From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-pl1-f202.google.com (mail-pl1-f202.google.com [209.85.214.202]) (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 5410726C38E for ; Tue, 24 Jun 2025 23:25:37 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.214.202 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750807538; cv=none; b=Z0KEmEUH+SIqsiB21cnQjqN3ICLgrImOES3GiLALyzW1I/kcYVGxpB4f5ONzsNqCFnHNKrIrjkGmj0hIN7ZwM266wJBTJgnqCcVNlzNYBOqBOndyXoq8CZuGn8wvUwdNLDXEsv3q9flRFk8IK7/MCO2yy7gboLkQpV9cQAK8d/I= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1750807538; c=relaxed/simple; bh=CAjW4qWEATQAhifD7XkDU8mnRpNkpHK/ka6oGRsQ4qs=; h=Date:In-Reply-To:Mime-Version:References:Message-ID:Subject:From: To:Cc:Content-Type; b=n06jcFBRdrhte62Dk7PI3CWoXDAGH6reSafvbAZBAHnN/nKxukdkdOvc5W/MO17sgTTThCIcjkr8cF1xOYltZiOF0OpjXD2xHdVqRrlOpbgNwBGUkThxMCNFwDcRoKbdCu9xdripZOO469tvqXS04uaqaBgCkEhl3qlpK8joVkY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=google.com; spf=pass smtp.mailfrom=flex--mmaurer.bounces.google.com; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b=mA+/KCOJ; arc=none smtp.client-ip=209.85.214.202 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--mmaurer.bounces.google.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="mA+/KCOJ" Received: by mail-pl1-f202.google.com with SMTP id d9443c01a7336-235c897d378so8614535ad.1 for ; Tue, 24 Jun 2025 16:25:37 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20230601; t=1750807536; x=1751412336; 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=gpUS+EX77lZKoaVBWmim3dqnGXias1I977cCfQoRsAA=; b=mA+/KCOJR5BUcUo88K/tgyFsrrlJVrB2VJn74HdXAkgdm8VWru7XcIQihLZk2pc2jF 6WZiDR6t7VjuZVLJCoHCsuGK2139dOwprsi3MT0mnnSzWAns2VGMPeqzHH5NXddaXvte VoNH9H1oMhMzaGpTLAqF40VvzwnA1qgs2+ExSSzC6UHU0CBADvY6pHOvFKeuFSBukXd9 LSlQSacpqov+6XF3yOHbNkbqDoIUJ3m2phCL0D7NpKT1niBOxm4vPueZvh2uRkexWmLH xs3vyMfSKW6dRdrtDowI9sX177Yqmu5XoyHyGu/p3vSe79OplqHFke0DWWena6ho8uBA UIXQ== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1750807536; x=1751412336; 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=gpUS+EX77lZKoaVBWmim3dqnGXias1I977cCfQoRsAA=; b=OLFuN/0DreQ2HyuKhktE8JFvz/68iV2ztuZQGJw8Uuh7WjcAovAi+mLl9pb0OuGiRj 0G17WakqOp/0GA9bS095/nS9MJvx9lDPSTcmi352MWyekVKfCyRZacSCp2H3WGbUi701 xvvt/4/xGFnzBy0VHKhGhv7JzlgA4e+073oPOZunD5muuPrNEbAluc3h0Gd7DOr0V4on UhRxVYMNaAvHL7gkKsKL5hMpUf5WDaJ8Y16ehCewdy1NeYC+GuM3Jz+21CJ3oZKaQNtD 2t0txXr9yb2U/qURmCTR9q+1g32ingbl2j8xj1KePSvy0L7V55wgdOVte2puD9wXMMEP rtrg== X-Gm-Message-State: AOJu0Yw1flV4QhCKBiX2oE9tmoMk3L0SUzvQoksqMv9pCUmIhj56RWhg jrrMx4s+APWAFOm9UiaKogurmyK/WrE1SoRDoXmQzESYY+b4fDxTn7g84/t0e0fqBWsPR0jCHwY NCFQhoNjxqg== X-Google-Smtp-Source: AGHT+IEDp9updf55BfUA08pmBhU8YEuSsF1HIz2zGLaUKLG0XPXQu8Q68M6BPJ2uiz0kFU7UI6Lz8+REqopx X-Received: from plbmi11.prod.google.com ([2002:a17:902:fccb:b0:234:c918:aa1b]) (user=mmaurer job=prod-delivery.src-stubby-dispatcher) by 2002:a17:902:ea0e:b0:235:f298:cbbe with SMTP id d9443c01a7336-23823fc3f70mr19229955ad.12.1750807536641; Tue, 24 Jun 2025 16:25:36 -0700 (PDT) Date: Tue, 24 Jun 2025 23:25:24 +0000 In-Reply-To: <20250624-debugfs-rust-v7-0-9c8835a7a20f@google.com> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 References: <20250624-debugfs-rust-v7-0-9c8835a7a20f@google.com> X-Developer-Key: i=mmaurer@google.com; a=ed25519; pk=2Ezhl7+fEjTOMVFpplDeak2AdQ8cjJieLRVJdNzrW+E= X-Developer-Signature: v=1; a=ed25519-sha256; t=1750807526; l=6428; i=mmaurer@google.com; s=20250429; h=from:subject:message-id; bh=CAjW4qWEATQAhifD7XkDU8mnRpNkpHK/ka6oGRsQ4qs=; b=kryJzDpp6myFWv9gqYuI4yuSx3w9/sqq3gr4Gp89vHVyREZmgBuhlYOpGJE/UjM6jQeBuhO4S wz+ISRrNIMID3mbPaFrE6bUgDWVhw0BmCwRrWduzSnMxF0qQE0uyTfV X-Mailer: b4 0.14.2 Message-ID: <20250624-debugfs-rust-v7-5-9c8835a7a20f@google.com> Subject: [PATCH v7 5/6] rust: debugfs: Support format hooks From: Matthew Maurer To: Miguel Ojeda , Alex Gaynor , Boqun Feng , Gary Guo , "=?utf-8?q?Bj=C3=B6rn_Roy_Baron?=" , Andreas Hindborg , Alice Ryhl , Trevor Gross , Danilo Krummrich , Greg Kroah-Hartman , "Rafael J. Wysocki" , Sami Tolvanen , Timur Tabi , Benno Lossin Cc: linux-kernel@vger.kernel.org, rust-for-linux@vger.kernel.org, Matthew Maurer Content-Type: text/plain; charset="utf-8" Rather than always using Display, allow hooking arbitrary functions to arbitrary files. Display technically has the expressiveness to do this, but requires a new type be declared for every different way to render things, which can be very clumsy. Signed-off-by: Matthew Maurer --- rust/kernel/debugfs.rs | 45 ++++++++++++++++++++ rust/kernel/debugfs/display_file.rs | 85 ++++++++++++++++++++++++++++++++++++- 2 files changed, 129 insertions(+), 1 deletion(-) diff --git a/rust/kernel/debugfs.rs b/rust/kernel/debugfs.rs index 929e55ee5629f6888edf29997b9ed77d274e11c8..d74b599e8534536b10502e6db8c6f3197f7ab4a5 100644 --- a/rust/kernel/debugfs.rs +++ b/rust/kernel/debugfs.rs @@ -10,7 +10,9 @@ #[cfg(CONFIG_DEBUG_FS)] use crate::sync::Arc; use crate::types::ForeignOwnable; +use core::fmt; use core::fmt::Display; +use core::ops::Deref; #[cfg(CONFIG_DEBUG_FS)] mod display_file; @@ -157,6 +159,49 @@ pub fn display_file(&self, name: &CStr, data: D self.create_file(name, data) } + /// Create a file in a DebugFS directory with the provided name, and contents from invoking `f` + /// on the provided reference. + /// + /// `f` must be a function item or a non-capturing closure, or this will fail to compile. + /// + /// # Examples + /// + /// ``` + /// # use core::sync::atomic::{AtomicU32, Ordering}; + /// # use kernel::c_str; + /// # use kernel::debugfs::Dir; + /// let dir = Dir::new(c_str!("foo")); + /// static MY_ATOMIC: AtomicU32 = AtomicU32::new(3); + /// let file = dir.fmt_file(c_str!("bar"), &MY_ATOMIC, &|val, f| { + /// let out = val.load(Ordering::Relaxed); + /// writeln!(f, "{out:#010x}") + /// }); + /// MY_ATOMIC.store(10, Ordering::Relaxed); + /// ``` + pub fn fmt_file< + D: ForeignOwnable + Send + Sync, + T, + F: Fn(&T, &mut fmt::Formatter<'_>) -> fmt::Result + Send + Sync, + >( + &self, + name: &CStr, + data: D, + f: &'static F, + ) -> File + where + for<'a> D::Borrowed<'a>: Deref, + { + #[cfg(CONFIG_DEBUG_FS)] + let data_adapted = display_file::FormatAdapter::new(data, f); + #[cfg(not(CONFIG_DEBUG_FS))] + let data_adapted = { + // Mark used + let (_, _) = (data, f); + &0 + }; + self.display_file(name, data_adapted) + } + /// Create a new directory in DebugFS at the root. /// /// # Examples diff --git a/rust/kernel/debugfs/display_file.rs