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 --- drivers/android/binder/context.rs | 175 ++++++++++++++++++++++++++++++++++++++ 1 file changed, 175 insertions(+) create mode 100644 drivers/android/binder/context.rs (limited to 'drivers/android/binder/context.rs') diff --git a/drivers/android/binder/context.rs b/drivers/android/binder/context.rs new file mode 100644 index 000000000..ddddb66b3 --- /dev/null +++ b/drivers/android/binder/context.rs @@ -0,0 +1,175 @@ +// SPDX-License-Identifier: GPL-2.0 + +// Copyright (C) 2025 Google LLC. + +use kernel::{ + alloc::kvec::KVVec, + error::code::*, + prelude::*, + security, + str::{CStr, CString}, + sync::{Arc, Mutex}, + task::Kuid, +}; + +use crate::{error::BinderError, node::NodeRef, process::Process}; + +kernel::sync::global_lock! { + // SAFETY: We call `init` in the module initializer, so it's initialized before first use. + pub(crate) unsafe(uninit) static CONTEXTS: Mutex = ContextList { + contexts: KVVec::new(), + }; +} + +pub(crate) struct ContextList { + contexts: KVVec>, +} + +pub(crate) fn get_all_contexts() -> Result>> { + let lock = CONTEXTS.lock(); + let mut ctxs = KVVec::with_capacity(lock.contexts.len(), GFP_KERNEL)?; + for ctx in lock.contexts.iter() { + ctxs.push(ctx.clone(), GFP_KERNEL)?; + } + Ok(ctxs) +} + +/// This struct keeps track of the processes using this context, and which process is the context +/// manager. +struct Manager { + node: Option, + uid: Option, + all_procs: KVVec>, +} + +/// There is one context per binder file (/dev/binder, /dev/hwbinder, etc) +#[pin_data] +pub(crate) struct Context { + #[pin] + manager: Mutex, + pub(crate) name: CString, +} + +impl Context { + pub(crate) fn new(name: &CStr) -> Result> { + let name = CString::try_from(name)?; + let ctx = Arc::pin_init( + try_pin_init!(Context { + name, + manager <- kernel::new_mutex!(Manager { + all_procs: KVVec::new(), + node: None, + uid: None, + }, "Context::manager"), + }), + GFP_KERNEL, + )?; + + CONTEXTS.lock().contexts.push(ctx.clone(), GFP_KERNEL)?; + + Ok(ctx) + } + + /// Called when the file for this context is unlinked. + /// + /// No-op if called twice. + pub(crate) fn deregister(self: &Arc) { + // Safe removal using retain + CONTEXTS.lock().contexts.retain(|c| !Arc::ptr_eq(c, self)); + } + + pub(crate) fn register_process(self: &Arc, proc: Arc) -> Result { + if !Arc::ptr_eq(self, &proc.ctx) { + pr_err!("Context::register_process called on the wrong context."); + return Err(EINVAL); + } + self.manager.lock().all_procs.push(proc, GFP_KERNEL)?; + Ok(()) + } + + pub(crate) fn deregister_process(self: &Arc, proc: &Arc) { + if !Arc::ptr_eq(self, &proc.ctx) { + pr_err!("Context::deregister_process called on the wrong context."); + return; + } + let mut manager = self.manager.lock(); + manager.all_procs.retain(|p| !Arc::ptr_eq(p, proc)); + + // Shrink the vector if it has significant unused capacity to avoid memory waste, + // but use a conservative strategy to prevent shrink-then-regrow oscillation. + // Only shrink when length drops below 1/4 of capacity, and shrink to twice the length. + let len = manager.all_procs.len(); + let cap = manager.all_procs.capacity(); + if len < cap / 4 { + // Shrink to twice the current length. Ignore allocation failures since this + // is just an optimization; the vector remains valid even if shrinking fails. + let _ = manager.all_procs.shrink_to(len * 2, GFP_KERNEL); + } + } + + pub(crate) fn set_manager_node(&self, node_ref: NodeRef) -> Result { + let mut manager = self.manager.lock(); + if manager.node.is_some() { + pr_warn!("BINDER_SET_CONTEXT_MGR already set"); + return Err(EBUSY); + } + security::binder_set_context_mgr(&node_ref.node.owner.cred)?; + + // If the context manager has been set before, ensure that we use the same euid. + let caller_uid = Kuid::current_euid(); + if let Some(ref uid) = manager.uid { + if *uid != caller_uid { + return Err(EPERM); + } + } + + manager.node = Some(node_ref); + manager.uid = Some(caller_uid); + Ok(()) + } + + pub(crate) fn unset_manager_node(&self) { + let node_ref = self.manager.lock().node.take(); + drop(node_ref); + } + + pub(crate) fn get_manager_node(&self, strong: bool) -> Result { + self.manager + .lock() + .node + .as_ref() + .ok_or_else(BinderError::new_dead)? + .clone(strong) + .map_err(BinderError::from) + } + + pub(crate) fn for_each_proc(&self, mut func: F) + where + F: FnMut(&Process), + { + let lock = self.manager.lock(); + for proc in &lock.all_procs { + func(proc); + } + } + + pub(crate) fn get_all_procs(&self) -> Result>> { + let lock = self.manager.lock(); + let mut procs = KVVec::with_capacity(lock.all_procs.len(), GFP_KERNEL)?; + for proc in lock.all_procs.iter() { + procs.push(Arc::clone(proc), GFP_KERNEL)?; + } + Ok(procs) + } + + pub(crate) fn get_procs_with_pid(&self, pid: i32) -> Result>> { + let lock = self.manager.lock(); + let mut matching_procs = KVVec::new(); + for proc in lock.all_procs.iter() { + if proc.task.pid() == pid { + matching_procs.push(Arc::clone(proc), GFP_KERNEL)?; + } + } + Ok(matching_procs) + } +} -- cgit v1.3.1