacd0b85a97d-4270a273b6eso1099016f8f.0 for ; Sat, 18 Oct 2025 11:03:30 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1760810609; x=1761415409; darn=vger.kernel.org; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:from:to:cc:subject:date:message-id:reply-to; bh=3hGW9wvWmko0jOtTzcTf0josI14Rm4dKhBHFVI9qV6E=; b=yZiDWGvgJhTn8S3Jcced4YXJ60edFgoE/GDYY9XQirKRPokllME9Auy+nV1F+9hKfA wgg1oE216xJviLmbrdb2bNL1utZ+8dY2jKMOhkG2LLAn6+j3IHi1joEa6uUs4ct+KCi3 HVvbQfUhHgg76HH27P68WyQ4/3de4YXdQJzAbCpjogZRWDjt6tae1asRp7thRa4aa49j 2Ao+qEu/rI8JzwEJr0grmxX4If5asGiQaSSzOBYGKcecBzZoi9sDIyelR9EtaWEr36Ew q4z/F0SCP0/FNlOhxHbFuvnGObNn4XxPLQXwF4/vYZptXniJTyP3UI2ER0DWXTjnlUBY 3zPQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1760810609; x=1761415409; h=cc:to:from:subject:message-id:references:mime-version:in-reply-to :date:x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=3hGW9wvWmko0jOtTzcTf0josI14Rm4dKhBHFVI9qV6E=; b=d4SsoHV/8hqWfNHLe9GcUprxQhRQMytIWrFy9QYYzacTPIsoXMWSxfye02irH8q/Ru 4v6Y29V8PLraCkRAtEsfnxLjmlnTYOt1Qo4F7uSVCG/G1bwJ8RnhsPGE3TpqBWnQo921 X+mmPB8+p+8nmy9q6xS0YTGWWZLxvkoTaaQ7wp2paWbYN6+7TIiZPFJungCBg9zalP8j NXcRQjQqGjTYPrk+fOG9LDDoQ/MxYdQoee/OD/gxQIleKCLoZObX4YOJWZcOWk1sS/57 r9lYF45zcQdufMKu3NriggxwI195d9W0mfE1cPEfA8qRkduJWSrXtKsRYrwQAFmGy3Np SZSg== X-Forwarded-Encrypted: i=1; AJvYcCVxOn/ABVAcXC3vlbbMd7OgNIbqiw9fSSxzQ8Rd6ePbm+yOhtPczLZqvggfEVtOuMZLpNsgw+9CxgnXlrY=@vger.kernel.org X-Gm-Message-State: AOJu0YwjjtYVvJciIG6zObqcmcOfqk2ueoQcq0wkwbVC2Xf3Vbs6gBKj +mxY61h5lyROBSPJC3WKQERrFtZ9PMt89hEkDsLztYoFmQzf6DmDesB8ZQumxt5Sb9TAqVfJAj2 ZZ0+SqH0V+Yo+rstqcQ== X-Google-Smtp-Source: AGHT+IG/FO8rWAikeqs5tUzrpiqkR4TRQ79qTSq2oIl/eJyJd7c6RbaDK56qoNSuHSIOJYj5yw9+qSnEpYh3S50= X-Received: from wmcn1.prod.google.com ([2002:a05:600c:c0c1:b0:46e:1ae9:749a]) (user=aliceryhl job=prod-delivery.src-stubby-dispatcher) by 2002:a05:6000:40da:b0:3ec:248f:f86a with SMTP id ffacd0b85a97d-42704e02b12mr4695190f8f.48.1760810608392; Sat, 18 Oct 2025 11:03:28 -0700 (PDT) Date: Sat, 18 Oct 2025 18:03:26 +0000 In-Reply-To: <20251018-cstr-core-v18-0-ef3d02760804@gmail.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20251018-cstr-core-v18-0-ef3d02760804@gmail.com> X-Mailer: git-send-email 2.51.0.915.g61a8936c21-goog Message-ID: <20251018180326.3616043-1-aliceryhl@google.com> Subject: [PATCH v18 15/16] rust: support formatting of foreign types From: Alice Ryhl To: tamird@gmail.com Cc: Liam.Howlett@oracle.com, a.hindborg@kernel.org, airlied@gmail.com, alex.gaynor@gmail.com, aliceryhl@google.com, arve@android.com, axboe@kernel.dk, bhelgaas@google.com, bjorn3_gh@protonmail.com, boqun.feng@gmail.com, brauner@kernel.org, broonie@kernel.org, cmllamas@google.com, dakr@kernel.org, dri-devel@lists.freedesktop.org, gary@garyguo.net, gregkh@linuxfoundation.org, jack@suse.cz, joelagnelf@nvidia.com, justinstitt@google.com, kwilczynski@kernel.org, leitao@debian.org, lgirdwood@gmail.com, linux-block@vger.kernel.org, linux-clk@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-pci@vger.kernel.org, linux-pm@vger.kernel.org, llvm@lists.linux.dev, longman@redhat.com, lorenzo.stoakes@oracle.com, lossin@kernel.org, maco@android.com, mcgrof@kernel.org, mingo@redhat.com, mmaurer@google.com, morbo@google.com, mturquette@baylibre.com, nathan@kernel.org, nick.desaulniers+lkml@gmail.com, nm@ti.com, ojeda@kernel.org, peterz@infradead.org, rafael@kernel.org, russ.weight@linux.dev, rust-for-linux@vger.kernel.org, sboyd@kernel.org, simona@ffwll.ch, surenb@google.com, tkjos@android.com, tmgross@umich.edu, urezki@gmail.com, vbabka@suse.cz, vireshk@kernel.org, viro@zeniv.linux.org.uk, will@kernel.org Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Tamir Duberstein Introduce a `fmt!