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SubjectRe: [rtc-linux] [PATCH 2/5] RTC/i.MX/DryIce: add the unit recovery code
On 14/04/2015 at 11:11:53 +0200, Juergen Borleis wrote :
> This code is requiered to recover the unit from a security violation.
required ^

> Hopefully this code can recover the unit from a hardware related invalid
> state as well.
>
> Signed-off-by: Juergen Borleis <jbe@pengutronix.de>
> Signed-off-by: Robert Schwebel <rsc@pengutronix.de>
> [rsc: got NDA clearance from Freescale]
> ---
> drivers/rtc/rtc-imxdi.c | 333 ++++++++++++++++++++++++++++++++++++++++++------
> 1 file changed, 295 insertions(+), 38 deletions(-)
>
> diff --git a/drivers/rtc/rtc-imxdi.c b/drivers/rtc/rtc-imxdi.c
> index 8750477..f8abf2b 100644
> --- a/drivers/rtc/rtc-imxdi.c
> +++ b/drivers/rtc/rtc-imxdi.c
> @@ -172,6 +172,296 @@ struct imxdi_dev {
> * task, we bring back this unit into life.
> */
>
> +/* do a write into the unit without interrupt support */
> +static void di_write_busy_wait(const struct imxdi_dev *imxdi, u32 val,
> + unsigned reg)

Alignment should match the open parenthesis, please fix all occurrences
in your patch.

> +{
> + /* do the register write */
> + __raw_writel(val, imxdi->ioaddr + reg);
> +
> + /*
> + * now it takes four 32,768 kHz clock cycles to take
> + * the change into effect = 122 us
> + */
> + udelay(200);

As the requirement is not that critical, you may want to use usleep_range()

> +}
> +
> +static void di_report_tamper_info(struct imxdi_dev *imxdi, u32 dsr)
> +{
> + u32 dtcr;
> +
> + dtcr = __raw_readl(imxdi->ioaddr + DTCR);
> +
> + dev_emerg(&imxdi->pdev->dev, "!! DryIce tamper event detected !!\n");
> + /* the following flags force a transition into the "FAILURE STATE" */
> + if (dsr & DSR_VTD) {
> + dev_emerg(&imxdi->pdev->dev, "!! Voltage Tamper event\n");
> + if (!(dtcr & DTCR_VTE))
> + dev_emerg(&imxdi->pdev->dev,
> + "!! But Voltage Tamper detection wasn't enabled. False positive?\n");

I'm not sure about prefixing all the messages with "!! ". dev_emerg()
seems important enough to be noticed.
I would remove " False positive?". What about
dev_emerg(&imxdi->pdev->dev,
"%sVoltage Tamper event\n",
(dtcr & DTCR_VTE) ? "" : "Spurious ");

