* [PATCH v14 1/3] rust: macros: reduce collections in `quote!` macro
2025-07-10 14:53 [PATCH v14 0/3] rust: replace kernel::str::CStr w/ core::ffi::CStr Tamir Duberstein
@ 2025-07-10 14:53 ` Tamir Duberstein
2025-07-10 14:53 ` [PATCH v14 2/3] rust: support formatting of foreign types Tamir Duberstein
` (2 subsequent siblings)
3 siblings, 0 replies; 10+ messages in thread
From: Tamir Duberstein @ 2025-07-10 14:53 UTC (permalink / raw)
To: Miguel Ojeda, Alex Gaynor, Boqun Feng, Gary Guo,
Björn Roy Baron, Benno Lossin, Andreas Hindborg, Alice Ryhl,
Trevor Gross, Danilo Krummrich, Greg Kroah-Hartman,
Rafael J. Wysocki, Luis Chamberlain, Russ Weight, Peter Zijlstra,
Ingo Molnar, Will Deacon, Waiman Long, Nathan Chancellor,
Nick Desaulniers, Bill Wendling, Justin Stitt, Christian Brauner
Cc: rust-for-linux, linux-kernel, llvm, Tamir Duberstein
Remove a handful of unncessary intermediate vectors and token streams;
mainly the top-level stream can be directly extended with the notable
exception of groups.
Remove an unnecessary `#[allow(dead_code)]` added in commit dbd5058ba60c
("rust: make pin-init its own crate").
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: Tamir Duberstein <tamird@gmail.com>
---
rust/macros/quote.rs | 104 ++++++++++++++++++++++++---------------------------
1 file changed, 49 insertions(+), 55 deletions(-)
diff --git a/rust/macros/quote.rs b/rust/macros/quote.rs
index 92cacc4067c9..acc140c18653 100644
--- a/rust/macros/quote.rs
+++ b/rust/macros/quote.rs
@@ -2,7 +2,6 @@
use proc_macro::{TokenStream, TokenTree};
-#[allow(dead_code)]
pub(crate) trait ToTokens {
fn to_tokens(&self, tokens: &mut TokenStream);
}
@@ -47,121 +46,116 @@ fn to_tokens(&self, tokens: &mut TokenStream) {
/// `quote` crate but provides only just enough functionality needed by the current `macros` crate.
macro_rules! quote_spanned {
($span:expr => $($tt:tt)*) => {{
- let mut tokens: ::std::vec::Vec<::proc_macro::TokenTree>;
- #[allow(clippy::vec_init_then_push)]
+ let mut tokens = ::proc_macro::TokenStream::new();
{
- tokens = ::std::vec::Vec::new();
let span = $span;
quote_spanned!(@proc tokens span $($tt)*);
}
- ::proc_macro::TokenStream::from_iter(tokens)
+ tokens
}};
(@proc $v:ident $span:ident) => {};
(@proc $v:ident $span:ident #$id:ident $($tt:tt)*) => {
- let mut ts = ::proc_macro::TokenStream::new();
- $crate::quote::ToTokens::to_tokens(&$id, &mut ts);
- $v.extend(ts);
+ $crate::quote::ToTokens::to_tokens(&$id, &mut $v);
quote_spanned!(@proc $v $span $($tt)*);
};
(@proc $v:ident $span:ident #(#$id:ident)* $($tt:tt)*) => {
for token in $id {
- let mut ts = ::proc_macro::TokenStream::new();
- $crate::quote::ToTokens::to_tokens(&token, &mut ts);
- $v.extend(ts);
+ $crate::quote::ToTokens::to_tokens(&token, &mut $v);
}
quote_spanned!(@proc $v $span $($tt)*);
};
(@proc $v:ident $span:ident ( $($inner:tt)* ) $($tt:tt)*) => {
#[allow(unused_mut)]
- let mut tokens = ::std::vec::Vec::<::proc_macro::TokenTree>::new();
+ let mut tokens = ::proc_macro::TokenStream::new();
quote_spanned!(@proc tokens $span $($inner)*);
- $v.push(::proc_macro::TokenTree::Group(::proc_macro::Group::new(
+ $v.extend([::proc_macro::TokenTree::Group(::proc_macro::Group::new(
::proc_macro::Delimiter::Parenthesis,
- ::proc_macro::TokenStream::from_iter(tokens)
- )));
+ tokens,
+ ))]);
quote_spanned!(@proc $v $span $($tt)*);
};
(@proc $v:ident $span:ident [ $($inner:tt)* ] $($tt:tt)*) => {
- let mut tokens = ::std::vec::Vec::new();
+ let mut tokens = ::proc_macro::TokenStream::new();
quote_spanned!(@proc tokens $span $($inner)*);
- $v.push(::proc_macro::TokenTree::Group(::proc_macro::Group::new(
+ $v.extend([::proc_macro::TokenTree::Group(::proc_macro::Group::new(
::proc_macro::Delimiter::Bracket,
- ::proc_macro::TokenStream::from_iter(tokens)
- )));
+ tokens,
+ ))]);
quote_spanned!(@proc $v $span $($tt)*);
};
(@proc $v:ident $span:ident { $($inner:tt)* } $($tt:tt)*) => {
- let mut tokens = ::std::vec::Vec::new();
+ let mut tokens = ::proc_macro::TokenStream::new();
quote_spanned!(@proc tokens $span $($inner)*);
- $v.push(::proc_macro::TokenTree::Group(::proc_macro::Group::new(
+ $v.extend([::proc_macro::TokenTree::Group(::proc_macro::Group::new(
::proc_macro::Delimiter::Brace,
- ::proc_macro::TokenStream::from_iter(tokens)
- )));
+ tokens,
+ ))]);
quote_spanned!(@proc $v $span $($tt)*);
};
(@proc $v:ident $span:ident :: $($tt:tt)*) => {
- $v.push(::proc_macro::TokenTree::Punct(
- ::proc_macro::Punct::new(':', ::proc_macro::Spacing::Joint)
- ));
- $v.push(::proc_macro::TokenTree::Punct(
- ::proc_macro::Punct::new(':', ::proc_macro::Spacing::Alone)
- ));
+ $v.extend([::proc_macro::Spacing::Joint, ::proc_macro::Spacing::Alone].map(|spacing| {
+ ::proc_macro::TokenTree::Punct(::proc_macro::Punct::new(':', spacing))
+ }));
quote_spanned!(@proc $v $span $($tt)*);
};
(@proc $v:ident $span:ident : $($tt:tt)*) => {
- $v.push(::proc_macro::TokenTree::Punct(
- ::proc_macro::Punct::new(':', ::proc_macro::Spacing::Alone)
- ));
+ $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)*) => {
- $v.push(::proc_macro::TokenTree::Punct(
- ::proc_macro::Punct::new(',', ::proc_macro::Spacing::Alone)
- ));
+ $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)*) => {
- $v.push(::proc_macro::TokenTree::Punct(
- ::proc_macro::Punct::new('@', ::proc_macro::Spacing::Alone)
- ));
+ $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)*) => {
- $v.push(::proc_macro::TokenTree::Punct(
- ::proc_macro::Punct::new('!', ::proc_macro::Spacing::Alone)
- ));
+ $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)*) => {
- $v.push(::proc_macro::TokenTree::Punct(
- ::proc_macro::Punct::new(';', ::proc_macro::Spacing::Alone)
- ));
+ $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)*) => {
- $v.push(::proc_macro::TokenTree::Punct(
- ::proc_macro::Punct::new('+', ::proc_macro::Spacing::Alone)
- ));
+ $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)*) => {
- $v.push(::proc_macro::TokenTree::Punct(
- ::proc_macro::Punct::new('=', ::proc_macro::Spacing::Alone)
- ));
+ $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)*) => {
- $v.push(::proc_macro::TokenTree::Punct(