` macro which wraps all arguments in `kernel::fmt::Adapter` and a `kernel::fmt::Display` trait. This enables formatting of foreign types (like `core::ffi::CStr`) that do not implement `core::fmt::Display` due to concerns around lossy conversions which do not apply in the kernel. Suggested-by: Alice Ryhl Link: https://rust-for-linux.zulipchat.com/#narrow/channel/288089-General/t= opic/Custom.20formatting/with/516476467 Acked-by: Greg Kroah-Hartman Reviewed-by: Alice Ryhl Acked-by: Danilo Krummrich Reviewed-by: Benno Lossin Signed-off-by: Tamir Duberstein Signed-off-by: Alice Ryhl --- rust/kernel/fmt.rs | 87 +++++++++++++++++++++++++++++++++++++- rust/kernel/prelude.rs | 3 +- rust/macros/fmt.rs | 94 ++++++++++++++++++++++++++++++++++++++++++ rust/macros/lib.rs | 19 +++++++++ rust/macros/quote.rs | 7 ++++ 5 files changed, 207 insertions(+), 3 deletions(-) create mode 100644 rust/macros/fmt.rs diff --git a/rust/kernel/fmt.rs b/rust/kernel/fmt.rs index 0306e8388968..84d634201d90 100644 --- a/rust/kernel/fmt.rs +++ b/rust/kernel/fmt.rs @@ -4,4 +4,89 @@ //! //! This module is intended to be used in place of `core::fmt` in kernel c= ode. =20 -pub use core::fmt::{Arguments, Debug, Display, Error, Formatter, Result, W= rite}; +pub use core::fmt::{Arguments, Debug, Error, Formatter, Result, Write}; + +/// Internal adapter used to route allow implementations of formatting tra= its for foreign types. +/// +/// It is inserted automatically by the [`fmt!`] macro and is not meant to= be used directly. +/// +/// [`fmt!`]: crate::prelude::fmt! +#[doc(hidden)] +pub struct Adapter(pub T); + +macro_rules! impl_fmt_adapter_forward { + ($($trait:ident),* $(,)?) =3D> { + $( + impl $trait for Adapter { + fn fmt(&self, f: &mut Formatter<'_>) -> Result { + let Self(t) =3D self; + $trait::fmt(t, f) + } + } + )* + }; +} + +use core::fmt::{Binary, LowerExp, LowerHex, Octal, Pointer, UpperExp, Uppe= rHex}; +impl_fmt_adapter_forward!(Debug, LowerHex, UpperHex, Octal, Binary, Pointe= r, LowerExp, UpperExp); + +/// A copy of [`core::fmt::Display`] that allows us to implement it for fo= reign types. +/// +/// Types should implement this trait rather than [`core::fmt::Display`]. = Together with the +/// [`Adapter`] type and [`fmt!`] macro, it allows for formatting foreign = types (e.g. types from +/// core) which do not implement [`core::fmt::Display`] directly. +/// +/// [`fmt!`]: crate::prelude::fmt! +pub trait Display { + /// Same as [`core::fmt::Display::fmt`]. + fn fmt(&self, f: &mut Formatter<'_>) -> Result; +} + +impl Display for &T { + fn fmt(&self, f: &mut Formatter<'_>) -> Result { + Display::fmt(*self, f) + } +} + +impl core::fmt::Display for Adapter<&T> { + fn fmt(&self, f: &mut Formatter<'_>) -> Result { + let Self(t) =3D self; + Display::fmt(t, f) + } +} + +macro_rules! impl_display_forward { + ($( + $( { $($generics:tt)* } )? $ty:ty $( { where $($where:tt)* } )? + ),* $(,)?) =3D> { + $( + impl$($($generics)*)? Display for $ty $(where $($where)*)? { + fn fmt(&self, f: &mut Formatter<'_>) -> Result { + core::fmt::Display::fmt(self, f) + } + } + )* + }; +} + +impl_display_forward!