Re: [PATCH v2] binder: use buffer offsets in debug logs

[Carlos Llamas <cmllamas@google.com>]

On Mon, Mar 24, 2025 at 06:07:18PM +0000, Tiffany Y. Yang wrote:
> Identify buffer addresses using vma offsets instead of full user
> addresses in debug logs.
> 
> Signed-off-by: Tiffany Y. Yang <ynaffit@google.com>
> ---
>  drivers/android/binder.c | 31 ++++++++++++++++---------------
>  1 file changed, 16 insertions(+), 15 deletions(-)
> 
> diff --git a/drivers/android/binder.c b/drivers/android/binder.c
> index d1aa6d24450a..994ae205aa07 100644
> --- a/drivers/android/binder.c
> +++ b/drivers/android/binder.c
> @@ -3261,20 +3261,20 @@ static void binder_transaction(struct binder_proc *proc,
>  
>  	if (reply)
>  		binder_debug(BINDER_DEBUG_TRANSACTION,
> -			     "%d:%d BC_REPLY %d -> %d:%d, data %016llx-%016llx size %lld-%lld-%lld\n",
> +			     "%d:%d BC_REPLY %d -> %d:%d, buffer offset %lx-%lx size %lld-%lld-%lld\n",
>  			     proc->pid, thread->pid, t->debug_id,
>  			     target_proc->pid, target_thread->pid,
> -			     (u64)tr->data.ptr.buffer,
> -			     (u64)tr->data.ptr.offsets,
> +			     (unsigned long)tr->data.ptr.buffer - proc->alloc.buffer,
> +			     (unsigned long)tr->data.ptr.offsets - proc->alloc.buffer,

These could be pointers to anywhere in user memory, not necessarily the
alloc->buffer. So there will be cases where this substraction doesn't
make sense. However, you are correct that we shouldn't log these addrs
so maybe just don't? wdyt?

>  			     (u64)tr->data_size, (u64)tr->offsets_size,
>  			     (u64)extra_buffers_size);
>  	else
>  		binder_debug(BINDER_DEBUG_TRANSACTION,
> -			     "%d:%d BC_TRANSACTION %d -> %d - node %d, data %016llx-%016llx size %lld-%lld-%lld\n",
> +			     "%d:%d BC_TRANSACTION %d -> %d - node %d, buffer offset %lx-%lx size %lld-%lld-%lld\n",
>  			     proc->pid, thread->pid, t->debug_id,
>  			     target_proc->pid, target_node->debug_id,
> -			     (u64)tr->data.ptr.buffer,
> -			     (u64)tr->data.ptr.offsets,
> +			     (unsigned long)tr->data.ptr.buffer - proc->alloc.buffer,
> +			     (unsigned long)tr->data.ptr.offsets - proc->alloc.buffer,
same here.

Regards,
--
Carlos Llamas