- ::proc_macro::Punct::new('#', ::proc_macro::Spacing::Alone)
- ));
+ $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)*) => {
- $v.push(::proc_macro::TokenTree::Ident(::proc_macro::Ident::new("_", $span)));
+ $v.extend([::proc_macro::TokenTree::Ident(
+ ::proc_macro::Ident::new("_", $span),
+ )]);
quote_spanned!(@proc $v $span $($tt)*);
};
(@proc $v:ident $span:ident $id:ident $($tt:tt)*) => {
- $v.push(::proc_macro::TokenTree::Ident(::proc_macro::Ident::new(stringify!($id), $span)));
+ $v.extend([::proc_macro::TokenTree::Ident(
+ ::proc_macro::Ident::new(stringify!($id), $span),
+ )]);
quote_spanned!(@proc $v $span $($tt)*);
};
}
--
2.50.0
^ permalink raw reply related [flat|nested] 10+ messages in thread* [PATCH v14 2/3] rust: support formatting of foreign types
2025-07-10 14:53 [PATCH v14 0/3] rust: replace kernel::str::CStr w/ core::ffi::CStr Tamir Duberstein
2025-07-10 14:53 ` [PATCH v14 1/3] rust: macros: reduce collections in `quote!` macro Tamir Duberstein
@ 2025-07-10 14:53 ` Tamir Duberstein
2025-08-12 7:27 ` Benno Lossin
2025-07-10 14:53 ` [PATCH v14 3/3] rust: replace `CStr` with `core::ffi::CStr` Tamir Duberstein
2025-07-14 11:25 ` [PATCH v14 0/3] rust: replace kernel::str::CStr w/ core::ffi::CStr Danilo Krummrich
3 siblings, 1 reply; 10+ messages in thread
From: Tamir Duberstein @ 2025-07-10 14:53 UTC (permalink / raw)
To: Miguel Ojeda, Alex Gaynor, Boqun Feng, Gary Guo,
Björn Roy Baron, Benno Lossin, Andreas Hindborg, Alice Ryhl,
Trevor Gross, Danilo Krummrich, Greg Kroah-Hartman,
Rafael J. Wysocki, Luis Chamberlain, Russ Weight, Peter Zijlstra,
Ingo Molnar, Will Deacon, Waiman Long, Nathan Chancellor,
Nick Desaulniers, Bill Wendling, Justin Stitt, Christian Brauner
Cc: rust-for-linux, linux-kernel, llvm, 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 <aliceryhl@google.com>
Link: https://rust-for-linux.zulipchat.com/#narrow/channel/288089-General/topic/Custom.20formatting/with/516476467
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: Tamir Duberstein <tamird@gmail.com>
---
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(-)
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 code.
-pub use core::fmt::{Arguments, Debug, Display, Error, Formatter, Result, Write};
+pub use core::fmt::{Arguments, Debug, Error, Formatter, Result, Write};
+
+/// Internal adapter used to route allow implementations of formatting traits 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<T>(pub T);
+
+macro_rules! impl_fmt_adapter_forward {
+ ($($trait:ident),* $(,)?) => {
+ $(
+ impl<T: $trait> $trait for Adapter<T> {
+ fn fmt(&self, f: &mut Formatter<'_>) -> Result {
+ let Self(t) = self;
+ $trait::fmt(t, f)
+ }
+ }
+ )*
+ };
+}
+
+use core::fmt::{Binary, LowerExp, LowerHex, Octal, Pointer, UpperExp, UpperHex};
+impl_fmt_adapter_forward!(Debug, LowerHex, UpperHex, Octal, Binary, Pointer, LowerExp, UpperExp);
+
+/// A copy of [`core::fmt::Display`] that allows us to implement it for foreign types.
+///
+/// Types should implement this trait rather than [`core::fmt::Display`]. Together with the
+/// [`Adapter`] type and [`fmt!`] macro, it allows for formatting foreign types (e.g. types from
+/// core) which do not implement [`core::fmt::Display`] directly.
+///
+/// [`fmt!`]: crate::prelude::fmt!
+pub trait Display {
+ /// Same as [`core::fmt::Display::fmt`].
+ fn fmt(&self, f: &mut Formatter<'_>) -> Result;
+}
+
+impl<T: ?Sized + Display> Display for &T {
+ fn fmt(&self, f: &mut Formatter<'_>) -> Result {
+ Display::fmt(*self, f)
+ }
+}
+
+impl<T: ?Sized + Display> core::fmt::Display for Adapter<&T> {
+ fn fmt(&self, f: &mut Formatter<'_>) -> Result {
+ let Self(t) = self;
+ Display::fmt(t, f)
+ }
+}
+
+macro_rules! impl_display_forward {
+ ($(
+ $( { $($generics:tt)* } )? $ty:ty $( { where $($where:tt)* } )?
+ ),* $(,)?) => {
+ $(
+ impl$($($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,
+ {<T: ?Sized>} crate::sync::Arc<T> {where crate::sync::Arc<T>: core::fmt::Display},
+ {<T: ?Sized>} crate::sync::UniqueArc<T> {where crate::sync::UniqueArc<T>: core::fmt::Display},
+);
diff --git a/rust/kernel/prelude.rs b/rust/kernel/prelude.rs
index 3ca934885797..41cebd906c4c 100644
--- a/rust/kernel/prelude.rs
+++ b/rust/kernel/prelude.rs
@@ -22,7 +22,7 @@
pub use crate::alloc::{flags::*, Box, KBox, KVBox, KVVec, KVec, VBox, VVec, Vec};
#[doc(no_inline)]
-pub use macros::{export, kunit_tests, module, vtable};
+pub use macros::{export, fmt, kunit_tests, module, vtable};
pub use pin_init::{init, pin_data, pin_init, pinned_drop, InPlaceWrite, Init, PinInit, Zeroable};
@@ -33,7 +33,6 @@
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;
pub use super::{try_init, try_pin_init};
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 = input.into_iter();
+
+ let first_opt = input.next();
+ let first_owned_str;
+ let mut names = BTreeSet::new();
+ let first_span = {
+ let Some((mut first_str, first_span)) = (match first_opt.as_ref() {
+ Some(TokenTree::Literal(first_lit)) => {
+ first_owned_str = first_lit.to_string();
+ Some(first_owned_str.as_str()).and_then(|first| {
+ let first = first.strip_prefix('"')?;
+ let first = first.strip_suffix('"')?;
+ Some((first, first_lit.span()))
+ })
+ }
+ _ => 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)) = first_str.split_once('{') {
+ first_str = rest;
+ if let Some(rest) = first_str.strip_prefix('{') {
+ first_str = rest;
+ continue;
+ }
+ if let Some((name, rest)) = first_str.split_once('}') {
+ first_str = rest;
+ let name = name.split_once(':').map_or(name, |(name, _)| name);
+ if !name.is_empty() && !name.chars().all(|c| c.is_ascii_digit()) {
+ names.insert(name);
+ }
+ }
+ }
+ first_span
+ };
+
+ let adapter = quote_spanned!(first_span => ::kernel::fmt::Adapter);
+
+ let mut args = TokenStream::from_iter(first_opt);
+ {
+ let mut flush = |args: &mut TokenStream, current: &mut TokenStream| {
+ let current = std::mem::take(current);
+ if !current.is_empty() {
+ let (lhs, rhs) = (|| {
+ let mut current = current.into_iter();
+ let mut acc = TokenStream::new();
+ while let Some(tt) = current.next() {
+ // Split on `=` only once to handle cases like `a = b = c`.
