Building a KASAN-enabled kernel with clang ends up in a case where too much is inlined into vivid_thread_vid_cap() and the stack usage grows a lot, possibly when the register allocation fails to produce efficient code and spills a lot of temporaries to the stack. This uses more than twice the amount of stack than the sum of the individual functions when they are not inlined:
drivers/media/platform/vivid/vivid-kthread-cap.c:766:12: error: stack frame size of 2208 bytes in function 'vivid_thread_vid_cap' [-Werror,-Wframe-larger-than=] Marking two of the key functions in here as 'noinline_for_stack' avoids the pathological case in clang without any apparent downside for gcc. Signed-off-by: Arnd Bergmann <[email protected]> --- Not sure how much effort we want to put into fixing clang to not get into this case. I could open an llvm bug report if something thinks this has a chance of getting fixed there. --- drivers/media/platform/vivid/vivid-kthread-cap.c | 7 ++++--- 1 file changed, 4 insertions(+), 3 deletions(-) diff --git a/drivers/media/platform/vivid/vivid-kthread-cap.c b/drivers/media/platform/vivid/vivid-kthread-cap.c index 6cf495a7d5cc..4f94897e6303 100644 --- a/drivers/media/platform/vivid/vivid-kthread-cap.c +++ b/drivers/media/platform/vivid/vivid-kthread-cap.c @@ -232,8 +232,8 @@ static void *plane_vaddr(struct tpg_data *tpg, struct vivid_buffer *buf, return vbuf; } -static int vivid_copy_buffer(struct vivid_dev *dev, unsigned p, u8 *vcapbuf, - struct vivid_buffer *vid_cap_buf) +static noinline_for_stack int vivid_copy_buffer(struct vivid_dev *dev, unsigned p, + u8 *vcapbuf, struct vivid_buffer *vid_cap_buf) { bool blank = dev->must_blank[vid_cap_buf->vb.vb2_buf.index]; struct tpg_data *tpg = &dev->tpg; @@ -670,7 +670,8 @@ static void vivid_cap_update_frame_period(struct vivid_dev *dev) dev->cap_frame_period = f_period; } -static void vivid_thread_vid_cap_tick(struct vivid_dev *dev, int dropped_bufs) +static noinline_for_stack void vivid_thread_vid_cap_tick(struct vivid_dev *dev, + int dropped_bufs) { struct vivid_buffer *vid_cap_buf = NULL; struct vivid_buffer *vbi_cap_buf = NULL; -- 2.20.0
