linux-kernel - Re: [PATCH v3] mmc: core: Return correct emmc response in case of ioctl error

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Date:   Wed, 25 Aug 2021 10:56:40 +0530
From:   Nishad Kamdar <nishadkamdar@...il.com>
To:     Ulf Hansson <ulf.hansson@...aro.org>
Cc:     Jens Axboe <axboe@...nel.dk>,
        Adrian Hunter <adrian.hunter@...el.com>,
        Bean Huo <beanhuo@...ron.com>,
        Shawn Lin <shawn.lin@...k-chips.com>,
        Avri Altman <avri.altman@....com>,
        Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
        linux-mmc <linux-mmc@...r.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH v3] mmc: core: Return correct emmc response in case of
 ioctl error

On Tue, Aug 24, 2021 at 02:44:42PM +0200, Ulf Hansson wrote:
> On Thu, 12 Aug 2021 at 08:57, Nishad Kamdar <nishadkamdar@...il.com> wrote:
> >
> > When a read/write command is sent via ioctl to the kernel,
> > and the command fails, the actual error response of the emmc
> > is not sent to the user.
> >
> > IOCTL read/write tests are carried out using commands
> > 17 (Single BLock Read), 24 (Single Block Write),
> > 18 (Multi Block Read), 25 (Multi Block Write)
> >
> > The tests are carried out on a 64Gb emmc device. All of these
> > tests try to access an "out of range" sector address (0x09B2FFFF).
> >
> > It is seen that without the patch the response received by the user
> > is not OUT_OF_RANGE error (R1 response 31st bit is not set) as per
> > JEDEC specification. After applying the patch proper response is seen.
> > This is because the function returns without copying the response to
> > the user in case of failure. This patch fixes the issue.
> >
> > The test code and the output of only the CMD17 is included in the
> > commit to limit the message length.
> >
> > CMD17 (Test Code Snippet):
> > ==========================
> >         printf("Forming CMD%d\n", opt_idx);
> >         /*  single block read */
> >         cmd.blksz = 512;
> >         cmd.blocks = 1;
> >         cmd.write_flag = 0;
> >         cmd.opcode = 17;
> >         //cmd.arg = atoi(argv[3]);
> >         cmd.arg = 0x09B2FFFF;
> >         /* Expecting response R1B */
> >         cmd.flags = MMC_RSP_SPI_R1 | MMC_RSP_R1 | MMC_CMD_ADTC;
> >
> >         memset(data, 0, sizeof(__u8) * 512);
> >         mmc_ioc_cmd_set_data(cmd, data);
> >
> >         printf("Sending CMD%d: ARG[0x%08x]\n", opt_idx, cmd.arg);
> >         if(ioctl(fd, MMC_IOC_CMD, &cmd))
> >                 perror("Error");
> >
> >         printf("\nResponse: %08x\n", cmd.response[0]);
> >
> > CMD17 (Output without patch):
> > =============================
> > test@...t-LIVA-Z:~$ sudo ./mmc cmd_test /dev/mmcblk0 17
> > Entering the do_mmc_commands:Device: /dev/mmcblk0 nargs:4
> > Entering the do_mmc_commands:Device: /dev/mmcblk0 options[17, 0x09B2FFF]
> > Forming CMD17
> > Sending CMD17: ARG[0x09b2ffff]
> > Error: Connection timed out
> >
> > Response: 00000000
> > (Incorrect response)
> >
> > CMD17 (Output with patch):
> > ==========================
> > test@...t-LIVA-Z:~$ sudo ./mmc cmd_test /dev/mmcblk0 17
> > [sudo] password for test:
> > Entering the do_mmc_commands:Device: /dev/mmcblk0 nargs:4
> > Entering the do_mmc_commands:Device: /dev/mmcblk0 options[17, 09B2FFFF]
> > Forming CMD17
> > Sending CMD17: ARG[0x09b2ffff]
> > Error: Connection timed out
> >
> > Response: 80000900
> > (Correct OUT_OF_ERROR response as per JEDEC specification)
> >
> > Signed-off-by: Nishad Kamdar <nishadkamdar@...il.com>
> > Reviewed-by: Avri Altman <avri.altman@....com>
> > ---
> > Changes in v2:
> >   - Make commit message clearer by adding test cases as outputs.
> > Changes in v3:
> >   - Shorten the commit message to include only CMD17 related
> >     code and test.
> >
> >  drivers/mmc/core/block.c | 2 ++
> >  1 file changed, 2 insertions(+)
> >
> > diff --git a/drivers/mmc/core/block.c b/drivers/mmc/core/block.c
> > index a9ad9f5fa9491..efa92aa7e2368 100644
> > --- a/drivers/mmc/core/block.c
> > +++ b/drivers/mmc/core/block.c
> > @@ -522,11 +522,13 @@ static int __mmc_blk_ioctl_cmd(struct mmc_card *card, struct mmc_blk_data *md,
> >         if (cmd.error) {
> >                 dev_err(mmc_dev(card->host), "%s: cmd error %d\n",
> >                                                 __func__, cmd.error);
> > +               memcpy(&idata->ic.response, cmd.resp, sizeof(cmd.resp));
> >                 return cmd.error;
> >         }
> >         if (data.error) {
> >                 dev_err(mmc_dev(card->host), "%s: data error %d\n",
> >                                                 __func__, data.error);
> > +               memcpy(&idata->ic.response, cmd.resp, sizeof(cmd.resp));
> 
> It looks like we should do this memcpy, no matter whether we get an
> error response or not.
> 
> In other words, I suggest you move the existing
> "memcpy(&(idata->ic.response), cmd.resp, sizeof(cmd.resp));" from a
> couple of lines further done in the code, up to immediately after we
> have called mmc_wait_for_req(). That should make it more clear as
> well, I think.
> 
I agree. I Have sent the updated version of the patch with this change.
Kindly review the same as well.

Thanks for the comment and review.

Regards,
Nishad
> >                 return data.error;
> >         }
> >
> > --
> > 2.17.1
> >
> 
> Kind regards
> Uffe