+ if matches!(&tt, TokenTree::Punct(p) if p.as_char() == '=') {
+ names.remove(acc.to_string().as_str());
+ // Include the `=` itself to keep the handling below uniform.
+ acc.extend([tt]);
+ return (Some(acc), current.collect::<TokenStream>());
+ }
+ acc.extend([tt]);
+ }
+ (None, acc)
+ })();
+ args.extend(quote_spanned!(first_span => #lhs #adapter(&#rhs)));
+ }
+ };
+
+ let mut current = TokenStream::new();
+ for tt in input {
+ match &tt {
+ TokenTree::Punct(p) if p.as_char() == ',' => {
+ flush(&mut args, &mut current);
+ &mut args
+ }
+ _ => &mut current,
+ }
+ .extend([tt]);
+ }
+ flush(&mut args, &mut current);
+ }
+
+ for name in names {
+ let name = Ident::new(name, first_span);
+ args.extend(quote_spanned!(first_span => , #name = #adapter(&#name)));
+ }
+
+ quote_spanned!(first_span => ::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) -> TokenStream {
export::export(attr, ts)
}
+/// Like [`core::format_args!`], but automatically wraps arguments in [`kernel::fmt::Adapter`].
+///
+/// This macro allows generating `fmt::Arguments` while ensuring that each argument is wrapped with
+/// `::kernel::fmt::Adapter`, which customizes formatting behavior for kernel 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 => $($tt:tt)*) => {{
let mut tokens = ::proc_macro::TokenStream::new();
{
+ #[allow(unused_variables)]
let span = $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)*) => {
+ $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)*) => {
$v.extend([::proc_macro::TokenTree::Ident(
::proc_macro::Ident::new("_", $span),
--
2.50.0
^ permalink raw reply related [flat|nested] 10+ messages in thread* Re: [PATCH v14 2/3] rust: support formatting of foreign types
2025-07-10 14:53 ` [PATCH v14 2/3] rust: support formatting of foreign types Tamir Duberstein
@ 2025-08-12 7:27 ` Benno Lossin
0 siblings, 0 replies; 10+ messages in thread
From: Benno Lossin @ 2025-08-12 7:27 UTC (permalink / raw)
To: Tamir Duberstein, Miguel Ojeda, Alex Gaynor, Boqun Feng, Gary Guo,
Björn Roy Baron, Andreas Hindborg, Alice Ryhl, Trevor Gross,
Danilo Krummrich, Greg Kroah-Hartman, Rafael J. Wysocki,
Luis Chamberlain, Russ Weight, Peter Zijlstra, Ingo Molnar,
Will Deacon, Waiman Long, Nathan Chancellor, Nick Desaulniers,
Bill Wendling, Justin Stitt, Christian Brauner
Cc: rust-for-linux, linux-kernel, llvm
On Thu Jul 10, 2025 at 4:53 PM CEST, Tamir Duberstein wrote:
> 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 <aliceryhl@google.com>
> Link: https://rust-for-linux.zulipchat.com/#narrow/channel/288089-General/topic/Custom.20formatting/with/516476467
> Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Reviewed-by: Alice Ryhl <aliceryhl@google.com>
> Signed-off-by: Tamir Duberstein <tamird@gmail.com>
I'm not 100% sure we need to always use `first_span`, but it's probably
fine.
Reviewed-by: Benno Lossin <lossin@kernel.org>
---
Cheers,
Benno
> ---
> 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(-)
^ permalink raw reply [flat|nested] 10+ messages in thread
* [PATCH v14 3/3] rust: replace `CStr` with `core::ffi::CStr`
2025-07-10 14:53 [PATCH v14 0/3] rust: replace kernel::str::CStr w/ core::ffi::CStr Tamir Duberstein
2025-07-10 14:53 ` [PATCH v14 1/3] rust: macros: reduce collections in `quote!` macro Tamir Duberstein
2025-07-10 14:53 ` [PATCH v14 2/3] rust: support formatting of foreign types Tamir Duberstein
@ 2025-07-10 14:53 ` Tamir Duberstein
2025-08-12 7:50 ` Benno Lossin
2025-07-14 11:25 ` [PATCH v14 0/3] rust: replace kernel::str::CStr w/ core::ffi::CStr Danilo Krummrich
3 siblings, 1 reply; 10+ messages in thread
From: Tamir Duberstein @ 2025-07-10 14:53 UTC (permalink / raw)
To: Miguel Ojeda, Alex Gaynor, Boqun Feng, Gary Guo,
Björn Roy Baron, Benno Lossin, Andreas Hindborg, Alice Ryhl,
Trevor Gross, Danilo Krummrich, Greg Kroah-Hartman,
Rafael J. Wysocki, Luis Chamberlain, Russ Weight, Peter Zijlstra,
Ingo Molnar, Will Deacon, Waiman Long, Nathan Chancellor,
Nick Desaulniers, Bill Wendling, Justin Stitt, Christian Brauner
Cc: rust-for-linux, linux-kernel, llvm, Tamir Duberstein
`kernel::ffi::CStr` was introduced in commit d126d2380131 ("rust: str:
add `CStr` type") in November 2022 as an upstreaming of earlier work
that was done in May 2021[0]. That earlier work, having predated the
inclusion of `CStr` in `core`, largely duplicated the implementation of
`std::ffi::CStr`.
`std::ffi::CStr` was moved to `core::ffi::CStr` in Rust 1.64 in
September 2022. Hence replace `kernel::str::CStr` with `core::ffi::CStr`
to reduce our custom code footprint, and retain needed custom
functionality through an extension trait.
Add `CStr` to `ffi` and the kernel prelude.
Link: https://github.com/Rust-for-Linux/linux/commit/faa3cbcca03d0dec8f8e43f1d8d5c0860d98a23f [0]
Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Reviewed-by: Alice Ryhl <aliceryhl@google.com>
Signed-off-by: Tamir Duberstein <tamird@gmail.com>
---
rust/ffi.rs | 2 +
rust/kernel/device.rs | 1 +
rust/kernel/error.rs | 2 +
rust/kernel/firmware.rs | 9 +-
rust/kernel/prelude.rs | 4 +-
rust/kernel/seq_file.rs | 2 +-
rust/kernel/str.rs | 395 +++++++++-------------------------------
rust/kernel/sync/condvar.rs | 2 +-
rust/kernel/sync/lock.rs | 2 +-
rust/kernel/sync/lock/global.rs | 2 +-
10 files changed, 106 insertions(+), 315 deletions(-)
diff --git a/rust/ffi.rs b/rust/ffi.rs
index d60aad792af4..f961e9728f59 100644
--- a/rust/ffi.rs
+++ b/rust/ffi.rs
@@ -46,3 +46,5 @@ macro_rules! alias {
}
pub use core::ffi::c_void;
+
+pub use core::ffi::CStr;
diff --git a/rust/kernel/device.rs b/rust/kernel/device.rs
index 9e9ecdb1beec..b34173536230 100644
--- a/rust/kernel/device.rs
+++ b/rust/kernel/device.rs
@@ -13,6 +13,7 @@
#[cfg(CONFIG_PRINTK)]
use crate::c_str;
+use crate::str::CStrExt as _;
/// A reference-counted device.
///
diff --git a/rust/kernel/error.rs b/rust/kernel/error.rs
index e29a5d76300e..6f7e4064adfd 100644
--- a/rust/kernel/error.rs
+++ b/rust/kernel/error.rs
@@ -164,6 +164,8 @@ pub fn name(&self) -> Option<&'static CStr> {
if ptr.is_null() {
None
} else {
+ use crate::str::CStrExt as _;
+
// SAFETY: The string returned by `errname` is static and `NUL`-terminated.
