Re: [PATCH] drm/i915: Use %p for pointer formatting

[Sebastian Brzezinka <sebastian.brzezinka@intel.com>]

Hi Sebastian,

On Fri Sep 18, 2026 at 12:37 PM CEST, Sebastian Andrzej Siewior wrote:
> Commit 2563a4524febe ("drm/i915: restrict kernel address leak in
> debugfs") introduced the %pK modifier in order not to leak kernel
> pointer.
> Since commit ad67b74d2469d ("printk: hash addresses printed with
> %p") pointers are hashed by default and the behaviour can be controller
> by `hash_pointers' boot argument.
> The policy on %p is to not introduce new ones. Keeping the %p allows
> to assign an id to the object.
> Removing %pK makes it possible to remove its handling from the library.
>
> Use %p instead %pK to allow debugging if needed.
>
> Signed-off-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
> ---
>  drivers/gpu/drm/i915/i915_debugfs.c | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/i915/i915_debugfs.c b/drivers/gpu/drm/i915/i915_debugfs.c
> index a3e27f9e4f476..93ba7369ba6e2 100644
> --- a/drivers/gpu/drm/i915/i915_debugfs.c
> +++ b/drivers/gpu/drm/i915/i915_debugfs.c
> @@ -179,7 +179,7 @@ i915_debugfs_describe_obj(struct seq_file *m, struct drm_i915_gem_object *obj)
>  	struct i915_vma *vma;
>  	int pin_count = 0;
>  
> -	seq_printf(m, "%pK: %c%c%c %8zdKiB %02x %02x %s%s%s",
> +	seq_printf(m, "%p: %c%c%c %8zdKiB %02x %02x %s%s%s",
Please, correct me if I'm wrong, but i915_debugfs_describe_obj() 
prints into a debugfs file read by userspace exactly the case where
Documentation/core-api/printk-formats.rst recommends %pK over %p.
>If (and only if) you are printing addresses as a content of a virtual file in
>e.g. procfs or sysfs (using e.g. seq_printf(), not printk()) read by a
>userspace process, use the %pK modifier described below instead of %p or %px.

And it was addedby 2563a4524feb, which explicitly wants to
guard it with kptr_restrict(i mean that it's intentionally stronger).

-- 
Best regards,
Sebastian