[PATCH v2] iommu/arm-smmu: Pretty-print context fault related regs
Rob Clark
robdclark at gmail.com
Wed Jun 26 12:42:31 PDT 2024
On Wed, Jun 26, 2024 at 12:08 PM Pranjal Shrivastava <praan at google.com> wrote:
>
> Hi Rob,
>
>
> On Wed, Jun 26, 2024 at 10:08 PM Rob Clark <robdclark at gmail.com> wrote:
> >
> > From: Rob Clark <robdclark at chromium.org>
> >
> > Parse out the bitfields for easier-to-read fault messages.
> >
> > Signed-off-by: Rob Clark <robdclark at chromium.org>
> > ---
> > I kept with the dev_err, which matches qcom_smmu_context_fault. It is
> > only adding two extra lines, and it is ratelimited.
> >
> > I also converted qcom_smmu_context_fault() to use the helpers to do the
> > parsing, rather than more or less duplicating.
> >
> > .../iommu/arm/arm-smmu/arm-smmu-qcom-debug.c | 21 +++---
> > drivers/iommu/arm/arm-smmu/arm-smmu.c | 70 ++++++++++++++++++-
> > drivers/iommu/arm/arm-smmu/arm-smmu.h | 58 +++++++++------
> > 3 files changed, 110 insertions(+), 39 deletions(-)
> >
> > diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom-debug.c b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom-debug.c
> > index 552199cbd9e2..ee7eab273e1a 100644
> > --- a/drivers/iommu/arm/arm-smmu/arm-smmu-qcom-debug.c
> > +++ b/drivers/iommu/arm/arm-smmu/arm-smmu-qcom-debug.c
> > @@ -429,22 +429,17 @@ irqreturn_t qcom_smmu_context_fault(int irq, void *dev)
> > phys_addr_t phys_atos = qcom_smmu_verify_fault(smmu_domain, iova, fsr);
> >
> > if (__ratelimit(&_rs)) {
> > + char buf[80];
>
> Super Nit: I'm not a fan of hardcoding the buffer size but I'm also not sure
> if this makes a strong enough case for a macro definition. Any thoughts, anyone?
>
> > +
> > dev_err(smmu->dev,
> > "Unhandled context fault: fsr=0x%x, iova=0x%08lx, fsynr=0x%x, cbfrsynra=0x%x, cb=%d\n",
> > fsr, iova, fsynr, cbfrsynra, idx);
> > - dev_err(smmu->dev,
> > - "FSR = %08x [%s%s%s%s%s%s%s%s%s], SID=0x%x\n",
> > - fsr,
> > - (fsr & 0x02) ? "TF " : "",
> > - (fsr & 0x04) ? "AFF " : "",
> > - (fsr & 0x08) ? "PF " : "",
> > - (fsr & 0x10) ? "EF " : "",
> > - (fsr & 0x20) ? "TLBMCF " : "",
> > - (fsr & 0x40) ? "TLBLKF " : "",
> > - (fsr & 0x80) ? "MHF " : "",
> > - (fsr & 0x40000000) ? "SS " : "",
> > - (fsr & 0x80000000) ? "MULTI " : "",
> > - cbfrsynra);
> > +
> > + arm_smmu_parse_fsr(buf, fsr);
> > + dev_err(smmu->dev, "FSR: %s\n", buf);
> > +
> > + arm_smmu_parse_fsynr0(buf, fsynr);
> > + dev_err(smmu->dev, "FSYNR0: %s\n", buf);
> >
> > dev_err(smmu->dev,
> > "soft iova-to-phys=%pa\n", &phys_soft);
> > diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.c b/drivers/iommu/arm/arm-smmu/arm-smmu.c
> > index 87c81f75cf84..7f5ca75d5ebe 100644
> > --- a/drivers/iommu/arm/arm-smmu/arm-smmu.c
> > +++ b/drivers/iommu/arm/arm-smmu/arm-smmu.c
> > @@ -405,12 +405,67 @@ static const struct iommu_flush_ops arm_smmu_s2_tlb_ops_v1 = {
> > .tlb_add_page = arm_smmu_tlb_add_page_s2_v1,
> > };
> >
> > +void arm_smmu_parse_fsr(char buf[80], u32 fsr)
> > +{
> > + static const struct {
> > + u32 mask;
> > + const char *name;
> > + } fsr_bits[] = {
> > + { ARM_SMMU_CB_FSR_MULTI, "MULTI" },
> > + { ARM_SMMU_CB_FSR_SS, "SS" },
> > + { ARM_SMMU_CB_FSR_UUT, "UUT" },
> > + { ARM_SMMU_CB_FSR_ASF, "ASF" },
> > + { ARM_SMMU_CB_FSR_TLBLKF, "TLBLKF" },
> > + { ARM_SMMU_CB_FSR_TLBMCF, "TLBMCF" },
> > + { ARM_SMMU_CB_FSR_EF, "EF" },
> > + { ARM_SMMU_CB_FSR_PF, "PF" },
> > + { ARM_SMMU_CB_FSR_AFF, "AFF" },
> > + { ARM_SMMU_CB_FSR_TF, "TF" },
> > + };
> > + char *p = buf;
> > +
> > + p += sprintf(p, "FORMAT=%u",
> > + (u32)FIELD_GET(ARM_SMMU_CB_FSR_FORMAT, fsr));
> > +
> > + for (int i = 0; i < ARRAY_SIZE(fsr_bits); i++)
> > + if (fsr & fsr_bits[i].mask)
> > + p += sprintf(p, "|%s", fsr_bits[i].name);
> > +}
>
> Buffer overflow alert: I suggest passing the buffer size as an
> additional "size" parameter to the function.