Some(unsafe { CStr::from_char_ptr(ptr) })
}
diff --git a/rust/kernel/firmware.rs b/rust/kernel/firmware.rs
index ca00aa2b4d85..4adcf39b475e 100644
--- a/rust/kernel/firmware.rs
+++ b/rust/kernel/firmware.rs
@@ -4,7 +4,14 @@
//!
//! C header: [`include/linux/firmware.h`](srctree/include/linux/firmware.h)
-use crate::{bindings, device::Device, error::Error, error::Result, ffi, str::CStr};
+use crate::{
+ bindings,
+ device::Device,
+ error::Error,
+ error::Result,
+ ffi,
+ str::{CStr, CStrExt as _},
+};
use core::ptr::NonNull;
/// # Invariants
diff --git a/rust/kernel/prelude.rs b/rust/kernel/prelude.rs
index 41cebd906c4c..620096a75a42 100644
--- a/rust/kernel/prelude.rs
+++ b/rust/kernel/prelude.rs
@@ -16,7 +16,7 @@
pub use ::ffi::{
c_char, c_int, c_long, c_longlong, c_schar, c_short, c_uchar, c_uint, c_ulong, c_ulonglong,
- c_ushort, c_void,
+ c_ushort, c_void, CStr,
};
pub use crate::alloc::{flags::*, Box, KBox, KVBox, KVVec, KVec, VBox, VVec, Vec};
@@ -40,7 +40,7 @@
pub use super::error::{code::*, Error, Result};
-pub use super::{str::CStr, ThisModule};
+pub use super::{str::CStrExt as _, ThisModule};
pub use super::init::InPlaceInit;
diff --git a/rust/kernel/seq_file.rs b/rust/kernel/seq_file.rs
index 59fbfc2473f8..855e533813a6 100644
--- a/rust/kernel/seq_file.rs
+++ b/rust/kernel/seq_file.rs
@@ -4,7 +4,7 @@
//!
//! C header: [`include/linux/seq_file.h`](srctree/include/linux/seq_file.h)
-use crate::{bindings, c_str, fmt, types::NotThreadSafe, types::Opaque};
+use crate::{bindings, c_str, fmt, str::CStrExt as _, types::NotThreadSafe, types::Opaque};
/// A utility for generating the contents of a seq file.
#[repr(transparent)]
diff --git a/rust/kernel/str.rs b/rust/kernel/str.rs
index 6c892550c0ba..61ebaacddc23 100644
--- a/rust/kernel/str.rs
+++ b/rust/kernel/str.rs
@@ -4,10 +4,12 @@
use crate::alloc::{flags::*, AllocError, KVec};
use crate::fmt::{self, Write};
-use core::ops::{self, Deref, DerefMut, Index};
+use core::ops::{Deref, DerefMut, Index};
use crate::prelude::*;
+pub use crate::prelude::CStr;
+
/// Byte string without UTF-8 validity guarantee.
#[repr(transparent)]
pub struct BStr([u8]);
@@ -181,58 +183,11 @@ macro_rules! b_str {
// - error[E0379]: functions in trait impls cannot be declared const
#[inline]
pub const fn as_char_ptr_in_const_context(c_str: &CStr) -> *const c_char {
- c_str.0.as_ptr()
-}
-
-/// Possible errors when using conversion functions in [`CStr`].
-#[derive(Debug, Clone, Copy)]
-pub enum CStrConvertError {
- /// Supplied bytes contain an interior `NUL`.
- InteriorNul,
-
- /// Supplied bytes are not terminated by `NUL`.
- NotNulTerminated,
+ c_str.as_ptr().cast()
}
-impl From<CStrConvertError> for Error {
- #[inline]
- fn from(_: CStrConvertError) -> Error {
- EINVAL
- }
-}
-
-/// A string that is guaranteed to have exactly one `NUL` byte, which is at the
-/// end.
-///
-/// Used for interoperability with kernel APIs that take C strings.
-#[repr(transparent)]
-pub struct CStr([u8]);
-
-impl CStr {
- /// Returns the length of this string excluding `NUL`.
- #[inline]
- pub const fn len(&self) -> usize {
- self.len_with_nul() - 1
- }
-
- /// Returns the length of this string with `NUL`.
- #[inline]
- pub const fn len_with_nul(&self) -> usize {
- if self.0.is_empty() {
- // SAFETY: This is one of the invariant of `CStr`.
- // We add a `unreachable_unchecked` here to hint the optimizer that
- // the value returned from this function is non-zero.
- unsafe { core::hint::unreachable_unchecked() };
- }
- self.0.len()
- }
-
- /// Returns `true` if the string only includes `NUL`.
- #[inline]
- pub const fn is_empty(&self) -> bool {
- self.len() == 0
- }
-
+/// Extensions to [`CStr`].
+pub trait CStrExt {
/// Wraps a raw C string pointer.
///
/// # Safety
@@ -240,54 +195,9 @@ pub const fn is_empty(&self) -> bool {
/// `ptr` must be a valid pointer to a `NUL`-terminated C string, and it must
/// last at least `'a`. When `CStr` is alive, the memory pointed by `ptr`
/// must not be mutated.
- #[inline]
- pub unsafe fn from_char_ptr<'a>(ptr: *const c_char) -> &'a Self {
- // SAFETY: The safety precondition guarantees `ptr` is a valid pointer
- // to a `NUL`-terminated C string.
- let len = unsafe { bindings::strlen(ptr) } + 1;
- // SAFETY: Lifetime guaranteed by the safety precondition.
- let bytes = unsafe { core::slice::from_raw_parts(ptr.cast(), len) };
- // SAFETY: As `len` is returned by `strlen`, `bytes` does not contain interior `NUL`.
- // As we have added 1 to `len`, the last byte is known to be `NUL`.
- unsafe { Self::from_bytes_with_nul_unchecked(bytes) }
- }
-
- /// Creates a [`CStr`] from a `[u8]`.
- ///
- /// The provided slice must be `NUL`-terminated, does not contain any
- /// interior `NUL` bytes.
- pub const fn from_bytes_with_nul(bytes: &[u8]) -> Result<&Self, CStrConvertError> {
- if bytes.is_empty() {
- return Err(CStrConvertError::NotNulTerminated);
- }
- if bytes[bytes.len() - 1] != 0 {
- return Err(CStrConvertError::NotNulTerminated);
- }
- let mut i = 0;
- // `i + 1 < bytes.len()` allows LLVM to optimize away bounds checking,
- // while it couldn't optimize away bounds checks for `i < bytes.len() - 1`.
- while i + 1 < bytes.len() {
- if bytes[i] == 0 {
- return Err(CStrConvertError::InteriorNul);
- }
- i += 1;
- }
- // SAFETY: We just checked that all properties hold.
- Ok(unsafe { Self::from_bytes_with_nul_unchecked(bytes) })
- }
-
- /// Creates a [`CStr`] from a `[u8]` without performing any additional
- /// checks.
- ///
- /// # Safety
- ///
- /// `bytes` *must* end with a `NUL` byte, and should only have a single
- /// `NUL` byte (or the string will be truncated).
- #[inline]
- pub const unsafe fn from_bytes_with_nul_unchecked(bytes: &[u8]) -> &CStr {
- // SAFETY: Properties of `bytes` guaranteed by the safety precondition.
- unsafe { core::mem::transmute(bytes) }
- }
+ // This function exists to paper over the fact that `CStr::from_ptr` takes a `*const
+ // core::ffi::c_char` rather than a `*const crate::ffi::c_char`.