> + }
> + if (dsr & DSR_CTD) {
> + dev_emerg(&imxdi->pdev->dev, "!! 32768 Hz Clock Tamper Event\n");
> + if (!(dtcr & DTCR_CTE))
> + dev_emerg(&imxdi->pdev->dev,
> + "!! But Clock Tamper detection wasn't enabled. False positive?\n");
> + }
> + if (dsr & DSR_TTD) {
> + dev_emerg(&imxdi->pdev->dev, "!! Temperature Tamper Event\n");
> + if (!(dtcr & DTCR_TTE))
> + dev_emerg(&imxdi->pdev->dev,
> + "!! But Temperature Tamper detection wasn't enabled. False positive?\n");
> + }
> + if (dsr & DSR_SAD) {
> + dev_emerg(&imxdi->pdev->dev, "!! Secure Controller Alarm Event\n");
> + if (!(dtcr & DTCR_SAIE))
> + dev_emerg(&imxdi->pdev->dev,
> + "!! But Secure Controller Alarm detection wasn't enabled. False positive?\n");
> + }
> + if (dsr & DSR_EBD) {
> + dev_emerg(&imxdi->pdev->dev, "!! External Boot Tamper Event\n");
> + if (!(dtcr & DTCR_EBE))
> + dev_emerg(&imxdi->pdev->dev,
> + "!! But External Boot detection wasn't enabled. False positive?\n");
> + }
> + if (dsr & DSR_ETAD) {
> + dev_emerg(&imxdi->pdev->dev, "!! External Tamper A Event\n");
> + if (!(dtcr & DTCR_ETAE))
> + dev_emerg(&imxdi->pdev->dev,
> + "!! But External Tamper A wasn't enabled. False positive?\n");
> + }
> + if (dsr & DSR_ETBD) {
> + dev_emerg(&imxdi->pdev->dev, "!! External Tamper B Event\n");
> + if (!(dtcr & DTCR_ETBE))
> + dev_emerg(&imxdi->pdev->dev,
> + "!! But External Tamper B wasn't enabled. False positive?\n");
> + }
> + if (dsr & DSR_WTD) {
> + dev_emerg(&imxdi->pdev->dev, "!! Wire-mesh Tamper Event\n");
> + if (!(dtcr & DTCR_WTE))
> + dev_emerg(&imxdi->pdev->dev,
> + "!! But wire-mesh Tamper detection wasn't enabled. False positive?\n");
> + }
> + if (dsr & DSR_MCO) {
> + dev_emerg(&imxdi->pdev->dev, "!! Monotonic-counter Overflow Event\n");
> + if (!(dtcr & DTCR_MOE))
> + dev_emerg(&imxdi->pdev->dev,
> + "!! But Monotonic-counter Overflow detection wasn't enabled. False positive?\n");
> + }
> + if (dsr & DSR_TCO) {
> + dev_emerg(&imxdi->pdev->dev, "!! Timer-counter Overflow Event\n");
> + if (!(dtcr & DTCR_TOE))
> + dev_emerg(&imxdi->pdev->dev,
> + "!! But Timer-counter Overflow detection wasn't enabled. False positive?\n");
> + }
> +}
> +
> +static void di_what_is_to_be_done(struct imxdi_dev *imxdi,
> + const char *power_supply)
> +{
> + dev_emerg(&imxdi->pdev->dev, " Please cycle the %s power supply in order to get the DryIce unit working again\n",
remove that heading space ^

I would also explain that the RTC is part of the DryIce unit.

> + power_supply);
> +}
> +
> +static int di_handle_failure_state(struct imxdi_dev *imxdi, u32 dsr)
> +{
> + u32 dcr;
> +
> + dev_dbg(&imxdi->pdev->dev, "DSR register reports: %08X\n", dsr);
> +
> + /* report the cause */
> + di_report_tamper_info(imxdi, dsr);
> +
> + dcr = __raw_readl(imxdi->ioaddr + DCR);

Even if it is used across the whole driver, I would avoid using
__raw_readx as this makes the driver only working in little endian mode.

> +
> + if (dcr & DCR_FSHL) {
> + /* we are out of luck */
> + di_what_is_to_be_done(imxdi, "battery");
> + return -ENODEV;
> + }
> + /*
> + * with the next SYSTEM POR we will transit from the "FAILURE STATE"
> + * into the "NON-VALID STATE" + "FAILURE STATE"
> + */
> + di_what_is_to_be_done(imxdi, "main");
> +
> + return -ENODEV;
> +}
> +
> +static int di_handle_valid_state(struct imxdi_dev *imxdi, u32 dsr)
> +{
> + /* initialize alarm */
> + di_write_busy_wait(imxdi, DCAMR_UNSET, DCAMR);
> + di_write_busy_wait(imxdi, 0, DCALR);
> +
> + /* clear alarm flag */
> + if (dsr & DSR_CAF)
> + di_write_busy_wait(imxdi, DSR_CAF, DSR);
> +
> + return 0;
> +}
> +
> +static int di_handle_invalid_state(struct imxdi_dev *imxdi, u32 dsr)
> +{
> + u32 dcr, sec;
> +
> + /*
> + * lets disable all sources which can force the DryIce unit into
> + * the "FAILURE STATE" for now
> + */
> + di_write_busy_wait(imxdi, 0x00000000, DTCR);
> + /* and lets protect them at runtime from any change */
> + di_write_busy_wait(imxdi, DCR_TDCSL, DCR);
> +
> + sec = __raw_readl(imxdi->ioaddr + DTCMR);
> + if (sec != 0)
> + dev_warn(&imxdi->pdev->dev,
> + "The security violation has happend at %u seconds\n",

Further improvement for this driver: use both DTCMR and DTCLR to be year
2038 proof

