From 5febf432df1cfa5b25d99b54c32103fafbdd0eb9 Mon Sep 17 00:00:00 2001 From: Miguel Ojeda Date: Sun, 16 Aug 2026 15:32:33 +0200 Subject: kbuild: rust: keep Rust objects out of Clang LTO with inline helpers Under `CONFIG_LTO_CLANG` + `CONFIG_RUST_INLINE_HELPERS`, one may hit `objtool` errors such as: vmlinux.o: error: objtool: _R..._3Gsp4boot+0xd6a: can't find jump dest instruction at .text._R..._3Gsp4boot+0x1dfd The reason is that in such builds, the Clang invocation that compiles the combined Rust plus helpers bitcode emits LLVM bitcode (again) -- the final code generation happens in the linker's LTO step, which the `-mllvm` trap options passed to Clang do not reach. This, in turn, means that unreachable traps are missing, and the impossible paths do not merely fallthrough to the next symbol, but past the end of their own section, since LTO builds place each function in its own section. Thus filter `CC_FLAGS_LTO` out of the Clang invocation, so that it always emits machine code directly, with the traps in place. Assisted-by: LLM Cc: Gary Guo Cc: Boqun Feng Cc: Alice Ryhl Cc: Matthew Maurer Cc: Josh Poimboeuf Cc: Peter Zijlstra Cc: stable@vger.kernel.org Fixes: 3a2486cc1da5 ("kbuild: rust: provide an option to inline C helpers into Rust") Acked-by: Gary Guo Link: https://patch.msgid.link/20260816133233.197500-2-ojeda@kernel.org Signed-off-by: Miguel Ojeda --- fs/ecryptfs/kthread.c | 159 ++++++++++++++++++++++++++++++++++++++++++++++++++ 1 file changed, 159 insertions(+) create mode 100644 fs/ecryptfs/kthread.c (limited to 'fs/ecryptfs/kthread.c') diff --git a/fs/ecryptfs/kthread.c b/fs/ecryptfs/kthread.c new file mode 100644 index 000000000..ae4cb4e2e --- /dev/null +++ b/fs/ecryptfs/kthread.c @@ -0,0 +1,159 @@ +// SPDX-License-Identifier: GPL-2.0-or-later +/* + * eCryptfs: Linux filesystem encryption layer + * + * Copyright (C) 2008 International Business Machines Corp. + * Author(s): Michael A. Halcrow + */ + +#include +#include +#include +#include +#include +#include "ecryptfs_kernel.h" + +struct ecryptfs_open_req { + struct file **lower_file; + struct path path; + struct completion done; + struct list_head kthread_ctl_list; +}; + +static struct ecryptfs_kthread_ctl { +#define ECRYPTFS_KTHREAD_ZOMBIE 0x00000001 + u32 flags; + struct mutex mux; + struct list_head req_list; + wait_queue_head_t wait; +} ecryptfs_kthread_ctl; + +static struct task_struct *ecryptfs_kthread; + +/** + * ecryptfs_threadfn + * @ignored: ignored + * + * The eCryptfs kernel thread that has the responsibility of getting + * the lower file with RW permissions. + * + * Returns zero on success; non-zero otherwise + */ +static int ecryptfs_threadfn(void *ignored) +{ + set_freezable(); + while (1) { + struct ecryptfs_open_req *req; + + wait_event_freezable( + ecryptfs_kthread_ctl.wait, + (!list_empty(&ecryptfs_kthread_ctl.req_list) + || kthread_should_stop())); + mutex_lock(&ecryptfs_kthread_ctl.mux); + if (ecryptfs_kthread_ctl.flags & ECRYPTFS_KTHREAD_ZOMBIE) { + mutex_unlock(&ecryptfs_kthread_ctl.mux); + goto