+ unsafe fn from_char_ptr<'a>(ptr: *const c_char) -> &'a Self;
/// Creates a mutable [`CStr`] from a `[u8]` without performing any
/// additional checks.
@@ -296,99 +206,16 @@ pub const fn from_bytes_with_nul(bytes: &[u8]) -> Result<&Self, CStrConvertError
///
/// `bytes` *must* end with a `NUL` byte, and should only have a single
/// `NUL` byte (or the string will be truncated).
- #[inline]
- pub unsafe fn from_bytes_with_nul_unchecked_mut(bytes: &mut [u8]) -> &mut CStr {
- // SAFETY: Properties of `bytes` guaranteed by the safety precondition.
- unsafe { &mut *(core::ptr::from_mut(bytes) as *mut CStr) }
- }
+ unsafe fn from_bytes_with_nul_unchecked_mut(bytes: &mut [u8]) -> &mut Self;
/// Returns a C pointer to the string.
- ///
- /// Using this function in a const context is deprecated in favor of
- /// [`as_char_ptr_in_const_context`] in preparation for replacing `CStr` with `core::ffi::CStr`
- /// which does not have this method.
- #[inline]
- pub const fn as_char_ptr(&self) -> *const c_char {
- as_char_ptr_in_const_context(self)
- }
-
- /// Convert the string to a byte slice without the trailing `NUL` byte.
- #[inline]
- pub fn to_bytes(&self) -> &[u8] {
- &self.0[..self.len()]
- }
-
- /// Convert the string to a byte slice without the trailing `NUL` byte.
- ///
- /// This function is deprecated in favor of [`Self::to_bytes`] in preparation for replacing
- /// `CStr` with `core::ffi::CStr` which does not have this method.
- #[inline]
- pub fn as_bytes(&self) -> &[u8] {
- self.to_bytes()
- }
-
- /// Convert the string to a byte slice containing the trailing `NUL` byte.
- #[inline]
- pub const fn to_bytes_with_nul(&self) -> &[u8] {
- &self.0
- }
-
- /// Convert the string to a byte slice containing the trailing `NUL` byte.
- ///
- /// This function is deprecated in favor of [`Self::to_bytes_with_nul`] in preparation for
- /// replacing `CStr` with `core::ffi::CStr` which does not have this method.
- #[inline]
- pub const fn as_bytes_with_nul(&self) -> &[u8] {
- self.to_bytes_with_nul()
- }
-
- /// Yields a [`&str`] slice if the [`CStr`] contains valid UTF-8.
- ///
- /// If the contents of the [`CStr`] are valid UTF-8 data, this
- /// function will return the corresponding [`&str`] slice. Otherwise,
- /// it will return an error with details of where UTF-8 validation failed.
- ///
- /// # Examples
- ///
- /// ```
- /// # use kernel::str::CStr;
- /// let cstr = CStr::from_bytes_with_nul(b"foo\0")?;
- /// assert_eq!(cstr.to_str(), Ok("foo"));
- /// # Ok::<(), kernel::error::Error>(())
- /// ```
- #[inline]
- pub fn to_str(&self) -> Result<&str, core::str::Utf8Error> {
- core::str::from_utf8(self.as_bytes())
- }
-
- /// Unsafely convert this [`CStr`] into a [`&str`], without checking for
- /// valid UTF-8.
- ///
- /// # Safety
- ///
- /// The contents must be valid UTF-8.
- ///
- /// # Examples
- ///
- /// ```
- /// # use kernel::c_str;
- /// # use kernel::str::CStr;
- /// let bar = c_str!("ツ");
- /// // SAFETY: String literals are guaranteed to be valid UTF-8
- /// // by the Rust compiler.
- /// assert_eq!(unsafe { bar.as_str_unchecked() }, "ツ");
- /// ```
- #[inline]
- pub unsafe fn as_str_unchecked(&self) -> &str {
- // SAFETY: TODO.
- unsafe { core::str::from_utf8_unchecked(self.as_bytes()) }
- }
+ // This function exists to paper over the fact that `CStr::as_ptr` returns a `*const
+ // core::ffi::c_char` rather than a `*const crate::ffi::c_char`.
+ fn as_char_ptr(&self) -> *const c_char;
/// Convert this [`CStr`] into a [`CString`] by allocating memory and
/// copying over the string data.
- pub fn to_cstring(&self) -> Result<CString, AllocError> {
- CString::try_from(self)
- }
+ fn to_cstring(&self) -> Result<CString, AllocError>;
/// Converts this [`CStr`] to its ASCII lower case equivalent in-place.
///
@@ -399,11 +226,7 @@ pub fn to_cstring(&self) -> Result<CString, AllocError> {
/// [`to_ascii_lowercase()`].
///
/// [`to_ascii_lowercase()`]: #method.to_ascii_lowercase
- pub fn make_ascii_lowercase(&mut self) {
- // INVARIANT: This doesn't introduce or remove NUL bytes in the C
- // string.
- self.0.make_ascii_lowercase();
- }
+ fn make_ascii_lowercase(&mut self);
/// Converts this [`CStr`] to its ASCII upper case equivalent in-place.
///
@@ -414,11 +237,7 @@ pub fn make_ascii_lowercase(&mut self) {
/// [`to_ascii_uppercase()`].
///
/// [`to_ascii_uppercase()`]: #method.to_ascii_uppercase
- pub fn make_ascii_uppercase(&mut self) {
- // INVARIANT: This doesn't introduce or remove NUL bytes in the C
- // string.
- self.0.make_ascii_uppercase();
- }
+ fn make_ascii_uppercase(&mut self);
/// Returns a copy of this [`CString`] where each character is mapped to its
/// ASCII lower case equivalent.
@@ -429,13 +248,7 @@ pub fn make_ascii_uppercase(&mut self) {
/// To lowercase the value in-place, use [`make_ascii_lowercase`].
///
/// [`make_ascii_lowercase`]: str::make_ascii_lowercase
- pub fn to_ascii_lowercase(&self) -> Result<CString, AllocError> {
- let mut s = self.to_cstring()?;
-
- s.make_ascii_lowercase();
-
- Ok(s)
- }
+ fn to_ascii_lowercase(&self) -> Result<CString, AllocError>;
/// Returns a copy of this [`CString`] where each character is mapped to its
/// ASCII upper case equivalent.
@@ -446,13 +259,7 @@ pub fn to_ascii_lowercase(&self) -> Result<CString, AllocError> {
/// To uppercase the value in-place, use [`make_ascii_uppercase`].
///
/// [`make_ascii_uppercase`]: str::make_ascii_uppercase
- pub fn to_ascii_uppercase(&self) -> Result<CString, AllocError> {
- let mut s = self.to_cstring()?;
-
- s.make_ascii_uppercase();
-
- Ok(s)
- }
+ fn to_ascii_uppercase(&self) -> Result<CString, AllocError>;
}
impl fmt::Display for CStr {
@@ -485,98 +292,75 @@ fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
}
}
-impl fmt::Debug for CStr {
- /// Formats printable ASCII characters with a double quote on either end, escaping the rest.
- ///
- /// ```
- /// # use kernel::c_str;
- /// # use kernel::prelude::fmt;
- /// # use kernel::str::CStr;
- /// # use kernel::str::CString;
- /// let penguin = c_str!("🐧");
- /// let s = CString::try_from_fmt(fmt!("{penguin:?}"))?;
- /// assert_eq!(s.as_bytes_with_nul(), "\"\\xf0\\x9f\\x90\\xa7\"\0".as_bytes());
- ///
- /// // Embedded double quotes are escaped.
