arm64: errata: Add detection for TRBE write to out-of-range

Arm Neoverse-N2 and Cortex-A710 cores are affected by an erratum where
the trbe, under some circumstances, might write upto 64bytes to an
address after the Limit as programmed by the TRBLIMITR_EL1.LIMIT.
This might -
  - Corrupt a page in the ring buffer, which may corrupt trace from a
    previous session, consumed by userspace.
  - Hit the guard page at the end of the vmalloc area and raise a fault.

To keep the handling simpler, we always leave the last page from the
range, which TRBE is allowed to write. This can be achieved by ensuring
that we always have more than a PAGE worth space in the range, while
calculating the LIMIT for TRBE. And then the LIMIT pointer can be
adjusted to leave the PAGE (TRBLIMITR.LIMIT -= PAGE_SIZE), out of the
TRBE range while enabling it. This makes sure that the TRBE will only
write to an area within its allowed limit (i.e, [head-head+size]) and
we do not have to handle address faults within the driver.

Cc: Anshuman Khandual <anshuman.khandual@arm.com>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>
Cc: Mike Leach <mike.leach@linaro.org>
Cc: Leo Yan <leo.yan@linaro.org>
Cc: Will Deacon <will@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>
Reviewed-by: Anshuman Khandual <anshuman.khandual@arm.com>
Reviewed-by: Mathieu Poirier <mathieu.poirier@linaro.org>
Acked-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Suzuki K Poulose <suzuki.poulose@arm.com>
Link: https://lore.kernel.org/r/20211019163153.3692640-5-suzuki.poulose@arm.com
Signed-off-by: Will Deacon <will@kernel.org>

1 files changed, 41 insertions, 0 deletions

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index ec3bb346957f..a500af15ebd5 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -740,6 +740,47 @@ config ARM64_ERRATUM_2067961
 
 	  If unsure, say Y.
 
+config ARM64_WORKAROUND_TRBE_WRITE_OUT_OF_RANGE
+	bool
+
+config ARM64_ERRATUM_2253138
+	bool "Neoverse-N2: 2253138: workaround TRBE writing to address out-of-range"
+	depends on COMPILE_TEST # Until the CoreSight TRBE driver changes are in
+	depends on CORESIGHT_TRBE
+	default y
+	select ARM64_WORKAROUND_TRBE_WRITE_OUT_OF_RANGE
+	help
+	  This option adds the workaround for ARM Neoverse-N2 erratum 2253138.
+
+	  Affected Neoverse-N2 cores might write to an out-of-range address, not reserved
+	  for TRBE. Under some conditions, the TRBE might generate a write to the next
+	  virtually addressed page following the last page of the TRBE address space
+	  (i.e., the TRBLIMITR_EL1.LIMIT), instead of wrapping around to the base.
+
+	  Work around this in the driver by always making sure that there is a
+	  page beyond the TRBLIMITR_EL1.LIMIT, within the space allowed for the TRBE.
+
+	  If unsure, say Y.
+
+config ARM64_ERRATUM_2224489
+	bool "Cortex-A710: 2224489: workaround TRBE writing to address out-of-range"
+	depends on COMPILE_TEST # Until the CoreSight TRBE driver changes are in
+	depends on CORESIGHT_TRBE
+	default y
+	select ARM64_WORKAROUND_TRBE_WRITE_OUT_OF_RANGE
+	help
+	  This option adds the workaround for ARM Cortex-A710 erratum 2224489.
+
+	  Affected Cortex-A710 cores might write to an out-of-range address, not reserved
+	  for TRBE. Under some conditions, the TRBE might generate a write to the next
+	  virtually addressed page following the last page of the TRBE address space
+	  (i.e., the TRBLIMITR_EL1.LIMIT), instead of wrapping around to the base.
+
+	  Work around this in the driver by always making sure that there is a
+	  page beyond the TRBLIMITR_EL1.LIMIT, within the space allowed for the TRBE.
+
+	  If unsure, say Y.
+
 config CAVIUM_ERRATUM_22375
 	bool "Cavium erratum 22375, 24313"
 	default y