diff options
Diffstat (limited to 'kernel/kcov.c')
| -rw-r--r-- | kernel/kcov.c | 46 |
1 files changed, 43 insertions, 3 deletions
diff --git a/kernel/kcov.c b/kernel/kcov.c index f0a69d402066..28a6be6e64fd 100644 --- a/kernel/kcov.c +++ b/kernel/kcov.c @@ -11,6 +11,7 @@ #include <linux/fs.h> #include <linux/hashtable.h> #include <linux/init.h> +#include <linux/jiffies.h> #include <linux/kmsan-checks.h> #include <linux/mm.h> #include <linux/preempt.h> @@ -161,6 +162,15 @@ static void kcov_remote_area_put(struct kcov_remote_area *area, kmsan_unpoison_memory(&area->list, sizeof(area->list)); } +/* + * Unlike in_serving_softirq(), this function returns false when called during + * a hardirq or an NMI that happened in the softirq context. + */ +static inline bool in_softirq_really(void) +{ + return in_serving_softirq() && !in_hardirq() && !in_nmi(); +} + static notrace bool check_kcov_mode(enum kcov_mode needed_mode, struct task_struct *t) { unsigned int mode; @@ -170,7 +180,7 @@ static notrace bool check_kcov_mode(enum kcov_mode needed_mode, struct task_stru * so we ignore code executed in interrupts, unless we are in a remote * coverage collection section in a softirq. */ - if (!in_task() && !(in_serving_softirq() && t->kcov_softirq)) + if (!in_task() && !(in_softirq_really() && t->kcov_softirq)) return false; mode = READ_ONCE(t->kcov_mode); /* @@ -849,7 +859,7 @@ void kcov_remote_start(u64 handle) if (WARN_ON(!kcov_check_handle(handle, true, true, true))) return; - if (!in_task() && !in_serving_softirq()) + if (!in_task() && !in_softirq_really()) return; local_lock_irqsave(&kcov_percpu_data.lock, flags); @@ -991,7 +1001,7 @@ void kcov_remote_stop(void) int sequence; unsigned long flags; - if (!in_task() && !in_serving_softirq()) + if (!in_task() && !in_softirq_really()) return; local_lock_irqsave(&kcov_percpu_data.lock, flags); @@ -1058,6 +1068,32 @@ u64 kcov_common_handle(void) } EXPORT_SYMBOL(kcov_common_handle); +#ifdef CONFIG_KCOV_SELFTEST +static void __init selftest(void) +{ + unsigned long start; + + pr_err("running self test\n"); + /* + * Test that interrupts don't produce spurious coverage. + * The coverage callback filters out interrupt code, but only + * after the handler updates preempt count. Some code periodically + * leaks out of that section and leads to spurious coverage. + * It's hard to call the actual interrupt handler directly, + * so we just loop here for a bit waiting for a timer interrupt. + * We set kcov_mode to enable tracing, but don't setup the area, + * so any attempt to trace will crash. Note: we must not call any + * potentially traced functions in this region. + */ + start = jiffies; + current->kcov_mode = KCOV_MODE_TRACE_PC; + while ((jiffies - start) * MSEC_PER_SEC / HZ < 300) + ; + current->kcov_mode = 0; + pr_err("done running self test\n"); +} +#endif + static int __init kcov_init(void) { int cpu; @@ -1077,6 +1113,10 @@ static int __init kcov_init(void) */ debugfs_create_file_unsafe("kcov", 0600, NULL, NULL, &kcov_fops); +#ifdef CONFIG_KCOV_SELFTEST + selftest(); +#endif + return 0; } |