- /// let ascii = c_str!("so \"cool\"");
- /// let s = CString::try_from_fmt(fmt!("{ascii:?}"))?;
- /// assert_eq!(s.as_bytes_with_nul(), "\"so \\\"cool\\\"\"\0".as_bytes());
- /// # Ok::<(), kernel::error::Error>(())
- /// ```
- fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
- f.write_str("\"")?;
- for &c in self.as_bytes() {
- match c {
- // Printable characters.
- b'\"' => f.write_str("\\\"")?,
- 0x20..=0x7e => f.write_char(c as char)?,
- _ => write!(f, "\\x{c:02x}")?,
- }
- }
- f.write_str("\"")
- }
+/// Converts a mutable C string to a mutable byte slice.
+///
+/// # Safety
+///
+/// The caller must ensure that the slice ends in a NUL byte and contains no other NUL bytes before
+/// the borrow ends and the underlying [`CStr`] is used.
+unsafe fn to_bytes_mut(s: &mut CStr) -> &mut [u8] {
+ // SAFETY: the cast from `&CStr` to `&[u8]` is safe since `CStr` has the same layout as `&[u8]`
+ // (this is technically not guaranteed, but we rely on it here). The pointer dereference is
+ // safe since it comes from a mutable reference which is guaranteed to be valid for writes.
+ unsafe { &mut *(core::ptr::from_mut(s) as *mut [u8]) }
}
-impl AsRef<BStr> for CStr {
+impl CStrExt for CStr {
#[inline]
- fn as_ref(&self) -> &BStr {
- BStr::from_bytes(self.as_bytes())
+ unsafe fn from_char_ptr<'a>(ptr: *const c_char) -> &'a Self {
+ // SAFETY: The safety preconditions are the same as for `CStr::from_ptr`.
+ unsafe { CStr::from_ptr(ptr.cast()) }
}
-}
-impl Deref for CStr {
- type Target = BStr;
+ #[inline]
+ unsafe fn from_bytes_with_nul_unchecked_mut(bytes: &mut [u8]) -> &mut Self {
+ // SAFETY: the cast from `&[u8]` to `&CStr` is safe since the properties of `bytes` are
+ // guaranteed by the safety precondition and `CStr` has the same layout as `&[u8]` (this is
+ // technically not guaranteed, but we rely on it here). The pointer dereference is safe
+ // since it comes from a mutable reference which is guaranteed to be valid for writes.
+ unsafe { &mut *(core::ptr::from_mut(bytes) as *mut CStr) }
+ }
#[inline]
- fn deref(&self) -> &Self::Target {
- self.as_ref()
+ fn as_char_ptr(&self) -> *const c_char {
+ self.as_ptr().cast()
}
-}
-impl Index<ops::RangeFrom<usize>> for CStr {
- type Output = CStr;
+ fn to_cstring(&self) -> Result<CString, AllocError> {
+ CString::try_from(self)
+ }
- #[inline]
- fn index(&self, index: ops::RangeFrom<usize>) -> &Self::Output {
- // Delegate bounds checking to slice.
- // Assign to _ to mute clippy's unnecessary operation warning.
- let _ = &self.as_bytes()[index.start..];
- // SAFETY: We just checked the bounds.
- unsafe { Self::from_bytes_with_nul_unchecked(&self.0[index.start..]) }
+ fn make_ascii_lowercase(&mut self) {
+ // SAFETY: This doesn't introduce or remove NUL bytes in the C string.
+ unsafe { to_bytes_mut(self) }.make_ascii_lowercase();
+ }
+
+ fn make_ascii_uppercase(&mut self) {
+ // SAFETY: This doesn't introduce or remove NUL bytes in the C string.
+ unsafe { to_bytes_mut(self) }.make_ascii_uppercase();
}
-}
-impl Index<ops::RangeFull> for CStr {
- type Output = CStr;
+ fn to_ascii_lowercase(&self) -> Result<CString, AllocError> {
+ let mut s = self.to_cstring()?;
- #[inline]
- fn index(&self, _index: ops::RangeFull) -> &Self::Output {
- self
+ s.make_ascii_lowercase();
+
+ Ok(s)
}
-}
-mod private {
- use core::ops;
+ fn to_ascii_uppercase(&self) -> Result<CString, AllocError> {
+ let mut s = self.to_cstring()?;
- // Marker trait for index types that can be forward to `BStr`.
- pub trait CStrIndex {}
+ s.make_ascii_uppercase();
- impl CStrIndex for usize {}
- impl CStrIndex for ops::Range<usize> {}
- impl CStrIndex for ops::RangeInclusive<usize> {}
- impl CStrIndex for ops::RangeToInclusive<usize> {}
+ Ok(s)
+ }
}
-impl<Idx> Index<Idx> for CStr
-where
- Idx: private::CStrIndex,
- BStr: Index<Idx>,
-{
- type Output = <BStr as Index<Idx>>::Output;
-
+impl AsRef<BStr> for CStr {
#[inline]
- fn index(&self, index: Idx) -> &Self::Output {
- &self.as_ref()[index]
+ fn as_ref(&self) -> &BStr {
+ BStr::from_bytes(self.to_bytes())
}
}
@@ -607,6 +391,13 @@ macro_rules! c_str {
mod tests {
use super::*;
+ impl From<core::ffi::FromBytesWithNulError> for Error {
+ #[inline]
+ fn from(_: core::ffi::FromBytesWithNulError) -> Error {
+ EINVAL
+ }
+ }
+
macro_rules! format {
($($f:tt)*) => ({
CString::try_from_fmt(fmt!($($f)*))?.to_str()?
@@ -629,40 +420,28 @@ macro_rules! format {
#[test]
fn test_cstr_to_str() -> Result {
- let good_bytes = b"\xf0\x9f\xa6\x80\0";
- let checked_cstr = CStr::from_bytes_with_nul(good_bytes)?;
- let checked_str = checked_cstr.to_str()?;
+ let cstr = c"\xf0\x9f\xa6\x80";
+ let checked_str = cstr.to_str()?;
assert_eq!(checked_str, "🦀");
Ok(())
}
#[test]
fn test_cstr_to_str_invalid_utf8() -> Result {
- let bad_bytes = b"\xc3\x28\0";
- let checked_cstr = CStr::from_bytes_with_nul(bad_bytes)?;
- assert!(checked_cstr.to_str().is_err());
- Ok(())
- }
-
- #[test]
- fn test_cstr_as_str_unchecked() -> Result {
- let good_bytes = b"\xf0\x9f\x90\xA7\0";
- let checked_cstr = CStr::from_bytes_with_nul(good_bytes)?;
- // SAFETY: The contents come from a string literal which contains valid UTF-8.
