Re: [PATCH v19 3/5] binder: introduce transaction reports via netlink

From: Li Li <redacted>

Introduce a generic netlink multicast event to report binder transaction
failures to userspace. This allows subscribers to monitor these events
and take appropriate actions, such as stopping a misbehaving application
that is spamming a service with huge amount of transactions.

The multicast event contains full details of the failed transactions,
including the sender/target PIDs, payload size and specific error code.
This interface is defined using a YAML spec, from which the UAPI and
kernel headers and source are auto-generated.

Signed-off-by: Li Li <redacted>
Signed-off-by: Carlos Llamas <cmllamas@google.com>
---
 Documentation/netlink/specs/binder.yaml     | 96 +++++++++++++++++++++
 MAINTAINERS                                 |  1 +
 drivers/android/Kconfig                     |  1 +
 drivers/android/Makefile                    |  2 +-
 drivers/android/binder.c                    | 85 +++++++++++++++++-
 drivers/android/binder_netlink.c            | 32 +++++++
 drivers/android/binder_netlink.h            | 21 +++++
 include/uapi/linux/android/binder_netlink.h | 37 ++++++++
 8 files changed, 270 insertions(+), 5 deletions(-)
 create mode 100644 Documentation/netlink/specs/binder.yaml
 create mode 100644 drivers/android/binder_netlink.c
 create mode 100644 drivers/android/binder_netlink.h
 create mode 100644 include/uapi/linux/android/binder_netlink.h

diff --git a/Documentation/netlink/specs/binder.yaml b/Documentation/netlink/specs/binder.yaml
new file mode 100644
index 000000000000..a2e54aa42448
--- /dev/null
+++ b/Documentation/netlink/specs/binder.yaml

@@ -0,0 +1,96 @@
+# SPDX-License-Identifier: ((GPL-2.0 WITH Linux-syscall-note) OR BSD-3-Clause)
+#
+# Copyright 2025 Google LLC
+#
+---
+name: binder
+protocol: genetlink
+uapi-header: linux/android/binder_netlink.h
+doc: Binder interface over generic netlink
+
+attribute-sets:
+  -
+    name: report
+    doc: |
+      Attributes included within a transaction failure report. The elements
+      correspond directly with the specific transaction that failed, along
+      with the error returned to the sender e.g. BR_DEAD_REPLY.
+
+    attributes:
+      -
+        name: error
+        type: u32
+        doc: The enum binder_driver_return_protocol returned to the sender.
+      -
+        name: context
+        type: string
+        doc: The binder context where the transaction occurred.
+      -
+        name: from_pid
+        type: u32
+        doc: The PID of the sender process.
+      -
+        name: from_tid
+        type: u32
+        doc: The TID of the sender thread.
+      -
+        name: to_pid
+        type: u32
+        doc: |
+          The PID of the recipient process. This attribute may not be present
+          if the target could not be determined.
+      -
+        name: to_tid
+        type: u32
+        doc: |
+          The TID of the recipient thread. This attribute may not be present
+          if the target could not be determined.
+      -
+        name: is_reply
+        type: flag
+        doc: When present, indicates the failed transaction is a reply.
+      -
+        name: flags
+        type: u32
+        doc: The bitmask of enum transaction_flags from the transaction.
+      -
+        name: code
+        type: u32
+        doc: The application-defined code from the transaction.
+      -
+        name: data_size
+        type: u32
+        doc: The transaction payload size in bytes.
+
+operations:
+  list:
+    -
+      name: report
+      doc: |
+        A multicast event sent to userspace subscribers to notify them about
+        binder transaction failures. The generated report provides the full
+        details of the specific transaction that failed. The intention is for
+        programs to monitor these events and react to the failures as needed.
+
+      attribute-set: report
+      mcgrp: report
+      event:
+        attributes:
+          - error
+          - context
+          - from_pid
+          - from_tid
+          - to_pid
+          - to_tid
+          - is_reply
+          - flags
+          - code
+          - data_size
+
+kernel-family:
+  headers: ["binder_internal.h"]