> Based on that size parameter, we must ensure that `p` doesn't reach
> out of bounds.
> Maybe using snprintf() to limit the num of characters to the "size"
> parameter would make more sense.
I thought about this, but decided that, since nothing about the string
length is attacker controlled, and there were really only two users,
the simpler "just make the buffer big enough" approach would be fine.
It isn't like there will be a whole bunch more bitfields added.
Perhaps I should just add a #define for buf length, and a WARN_ON() if
that is exceeded. That plus a selftest which calls both the fxns with
register value of ~0 should be enough to prevent any future change
from introducing an overflow.
BR,
-R
> > +
> > +void arm_smmu_parse_fsynr0(char buf[80], u32 fsynr)
>
> Ditto, for this function and also for the signatures in the .h file.
>
>
> > +{
> > + static const struct {
> > + u32 mask;
> > + const char *name;
> > + } fsynr0_bits[] = {
> > + { ARM_SMMU_CB_FSYNR0_WNR, "WNR" },
> > + { ARM_SMMU_CB_FSYNR0_PNU, "PNU" },
> > + { ARM_SMMU_CB_FSYNR0_IND, "IND" },
> > + { ARM_SMMU_CB_FSYNR0_NSATTR, "NSATTR" },
> > + { ARM_SMMU_CB_FSYNR0_PTWF, "PTWF" },
> > + { ARM_SMMU_CB_FSYNR0_AFR, "AFR" },
> > + };
> > + char *p = buf;
> > +
> > + p += sprintf(p, "S1CBNDX=%u",
> > + (u32)FIELD_GET(ARM_SMMU_CB_FSYNR0_S1CBNDX, fsynr));
> > +
> > + for (int i = 0; i < ARRAY_SIZE(fsynr0_bits); i++)
> > + if (fsynr & fsynr0_bits[i].mask)
> > + p += sprintf(p, "|%s", fsynr0_bits[i].name);
> > +
> > + p += sprintf(p, "|PLVL=%u",
> > + (u32)FIELD_GET(ARM_SMMU_CB_FSYNR0_PLVL, fsynr));
> > +}
> > +
> > static irqreturn_t arm_smmu_context_fault(int irq, void *dev)
> > {
> > u32 fsr, fsynr, cbfrsynra;
> > unsigned long iova;
> > struct arm_smmu_domain *smmu_domain = dev;
> > struct arm_smmu_device *smmu = smmu_domain->smmu;
> > + static DEFINE_RATELIMIT_STATE(rs, DEFAULT_RATELIMIT_INTERVAL,
> > + DEFAULT_RATELIMIT_BURST);
> > int idx = smmu_domain->cfg.cbndx;
> > int ret;
> >
> > @@ -423,13 +478,22 @@ static irqreturn_t arm_smmu_context_fault(int irq, void *dev)
> > cbfrsynra = arm_smmu_gr1_read(smmu, ARM_SMMU_GR1_CBFRSYNRA(idx));
> >
> > ret = report_iommu_fault(&smmu_domain->domain, NULL, iova,
> > - fsynr & ARM_SMMU_FSYNR0_WNR ? IOMMU_FAULT_WRITE : IOMMU_FAULT_READ);
> > + fsynr & ARM_SMMU_CB_FSYNR0_WNR ? IOMMU_FAULT_WRITE : IOMMU_FAULT_READ);
> > +
> > + if (ret == -ENOSYS && __ratelimit(&rs)) {
> > + char buf[80];
> >
> > - if (ret == -ENOSYS)
> > - dev_err_ratelimited(smmu->dev,
> > + dev_err(smmu->dev,
> > "Unhandled context fault: fsr=0x%x, iova=0x%08lx, fsynr=0x%x, cbfrsynra=0x%x, cb=%d\n",
> > fsr, iova, fsynr, cbfrsynra, idx);
> >
> > + arm_smmu_parse_fsr(buf, fsr);
> > + dev_err(smmu->dev, "FSR: %s\n", buf);
> > +
> > + arm_smmu_parse_fsynr0(buf, fsynr);
> > + dev_err(smmu->dev, "FSYNR0: %s\n", buf);
