When a user-space application sends malformed data or makes a
lifecycle mistake, the driver rejects it with a generic error code
(like -EINVAL). Without internal logs, the driver acts as a
"black box," forcing developers to guess which check failed.
In the legacy C Binder driver, this issue is solved using a dynamic
debug_mask module parameter that toggles verbose logs for specific
subsystems. This series brings the same critical capability to the
Rust Binder driver to provide developers with clear, real-time
feedback.
Instead of rebuilds, reboots, or guessing:
- Developers can enable logs instantly on a running device by writing to
`/sys/module/rust_binder/parameters/debug_mask`.
- It prints the exact reason for failures (such as alignment errors,
mismatched call stacks, or invalid handle references) directly into
`dmesg`, reducing debugging time from hours to seconds.
- It protects system logs by keeping logging off by default and only
enabling it when developers are actively troubleshooting.
Based on top of:
https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/char-misc.git
Signed-off-by: Jahnavi MN <jahnavimn@google.com>
---
Changes in v4:
- Rebase the entire series on top of the latest char-misc-testing tree.
- Link to v3: https://lore.kernel.org/r/20260713-rust_binder_debug_mask-v3-0-0de91bbbbf69@google.com
Changes in v3:
- Rebase the entire series on top of the latest char-misc-testing tree.
- Define `rust_binder_debug_mask` in Rust as an `Atomic<u32>` and export it to
C as `extern u32` to avoid raw volatile reads and FFI UB.
- Use `kernel::bits::bit_u32` instead of raw bit shifts.
- Simplify `binder_debug!` macro rules and remove the redundant `raw` helper.
- Wrap the raw mask in `DebugMasks` to use type-safe `.contains(mask)`.
- Link to v2: https://lore.kernel.org/r/20260710-rust_binder_debug_mask-v2-0-2846410e3ae6@google.com
Changes in v2:
- Defined the debug mask categories using bitflags (impl_flags) to
resolve potential Undefined Behavior and match Rust idioms.
- Added a tgid helper to rust/kernel/task.rs to expose the task
group ID and optimize default "PID:TID" prefixing.
- Implemented the BINDER_DEBUG_DEATH_NOTIFICATION mask to log OOM
failures, lifecycle updates, and async delivery to user-space.
- Added pid fields to ThreadError, DeliverCode, and FreezeMessage
to ensure cancellation logs show the correct process PID instead
of background kworker PIDs.
- Removed duplicate PID printing across workqueue, transaction
failure, and stack unwinding logs.
- Refactored log formatting (e.g. formatted BinderError with {:?},
used "strong"/"weak" strings, and improved message wording).
- Fixed logic bugs (restored missing update_ref block, moved manager
lookup warnings).
- Cleaned up spurious newlines, corrected indentations, and adjusted
all commit titles to be shorter and more meaningful.
- Link to v1: https://lore.kernel.org/r/20260703-rust_binder_debug_mask-v1-0-9bdf12b5325c@google.com
---
Jahnavi MN (7):
rust_binder: Add dynamic debug logging mask
rust_binder: Implement BINDER_DEBUG_USER_ERROR for freezer-related operation
rust_binder: Implement BINDER_DEBUG_USER_ERROR for refcounting and death notifications
rust_binder: Implement BINDER_DEBUG_USER_ERROR for transaction parsing failures
rust_binder: Implement BINDER_DEBUG_FAILED_TRANSACTION
rust_binder: Implement BINDER_DEBUG_DEATH_NOTIFICATION
rust_binder: Implement BINDER_DEBUG_DEAD_TRANSACTION
drivers/android/binder/debug.rs | 76 +++++++++++++++++++
drivers/android/binder/freeze.rs | 64 +++++++++++-----
drivers/android/binder/node.rs | 24 ++++--
drivers/android/binder/process.rs | 56 ++++++++++++--
drivers/android/binder/rust_binder_main.rs | 16 +++-
drivers/android/binder/rust_binderfs.c | 3 +
drivers/android/binder/thread.rs | 117 ++++++++++++++++++++---------
drivers/android/binder/transaction.rs | 15 ++++
rust/kernel/task.rs | 7 ++
9 files changed, 309 insertions(+), 69 deletions(-)
---
base-commit: 775553d19b163446c38c5ff24dd0a01065376932
change-id: 20260702-rust_binder_debug_mask-636737015624
Best regards,
--
Jahnavi MN <jahnavimn@google.com>