( + bool, + char, + core::panic::PanicInfo<'_>, + Arguments<'_>, + i128, + i16, + i32, + i64, + i8, + isize, + str, + u128, + u16, + u32, + u64, + u8, + usize, + {} crate::sync::Arc {where crate::sync::Arc: core::fm= t::Display}, + {} crate::sync::UniqueArc {where crate::sync::UniqueArc<= T>: core::fmt::Display}, +); diff --git a/rust/kernel/prelude.rs b/rust/kernel/prelude.rs index 198d09a31449..26424ad7e989 100644 --- a/rust/kernel/prelude.rs +++ b/rust/kernel/prelude.rs @@ -25,7 +25,7 @@ pub use crate::alloc::{flags::*, Box, KBox, KVBox, KVVec, KVec, VBox, VVec= , Vec}; =20 #[doc(no_inline)] -pub use macros::{export, kunit_tests, module, vtable}; +pub use macros::{export, fmt, kunit_tests, module, vtable}; =20 pub use pin_init::{init, pin_data, pin_init, pinned_drop, InPlaceWrite, In= it, PinInit, Zeroable}; =20 @@ -36,7 +36,6 @@ pub use super::dbg; pub use super::{dev_alert, dev_crit, dev_dbg, dev_emerg, dev_err, dev_info= , dev_notice, dev_warn}; pub use super::{pr_alert, pr_crit, pr_debug, pr_emerg, pr_err, pr_info, pr= _notice, pr_warn}; -pub use core::format_args as fmt; =20 pub use super::{try_init, try_pin_init}; =20 diff --git a/rust/macros/fmt.rs b/rust/macros/fmt.rs new file mode 100644 index 000000000000..2f4b9f6e2211 --- /dev/null +++ b/rust/macros/fmt.rs @@ -0,0 +1,94 @@ +// SPDX-License-Identifier: GPL-2.0 + +use proc_macro::{Ident, TokenStream, TokenTree}; +use std::collections::BTreeSet; + +/// Please see [`crate::fmt`] for documentation. +pub(crate) fn fmt(input: TokenStream) -> TokenStream { + let mut input =3D input.into_iter(); + + let first_opt =3D input.next(); + let first_owned_str; + let mut names =3D BTreeSet::new(); + let first_span =3D { + let Some((mut first_str, first_span)) =3D (match first_opt.as_ref(= ) { + Some(TokenTree::Literal(first_lit)) =3D> { + first_owned_str =3D first_lit.to_string(); + Some(first_owned_str.as_str()).and_then(|first| { + let first =3D first.strip_prefix('"')?; + let first =3D first.strip_suffix('"')?; + Some((first, first_lit.span())) + }) + } + _ =3D> None, + }) else { + return first_opt.into_iter().chain(input).collect(); + }; + + // Parse `identifier`s from the format string. + // + // See https://doc.rust-lang.org/std/fmt/index.html#syntax. + while let Some((_, rest)) =3D first_str.split_once('{') { + first_str =3D rest; + if let Some(rest) =3D first_str.strip_prefix('{') { + first_str =3D rest; + continue; + } + if let Some((name, rest)) =3D first_str.split_once('}') { + first_str =3D rest; + let name =3D name.split_once(':').map_or(name, |(name, _)|= name); + if !name.is_empty() && !name.chars().all(|c| c.is_ascii_di= git()) { + names.insert(name); + } + } + } + first_span + }; + + let adapter =3D quote_spanned!(first_span =3D> ::kernel::fmt::Adapter); + + let mut args =3D TokenStream::from_iter(first_opt); + { + let mut flush =3D |args: &mut TokenStream, current: &mut TokenStre= am| { + let current =3D std::mem::take(current); + if !current.is_empty() { + let (lhs, rhs) =3D (|| { + let mut current =3D current.into_iter(); + let mut acc =3D TokenStream::new(); + while let Some(tt) =3D current.next() { + // Split on `=3D` only once to handle cases like `= a =3D b =3D c`. + if matches!