out; + } + while (!list_empty(&ecryptfs_kthread_ctl.req_list)) { + req = list_first_entry(&ecryptfs_kthread_ctl.req_list, + struct ecryptfs_open_req, + kthread_ctl_list); + list_del(&req->kthread_ctl_list); + *req->lower_file = dentry_open(&req->path, + (O_RDWR | O_LARGEFILE), current_cred()); + complete(&req->done); + } + mutex_unlock(&ecryptfs_kthread_ctl.mux); + } +out: + return 0; +} + +int __init ecryptfs_init_kthread(void) +{ + int rc = 0; + + mutex_init(&ecryptfs_kthread_ctl.mux); + init_waitqueue_head(&ecryptfs_kthread_ctl.wait); + INIT_LIST_HEAD(&ecryptfs_kthread_ctl.req_list); + ecryptfs_kthread = kthread_run(&ecryptfs_threadfn, NULL, + "ecryptfs-kthread"); + if (IS_ERR(ecryptfs_kthread)) { + rc = PTR_ERR(ecryptfs_kthread); + printk(KERN_ERR "%s: Failed to create kernel thread; rc = [%d]" + "\n", __func__, rc); + } + return rc; +} + +void ecryptfs_destroy_kthread(void) +{ + struct ecryptfs_open_req *req, *tmp; + + mutex_lock(&ecryptfs_kthread_ctl.mux); + ecryptfs_kthread_ctl.flags |= ECRYPTFS_KTHREAD_ZOMBIE; + list_for_each_entry_safe(req, tmp, &ecryptfs_kthread_ctl.req_list, + kthread_ctl_list) { + list_del(&req->kthread_ctl_list); + *req->lower_file = ERR_PTR(-EIO); + complete(&req->done); + } + mutex_unlock(&ecryptfs_kthread_ctl.mux); + kthread_stop(ecryptfs_kthread); + wake_up(&ecryptfs_kthread_ctl.wait); +} + +/** + * ecryptfs_privileged_open + * @lower_file: Result of dentry_open by root on lower dentry + * @lower_dentry: Lower dentry for file to open + * @lower_mnt: Lower vfsmount for file to open + * @cred: credential to use for this call + * + * This function gets a r/w file opened against the lower dentry. + * + * Returns zero on success; non-zero otherwise + */ +int ecryptfs_privileged_open(struct file **lower_file, + struct dentry *lower_dentry, + struct vfsmount *lower_mnt, + const struct cred *cred) +{ + struct ecryptfs_open_req req; + int flags = O_LARGEFILE; + int rc = 0; + + init_completion(&req.done); + req.lower_file = lower_file; + req.path.dentry = lower_dentry; + req.path.mnt = lower_mnt; + + /* Corresponding dput() and mntput() are done when the + * lower file is fput() when all eCryptfs files for the inode are + * released. */ + flags |= IS_RDONLY(d_inode(lower_dentry)) ? O_RDONLY : O_RDWR; + (*lower_file) = dentry_open(&req.path, flags, cred); + if (!IS_ERR(*lower_file)) + goto out; + if ((flags & O_ACCMODE) == O_RDONLY) { + rc = PTR_ERR((*lower_file)); + goto out; + } + mutex_lock(&ecryptfs_kthread_ctl.mux); + if (ecryptfs_kthread_ctl.flags & ECRYPTFS_KTHREAD_ZOMBIE) { + rc = -EIO; + mutex_unlock(&ecryptfs_kthread_ctl.mux); + printk(KERN_ERR "%s: We are in the middle of shutting down; " + "aborting privileged request to open lower file\n", + __func__); + goto out; + } + list_add_tail(&req.kthread_ctl_list, &ecryptfs_kthread_ctl.req_list); + mutex_unlock(&ecryptfs_kthread_ctl.mux); + wake_up(&ecryptfs_kthread_ctl.wait); + wait_for_completion(&req.done); + if (IS_ERR(*lower_file)) + rc = PTR_ERR(*lower_file); +out: + return rc; +} -- cgit v1.3.1