Re: [PATCH] wifi: iwlegacy: work around excessive stack usage on clang/kasan

[Stanislaw Gruszka <stf_xl@wp.pl>]

On Fri, Jun 20, 2025 at 01:39:42PM +0200, Arnd Bergmann wrote:
> From: Arnd Bergmann <arnd@arndb.de>
> 
> In some rare randconfig builds, I seem to trigger a bug in clang where
> it unrolls a loop but then runs out of registers, which then get
> spilled to the stack:
> 
> net/wireless/intel/iwlegacy/4965-rs.c:2262:1: error: stack frame size (1696) exceeds limit (1280) in 'il4965_rs_rate_init' [-Werror,-Wframe-larger-than]
> 
> This seems to be the same one I saw in the omapdrm driver, and there is
> an easy workaround by not inlining the il4965_rs_rate_scale_clear_win
> function.
> 
> Link: https://github.com/llvm/llvm-project/issues/143908
> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Acked-by: Stanislaw Gruszka <stf_xl@wp.pl>

> ---
>  drivers/net/wireless/intel/iwlegacy/4965-rs.c | 3 ++-
>  1 file changed, 2 insertions(+), 1 deletion(-)
> 
> diff --git a/drivers/net/wireless/intel/iwlegacy/4965-rs.c b/drivers/net/wireless/intel/iwlegacy/4965-rs.c
> index 0e5130d1fccd..031d88bf6393 100644
> --- a/drivers/net/wireless/intel/iwlegacy/4965-rs.c
> +++ b/drivers/net/wireless/intel/iwlegacy/4965-rs.c
> @@ -203,7 +203,8 @@ il4965_rs_extract_rate(u32 rate_n_flags)
>  	return (u8) (rate_n_flags & 0xFF);
>  }
>  
> -static void
> +/* noinline works around https://github.com/llvm/llvm-project/issues/143908 */
> +static noinline_for_stack void
>  il4965_rs_rate_scale_clear_win(struct il_rate_scale_data *win)
>  {
>  	win->data = 0;
> -- 
> 2.39.5
>