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Message-Id: <20241018151448.3694052-1-arnd@kernel.org>
Date: Fri, 18 Oct 2024 15:14:42 +0000
From: Arnd Bergmann <arnd@...nel.org>
To: Tiffany Lin <tiffany.lin@...iatek.com>,
Andrew-CT Chen <andrew-ct.chen@...iatek.com>,
Yunfei Dong <yunfei.dong@...iatek.com>,
Mauro Carvalho Chehab <mchehab@...nel.org>,
Matthias Brugger <matthias.bgg@...il.com>,
AngeloGioacchino Del Regno <angelogioacchino.delregno@...labora.com>,
Nathan Chancellor <nathan@...nel.org>
Cc: Arnd Bergmann <arnd@...db.de>,
Nick Desaulniers <ndesaulniers@...gle.com>,
Bill Wendling <morbo@...gle.com>,
Justin Stitt <justinstitt@...gle.com>,
Hans Verkuil <hverkuil@...all.nl>,
Sebastian Fricke <sebastian.fricke@...labora.com>,
Benjamin Gaignard <benjamin.gaignard@...labora.com>,
linux-media@...r.kernel.org,
linux-kernel@...r.kernel.org,
linux-arm-kernel@...ts.infradead.org,
linux-mediatek@...ts.infradead.org,
llvm@...ts.linux.dev
Subject: [PATCH] media: mediatek: vcodec: mark vdec_vp9_slice_map_counts_eob_coef noinline
From: Arnd Bergmann <arnd@...db.de>
With KASAN enabled, clang fails to optimize the inline version of
vdec_vp9_slice_map_counts_eob_coef() properly, leading to kilobytes
of temporary values spilled to the stack:
drivers/media/platform/mediatek/vcodec/decoder/vdec/vdec_vp9_req_lat_if.c:1526:12: error: stack frame size (2160) exceeds limit (2048) in 'vdec_vp9_slice_update_prob' [-Werror,-Wframe-larger-than]
This seems to affect all versions of clang including the latest (clang-20),
but the degree of stack overhead is different per release.
Marking the function as noinline_for_stack is harmless here and avoids
the problem completely.
Signed-off-by: Arnd Bergmann <arnd@...db.de>
---
I have not come to a conclusion on how exactly clang fails to do this
right, but can provide the .config and/or preprocessed source files
and command line if we think this should be fixed in clang.
---
.../mediatek/vcodec/decoder/vdec/vdec_vp9_req_lat_if.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
diff --git a/drivers/media/platform/mediatek/vcodec/decoder/vdec/vdec_vp9_req_lat_if.c b/drivers/media/platform/mediatek/vcodec/decoder/vdec/vdec_vp9_req_lat_if.c
index eea709d93820..47c302745c1d 100644
--- a/drivers/media/platform/mediatek/vcodec/decoder/vdec/vdec_vp9_req_lat_if.c
+++ b/drivers/media/platform/mediatek/vcodec/decoder/vdec/vdec_vp9_req_lat_if.c
@@ -1188,7 +1188,8 @@ static int vdec_vp9_slice_setup_lat(struct vdec_vp9_slice_instance *instance,
return ret;
}
-static
+/* clang stack usage explodes if this is inlined */
+static noinline_for_stack
void vdec_vp9_slice_map_counts_eob_coef(unsigned int i, unsigned int j, unsigned int k,
struct vdec_vp9_slice_frame_counts *counts,
struct v4l2_vp9_frame_symbol_counts *counts_helper)
--
2.39.5
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