Re: [PATCH v2 2/5] binder: add BINDER_GET_EXTENDED_ERROR ioctl

On Fri, Apr 29, 2022 at 11:56:41PM +0000, Carlos Llamas wrote:

Provide a userspace mechanism to pull precise error information upon failed operations. Extending the current error codes returned by the interfaces allows userspace to better determine the course of action. This could be for instance, retrying a failed transaction at a later point and thus offloading the error handling from the driver.

Signed-off-by: Carlos Llamas cmllamas@google.com

One comment below otherwise looks good to me, Acked-by: Christian Brauner (Microsoft) brauner@kernel.org

drivers/android/binder.c | 60 +++++++++++++++++++++++++++++ drivers/android/binder_internal.h | 3 ++ include/uapi/linux/android/binder.h | 16 ++++++++ 3 files changed, 79 insertions(+)

diff --git a/drivers/android/binder.c b/drivers/android/binder.c index f0885baa53a1..b9df0c8a68d3 100644 --- a/drivers/android/binder.c +++ b/drivers/android/binder.c @@ -147,6 +147,13 @@ module_param_call(stop_on_user_error, binder_set_stop_on_user_error, binder_stop_on_user_error = 2; \ } while (0) +#define binder_set_extended_error(ee, _id, _command, _param) \

• do { \

• (ee)->id = _id; \
  

• (ee)->command = _command; \
  

• (ee)->param = _param; \
  

• } while (0)

#define to_flat_binder_object(hdr) \ container_of(hdr, struct flat_binder_object, hdr) @@ -2697,6 +2704,24 @@ static struct binder_node *binder_get_node_refs_for_txn( return target_node; } +static void binder_set_txn_from_error(struct binder_transaction *t, int id,

• 		      uint32_t command, int32_t param)
  

+{

• struct binder_thread *from = binder_get_txn_from_and_acq_inner(t);
• if (!from) {

• /* annotation for sparse */
  

• __release(&from->proc->inner_lock);
  

• return;
  

• }
• /* don't override existing errors */
• if (from->ee.command == BR_OK)

• binder_set_extended_error(&from->ee, id, command, param);
  

• binder_inner_proc_unlock(from->proc);
• binder_thread_dec_tmpref(from);

+}

static void binder_transaction(struct binder_proc *proc, struct binder_thread *thread, struct binder_transaction_data *tr, int reply, @@ -2742,6 +2767,10 @@ static void binder_transaction(struct binder_proc *proc, e->offsets_size = tr->offsets_size; strscpy(e->context_name, proc->context->name, BINDERFS_MAX_NAME);

• binder_inner_proc_lock(proc);
• binder_set_extended_error(&thread->ee, t_debug_id, BR_OK, 0);
• binder_inner_proc_unlock(proc);
• if (reply) { binder_inner_proc_lock(proc); in_reply_to = thread->transaction_stack;

@@ -3487,10 +3516,16 @@ static void binder_transaction(struct binder_proc *proc, BUG_ON(thread->return_error.cmd != BR_OK); if (in_reply_to) {

• binder_set_txn_from_error(in_reply_to, t_debug_id,
  

• 		return_error, return_error_param);
  

  thread->return_error.cmd = BR_TRANSACTION_COMPLETE; binder_enqueue_thread_work(thread, &thread->return_error.work); binder_send_failed_reply(in_reply_to, return_error); } else {

• binder_inner_proc_lock(proc);
  

• binder_set_extended_error(&thread->ee, t_debug_id,
  

• 		return_error, return_error_param);
  

• binder_inner_proc_unlock(proc);
  

  thread->return_error.cmd = return_error; binder_enqueue_thread_work(thread, &thread->return_error.work); }

@@ -4628,6 +4663,7 @@ static struct binder_thread *binder_get_thread_ilocked( thread->return_error.cmd = BR_OK; thread->reply_error.work.type = BINDER_WORK_RETURN_ERROR; thread->reply_error.cmd = BR_OK;

