From patchwork Wed Jul 26 16:45:28 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ariel Miculas X-Patchwork-Id: 13328374 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 6BBD6C001DF for ; Wed, 26 Jul 2023 16:48:13 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229548AbjGZQsL (ORCPT ); Wed, 26 Jul 2023 12:48:11 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:34700 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231685AbjGZQrx (ORCPT ); Wed, 26 Jul 2023 12:47:53 -0400 Received: from aer-iport-8.cisco.com (aer-iport-8.cisco.com [173.38.203.70]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C573F2703 for ; Wed, 26 Jul 2023 09:47:18 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=cisco.com; i=@cisco.com; l=7763; q=dns/txt; s=iport; t=1690390038; x=1691599638; h=from:to:cc:subject:date:message-id:in-reply-to: references:mime-version:content-transfer-encoding; bh=KpPr0Hy4pGpqEy0mTBFyST7zmNlk6KLH8UX7VvAwlLA=; b=HFhS/J0Htc/sn61h3X+U+gm8NDal+s/ng2smrA6WZooMUAPfuLI6wxUV mMHM5J1RQuiuk7JrZGnYwWbYhL3q169NFOg2QZkRgI/kS7pRyDtGuWisw OBdVW8TeoQBXwMlK9Nw2NrhrC8ZJ63yaO3khfCoddhH6V0yYtubznks1n c=; X-IronPort-AV: E=Sophos;i="6.01,232,1684800000"; d="scan'208";a="5816071" Received: from aer-iport-nat.cisco.com (HELO aer-core-7.cisco.com) ([173.38.203.22]) by aer-iport-8.cisco.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 26 Jul 2023 16:46:13 +0000 Received: from archlinux-cisco.cisco.com (dhcp-10-61-98-211.cisco.com [10.61.98.211]) (authenticated bits=0) by aer-core-7.cisco.com (8.15.2/8.15.2) with ESMTPSA id 36QGjqTu022602 (version=TLSv1.2 cipher=DHE-RSA-AES256-GCM-SHA384 bits=256 verify=NO); Wed, 26 Jul 2023 16:46:13 GMT From: Ariel Miculas To: rust-for-linux@vger.kernel.org Cc: linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, tycho@tycho.pizza, brauner@kernel.org, viro@zeniv.linux.org.uk, ojeda@kernel.org, alex.gaynor@gmail.com, wedsonaf@gmail.com, Ariel Miculas Subject: [RFC PATCH v2 04/10] rust: file: Add a new RegularFile newtype useful for reading files Date: Wed, 26 Jul 2023 19:45:28 +0300 Message-ID: <20230726164535.230515-5-amiculas@cisco.com> X-Mailer: git-send-email 2.41.0 In-Reply-To: <20230726164535.230515-1-amiculas@cisco.com> References: <20230726164535.230515-1-amiculas@cisco.com> MIME-Version: 1.0 X-Authenticated-User: amiculas X-Outbound-SMTP-Client: 10.61.98.211, dhcp-10-61-98-211.cisco.com X-Outbound-Node: aer-core-7.cisco.com Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org Implement from_path, from_path_in_root_mnt, read_with_offset, read_to_end and get_file_size methods for a RegularFile newtype. Signed-off-by: Ariel Miculas --- rust/helpers.c | 6 ++ rust/kernel/error.rs | 4 +- rust/kernel/file.rs | 129 ++++++++++++++++++++++++++++++++++++++++++- 3 files changed, 135 insertions(+), 4 deletions(-) diff --git a/rust/helpers.c b/rust/helpers.c index eed8ace52fb5..9e860a554cda 100644 --- a/rust/helpers.c +++ b/rust/helpers.c @@ -213,6 +213,12 @@ void *rust_helper_alloc_inode_sb(struct super_block *sb, } EXPORT_SYMBOL_GPL(rust_helper_alloc_inode_sb); +loff_t rust_helper_i_size_read(const struct inode *inode) +{ + return i_size_read(inode); +} +EXPORT_SYMBOL_GPL(rust_helper_i_size_read); + /* * We use `bindgen`'s `--size_t-is-usize` option to bind the C `size_t` type * as the Rust `usize` type, so we can use it in contexts where Rust diff --git a/rust/kernel/error.rs b/rust/kernel/error.rs index 05fcab6abfe6..e061c83f806a 100644 --- a/rust/kernel/error.rs +++ b/rust/kernel/error.rs @@ -273,9 +273,7 @@ pub fn to_result(err: core::ffi::c_int) -> Result { /// } /// } /// ``` -// TODO: Remove `dead_code` marker once an in-kernel client is available. -#[allow(dead_code)] -pub(crate) fn from_err_ptr(ptr: *mut T) -> Result<*mut T> { +pub fn from_err_ptr(ptr: *mut T) -> Result<*mut T> { // CAST: Casting a pointer to `*const core::ffi::c_void` is always valid. let const_ptr: *const core::ffi::c_void = ptr.cast(); // SAFETY: The FFI function does not deref the pointer. diff --git a/rust/kernel/file.rs b/rust/kernel/file.rs index 494939ba74df..a3002c416dbb 100644 --- a/rust/kernel/file.rs +++ b/rust/kernel/file.rs @@ -8,11 +8,13 @@ use crate::{ bindings, cred::Credential, - error::{code::*, from_result, Error, Result}, + error::{code::*, from_err_ptr, from_result, Error, Result}, fs, io_buffer::{IoBufferReader, IoBufferWriter}, iov_iter::IovIter, mm, + mount::Vfsmount, + str::CStr, sync::CondVar, types::ARef, types::AlwaysRefCounted, @@ -20,6 +22,7 @@ types::Opaque, user_ptr::{UserSlicePtr, UserSlicePtrReader, UserSlicePtrWriter}, }; +use alloc::vec::Vec; use core::convert::{TryFrom, TryInto}; use core::{marker, mem, ptr}; use macros::vtable; @@ -201,6 +204,130 @@ unsafe fn dec_ref(obj: ptr::NonNull) { } } +/// A newtype over file, specific to regular files +pub struct RegularFile(ARef); +impl RegularFile { + /// Creates a new instance of Self if the file is a regular file + /// + /// # Safety + /// + /// The caller must ensure file_ptr.f_inode is initialized to a valid pointer (e.g. file_ptr is + /// a pointer returned by path_openat); It must also ensure that file_ptr's reference count was + /// incremented at least once + fn create_if_regular(file_ptr: ptr::NonNull) -> Result { + // SAFETY: file_ptr is a NonNull pointer + let inode = unsafe { core::ptr::addr_of!((*file_ptr.as_ptr()).f_inode).read() }; + // SAFETY: the caller must ensure f_inode is initialized to a valid pointer + unsafe { + if bindings::S_IFMT & ((*inode).i_mode) as u32 != bindings::S_IFREG { + return Err(EINVAL); + } + } + // SAFETY: the safety requirements state that file_ptr's reference count was incremented at + // least once + Ok(RegularFile(unsafe { ARef::from_raw(file_ptr.cast()) })) + } + /// Constructs a new [`struct file`] wrapper from a path. + pub fn from_path(filename: &CStr, flags: i32, mode: u16) -> Result { + let file_ptr = unsafe { + // SAFETY: filename is a reference, so it's a valid pointer + from_err_ptr(bindings::filp_open( + filename.as_ptr() as *const i8, + flags, + mode, + ))? + }; + let file_ptr = ptr::NonNull::new(file_ptr).ok_or(ENOENT)?; + + // SAFETY: `filp_open` initializes the refcount with 1 + Self::create_if_regular(file_ptr) + } + + /// Constructs a new [`struct file`] wrapper from a path and a vfsmount. + pub fn from_path_in_root_mnt( + mount: &Vfsmount, + filename: &CStr, + flags: i32, + mode: u16, + ) -> Result { + let file_ptr = { + let mnt = mount.get(); + // construct a path from vfsmount, see file_open_root_mnt + let raw_path = bindings::path { + mnt, + // SAFETY: Vfsmount structure stores a valid vfsmount object + dentry: unsafe { (*mnt).mnt_root }, + }; + unsafe { + // SAFETY: raw_path and filename are both references + from_err_ptr(bindings::file_open_root( + &raw_path, + filename.as_ptr() as *const i8, + flags, + mode, + ))? + } + }; + let file_ptr = ptr::NonNull::new(file_ptr).ok_or(ENOENT)?; + + // SAFETY: `file_open_root` initializes the refcount with 1 + Self::create_if_regular(file_ptr) + } + + /// Read from the file into the specified buffer + pub fn read_with_offset(&self, buf: &mut [u8], offset: u64) -> Result { + Ok({ + // kernel_read_file expects a pointer to a "void *" buffer + let mut ptr_to_buf = buf.as_mut_ptr() as *mut core::ffi::c_void; + // Unless we give a non-null pointer to the file size: + // 1. we cannot give a non-zero value for the offset + // 2. we cannot have offset 0 and buffer_size > file_size + let mut file_size = 0; + + // SAFETY: 'file' is valid because it's taken from Self, 'buf' and 'file_size` are + // references to the stack variables 'ptr_to_buf' and 'file_size'; ptr_to_buf is also + // a pointer to a valid buffer that was obtained from a reference + let result = unsafe { + bindings::kernel_read_file( + self.0 .0.get(), + offset.try_into()?, + &mut ptr_to_buf, + buf.len(), + &mut file_size, + bindings::kernel_read_file_id_READING_UNKNOWN, + ) + }; + + // kernel_read_file returns the number of bytes read on success or negative on error. + if result < 0 { + return Err(Error::from_errno(result.try_into()?)); + } + + result.try_into()? + }) + } + + /// Allocate and return a vector containing the contents of the entire file + pub fn read_to_end(&self) -> Result> { + let file_size = self.get_file_size()?; + let mut buffer = Vec::try_with_capacity(file_size)?; + buffer.try_resize(file_size, 0)?; + self.read_with_offset(&mut buffer, 0)?; + Ok(buffer) + } + + fn get_file_size(&self) -> Result { + // SAFETY: 'file' is valid because it's taken from Self + let file_size = unsafe { bindings::i_size_read((*self.0 .0.get()).f_inode) }; + + if file_size < 0 { + return Err(EINVAL); + } + + Ok(file_size.try_into()?) + } +} + /// A file descriptor reservation. /// /// This allows the creation of a file descriptor in two steps: first, we reserve a slot for it,