Re: [PATCH 3/3] media: mediatek: vcodedc: Fix Wcast-function-type-strict warnings
From: Nathan Chancellor <nathan@kernel.org>
Date: 2024-02-01 22:16:56
Also in:
linux-media, linux-mediatek, lkml, llvm
On Sun, Jan 28, 2024 at 02:12:22AM +0000, Ricardo Ribalda wrote:
Building with LLVM=1 throws the following warning: drivers/media/platform/mediatek/vcodec/common/mtk_vcodec_fw_vpu.c:38:32: warning: cast from 'mtk_vcodec_ipi_handler' (aka 'void (*)(void *, unsigned int, void *)') to 'ipi_handler_t' (aka 'void (*)(const void *, unsigned int, void *)') converts to incompatible function type [-Wcast-function-type-strict] Signed-off-by: Ricardo Ribalda <redacted>
I am not positive because I don't have any hardware to test this driver but I suspect this patch is just hiding the warning without actually addressing the issue that it is pointing out. If handler is called through vpu_ipi_register() indirectly (which it obviously is if it is being passed down), there will be a CFI failure because the type of mtk_vcodec_ipi_handler is not the same as ipi_handler_t, as the comment mentions. Has this seen testing on real hardware with kCFI?
quoted hunk ↗ jump to hunk
--- drivers/media/platform/mediatek/vcodec/common/mtk_vcodec_fw_vpu.c | 6 ++++-- 1 file changed, 4 insertions(+), 2 deletions(-)diff --git a/drivers/media/platform/mediatek/vcodec/common/mtk_vcodec_fw_vpu.c b/drivers/media/platform/mediatek/vcodec/common/mtk_vcodec_fw_vpu.c index 9f6e4b59455d..781a0359afdc 100644 --- a/drivers/media/platform/mediatek/vcodec/common/mtk_vcodec_fw_vpu.c +++ b/drivers/media/platform/mediatek/vcodec/common/mtk_vcodec_fw_vpu.c@@ -33,9 +33,11 @@ static int mtk_vcodec_vpu_set_ipi_register(struct mtk_vcodec_fw *fw, int id, * The handler we receive takes a void * as its first argument. We * cannot change this because it needs to be passed down to the rproc * subsystem when SCP is used. VPU takes a const argument, which is - * more constrained, so the conversion below is safe. + * more constrained, so the conversion below is safe. We use the void + * casting, to convince clang with -Wcast-function-type-sctrict that + * this is safe. */ - ipi_handler_t handler_const = (ipi_handler_t)handler; + ipi_handler_t handler_const = (ipi_handler_t)((void *)handler); return vpu_ipi_register(fw->pdev, id, handler_const, name, priv); }-- 2.43.0.429.g432eaa2c6b-goog
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