(&tt, TokenTree::Punct(p) if p.as_char(= ) =3D=3D '=3D') { + names.remove(acc.to_string().as_str()); + // Include the `=3D` itself to keep the handli= ng below uniform. + acc.extend([tt]); + return (Some(acc), current.collect::()); + } + acc.extend([tt]); + } + (None, acc) + })(); + args.extend(quote_spanned!(first_span =3D> #lhs #adapter(&= #rhs))); + } + }; + + let mut current =3D TokenStream::new(); + for tt in input { + match &tt { + TokenTree::Punct(p) if p.as_char() =3D=3D ',' =3D> { + flush(&mut args, &mut current); + &mut args + } + _ =3D> &mut current, + } + .extend([tt]); + } + flush(&mut args, &mut current); + } + + for name in names { + let name =3D Ident::new(name, first_span); + args.extend(quote_spanned!(first_span =3D> , #name =3D #adapter(&#= name))); + } + + quote_spanned!(first_span =3D> ::core::format_args!(#args)) +} diff --git a/rust/macros/lib.rs b/rust/macros/lib.rs index fa847cf3a9b5..793f712dbf7c 100644 --- a/rust/macros/lib.rs +++ b/rust/macros/lib.rs @@ -15,6 +15,7 @@ mod quote; mod concat_idents; mod export; +mod fmt; mod helpers; mod kunit; mod module; @@ -201,6 +202,24 @@ pub fn export(attr: TokenStream, ts: TokenStream) -> T= okenStream { export::export(attr, ts) } =20 +/// Like [`core::format_args!`], but automatically wraps arguments in [`ke= rnel::fmt::Adapter`]. +/// +/// This macro allows generating `fmt::Arguments` while ensuring that each= argument is wrapped with +/// `::kernel::fmt::Adapter`, which customizes formatting behavior for ker= nel logging. +/// +/// Named arguments used in the format string (e.g. `{foo}`) are detected = and resolved from local +/// bindings. All positional and named arguments are automatically wrapped. +/// +/// This macro is an implementation detail of other kernel logging macros = like [`pr_info!`] and +/// should not typically be used directly. +/// +/// [`kernel::fmt::Adapter`]: ../kernel/fmt/struct.Adapter.html +/// [`pr_info!`]: ../kernel/macro.pr_info.html +#[proc_macro] +pub fn fmt(input: TokenStream) -> TokenStream { + fmt::fmt(input) +} + /// Concatenate two identifiers. /// /// This is useful in macros that need to declare or reference items with = names diff --git a/rust/macros/quote.rs b/rust/macros/quote.rs index acc140c18653..ddfc21577539 100644 --- a/rust/macros/quote.rs +++ b/rust/macros/quote.rs @@ -48,6 +48,7 @@ macro_rules! quote_spanned { ($span:expr =3D> $($tt:tt)*) =3D> {{ let mut tokens =3D ::proc_macro::TokenStream::new(); { + #[allow(unused_variables)] let span =3D $span; quote_spanned!(@proc tokens span $($tt)*); } @@ -146,6 +147,12 @@ macro_rules! quote_spanned { )]); quote_spanned!(@proc $v $span $($tt)*); }; + (@proc $v:ident $span:ident & $($tt:tt)*) =3D> { + $v.extend([::proc_macro::TokenTree::Punct( + ::proc_macro::Punct::new('&', ::proc_macro::Spacing::Alone), + )]); + quote_spanned!(@proc $v $span $($tt)*); + }; (@proc $v:ident $span:ident _ $($tt:tt)*) =3D> { $v.extend([::proc_macro::TokenTree::Ident( ::proc_macro::Ident::new("_", $span), --=20 2.51.0.915.g61a8936c21-goog