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From: Mark Rutland <mark.rutland@arm.com>
To: linux-kernel@vger.kernel.org
Cc: akpm@linux-foundation.org, aryabinin@virtuozzo.com,
	dvyukov@google.com, mark.rutland@arm.com, mingo@redhat.com,
	peterz@infradead.org
Subject: [PATCH 0/3] kcov: fix unexpected faults
Date: Fri,  4 May 2018 14:55:32 +0100	[thread overview]
Message-ID: <20180504135535.53744-1-mark.rutland@arm.com> (raw)

Hi,

These patches fix a few issues where KCOV code could trigger recursive
faults, discovered while debugging a patch enabling KCOV for arch/arm:

* On CONFIG_PREEMPT kernels, there's a small race window where
  __sanitizer_cov_trace_pc() can see a bogus kcov_area.

* Lazy faulting of the vmalloc area can cause mutual recursion between
  fault handling code and __sanitizer_cov_trace_pc().

* During the context switch, switching the mm can cause the kcov_area to
  be transiently unmapped.

These are prerequisites for enabling KCOV on arm, but the issues
themsevles are generic -- we just happen to avoid them by chance rather
than design on x86-64 and arm64.

I've tested this on arm atop of v4.17-rc3, with KCOV enabled.

Thanks,
Mark.

Mark Rutland (3):
  kcov: ensure irq code sees a valid area
  kcov: prefault the kcov_area
  sched/core / kcov: avoid kcov_area during task switch

 include/linux/kcov.h  | 14 ++++++++++++++
 include/linux/sched.h |  2 +-
 kernel/kcov.c         | 17 +++++++++++++++--
 kernel/sched/core.c   |  4 ++++
 4 files changed, 34 insertions(+), 3 deletions(-)

-- 
2.11.0

             reply	other threads:[~2018-05-04 13:55 UTC|newest]

Thread overview: 12+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-05-04 13:55 Mark Rutland [this message]
2018-05-04 13:55 ` [PATCH 1/3] kcov: ensure irq code sees a valid area Mark Rutland
2018-05-04 14:56   ` Mark Rutland
2018-05-04 13:55 ` [PATCH 2/3] kcov: prefault the kcov_area Mark Rutland
2018-05-04 14:36   ` Andrey Ryabinin
2018-05-04 14:38     ` Mark Rutland
2018-05-04 14:42       ` Andrey Ryabinin
2018-05-08 22:51   ` Andrew Morton
2018-05-09  9:41     ` Mark Rutland
2018-05-04 13:55 ` [PATCH 3/3] sched/core / kcov: avoid kcov_area during task switch Mark Rutland
2018-05-04 14:32   ` Andrey Ryabinin
2018-05-04 14:36     ` Mark Rutland

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