Re: [PRE-REVIEW PATCH 12/16] tasklet: Pass tasklet_struct pointer as .data in DECLARE_TASKLET

[Kees Cook <keescook@chromium.org>]

On Sun, Sep 29, 2019 at 06:30:24PM +0200, Romain Perier wrote:
> Now that all tasklet initializations have been replaced, this updates
> the core of the DECLARE_TASKLET macros by passing the pointer of the
> tasklet structure as .data, so current static tasklets will continue to
> work by deadling with the tasklet_struct pointer in their handler,

typo: dealing

> without have to change the API of the macro. It also updates all
> callbacks of all tasklets statically allocated via DECLARE_TASKLET() for
> extracting the the parent data structure of the tasklet by using
> from_tasklet().

I think this patch needs to be broken up... the users of
DECLARE_TASKLET() shouldn't need to be changed along with
DECLARE_TASKLET() since there are casts protecting the arguments.

> [...]
> diff --git a/include/linux/interrupt.h b/include/linux/interrupt.h
> index f5332ae2dbeb..949bbaeaff0e 100644
> --- a/include/linux/interrupt.h
> +++ b/include/linux/interrupt.h
> @@ -598,11 +598,14 @@ struct tasklet_struct
>  	unsigned long data;
>  };
>  
> +#define TASKLET_DATA_TYPE		unsigned long
> +#define TASKLET_FUNC_TYPE		void (*)(TASKLET_DATA_TYPE)
> +
>  #define DECLARE_TASKLET(name, func, data) \
> -struct tasklet_struct name = { NULL, 0, ATOMIC_INIT(0), func, data }
> +struct tasklet_struct name = { NULL, 0, ATOMIC_INIT(0), (TASKLET_FUNC_TYPE)func, (TASKLET_DATA_TYPE)&name }
>  
>  #define DECLARE_TASKLET_DISABLED(name, func, data) \
> -struct tasklet_struct name = { NULL, 0, ATOMIC_INIT(1), func, data }
> +struct tasklet_struct name = { NULL, 0, ATOMIC_INIT(1), (TASKLET_FUNC_TYPE)func, (TASKLET_DATA_TYPE)&name }
>  
>  
>  enum
> @@ -673,9 +676,6 @@ extern void tasklet_kill_immediate(struct tasklet_struct *t, unsigned int cpu);
>  extern void tasklet_init(struct tasklet_struct *t,
>  			 void (*func)(unsigned long), unsigned long data);
>  
> -#define TASKLET_DATA_TYPE		unsigned long
> -#define TASKLET_FUNC_TYPE		void (*)(TASKLET_DATA_TYPE)
> -

This patch feels like it should be combined with the first one, and only
make the changes to the macros. (And keep them one place: we shouldn't
have to move them later.)

>  #define from_tasklet(var, callback_tasklet, tasklet_fieldname) \
>  	container_of(callback_tasklet, typeof(*var), tasklet_fieldname)
>  
> diff --git a/kernel/backtracetest.c b/kernel/backtracetest.c
> index a2a97fa3071b..b5b9e16f0083 100644
> --- a/kernel/backtracetest.c
> +++ b/kernel/backtracetest.c
> @@ -23,7 +23,7 @@ static void backtrace_test_normal(void)
>  
>  static DECLARE_COMPLETION(backtrace_work);
>  
> -static void backtrace_test_irq_callback(unsigned long data)
> +static void backtrace_test_irq_callback(struct tasklet_struct *unused)
>  {
>  	dump_stack();
>  	complete(&backtrace_work);

And all these other changes should be separated out in a different pass.

-- 
Kees Cook