> + sec);
> + /*
> + * the timer cannot be set/modified if
> + * - the TCHL or TCSL bit is set in DCR
> + */
> + dcr = __raw_readl(imxdi->ioaddr + DCR);
> + if (!(dcr & DCR_TCE)) {
> + if (dcr & DCR_TCHL) {
> + /* we are out of luck */
> + di_what_is_to_be_done(imxdi, "battery");
> + return -ENODEV;
> + }
> + if (dcr & DCR_TCSL) {
> + di_what_is_to_be_done(imxdi, "main");
> + return -ENODEV;
> + }
> +
Unnecessary blank line

> + }
> + /*
> + * - the timer counter stops/is stopped if
> + * - its overflow flag is set (TCO in DSR)
> + * -> clear overflow bit to make it count again
> + * - NVF is set in DSR
> + * -> clear non-valid bit to make it count again
> + * - its TCE (DCR) is cleared
> + * -> set TCE to make it count
> + * - it was never set before
> + * -> write a time into it (required again if the NVF was set)
> + */
> + /* state handled */
> + di_write_busy_wait(imxdi, DSR_NVF, DSR);
> + /* clear overflow flag */
> + di_write_busy_wait(imxdi, DSR_TCO, DSR);
> + /* enable the counter */
> + di_write_busy_wait(imxdi, dcr | DCR_TCE, DCR);
> + /* set and trigger it to make it count */
> + di_write_busy_wait(imxdi, sec, DTCMR);
> +
> + /* now prepare for the valid state */
> + return di_handle_valid_state(imxdi, __raw_readl(imxdi->ioaddr + DSR));
> +}
> +
> +static int di_handle_invalid_and_failure_state(struct imxdi_dev *imxdi, u32 dsr)
> +{
> + u32 dcr;
> +
> + /*
> + * now we must first remove the tamper sources in order to get the
> + * device out of the "FAILURE STATE"
> + * To disable any of the following sources we need to modify the DTCR
> + */
> + if (dsr & (DSR_WTD | DSR_ETBD | DSR_ETAD | DSR_EBD | DSR_SAD |
> + DSR_TTD | DSR_CTD | DSR_VTD | DSR_MCO | DSR_TCO)) {
> + dcr = __raw_readl(imxdi->ioaddr + DCR);
> + if (dcr & DCR_TDCHL) {
> + /*
> + * the tamper register is locked. We cannot disable the
> + * tamper detection. The TDCHL can only be reset by a
> + * DRYICE POR, but we cannot force a DRYICE POR in
> + * softwere because we are still in "FAILURE STATE".
> + * We need a DRYICE POR via battery power cycling....
> + */
> + /*
> + * out of luck!
> + * we cannot disable them without a DRYICE POR
> + */
> + di_what_is_to_be_done(imxdi, "battery");
> + return -ENODEV;
> + }
> + if (dcr & DCR_TDCSL) {
> + /* a soft lock can be removed by a SYSTEM POR */
> + di_what_is_to_be_done(imxdi, "main");
> + return -ENODEV;
> + }
> + }
> +
> + /* disable all sources */
> + di_write_busy_wait(imxdi, 0x00000000, DTCR);
> +
> + /* clear the status bits now */
> + di_write_busy_wait(imxdi, dsr & (DSR_WTD | DSR_ETBD | DSR_ETAD |
> + DSR_EBD | DSR_SAD | DSR_TTD | DSR_CTD | DSR_VTD |
> + DSR_MCO | DSR_TCO), DSR);
> +
> + dsr = __raw_readl(imxdi->ioaddr + DSR);
> + if ((dsr & ~(DSR_NVF | DSR_SVF | DSR_WBF | DSR_WNF |
> + DSR_WCF | DSR_WEF)) != 0)
> + dev_warn(&imxdi->pdev->dev,
> + "There are still some sources of pain in DSR: %08x!\n",
> + dsr & ~(DSR_NVF | DSR_SVF | DSR_WBF | DSR_WNF |
> + DSR_WCF | DSR_WEF));
> +
> + /*
> + * now we are trying to clear the "Security-violation flag" to
> + * get the DryIce out of this state
> + */
> + di_write_busy_wait(imxdi, DSR_SVF, DSR);
> +
> + /* success? */
> + dsr = __raw_readl(imxdi->ioaddr + DSR);
> + if (dsr & DSR_SVF) {
> + dev_crit(&imxdi->pdev->dev,
> + "Cannot clear the security violation flag. We are ending up in an endless loop!\n");
> + /* last resourt */
resort ^
> + di_what_is_to_be_done(imxdi, "battery");
> + return -ENODEV;
> + }
> +
> + /*
> + * now we have left the "FAILURE STATE" and ending up in the
> + * "NON-VALID STATE" time to recover everything
> + */
> + return di_handle_invalid_state(imxdi, dsr);
> +}
> +
> +static int di_handle_state(struct imxdi_dev *imxdi)
> +{
> + int rc;
> + u32 dsr;
> +
> + dsr = __raw_readl(imxdi->ioaddr + DSR);
> +
> + switch (dsr & (DSR_NVF | DSR_SVF)) {
> + case DSR_NVF:
> + dev_warn(&imxdi->pdev->dev, "Invalid stated unit detected\n");
> + rc = di_handle_invalid_state(imxdi, dsr);
> + break;
> + case DSR_SVF:
> + dev_warn(&imxdi->pdev->dev, "Failure stated unit detected\n");
> + rc = di_handle_failure_state(imxdi, dsr);
> + break;
> + case DSR_NVF | DSR_SVF:
> + dev_warn(&imxdi->pdev->dev,
> + "Failure+Invalid stated unit detected\n");
> + rc = di_handle_invalid_and_failure_state(imxdi, dsr);
> + break;
> + default:
> + dev_notice(&imxdi->pdev->dev, "Unlocked unit detected\n");
> + rc = di_handle_valid_state(imxdi, dsr);
> + }
> +
> + return rc;
> +}
> +
> +
Unnecessary blank line

