Re: [PATCH] drm/edid: reduce update_display_info() stack usage

[Arnd Bergmann]

On Mon, Oct 19, 2026, at 15:28, Jani Nikula wrote:
> On Tue, 13 Oct 2026, Arnd Bergmann <arnd@xxxxxxxxxx> wrote:
>> From: Arnd Bergmann <arnd@xxxxxxxx>
>>
>> The drm_parse_cea_ext() calls into nine individual parser functions
>> based on the data format. If all of those get inlined and KASAN_STACK
>> is enabled, this can explode the combined stack usage beyond a
>> reasonable amount:
>>
>> drivers/gpu/drm/drm_edid.c: In function 'update_display_info':
>> drivers/gpu/drm/drm_edid.c:7040:1: error: the frame size of 1888 bytes is larger than 1536 bytes [-Werror=frame-larger-than=]
>>  7040 | }
>>       | ^
>>
>> Mark all of the individual parser functions as noinline_for_stack
>> to avoid this and keep their stack frames separate. This reduces
>> the stack usage for update_display_info/drm_parse_cea_ext to
>> a more manageable 744 bytes, while each parser only adds at most
>> 200 bytes on top.
>
> Is there really no way to tell the compiler to not do silly things in a
> more generic way?

The problem is really the sanitizers here, which turn off the
optimizations that gcc relies on for its normal behavior and
which cause additional register pressure for the inserted function
calls.

       Arnd