1 files changed, 175 insertions, 0 deletions
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> = ContextList {
+        contexts: KVVec::new(),
+    };
+}
+
+pub(crate) struct ContextList {
+    contexts: KVVec<Arc<Context>>,
+}
+
+pub(crate) fn get_all_contexts() -> Result<KVVec<Arc<Context>>> {
+    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<NodeRef>,
+    uid: Option<Kuid>,
+    all_procs: KVVec<Arc<Process>>,
+}
+
+/// There is one context per binder file (/dev/binder, /dev/hwbinder, etc)
+#[pin_data]
+pub(crate) struct Context {
+    #[pin]
+    manager: Mutex<Manager>,
+    pub(crate) name: CString,
+}
+
+impl Context {
+    pub(crate) fn new(name: &CStr) -> Result<Arc<Self>> {
+        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<Self>) {
+        // Safe removal using retain
+        CONTEXTS.lock().contexts.retain(|c| !Arc::ptr_eq(c, self));
+    }
+
+    pub(crate) fn register_process(self: &Arc<Self>, proc: Arc<Process>) -> 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<Self>, proc: &Arc<Process>) {
+        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<NodeRef, BinderError> {
+        self.manager
+            .lock()
+            .node
+            .as_ref()
+            .ok_or_else(BinderError::new_dead)?
+            .clone(strong)
+            .map_err(BinderError::from)
+    }
+
+    pub(crate) fn for_each_proc<F>(&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<KVVec<Arc<Process>>> {
+        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<KVVec<Arc<Process>>> {
+        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)
+    }
+}