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

[Carlos Llamas <cmllamas@google.com>]

On Fri, Jul 25, 2025 at 06:37:46PM +0000, Carlos Llamas wrote:
> From: Li Li <dualli@google.com>
> 
> 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 <dualli@google.com>
> 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"]

Hmm, it seems this header inclusion was left in from patchset v13, where
the 'struct binder_context' needed to be exposed. Not anymore though, so
I'll send out a new version that drops this part.