> /*
> * enable a dryice interrupt
> */
> @@ -491,6 +781,11 @@ static int __init dryice_rtc_probe(struct platform_device *pdev)
> /* mask all interrupts */
> __raw_writel(0, imxdi->ioaddr + DIER);
>
> + rc = di_handle_state(imxdi);
> + if (rc != 0)
> + goto err;
> +
> +
Unnecessary blank line

> rc = devm_request_irq(&pdev->dev, imxdi->irq, dryice_norm_irq,
> IRQF_SHARED, pdev->name, imxdi);
> if (rc) {
> @@ -498,44 +793,6 @@ static int __init dryice_rtc_probe(struct platform_device *pdev)
> goto err;
> }
>
> - /* put dryice into valid state */
> - if (__raw_readl(imxdi->ioaddr + DSR) & DSR_NVF) {
> - rc = di_write_wait(imxdi, DSR_NVF | DSR_SVF, DSR);

Multiple writes have switched from di_write_wait() which is checking
for a write error to di_write_busy_wait() which is not doing that check
is waiting 200us enough to ensure that the write has been done?

> - if (rc)
> - goto err;
> - }
> -
> - /* initialize alarm */
> - rc = di_write_wait(imxdi, DCAMR_UNSET, DCAMR);
> - if (rc)
> - goto err;
> - rc = di_write_wait(imxdi, 0, DCALR);
> - if (rc)
> - goto err;
> -
> - /* clear alarm flag */
> - if (__raw_readl(imxdi->ioaddr + DSR) & DSR_CAF) {
> - rc = di_write_wait(imxdi, DSR_CAF, DSR);
> - if (rc)
> - goto err;
> - }
> -
> - /* the timer won't count if it has never been written to */
> - if (__raw_readl(imxdi->ioaddr + DTCMR) == 0) {
> - rc = di_write_wait(imxdi, 0, DTCMR);
> - if (rc)
> - goto err;
> - }
> -
> - /* start keeping time */
> - if (!(__raw_readl(imxdi->ioaddr + DCR) & DCR_TCE)) {
> - rc = di_write_wait(imxdi,
> - __raw_readl(imxdi->ioaddr + DCR) | DCR_TCE,
> - DCR);
> - if (rc)
> - goto err;
> - }
> -
> platform_set_drvdata(pdev, imxdi);
> imxdi->rtc = devm_rtc_device_register(&pdev->dev, pdev->name,
> &dryice_rtc_ops, THIS_MODULE);
> --
> 2.1.4
>

--
Alexandre Belloni, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com


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