From patchwork Fri Mar 7 22:49:51 2025 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Miguel Ojeda X-Patchwork-Id: 14009014 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id DE69A20DD67; Fri, 7 Mar 2025 22:52:35 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741387956; cv=none; b=Ev63pLSlIShyp/UnBV/Jmr5WM6xcRk1ML1W5vL3Ds8vYZTOHM25+x1pRtO/z0A4tU5Tu19MRXqrWF6mlysVgVTUWU3YTAOX1dCP1s5sIBSRDDCwlXNokb3nVe5kqdwD1SmmB8xXRj+HdccA7uiEOqGzzjNUAIRPwywQgp8bP+c4= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1741387956; c=relaxed/simple; bh=sdjp1uyhOF0jVGvyXjgziv2UFXoFIS/gs2td7u/ciXQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=svRAC730vbLEJNoCmbcv66l3TYUgyWqbLSADqZx3YQ1xbm6OAFsa6Sepye7kHCxATCUmpghfCxUoeterhYfP1RTg6jVW+LHnIexr7v5LRKL9+YG/oiAL60hckciiCwZy2ac7vBzuLwzgGPfWXsJ71fwlNmhdeUkAyeqbTG7bG/E= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=pZXFFnGO; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="pZXFFnGO" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 8F3EFC4CEE3; Fri, 7 Mar 2025 22:52:33 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1741387955; bh=sdjp1uyhOF0jVGvyXjgziv2UFXoFIS/gs2td7u/ciXQ=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=pZXFFnGO69Qxhre162AhPx0Q745F7drrLwyETmegSRfNejkpc5Q4lB2MPjUUQJ5eU 3NrzhMQ8LFruYKhtrqHeN3mWWzgIcvzRd/7IgK7kSsTmUu3i4BFTOu0x6Ip0Ty1R3L kPdLH2GnjXtXK5Pk1Df8VWOsZWksosY5/crsksRX3/J0z/m59X7/DmdUrwGPmztofs blaSyE+aOsI7MFLS2yBm8m+lGICV73wvrAlbgPBYc2qOnNFGwxCDgtVMnay4k1sqn1 TZxTa7vm8x0cyxkOtZ1TXwYzKq0MN5h9+wWe/Or9LFgkdTWWSsOk4Y38Zht6wCwhKn fbyRDC2Gcseeg== From: Miguel Ojeda To: Greg Kroah-Hartman , Sasha Levin , stable@vger.kernel.org Cc: Danilo Krummrich , Alice Ryhl , Alyssa Ross , NoisyCoil , patches@lists.linux.dev, Miguel Ojeda Subject: [PATCH 6.12.y 44/60] rust: alloc: implement `Cmalloc` in module allocator_test Date: Fri, 7 Mar 2025 23:49:51 +0100 Message-ID: <20250307225008.779961-45-ojeda@kernel.org> In-Reply-To: <20250307225008.779961-1-ojeda@kernel.org> References: <20250307225008.779961-1-ojeda@kernel.org> Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 From: Danilo Krummrich commit dd09538fb4093176a818fcecd45114430cc5840f upstream. So far the kernel's `Box` and `Vec` types can't be used by userspace test cases, since all users of those types (e.g. `CString`) use kernel allocators for instantiation. In order to allow userspace test cases to make use of such types as well, implement the `Cmalloc` allocator within the allocator_test module and type alias all kernel allocators to `Cmalloc`. The `Cmalloc` allocator uses libc's `realloc()` function as allocator backend. Reviewed-by: Benno Lossin Reviewed-by: Gary Guo Signed-off-by: Danilo Krummrich Link: https://lore.kernel.org/r/20241004154149.93856-26-dakr@kernel.org [ Removed the temporary `allow(dead_code)` as discussed in the list and fixed typo, added backticks. - Miguel ] Signed-off-by: Miguel Ojeda --- rust/kernel/alloc.rs | 1 - rust/kernel/alloc/allocator_test.rs | 89 ++++++++++++++++++++++++++--- 2 files changed, 81 insertions(+), 9 deletions(-) diff --git a/rust/kernel/alloc.rs b/rust/kernel/alloc.rs index 049fca7a514d..c6024afa3739 100644 --- a/rust/kernel/alloc.rs +++ b/rust/kernel/alloc.rs @@ -215,7 +215,6 @@ unsafe fn free(ptr: NonNull, layout: Layout) { } } -#[allow(dead_code)] /// Returns a properly aligned dangling pointer from the given `layout`. pub(crate) fn dangling_from_layout(layout: Layout) -> NonNull { let ptr = layout.align() as *mut u8; diff --git a/rust/kernel/alloc/allocator_test.rs b/rust/kernel/alloc/allocator_test.rs index bd0cbcd93e52..54ca85964d4a 100644 --- a/rust/kernel/alloc/allocator_test.rs +++ b/rust/kernel/alloc/allocator_test.rs @@ -1,22 +1,95 @@ // SPDX-License-Identifier: GPL-2.0 +//! So far the kernel's `Box` and `Vec` types can't be used by userspace test cases, since all users +//! of those types (e.g. `CString`) use kernel allocators for instantiation. +//! +//! In order to allow userspace test cases to make use of such types as well, implement the +//! `Cmalloc` allocator within the allocator_test module and type alias all kernel allocators to +//! `Cmalloc`. The `Cmalloc` allocator uses libc's `realloc()` function as allocator backend. + #![allow(missing_docs)] -use super::{AllocError, Allocator, Flags}; +use super::{flags::*, AllocError, Allocator, Flags}; use core::alloc::Layout; +use core::cmp; +use core::ptr; use core::ptr::NonNull; -pub struct Kmalloc; +/// The userspace allocator based on libc. +pub struct Cmalloc; + +pub type Kmalloc = Cmalloc; pub type Vmalloc = Kmalloc; pub type KVmalloc = Kmalloc; -unsafe impl Allocator for Kmalloc { +extern "C" { + #[link_name = "aligned_alloc"] + fn libc_aligned_alloc(align: usize, size: usize) -> *mut core::ffi::c_void; + + #[link_name = "free"] + fn libc_free(ptr: *mut core::ffi::c_void); +} + +// SAFETY: +// - memory remains valid until it is explicitly freed, +// - passing a pointer to a valid memory allocation created by this `Allocator` is always OK, +// - `realloc` provides the guarantees as provided in the `# Guarantees` section. +unsafe impl Allocator for Cmalloc { unsafe fn realloc( - _ptr: Option>, - _layout: Layout, - _old_layout: Layout, - _flags: Flags, + ptr: Option>, + layout: Layout, + old_layout: Layout, + flags: Flags, ) -> Result, AllocError> { - panic!(); + let src = match ptr { + Some(src) => { + if old_layout.size() == 0 { + ptr::null_mut() + } else { + src.as_ptr() + } + } + None => ptr::null_mut(), + }; + + if layout.size() == 0 { + // SAFETY: `src` is either NULL or was previously allocated with this `Allocator` + unsafe { libc_free(src.cast()) }; + + return Ok(NonNull::slice_from_raw_parts( + crate::alloc::dangling_from_layout(layout), + 0, + )); + } + + // SAFETY: Returns either NULL or a pointer to a memory allocation that satisfies or + // exceeds the given size and alignment requirements. + let dst = unsafe { libc_aligned_alloc(layout.align(), layout.size()) } as *mut u8; + let dst = NonNull::new(dst).ok_or(AllocError)?; + + if flags.contains(__GFP_ZERO) { + // SAFETY: The preceding calls to `libc_aligned_alloc` and `NonNull::new` + // guarantee that `dst` points to memory of at least `layout.size()` bytes. + unsafe { dst.as_ptr().write_bytes(0, layout.size()) }; + } + + if !src.is_null() { + // SAFETY: + // - `src` has previously been allocated with this `Allocator`; `dst` has just been + // newly allocated, hence the memory regions do not overlap. + // - both` src` and `dst` are properly aligned and valid for reads and writes + unsafe { + ptr::copy_nonoverlapping( + src, + dst.as_ptr(), + cmp::min(layout.size(), old_layout.size()), + ) + }; + } + + // SAFETY: `src` is either NULL or was previously allocated with this `Allocator` + unsafe { libc_free(src.cast()) }; + + Ok(NonNull::slice_from_raw_parts(dst, layout.size())) } }