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SubjectRe: [PATCH] media: mtk-vpu: avoid unaligned access to DTCM buffer.
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Hi Hsin-Yi Wang,

On 2/10/20 4:53 AM, Hsin-Yi Wang wrote:
> struct vpu_run *run in vpu_init_ipi_handler() is an ioremapped DTCM (Data
> Tightly Coupled Memory) buffer shared with AP. It's not able to do
> unaligned access. Otherwise kernel would crash due to unable to handle
> kernel paging request.
>
> struct vpu_run {
> u32 signaled;
> char fw_ver[VPU_FW_VER_LEN];
> unsigned int dec_capability;
> unsigned int enc_capability;
> wait_queue_head_t wq;
> };
>
> fw_ver starts at 4 byte boundary. If system enables
> CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS, strscpy() will do
> read_word_at_a_time(), which tries to read 8-byte: *(unsigned long *)addr
>
> Copy the string by memcpy_fromio() for this buffer to avoid unaligned
> access.
>
> Fixes: 85709cbf1524 ("media: replace strncpy() by strscpy()")
> Signed-off-by: Hsin-Yi Wang <hsinyi@chromium.org>

This patch results in the following sparse warnings:

sparse: WARNINGS
SPARSE:mtk-vpu/mtk_vpu.c mtk-vpu/mtk_vpu.c:834:52: warning: incorrect type in argument 3 (incompatible argument 1 (different address spaces))
SPARSE:mtk-vpu/mtk_vpu.c mtk-vpu/mtk_vpu.c:609:29: warning: dereference of noderef expression
SPARSE:mtk-vpu/mtk_vpu.c mtk-vpu/mtk_vpu.c:613:35: warning: dereference of noderef expression
SPARSE:mtk-vpu/mtk_vpu.c mtk-vpu/mtk_vpu.c:614:35: warning: dereference of noderef expression

Can you take a look?

Regards,

Hans

> ---
> drivers/media/platform/mtk-vpu/mtk_vpu.c | 9 ++++++---
> 1 file changed, 6 insertions(+), 3 deletions(-)
>
> diff --git a/drivers/media/platform/mtk-vpu/mtk_vpu.c b/drivers/media/platform/mtk-vpu/mtk_vpu.c
> index a768707abb94..e705e85d6f5a 100644
> --- a/drivers/media/platform/mtk-vpu/mtk_vpu.c
> +++ b/drivers/media/platform/mtk-vpu/mtk_vpu.c
> @@ -600,13 +600,16 @@ int vpu_load_firmware(struct platform_device *pdev)
> }
> EXPORT_SYMBOL_GPL(vpu_load_firmware);
>
> -static void vpu_init_ipi_handler(void *data, unsigned int len, void *priv)
> +static void vpu_init_ipi_handler(void __iomem *data, unsigned int len,
> + void *priv)
> {
> struct mtk_vpu *vpu = (struct mtk_vpu *)priv;
> - struct vpu_run *run = (struct vpu_run *)data;
> + struct vpu_run __iomem *run = data;
>
> vpu->run.signaled = run->signaled;
> - strscpy(vpu->run.fw_ver, run->fw_ver, sizeof(vpu->run.fw_ver));
> + memcpy_fromio(vpu->run.fw_ver, run->fw_ver, sizeof(vpu->run.fw_ver));
> + /* Make sure the string is NUL-terminated */
> + vpu->run.fw_ver[sizeof(vpu->run.fw_ver) - 1] = '\0';
> vpu->run.dec_capability = run->dec_capability;
> vpu->run.enc_capability = run->enc_capability;
> wake_up_interruptible(&vpu->run.wq);
>

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