> > + }
> > +
> > arm_smmu_cb_write(smmu, idx, ARM_SMMU_CB_FSR, fsr);
> > return IRQ_HANDLED;
> > }
> > diff --git a/drivers/iommu/arm/arm-smmu/arm-smmu.h b/drivers/iommu/arm/arm-smmu/arm-smmu.h
> > index 4765c6945c34..763ea52fca64 100644
> > --- a/drivers/iommu/arm/arm-smmu/arm-smmu.h
> > +++ b/drivers/iommu/arm/arm-smmu/arm-smmu.h
> > @@ -196,34 +196,46 @@ enum arm_smmu_cbar_type {
> > #define ARM_SMMU_CB_PAR_F BIT(0)
> >
> > #define ARM_SMMU_CB_FSR 0x58
> > -#define ARM_SMMU_FSR_MULTI BIT(31)
> > -#define ARM_SMMU_FSR_SS BIT(30)
> > -#define ARM_SMMU_FSR_UUT BIT(8)
> > -#define ARM_SMMU_FSR_ASF BIT(7)
> > -#define ARM_SMMU_FSR_TLBLKF BIT(6)
> > -#define ARM_SMMU_FSR_TLBMCF BIT(5)
> > -#define ARM_SMMU_FSR_EF BIT(4)
> > -#define ARM_SMMU_FSR_PF BIT(3)
> > -#define ARM_SMMU_FSR_AFF BIT(2)
> > -#define ARM_SMMU_FSR_TF BIT(1)
> > -
> > -#define ARM_SMMU_FSR_IGN (ARM_SMMU_FSR_AFF | \
> > - ARM_SMMU_FSR_ASF | \
> > - ARM_SMMU_FSR_TLBMCF | \
> > - ARM_SMMU_FSR_TLBLKF)
> > -
> > -#define ARM_SMMU_FSR_FAULT (ARM_SMMU_FSR_MULTI | \
> > - ARM_SMMU_FSR_SS | \
> > - ARM_SMMU_FSR_UUT | \
> > - ARM_SMMU_FSR_EF | \
> > - ARM_SMMU_FSR_PF | \
> > - ARM_SMMU_FSR_TF | \
> > +#define ARM_SMMU_CB_FSR_MULTI BIT(31)
> > +#define ARM_SMMU_CB_FSR_SS BIT(30)
> > +#define ARM_SMMU_CB_FSR_FORMAT GENMASK(10, 9)
> > +#define ARM_SMMU_CB_FSR_UUT BIT(8)
> > +#define ARM_SMMU_CB_FSR_ASF BIT(7)
> > +#define ARM_SMMU_CB_FSR_TLBLKF BIT(6)
> > +#define ARM_SMMU_CB_FSR_TLBMCF BIT(5)
> > +#define ARM_SMMU_CB_FSR_EF BIT(4)
> > +#define ARM_SMMU_CB_FSR_PF BIT(3)
> > +#define ARM_SMMU_CB_FSR_AFF BIT(2)
> > +#define ARM_SMMU_CB_FSR_TF BIT(1)
> > +
> > +void arm_smmu_parse_fsr(char buf[80], u32 fsr);
> > +
> > +#define ARM_SMMU_FSR_IGN (ARM_SMMU_CB_FSR_AFF | \
> > + ARM_SMMU_CB_FSR_ASF | \
> > + ARM_SMMU_CB_FSR_TLBMCF | \
> > + ARM_SMMU_CB_FSR_TLBLKF)
> > +
> > +#define ARM_SMMU_FSR_FAULT (ARM_SMMU_CB_FSR_MULTI | \
> > + ARM_SMMU_CB_FSR_SS | \
> > + ARM_SMMU_CB_FSR_UUT | \
> > + ARM_SMMU_CB_FSR_EF | \
> > + ARM_SMMU_CB_FSR_PF | \
> > + ARM_SMMU_CB_FSR_TF | \
> > ARM_SMMU_FSR_IGN)
> >
> > #define ARM_SMMU_CB_FAR 0x60
> >
> > #define ARM_SMMU_CB_FSYNR0 0x68
> > -#define ARM_SMMU_FSYNR0_WNR BIT(4)
> > +#define ARM_SMMU_CB_FSYNR0_PLVL GENMASK(1, 0)
> > +#define ARM_SMMU_CB_FSYNR0_WNR BIT(4)
> > +#define ARM_SMMU_CB_FSYNR0_PNU BIT(5)
> > +#define ARM_SMMU_CB_FSYNR0_IND BIT(6)
> > +#define ARM_SMMU_CB_FSYNR0_NSATTR BIT(8)
> > +#define ARM_SMMU_CB_FSYNR0_PTWF BIT(10)
> > +#define ARM_SMMU_CB_FSYNR0_AFR BIT(11)
> > +#define ARM_SMMU_CB_FSYNR0_S1CBNDX GENMASK(23, 16)
> > +
> > +void arm_smmu_parse_fsynr0(char buf[80], u32 fsynr);
>
> Apart from the buffer overflow, everything else looks fine to me.
>
> >
> > #define ARM_SMMU_CB_FSYNR1 0x6c
> >
> > --
> > 2.45.2
> >
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