binder: tell userspace to dump current backtrace when detected oneway spamming

When async binder buffer got exhausted, some normal oneway transactions
will also be discarded and may cause system or application failures. By
that time, the binder debug information we dump may not be relevant to
the root cause. And this issue is difficult to debug if without the
backtrace of the thread sending spam.

This change will send BR_ONEWAY_SPAM_SUSPECT to userspace when oneway
spamming is detected, request to dump current backtrace. Oneway spamming
will be reported only once when exceeding the threshold (target process
dips below 80% of its oneway space, and current process is responsible for
either more than 50 transactions, or more than 50% of the oneway space).
And the detection will restart when the async buffer has returned to a
healthy state.

Acked-by: Todd Kjos <tkjos@google.com>
Signed-off-by: Hang Lu <hangl@codeaurora.org>
Link: https://lore.kernel.org/r/1617961246-4502-3-git-send-email-hangl@codeaurora.org
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 7 insertions, 1 deletions

diff --git a/drivers/android/binder_alloc.h b/drivers/android/binder_alloc.h
index 6e8e001381af..7dea57a84c79 100644
--- a/drivers/android/binder_alloc.h
+++ b/drivers/android/binder_alloc.h
@@ -26,6 +26,8 @@ struct binder_transaction;
  * @clear_on_free:      %true if buffer must be zeroed after use
  * @allow_user_free:    %true if user is allowed to free buffer
  * @async_transaction:  %true if buffer is in use for an async txn
+ * @oneway_spam_suspect: %true if total async allocate size just exceed
+ * spamming detect threshold
  * @debug_id:           unique ID for debugging
  * @transaction:        pointer to associated struct binder_transaction
  * @target_node:        struct binder_node associated with this buffer
@@ -45,7 +47,8 @@ struct binder_buffer {
 	unsigned clear_on_free:1;
 	unsigned allow_user_free:1;
 	unsigned async_transaction:1;
-	unsigned debug_id:28;
+	unsigned oneway_spam_suspect:1;
+	unsigned debug_id:27;
 
 	struct binder_transaction *transaction;
 
@@ -87,6 +90,8 @@ struct binder_lru_page {
  * @buffer_size:        size of address space specified via mmap
  * @pid:                pid for associated binder_proc (invariant after init)
  * @pages_high:         high watermark of offset in @pages
+ * @oneway_spam_detected: %true if oneway spam detection fired, clear that
+ * flag once the async buffer has returned to a healthy state
  *
  * Bookkeeping structure for per-proc address space management for binder
  * buffers. It is normally initialized during binder_init() and binder_mmap()
@@ -107,6 +112,7 @@ struct binder_alloc {
 	uint32_t buffer_free;
 	int pid;
 	size_t pages_high;
+	bool oneway_spam_detected;
 };
 
 #ifdef CONFIG_ANDROID_BINDER_IPC_SELFTEST