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Subject[PATCH] ANDROID: binder: Add BINDER_GET_NODE_INFO_FOR_REF ioctl.
Date
This allows the context manager to retrieve information about nodes
that it holds a reference to, such as the current number of
references to those nodes.

Such information can for example be used to determine whether the
servicemanager is the only process holding a reference to a node.
This information can then be passed on to the process holding the
node, which can in turn decide whether it wants to shut down to
reduce resource usage.

Signed-off-by: Martijn Coenen <maco@android.com>
---
drivers/android/binder.c | 50 +++++++++++++++++++++++++++++
include/uapi/linux/android/binder.h | 8 +++++
2 files changed, 58 insertions(+)

diff --git a/drivers/android/binder.c b/drivers/android/binder.c
index d58763b6b0090..1c7e965241fb8 100644
--- a/drivers/android/binder.c
+++ b/drivers/android/binder.c
@@ -4544,6 +4544,37 @@ static int binder_ioctl_set_ctx_mgr(struct file *filp)
return ret;
}

+static int binder_ioctl_get_node_info_for_ref(struct binder_proc *proc,
+ struct binder_node_info_for_ref *info)
+{
+ struct binder_node *node;
+ struct binder_context *context = proc->context;
+ __u32 handle = info->handle;
+
+ memset(info, 0, sizeof(*info));
+
+ /* This ioctl may only be used by the context manager */
+ mutex_lock(&context->context_mgr_node_lock);
+ if (!context->binder_context_mgr_node ||
+ context->binder_context_mgr_node->proc != proc) {
+ mutex_unlock(&context->context_mgr_node_lock);
+ return -EPERM;
+ }
+ mutex_unlock(&context->context_mgr_node_lock);
+
+ node = binder_get_node_from_ref(proc, handle, true, NULL);
+ if (!node)
+ return -EINVAL;
+
+ info->strong_count = node->local_strong_refs +
+ node->internal_strong_refs;
+ info->weak_count = node->local_weak_refs;
+
+ binder_put_node(node);
+
+ return 0;
+}
+
static int binder_ioctl_get_node_debug_info(struct binder_proc *proc,
struct binder_node_debug_info *info)
{
@@ -4638,6 +4669,25 @@ static long binder_ioctl(struct file *filp, unsigned int cmd, unsigned long arg)
}
break;
}
+ case BINDER_GET_NODE_INFO_FOR_REF: {
+ struct binder_node_info_for_ref info;
+
+ if (copy_from_user(&info, ubuf, sizeof(info))) {
+ ret = -EFAULT;
+ goto err;
+ }
+
+ ret = binder_ioctl_get_node_info_for_ref(proc, &info);
+ if (ret < 0)
+ goto err;
+
+ if (copy_to_user(ubuf, &info, sizeof(info))) {
+ ret = -EFAULT;
+ goto err;
+ }
+
+ break;
+ }
case BINDER_GET_NODE_DEBUG_INFO: {
struct binder_node_debug_info info;

diff --git a/include/uapi/linux/android/binder.h b/include/uapi/linux/android/binder.h
index bfaec6903b8bc..a54a680ff2936 100644
--- a/include/uapi/linux/android/binder.h
+++ b/include/uapi/linux/android/binder.h
@@ -200,6 +200,13 @@ struct binder_node_debug_info {
__u32 has_weak_ref;
};

+struct binder_node_info_for_ref {
+ __u32 handle;
+ __u32 strong_count;
+ __u32 weak_count;
+ __u64 reserved;
+};
+
#define BINDER_WRITE_READ _IOWR('b', 1, struct binder_write_read)
#define BINDER_SET_IDLE_TIMEOUT _IOW('b', 3, __s64)
#define BINDER_SET_MAX_THREADS _IOW('b', 5, __u32)
@@ -208,6 +215,7 @@ struct binder_node_debug_info {
#define BINDER_THREAD_EXIT _IOW('b', 8, __s32)
#define BINDER_VERSION _IOWR('b', 9, struct binder_version)
#define BINDER_GET_NODE_DEBUG_INFO _IOWR('b', 11, struct binder_node_debug_info)
+#define BINDER_GET_NODE_INFO_FOR_REF _IOWR('b', 12, struct binder_node_info_for_ref)

/*
* NOTE: Two special error codes you should check for when calling
--
2.19.0.rc1.350.ge57e33dbd1-goog
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