diff options
| -rw-r--r-- | kernel/kcsan/core.c | 34 | ||||
| -rw-r--r-- | lib/Kconfig.kcsan | 11 |
2 files changed, 21 insertions, 24 deletions
diff --git a/kernel/kcsan/core.c b/kernel/kcsan/core.c index 589b1e7f0f25..e7387fec6679 100644 --- a/kernel/kcsan/core.c +++ b/kernel/kcsan/core.c @@ -21,6 +21,7 @@ static bool kcsan_early_enable = IS_ENABLED(CONFIG_KCSAN_EARLY_ENABLE); static unsigned int kcsan_udelay_task = CONFIG_KCSAN_UDELAY_TASK; static unsigned int kcsan_udelay_interrupt = CONFIG_KCSAN_UDELAY_INTERRUPT; static long kcsan_skip_watch = CONFIG_KCSAN_SKIP_WATCH; +static bool kcsan_interrupt_watcher = IS_ENABLED(CONFIG_KCSAN_INTERRUPT_WATCHER); #ifdef MODULE_PARAM_PREFIX #undef MODULE_PARAM_PREFIX @@ -30,6 +31,7 @@ module_param_named(early_enable, kcsan_early_enable, bool, 0); module_param_named(udelay_task, kcsan_udelay_task, uint, 0644); module_param_named(udelay_interrupt, kcsan_udelay_interrupt, uint, 0644); module_param_named(skip_watch, kcsan_skip_watch, long, 0644); +module_param_named(interrupt_watcher, kcsan_interrupt_watcher, bool, 0444); bool kcsan_enabled; @@ -354,7 +356,7 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type) unsigned long access_mask; enum kcsan_value_change value_change = KCSAN_VALUE_CHANGE_MAYBE; unsigned long ua_flags = user_access_save(); - unsigned long irq_flags; + unsigned long irq_flags = 0; /* * Always reset kcsan_skip counter in slow-path to avoid underflow; see @@ -370,26 +372,9 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type) goto out; } - /* - * Disable interrupts & preemptions to avoid another thread on the same - * CPU accessing memory locations for the set up watchpoint; this is to - * avoid reporting races to e.g. CPU-local data. - * - * An alternative would be adding the source CPU to the watchpoint - * encoding, and checking that watchpoint-CPU != this-CPU. There are - * several problems with this: - * 1. we should avoid stealing more bits from the watchpoint encoding - * as it would affect accuracy, as well as increase performance - * overhead in the fast-path; - * 2. if we are preempted, but there *is* a genuine data race, we - * would *not* report it -- since this is the common case (vs. - * CPU-local data accesses), it makes more sense (from a data race - * detection point of view) to simply disable preemptions to ensure - * as many tasks as possible run on other CPUs. - * - * Use raw versions, to avoid lockdep recursion via IRQ flags tracing. - */ - raw_local_irq_save(irq_flags); + if (!kcsan_interrupt_watcher) + /* Use raw to avoid lockdep recursion via IRQ flags tracing. */ + raw_local_irq_save(irq_flags); watchpoint = insert_watchpoint((unsigned long)ptr, size, is_write); if (watchpoint == NULL) { @@ -507,7 +492,7 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type) if (is_assert && value_change == KCSAN_VALUE_CHANGE_TRUE) kcsan_counter_inc(KCSAN_COUNTER_ASSERT_FAILURES); - kcsan_report(ptr, size, type, value_change, smp_processor_id(), + kcsan_report(ptr, size, type, value_change, raw_smp_processor_id(), KCSAN_REPORT_RACE_SIGNAL); } else if (value_change == KCSAN_VALUE_CHANGE_TRUE) { /* Inferring a race, since the value should not have changed. */ @@ -518,13 +503,14 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type) if (IS_ENABLED(CONFIG_KCSAN_REPORT_RACE_UNKNOWN_ORIGIN) || is_assert) kcsan_report(ptr, size, type, KCSAN_VALUE_CHANGE_TRUE, - smp_processor_id(), + raw_smp_processor_id(), KCSAN_REPORT_RACE_UNKNOWN_ORIGIN); } kcsan_counter_dec(KCSAN_COUNTER_USED_WATCHPOINTS); out_unlock: - raw_local_irq_restore(irq_flags); + if (!kcsan_interrupt_watcher) + raw_local_irq_restore(irq_flags); out: user_access_restore(ua_flags); } 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 |