- let unchecked_str = unsafe { checked_cstr.as_str_unchecked() };
- assert_eq!(unchecked_str, "🐧");
+ let cstr = c"\xc3\x28";
+ assert!(cstr.to_str().is_err());
Ok(())
}
#[test]
fn test_cstr_display() -> Result {
- let hello_world = CStr::from_bytes_with_nul(b"hello, world!\0")?;
+ let hello_world = c"hello, world!";
assert_eq!(format!("{hello_world}"), "hello, world!");
- let non_printables = CStr::from_bytes_with_nul(b"\x01\x09\x0a\0")?;
+ let non_printables = c"\x01\x09\x0a";
assert_eq!(format!("{non_printables}"), "\\x01\\x09\\x0a");
- let non_ascii = CStr::from_bytes_with_nul(b"d\xe9j\xe0 vu\0")?;
+ let non_ascii = c"d\xe9j\xe0 vu";
assert_eq!(format!("{non_ascii}"), "d\\xe9j\\xe0 vu");
- let good_bytes = CStr::from_bytes_with_nul(b"\xf0\x9f\xa6\x80\0")?;
+ let good_bytes = c"\xf0\x9f\xa6\x80";
assert_eq!(format!("{good_bytes}"), "\\xf0\\x9f\\xa6\\x80");
Ok(())
}
@@ -681,13 +460,13 @@ fn test_cstr_display_all_bytes() -> Result {
#[test]
fn test_cstr_debug() -> Result {
- let hello_world = CStr::from_bytes_with_nul(b"hello, world!\0")?;
+ let hello_world = c"hello, world!";
assert_eq!(format!("{hello_world:?}"), "\"hello, world!\"");
- let non_printables = CStr::from_bytes_with_nul(b"\x01\x09\x0a\0")?;
- assert_eq!(format!("{non_printables:?}"), "\"\\x01\\x09\\x0a\"");
- let non_ascii = CStr::from_bytes_with_nul(b"d\xe9j\xe0 vu\0")?;
+ let non_printables = c"\x01\x09\x0a";
+ assert_eq!(format!("{non_printables:?}"), "\"\\x01\\t\\n\"");
+ let non_ascii = c"d\xe9j\xe0 vu";
assert_eq!(format!("{non_ascii:?}"), "\"d\\xe9j\\xe0 vu\"");
- let good_bytes = CStr::from_bytes_with_nul(b"\xf0\x9f\xa6\x80\0")?;
+ let good_bytes = c"\xf0\x9f\xa6\x80";
assert_eq!(format!("{good_bytes:?}"), "\"\\xf0\\x9f\\xa6\\x80\"");
Ok(())
}
diff --git a/rust/kernel/sync/condvar.rs b/rust/kernel/sync/condvar.rs
index caebf03f553b..0b6bc7f2878d 100644
--- a/rust/kernel/sync/condvar.rs
+++ b/rust/kernel/sync/condvar.rs
@@ -8,7 +8,7 @@
use super::{lock::Backend, lock::Guard, LockClassKey};
use crate::{
ffi::{c_int, c_long},
- str::CStr,
+ str::{CStr, CStrExt as _},
task::{
MAX_SCHEDULE_TIMEOUT, TASK_FREEZABLE, TASK_INTERRUPTIBLE, TASK_NORMAL, TASK_UNINTERRUPTIBLE,
},
diff --git a/rust/kernel/sync/lock.rs b/rust/kernel/sync/lock.rs
index e82fa5be289c..a777a22976e0 100644
--- a/rust/kernel/sync/lock.rs
+++ b/rust/kernel/sync/lock.rs
@@ -7,7 +7,7 @@
use super::LockClassKey;
use crate::{
- str::CStr,
+ str::{CStr, CStrExt as _},
types::{NotThreadSafe, Opaque, ScopeGuard},
};
use core::{cell::UnsafeCell, marker::PhantomPinned, pin::Pin};
diff --git a/rust/kernel/sync/lock/global.rs b/rust/kernel/sync/lock/global.rs
index d65f94b5caf2..79d0ef7fda86 100644
--- a/rust/kernel/sync/lock/global.rs
+++ b/rust/kernel/sync/lock/global.rs
@@ -5,7 +5,7 @@
//! Support for defining statics containing locks.
use crate::{
- str::CStr,
+ str::{CStr, CStrExt as _},
sync::lock::{Backend, Guard, Lock},
sync::{LockClassKey, LockedBy},
types::Opaque,
--
2.50.0
^ permalink raw reply related [flat|nested] 10+ messages in thread* Re: [PATCH v14 3/3] rust: replace `CStr` with `core::ffi::CStr`
2025-07-10 14:53 ` [PATCH v14 3/3] rust: replace `CStr` with `core::ffi::CStr` Tamir Duberstein
@ 2025-08-12 7:50 ` Benno Lossin
2025-08-13 14:06 ` Tamir Duberstein
0 siblings, 1 reply; 10+ messages in thread
From: Benno Lossin @ 2025-08-12 7:50 UTC (permalink / raw)
To: Tamir Duberstein, Miguel Ojeda, Alex Gaynor, Boqun Feng, Gary Guo,
Björn Roy Baron, Andreas Hindborg, Alice Ryhl, Trevor Gross,
Danilo Krummrich, Greg Kroah-Hartman, Rafael J. Wysocki,
Luis Chamberlain, Russ Weight, Peter Zijlstra, Ingo Molnar,
Will Deacon, Waiman Long, Nathan Chancellor, Nick Desaulniers,
Bill Wendling, Justin Stitt, Christian Brauner
Cc: rust-for-linux, linux-kernel, llvm
On Thu Jul 10, 2025 at 4:53 PM CEST, Tamir Duberstein wrote:
> `kernel::ffi::CStr` was introduced in commit d126d2380131 ("rust: str:
> add `CStr` type") in November 2022 as an upstreaming of earlier work
> that was done in May 2021[0]. That earlier work, having predated the
> inclusion of `CStr` in `core`, largely duplicated the implementation of
> `std::ffi::CStr`.
>
> `std::ffi::CStr` was moved to `core::ffi::CStr` in Rust 1.64 in
> September 2022. Hence replace `kernel::str::CStr` with `core::ffi::CStr`
> to reduce our custom code footprint, and retain needed custom
> functionality through an extension trait.
>
> Add `CStr` to `ffi` and the kernel prelude.
>
> Link: https://github.com/Rust-for-Linux/linux/commit/faa3cbcca03d0dec8f8e43f1d8d5c0860d98a23f [0]
> Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> Reviewed-by: Alice Ryhl <aliceryhl@google.com>
> Signed-off-by: Tamir Duberstein <tamird@gmail.com>
Reviewed-by: Benno Lossin <lossin@kernel.org>
> ---
> rust/ffi.rs | 2 +
> rust/kernel/device.rs | 1 +
> rust/kernel/error.rs | 2 +
> rust/kernel/firmware.rs | 9 +-
> rust/kernel/prelude.rs | 4 +-
> rust/kernel/seq_file.rs | 2 +-
> rust/kernel/str.rs | 395 +++++++++-------------------------------
> rust/kernel/sync/condvar.rs | 2 +-
> rust/kernel/sync/lock.rs | 2 +-
> rust/kernel/sync/lock/global.rs | 2 +-
> 10 files changed, 106 insertions(+), 315 deletions(-)
> +/// Extensions to [`CStr`].
> +pub trait CStrExt {
Should we make this trait sealed?
---
Cheers,
Benno
> /// Wraps a raw C string pointer.
> ///
> /// # Safety
^ permalink raw reply [flat|nested] 10+ messages in thread* Re: [PATCH v14 3/3] rust: replace `CStr` with `core::ffi::CStr`
2025-08-12 7:50 ` Benno Lossin
@ 2025-08-13 14:06 ` Tamir Duberstein
2025-08-13 14:39 ` Benno Lossin
0 siblings, 1 reply; 10+ messages in thread
From: Tamir Duberstein @ 2025-08-13 14:06 UTC (permalink / raw)
To: Benno Lossin
Cc: Miguel Ojeda, Alex Gaynor, Boqun Feng, Gary Guo,
Björn Roy Baron, Andreas Hindborg, Alice Ryhl, Trevor Gross,
Danilo Krummrich, Greg Kroah-Hartman, Rafael J. Wysocki,
Luis Chamberlain, Russ Weight, Peter Zijlstra, Ingo Molnar,
Will Deacon, Waiman Long, Nathan Chancellor, Nick Desaulniers,
Bill Wendling, Justin Stitt, Christian Brauner, rust-for-linux,
linux-kernel, llvm
On Tue, Aug 12, 2025 at 3:50 AM Benno Lossin <lossin@kernel.org> wrote:
>
> On Thu Jul 10, 2025 at 4:53 PM CEST, Tamir Duberstein wrote:
> > `kernel::ffi::CStr` was introduced in commit d126d2380131 ("rust: str:
> > add `CStr` type") in November 2022 as an upstreaming of earlier work
> > that was done in May 2021[0]. That earlier work, having predated the
> > inclusion of `CStr` in `core`, largely duplicated the implementation of
> > `std::ffi::CStr`.
