From 48b1fc190a180d971fb69217c88c7247f4f2ca19 Mon Sep 17 00:00:00 2001 From: Marco Elver Date: Fri, 21 Feb 2020 23:02:09 +0100 Subject: kcsan: Add option to allow watcher interruptions 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 Signed-off-by: Paul E. McKenney --- lib/Kconfig.kcsan | 11 +++++++++++ 1 file changed, 11 insertions(+) (limited to 'lib') diff --git a/lib/Kconfig.kcsan b/lib/Kconfig.kcsan index f0b791143c6a..081ed2e1bf7b 100644 --- a/lib/Kconfig.kcsan +++ b/lib/Kconfig.kcsan @@ -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 -- cgit From 2402d0eae589a31ee7b1774cb220d84d0f5605b4 Mon Sep 17 00:00:00 2001 From: Marco Elver Date: Sat, 22 Feb 2020 00:10:27 +0100 Subject: kcsan: Add option for verbose reporting Adds CONFIG_KCSAN_VERBOSE to optionally enable more verbose reports. Currently information about the reporting task's held locks and IRQ trace events are shown, if they are enabled. Signed-off-by: Marco Elver Suggested-by: Qian Cai Signed-off-by: Paul E. McKenney --- lib/Kconfig.kcsan | 13 +++++++++++++ 1 file changed, 13 insertions(+) (limited to 'lib') diff --git a/lib/Kconfig.kcsan b/lib/Kconfig.kcsan index 081ed2e1bf7b..0f1447ff8f55 100644 --- a/lib/Kconfig.kcsan +++ b/lib/Kconfig.kcsan @@ -20,6 +20,19 @@ menuconfig KCSAN if KCSAN +config KCSAN_VERBOSE + bool "Show verbose reports with more information about system state" + depends on PROVE_LOCKING + help + If enabled, reports show more information about the system state that + may help better analyze and debug races. This includes held locks and + IRQ trace events. + + While this option should generally be benign, we call into more + external functions on report generation; if a race report is + generated from any one of them, system stability may suffer due to + deadlocks or recursion. If in doubt, say N. + config KCSAN_DEBUG bool "Debugging of KCSAN internals" -- cgit From eba9c444d34c9f10cbb463329c2c8e14f2adff25 Mon Sep 17 00:00:00 2001 From: Ingo Molnar Date: Mon, 13 Apr 2020 11:03:05 +0200 Subject: Improve KCSAN documentation a bit This commit simplifies and clarifies the highest level KCSAN Kconfig help text. Signed-off-by: Ingo Molnar Signed-off-by: Paul E. McKenney --- lib/Kconfig.kcsan | 15 ++++++++------- 1 file changed, 8 insertions(+), 7 deletions(-) (limited to 'lib') diff --git a/lib/Kconfig.kcsan b/lib/Kconfig.kcsan index 0f1447ff8f55..689b6b81f272 100644 --- a/lib/Kconfig.kcsan +++ b/lib/Kconfig.kcsan @@ -4,17 +4,18 @@ config HAVE_ARCH_KCSAN bool menuconfig KCSAN - bool "KCSAN: dynamic race detector" + bool "KCSAN: dynamic data race detector" depends on HAVE_ARCH_KCSAN && DEBUG_KERNEL && !KASAN select STACKTRACE help - The Kernel Concurrency Sanitizer (KCSAN) is a dynamic race detector, - which relies on compile-time instrumentation, and uses a - watchpoint-based sampling approach to detect races. + The Kernel Concurrency Sanitizer (KCSAN) is a dynamic + data-race detector that relies on compile-time instrumentation. + KCSAN uses a watchpoint-based sampling approach to detect races. - KCSAN's primary purpose is to detect data races. KCSAN can also be - used to check properties, with the help of provided assertions, of - concurrent code where bugs do not manifest as data races. + While KCSAN's primary purpose is to detect data races, it + also provides assertions to check data access constraints. + These assertions can expose bugs that do not manifest as + data races. See for more details. -- cgit