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kcsan: Add option to allow watcher interruptions

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Add option to allow interrupts while a watchpoint is set up. This can be
enabled either via CONFIG_KCSAN_INTERRUPT_WATCHER or via the boot
parameter 'kcsan.interrupt_watcher=1'.

Note that, currently not all safe per-CPU access primitives and patterns
are accounted for, which could result in false positives. For example,
asm-generic/percpu.h uses plain operations, which by default are
instrumented. On interrupts and subsequent accesses to the same
variable, KCSAN would currently report a data race with this option.

Therefore, this option should currently remain disabled by default, but
may be enabled for specific test scenarios.

To avoid new warnings, changes all uses of smp_processor_id() to use the
raw version (as already done in kcsan_found_watchpoint()). The exact SMP
processor id is for informational purposes in the report, and
correctness is not affected.

Signed-off-by: Marco Elver <elver@google.com>
Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
This commit is contained in:
Marco Elver
2020-02-21 23:02:09 +01:00
committed by Paul E. McKenney
parent f5d2313bd3
commit 48b1fc190a
2 changed files with 21 additions and 24 deletions
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11
lib/Kconfig.kcsan
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@@ -88,6 +88,17 @@ config KCSAN_SKIP_WATCH_RANDOMIZE
KCSAN_WATCH_SKIP. If false, the chosen value is always
KCSAN_WATCH_SKIP.
config KCSAN_INTERRUPT_WATCHER
bool "Interruptible watchers"
help
If enabled, a task that set up a watchpoint may be interrupted while
delayed. This option will allow KCSAN to detect races between
interrupted tasks and other threads of execution on the same CPU.
Currently disabled by default, because not all safe per-CPU access
primitives and patterns may be accounted for, and therefore could
result in false positives.
config KCSAN_REPORT_ONCE_IN_MS
int "Duration in milliseconds, in which any given race is only reported once"
default 3000