> >
> > `std::ffi::CStr` was moved to `core::ffi::CStr` in Rust 1.64 in
> > September 2022. Hence replace `kernel::str::CStr` with `core::ffi::CStr`
> > to reduce our custom code footprint, and retain needed custom
> > functionality through an extension trait.
> >
> > Add `CStr` to `ffi` and the kernel prelude.
> >
> > Link: https://github.com/Rust-for-Linux/linux/commit/faa3cbcca03d0dec8f8e43f1d8d5c0860d98a23f [0]
> > Acked-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
> > Reviewed-by: Alice Ryhl <aliceryhl@google.com>
> > Signed-off-by: Tamir Duberstein <tamird@gmail.com>
>
> Reviewed-by: Benno Lossin <lossin@kernel.org>
Thanks!
> > ---
> > rust/ffi.rs | 2 +
> > rust/kernel/device.rs | 1 +
> > rust/kernel/error.rs | 2 +
> > rust/kernel/firmware.rs | 9 +-
> > rust/kernel/prelude.rs | 4 +-
> > rust/kernel/seq_file.rs | 2 +-
> > rust/kernel/str.rs | 395 +++++++++-------------------------------
> > rust/kernel/sync/condvar.rs | 2 +-
> > rust/kernel/sync/lock.rs | 2 +-
> > rust/kernel/sync/lock/global.rs | 2 +-
> > 10 files changed, 106 insertions(+), 315 deletions(-)
>
> > +/// Extensions to [`CStr`].
> > +pub trait CStrExt {
>
> Should we make this trait sealed?
We can -- but is it harmful for someone to implement? I think probably not.
>
> ---
> Cheers,
> Benno
>
> > /// Wraps a raw C string pointer.
> > ///
> > /// # Safety
^ permalink raw reply [flat|nested] 10+ messages in thread* Re: [PATCH v14 3/3] rust: replace `CStr` with `core::ffi::CStr`
2025-08-13 14:06 ` Tamir Duberstein
@ 2025-08-13 14:39 ` Benno Lossin
2025-08-13 15:46 ` Tamir Duberstein
0 siblings, 1 reply; 10+ messages in thread
From: Benno Lossin @ 2025-08-13 14:39 UTC (permalink / raw)
To: Tamir Duberstein
Cc: Miguel Ojeda, Alex Gaynor, Boqun Feng, Gary Guo,
Björn Roy Baron, Andreas Hindborg, Alice Ryhl, Trevor Gross,
Danilo Krummrich, Greg Kroah-Hartman, Rafael J. Wysocki,
Luis Chamberlain, Russ Weight, Peter Zijlstra, Ingo Molnar,
Will Deacon, Waiman Long, Nathan Chancellor, Nick Desaulniers,
Bill Wendling, Justin Stitt, Christian Brauner, rust-for-linux,
linux-kernel, llvm
On Wed Aug 13, 2025 at 4:06 PM CEST, Tamir Duberstein wrote:
> On Tue, Aug 12, 2025 at 3:50 AM Benno Lossin <lossin@kernel.org> wrote:
>> On Thu Jul 10, 2025 at 4:53 PM CEST, Tamir Duberstein wrote:
>> > +/// Extensions to [`CStr`].
>> > +pub trait CStrExt {
>>
>> Should we make this trait sealed?
>
> We can -- but is it harmful for someone to implement? I think probably not.
I don't think anything aside from `CStr` should implement it, so I'd say
we make it sealed. There are also safe functions that return raw
pointers & an implementation could just return a bogus pointer...
---
Cheers,
Benno
^ permalink raw reply [flat|nested] 10+ messages in thread* Re: [PATCH v14 3/3] rust: replace `CStr` with `core::ffi::CStr`
2025-08-13 14:39 ` Benno Lossin
@ 2025-08-13 15:46 ` Tamir Duberstein
0 siblings, 0 replies; 10+ messages in thread
From: Tamir Duberstein @ 2025-08-13 15:46 UTC (permalink / raw)
To: Benno Lossin
Cc: Miguel Ojeda, Alex Gaynor, Boqun Feng, Gary Guo,
Björn Roy Baron, Andreas Hindborg, Alice Ryhl, Trevor Gross,
Danilo Krummrich, Greg Kroah-Hartman, Rafael J. Wysocki,
Luis Chamberlain, Russ Weight, Peter Zijlstra, Ingo Molnar,
Will Deacon, Waiman Long, Nathan Chancellor, Nick Desaulniers,
Bill Wendling, Justin Stitt, Christian Brauner, rust-for-linux,
linux-kernel, llvm
On Wed, Aug 13, 2025 at 10:40 AM Benno Lossin <lossin@kernel.org> wrote:
>
> On Wed Aug 13, 2025 at 4:06 PM CEST, Tamir Duberstein wrote:
> > On Tue, Aug 12, 2025 at 3:50 AM Benno Lossin <lossin@kernel.org> wrote:
> >> On Thu Jul 10, 2025 at 4:53 PM CEST, Tamir Duberstein wrote:
> >> > +/// Extensions to [`CStr`].
> >> > +pub trait CStrExt {
> >>
> >> Should we make this trait sealed?
> >
> > We can -- but is it harmful for someone to implement? I think probably not.
>
> I don't think anything aside from `CStr` should implement it, so I'd say
> we make it sealed. There are also safe functions that return raw
> pointers & an implementation could just return a bogus pointer...
Done in v15.
^ permalink raw reply [flat|nested] 10+ messages in thread
* Re: [PATCH v14 0/3] rust: replace kernel::str::CStr w/ core::ffi::CStr
2025-07-10 14:53 [PATCH v14 0/3] rust: replace kernel::str::CStr w/ core::ffi::CStr Tamir Duberstein
` (2 preceding siblings ...)
2025-07-10 14:53 ` [PATCH v14 3/3] rust: replace `CStr` with `core::ffi::CStr` Tamir Duberstein
@ 2025-07-14 11:25 ` Danilo Krummrich
3 siblings, 0 replies; 10+ messages in thread
From: Danilo Krummrich @ 2025-07-14 11:25 UTC (permalink / raw)
To: Tamir Duberstein
Cc: Miguel Ojeda, Alex Gaynor, Boqun Feng, Gary Guo,
Björn Roy Baron, Benno Lossin, Andreas Hindborg, Alice Ryhl,
Trevor Gross, Greg Kroah-Hartman, Rafael J. Wysocki,
Luis Chamberlain, Russ Weight, Peter Zijlstra, Ingo Molnar,
Will Deacon, Waiman Long, Nathan Chancellor, Nick Desaulniers,
Bill Wendling, Justin Stitt, Christian Brauner, rust-for-linux,
linux-kernel, llvm
On Thu Jul 10, 2025 at 4:53 PM CEST, Tamir Duberstein wrote:
> This picks up from Michal Rostecki's work[0]. Per Michal's guidance I
> have omitted Co-authored tags, as the end result is quite different.
For device and firmware,
Acked-by: Danilo Krummrich <dakr@kernel.org>
^ permalink raw reply [flat|nested] 10+ messages in thread