[PATCH] optee/rpmb.c: Fix driver routing memory alignment using a temporary buffer

[litchi.pi]

I agree, the most generic way to fix this problem would be to ensure memory alignment inside the general RPMB driver.
the drivers/tee/optee/rpmb.c driver uses `mmc_rpmb_route_frames`, which is a parallel API used to drive RPMB frames directly into the MMC driver.

I thought that the MMC driver expecting aligned buffer (and panicking if not) was a normal behaviour, and the memory alignment had to be fixed before that.
The problem is that it comes from a shared memory allocation from OP-TEE, which is far less easy to fix using `ALLOC_CACHE_ALIGN_BUFFER` or so.

If the MMC driver has to handle unaligned addresses, then the fix should maybe be on the MMC driver itself indeed,
Regards,

‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Tuesday, June 8, 2021 2:20 PM, Heinrich Schuchardt <xypron.glpk at gmx.de> wrote:

> On 08.06.21 12:07, Timothée Cercueil wrote:
>
> > From: Timothée Cercueil timothee.cercueil at st.com
> > OP-TEE OS inserts a 6-byte header before a raw RPMB frame which makes
> > RPMB data buffer not 32bit aligned. Many RPMB drivers implicitly expect
> > 32bit alignment of the eMMC frame including arm_pl180_mmci.c, sandbox_mmc.c
> > and stm32_sdmmc2.c
>
> Generally block device drivers expect ARCH_DMA_MINALIGN. Have a look at
> mmc_rpmb_read(), mmc_rpmb_write().
>
> Why would we care about alignment in two different modules:
> drivers/tee/optee/rpmb.c and drivers/mmc/rpmb.c?
>
> Shouldn't the fix be in drivers/mmc/rpmb.c?
>
> Let't include the MMC maintainer in the discussion.
>
> Best regards
>
> Heinrich
>
> > To prevent breaking ABI with OPTEE-OS RPC memrefs, allocate a temporary
> > buffer to copy the data into an aligned memory.
> >
> > Signed-off-by: Timothée Cercueil timothee.cercueil at st.com
> > Change-Id: Id78d638851a666a35af907ca8de71dae00946457
> > Signed-off-by: Timothée Cercueil litchi.pi at protonmail.com
> >
> > -------------------------------------------------------------------------------------------------------------------------------------------------------------------------
> >
> > drivers/tee/optee/rpmb.c | 24 +++++++++++++++++++++---
> > 1 file changed, 21 insertions(+), 3 deletions(-)
> > diff --git a/drivers/tee/optee/rpmb.c b/drivers/tee/optee/rpmb.c
> > index 0804fc963c..4713df711c 100644
> > --- a/drivers/tee/optee/rpmb.c
> > +++ b/drivers/tee/optee/rpmb.c
> > @@ -122,6 +122,10 @@ static u32 rpmb_process_request(struct optee_private *priv, void *req,
> > {
> > struct rpmb_req *sreq = req;
> > struct mmc *mmc;
> >
> > -   void *rpmb_data;
> >
> > -   void *rpmb_frame_buffer = NULL;
> >
> > -   size_t rpmb_data_sz;
> >
> > -   int ret;
> >     if (req_size < sizeof(*sreq))
> >     return TEE_ERROR_BAD_PARAMETERS;
> >     @@ -131,9 +135,23 @@ static u32 rpmb_process_request(struct optee_private *priv, void *req,
> >     mmc = get_mmc(priv, sreq->dev_id);
> >     if (!mmc)
> >     return TEE_ERROR_ITEM_NOT_FOUND;
> >
> >
> > -       if (mmc_rpmb_route_frames(mmc, RPMB_REQ_DATA(req),
> >
> >
> > -       			  req_size - sizeof(struct rpmb_req),
> >
> >
> > -       			  rsp, rsp_size))
> >
> >
> >
> > -
> > -       rpmb_data = RPMB_REQ_DATA(req);
> >
> >
> > -       rpmb_data_sz = req_size - sizeof(struct rpmb_req);
> >
> >
> > -       if (!IS_ALIGNED((uintptr_t)rpmb_data, sizeof(u32))) {
> >
> >
> > -       	/* 32bit data alignment is required by RPMB driver */
> >
> >
> > -       	rpmb_frame_buffer = malloc(rpmb_data_sz);
> >
> >
> > -       	if (!rpmb_frame_buffer)
> >
> >
> > -       		return TEE_ERROR_OUT_OF_MEMORY;
> >
> >
> > -
> > -       	memcpy(rpmb_frame_buffer, rpmb_data, rpmb_data_sz);
> >
> >
> > -       	rpmb_data = rpmb_frame_buffer;
> >
> >
> > -       }
> >
> >
> > -
> > -       ret = mmc_rpmb_route_frames(mmc, rpmb_data, rpmb_data_sz,
> >
> >
> > -       			    rsp, rsp_size);
> >
> >
> > -       free(rpmb_frame_buffer);
> >
> >
> > -       if (ret)
> >         	return TEE_ERROR_BAD_PARAMETERS;
> >         return TEE_SUCCESS;
> >
> >
> >
> > --
> > 2.17.1