Re: [PATCH v2 1/7] rust_binder: Add dynamic debug logging mask

[Carlos Llamas <cmllamas@google.com>]

On Fri, Jul 10, 2026 at 09:27:37PM +0100, Gary Guo wrote:
> On Fri Jul 10, 2026 at 8:47 PM BST, Carlos Llamas wrote:
> > On Fri, Jul 10, 2026 at 02:32:52PM +0000, Jahnavi MN via B4 Relay wrote:
> >> From: Jahnavi MN <jahnavimn@google.com>
> >> 
> >> Implement a dynamic debug logging mask (`debug_mask`) for the
> >> `rust_binder` module to allow dynamic runtime configuration of log
> >> levels. This enables parity with the legacy C driver's debug mask.
> >> 
> >> Since the Rust `module!` macro in the current kernel build does not yet
> >> support declaring module parameters directly in Rust, we define the
> >> `debug_mask` variable in a C companion file to expose it to the kernel
> >> runtime and import it using FFI with volatile reads.
> >> 
> >> To verify the setup, instrument process lifecycle events (open, flush,
> >> and release) in `process.rs` under the new `BINDER_DEBUG_OPEN_CLOSE`
> >> logging mask. These entry-point events are chosen for initial validation
> >> because they represent the start of the Binder lifecycle and occur
> >> at low frequency, allowing simple runtime verification of the dynamic
> >> toggle without log noise.
> >> 
> >> Signed-off-by: Jahnavi MN <jahnavimn@google.com>
> >> ---
> >>  drivers/android/binder/debug.rs            | 80 ++++++++++++++++++++++++++++++
> >>  drivers/android/binder/process.rs          |  7 ++-
> >>  drivers/android/binder/rust_binder_main.rs |  2 +
> >>  drivers/android/binder/rust_binderfs.c     |  3 ++
> >>  rust/kernel/task.rs                        |  7 +++
> >>  5 files changed, 98 insertions(+), 1 deletion(-)
> >> 
> >> diff --git a/drivers/android/binder/debug.rs b/drivers/android/binder/debug.rs
> >> new file mode 100644
> >> index 000000000000..da48bce3df54
> >> --- /dev/null
> >> +++ b/drivers/android/binder/debug.rs
> >> @@ -0,0 +1,80 @@
> >> +// SPDX-License-Identifier: GPL-2.0
> >> +// Copyright (C) 2026 Google LLC.
> >> +
> >> +//! Binder debugging helpers.
> >> +
> >> +#![allow(dead_code)]
> >> +
> >> +kernel::impl_flags!(
> >> +    /// Represents multiple debug mask flags.
> >> +    #[derive(Debug, Clone, Default, Copy, PartialEq, Eq)]
> >> +    pub struct DebugMasks(u32);
> >
> > Where is this being used? I can't find it on subsequent patches.
> > Maybe leftover from previous implementation?
> 
> impl_flags macro requires a type for a single flag and a type for flag masks.

Oh I see. I was expecting the bitops to be peformed on this type
somewhere. I guess the reason it wasn't is because of the issue with
module parameters and their C macros.

> 
> >
> >> +
> >> +    /// Represents a single debug mask category.
> >> +    #[derive(Debug, Clone, Copy, PartialEq, Eq)]
> >> +    pub enum DebugMask {
> >> +        UserError = 1 << 0,
> >> +        FailedTransaction = 1 << 1,
> >> +        DeadTransaction = 1 << 2,
> >> +        OpenClose = 1 << 3,
> >> +        DeadBinder = 1 << 4,
> >> +        DeathNotification = 1 << 5,
> >> +        ReadWrite = 1 << 6,
> >> +        UserRefs = 1 << 7,
> >> +        Threads = 1 << 8,
> >> +        Transaction = 1 << 9,
> >> +        TransactionComplete = 1 << 10,
> >> +        FreeBuffer = 1 << 11,
> >> +        InternalRefs = 1 << 12,
> >> +        PriorityCap = 1 << 13,
> >> +        Spinlocks = 1 << 14,
> >> +    }
> >> +);
> >> diff --git a/drivers/android/binder/rust_binder_main.rs b/drivers/android/binder/rust_binder_main.rs
> >> index df47aba05133..995e6131bb77 100644
> >> --- a/drivers/android/binder/rust_binder_main.rs
> >> +++ b/drivers/android/binder/rust_binder_main.rs
> >> @@ -31,6 +31,8 @@
> >>  mod context;
> >>  mod deferred_close;
> >>  mod defs;
> >> +#[macro_use]
> >> +mod debug;
> >>  mod error;
> >>  mod netlink;
> >>  mod node;
> >> diff --git a/drivers/android/binder/rust_binderfs.c b/drivers/android/binder/rust_binderfs.c
> >> index ade1c4d92499..fa8b38465550 100644
> >> --- a/drivers/android/binder/rust_binderfs.c
> >> +++ b/drivers/android/binder/rust_binderfs.c
> >> @@ -51,6 +51,9 @@ DEFINE_SHOW_ATTRIBUTE(rust_binder_proc);
> >>  char *rust_binder_devices_param = CONFIG_ANDROID_BINDER_DEVICES;
> >>  module_param_named(rust_devices, rust_binder_devices_param, charp, 0444);
> >>  
> >> +u32 rust_binder_debug_mask = 7;
> >
> > hmm, I'm not sure about this magic number. Do you think we can
> > initialize on the rust end at init()? Or at least a comment about what
> > flags we are setting as default here?
> 
> It doesn't even need that, just a
> 
> static rust_binder_debug_mask: Atomic<u32> = Atomic::new((FLAG_A as u32) | (FLAG_B as u32) | ...);
> 
> and a `extern u32` on C side should do.

ha sure, reversing the declaration and extern would also work.