b/rust/kernel/debugfs/display_file.rs index 0c2dd756fa866425d1b7771beceaa2fb43bf11e5..b38675a90e1b2e359fb54afd91062b26d1c32ba2 100644 --- a/rust/kernel/debugfs/display_file.rs +++ b/rust/kernel/debugfs/display_file.rs @@ -5,7 +5,9 @@ use crate::seq_file::SeqFile; use crate::seq_print; use crate::types::ForeignOwnable; -use core::fmt::Display; +use core::fmt::{Display, Formatter, Result}; +use core::marker::PhantomData; +use core::ops::Deref; /// Implements `open` for `file_operations` via `single_open` to fill out a `seq_file`. /// @@ -70,3 +72,84 @@ impl DisplayFile for D ..unsafe { core::mem::zeroed() } }; } + +/// Adapter to implement `Display` via a callback with the same representation as `T`. +/// +/// # Invariants +/// +/// If an instance for `FormatAdapter<_, F>` is constructed, `F` is inhabited. +#[repr(transparent)] +pub(crate) struct FormatAdapter { + inner: D, + _formatter: PhantomData, +} + +impl FormatAdapter { + pub(crate) fn new(inner: D, _f: &'static F) -> Self { + // INVARIANT: We were passed a reference to F, so it is inhabited. + FormatAdapter { + inner, + _formatter: PhantomData, + } + } +} + +pub(crate) struct BorrowedAdapter<'a, D: ForeignOwnable, F> { + borrowed: D::Borrowed<'a>, + _formatter: PhantomData, +} + +// SAFETY: We delegate to D's implementation of `ForeignOwnable`, so `into_foreign` produced aligned +// pointers. +unsafe impl ForeignOwnable for FormatAdapter { + type PointedTo = D::PointedTo; + type Borrowed<'a> = BorrowedAdapter<'a, D, F>; + type BorrowedMut<'a> = Self::Borrowed<'a>; + fn into_foreign(self) -> *mut Self::PointedTo { + self.inner.into_foreign() + } + unsafe fn from_foreign(foreign: *mut Self::PointedTo) -> Self { + Self { + // SAFETY: `into_foreign` is delegated, so a delegated `from_foreign` is safe. + inner: unsafe { D::from_foreign(foreign) }, + _formatter: PhantomData, + } + } + unsafe fn borrow<'a>(foreign: *mut Self::PointedTo) -> Self::Borrowed<'a> { + BorrowedAdapter { + // SAFETY: `into_foreign` is delegated, so a delegated `borrow` is safe. + borrowed: unsafe { D::borrow(foreign) }, + _formatter: PhantomData, + } + } + unsafe fn borrow_mut<'a>(foreign: *mut Self::PointedTo) -> Self::BorrowedMut<'a> { + // SAFETY: `borrow_mut` has stricter requirements than `borrow` + unsafe { Self::borrow(foreign) } + } +} + +impl<'a, D: ForeignOwnable: Deref>, T, F> Display + for BorrowedAdapter<'a, D, F> +where + F: Fn(&T, &mut Formatter<'_>) -> Result + 'static, +{ + fn fmt(&self, fmt: &mut Formatter<'_>) -> Result { + // SAFETY: FormatAdapter<_, F> can only be constructed if F is inhabited + let f: &F = unsafe { materialize_zst_fmt() }; + f(&self.borrowed, fmt) + } +} + +/// For types with a unique value, produce a static reference to it. +/// +/// # Safety +/// +/// The caller asserts that F is inhabited +unsafe fn materialize_zst_fmt() -> &'static F { + const { assert!(core::mem::size_of::() == 0) }; + let zst_dangle: core::ptr::NonNull = core::ptr::NonNull::dangling(); + // SAFETY: While the pointer is dangling, it is a dangling pointer to a ZST, based on the + // assertion above. The type is also inhabited, by the caller's assertion. This means + // we can materialize it. + unsafe { zst_dangle.as_ref() } +} -- 2.50.0.714.g196bf9f422-goog