• thread->ee.command = BR_OK; INIT_LIST_HEAD(&new_thread->waiting_thread_node); return thread;

} @@ -5066,6 +5102,25 @@ static int binder_ioctl_get_freezer_info( return 0; } +static int binder_ioctl_get_extended_error(struct binder_thread *thread,

• 			   void __user *ubuf)
  

+{

• struct binder_extended_error *ee = &thread->ee;
• binder_inner_proc_lock(thread->proc);
• if (copy_to_user(ubuf, ee, sizeof(*ee))) {

• binder_inner_proc_unlock(thread->proc);
  

• return -EFAULT;
  

• }
• ee->id = 0;
• ee->command = BR_OK;
• ee->param = 0;
• binder_inner_proc_unlock(thread->proc);
• return 0;

+}

Fwiw, could be:

static int binder_ioctl_get_extended_error(struct binder_thread *thread, void __user *ubuf) { int ret; struct binder_extended_error *ee = &thread->ee;

binder_inner_proc_lock(thread->proc); if (copy_to_user(ubuf, ee, sizeof(*ee))) { ret = -EFAULT; } else { ee->id = 0; ee->command = BR_OK; ee->param = 0; } binder_inner_proc_unlock(thread->proc);

return ret; }

static long binder_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) { int ret; @@ -5274,6 +5329,11 @@ static long binder_ioctl(struct file *filp, unsigned int cmd, unsigned long arg) binder_inner_proc_unlock(proc); break; }

• case BINDER_GET_EXTENDED_ERROR:

• ret = binder_ioctl_get_extended_error(thread, ubuf);
  

• if (ret < 0)
  

• 	goto err;
  

• break;
  

  default: ret = -EINVAL; goto err;

diff --git a/drivers/android/binder_internal.h b/drivers/android/binder_internal.h index d6b6b8cb7346..7c366a854125 100644 --- a/drivers/android/binder_internal.h +++ b/drivers/android/binder_internal.h @@ -480,6 +480,8 @@ struct binder_proc {

•                    (only accessed by this thread)
  

• @reply_error: transaction errors reported by target thread

•                    (protected by @proc->inner_lock)
  

• • @ee: extended error information from this thread

• •                    (protected by @proc->inner_lock)
    

  • @wait: wait queue for thread work
  • @stats: per-thread statistics

  •                    (atomics, no lock needed)
    

@@ -504,6 +506,7 @@ struct binder_thread { bool process_todo; struct binder_error return_error; struct binder_error reply_error;

• struct binder_extended_error ee; wait_queue_head_t wait; struct binder_stats stats; atomic_t tmp_ref;

diff --git a/include/uapi/linux/android/binder.h b/include/uapi/linux/android/binder.h index 11157fae8a8e..e6ee8cae303b 100644 --- a/include/uapi/linux/android/binder.h +++ b/include/uapi/linux/android/binder.h @@ -236,6 +236,21 @@ struct binder_frozen_status_info { __u32 async_recv; }; +/* struct binder_extened_error - extended error information

• • @id: identifier for the failed operation
• • @command: command as defined by binder_driver_return_protocol
• • @param: parameter holding a negative errno value
• • Used with BINDER_GET_EXTENDED_ERROR. This extends the error information
• • returned by the driver upon a failed operation. Userspace can pull this
• • data to properly handle specific error scenarios.
• */

+struct binder_extended_error {

• __u32 id;
• __u32 command;
• __s32 param;

+};

#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) @@ -249,6 +264,7 @@ struct binder_frozen_status_info { #define BINDER_FREEZE _IOW('b', 14, struct binder_freeze_info) #define BINDER_GET_FROZEN_INFO _IOWR('b', 15, struct binder_frozen_status_info) #define BINDER_ENABLE_ONEWAY_SPAM_DETECTION _IOW('b', 16, __u32) +#define BINDER_GET_EXTENDED_ERROR _IOWR('b', 17, struct binder_extended_error) /*

• NOTE: Two special error codes you should check for when calling

-- 2.36.0.464.gb9c8b46e94-goog