From c49cdaafa443ccf861a72d3191121294742c28c7 Mon Sep 17 00:00:00 2001 From: Arnd Bergmann Date: Thu, 18 Jun 2026 16:32:47 +0200 Subject: [PATCH] media: v4l2-tpg: reduce stack usage for kasan builds tpg_fill_plane_buffer() is a rather complex function. While there is nothing wrong with it per se, I have run into corner cases with clang-22 on s390 using KASAN that makes it run out of registers and blow the stack warning limit from excessive spills: drivers/media/common/v4l2-tpg/v4l2-tpg-core.c:2629:6: error: stack frame size (1560) exceeds limit (1536) in 'tpg_fill_plane_buffer' [-Werror,-Wframe-larger-than] 2629 | void tpg_fill_plane_buffer(struct tpg_data *tpg, v4l2_std_id std, Forcing the two largest callees out of line completely avoids the problem and prevents all the register spills, with the stack usage for each function going down to a few bytes for the local variables. Arguably this is a problem caused by clang rather than the code, but a noinline_for_stack annotation is an easy workaround. Signed-off-by: Arnd Bergmann Signed-off-by: Hans Verkuil --- drivers/media/common/v4l2-tpg/v4l2-tpg-core.c | 14 ++++++++------ 1 file changed, 8 insertions(+), 6 deletions(-) diff --git a/drivers/media/common/v4l2-tpg/v4l2-tpg-core.c b/drivers/media/common/v4l2-tpg/v4l2-tpg-core.c index 931e5dc453b9..e1d5c220f738 100644 --- a/drivers/media/common/v4l2-tpg/v4l2-tpg-core.c +++ b/drivers/media/common/v4l2-tpg/v4l2-tpg-core.c @@ -2346,9 +2346,11 @@ static void tpg_fill_params_extras(const struct tpg_data *tpg, (params->is_60hz ? V4L2_FIELD_TOP : V4L2_FIELD_BOTTOM); } -static void tpg_fill_plane_extras(const struct tpg_data *tpg, - const struct tpg_draw_params *params, - unsigned p, unsigned h, u8 *vbuf) +/* noinline to work around clang KASAN issues */ +static noinline_for_stack void +tpg_fill_plane_extras(const struct tpg_data *tpg, + const struct tpg_draw_params *params, + unsigned p, unsigned h, u8 *vbuf) { unsigned twopixsize = params->twopixsize; unsigned img_width = params->img_width; @@ -2483,9 +2485,9 @@ static void tpg_fill_plane_extras(const struct tpg_data *tpg, } } -static void tpg_fill_plane_pattern(const struct tpg_data *tpg, - const struct tpg_draw_params *params, - unsigned p, unsigned h, u8 *vbuf) +static noinline_for_stack void +tpg_fill_plane_pattern(const struct tpg_data *tpg, const struct tpg_draw_params *params, + unsigned p, unsigned h, u8 *vbuf) { unsigned twopixsize = params->twopixsize; unsigned img_width = params->img_width;