diff options
| -rw-r--r-- | kernel/kcsan/report.c | 110 | ||||
| -rw-r--r-- | lib/Kconfig.kcsan | 10 |
2 files changed, 110 insertions, 10 deletions
diff --git a/kernel/kcsan/report.c b/kernel/kcsan/report.c index 9f503ca2ff7a..b5b4feea49de 100644 --- a/kernel/kcsan/report.c +++ b/kernel/kcsan/report.c @@ -1,5 +1,6 @@ // SPDX-License-Identifier: GPL-2.0 +#include <linux/jiffies.h> #include <linux/kernel.h> #include <linux/preempt.h> #include <linux/printk.h> @@ -32,12 +33,99 @@ static struct { } other_info = { .ptr = NULL }; /* + * Information about reported data races; used to rate limit reporting. + */ +struct report_time { + /* + * The last time the data race was reported. + */ + unsigned long time; + + /* + * The frames of the 2 threads; if only 1 thread is known, one frame + * will be 0. + */ + unsigned long frame1; + unsigned long frame2; +}; + +/* + * Since we also want to be able to debug allocators with KCSAN, to avoid + * deadlock, report_times cannot be dynamically resized with krealloc in + * rate_limit_report. + * + * Therefore, we use a fixed-size array, which at most will occupy a page. This + * still adequately rate limits reports, assuming that a) number of unique data + * races is not excessive, and b) occurrence of unique data races within the + * same time window is limited. + */ +#define REPORT_TIMES_MAX (PAGE_SIZE / sizeof(struct report_time)) +#define REPORT_TIMES_SIZE \ + (CONFIG_KCSAN_REPORT_ONCE_IN_MS > REPORT_TIMES_MAX ? \ + REPORT_TIMES_MAX : \ + CONFIG_KCSAN_REPORT_ONCE_IN_MS) +static struct report_time report_times[REPORT_TIMES_SIZE]; + +/* * This spinlock protects reporting and other_info, since other_info is usually * required when reporting. */ static DEFINE_SPINLOCK(report_lock); /* + * Checks if the data race identified by thread frames frame1 and frame2 has + * been reported since (now - KCSAN_REPORT_ONCE_IN_MS). + */ +static bool rate_limit_report(unsigned long frame1, unsigned long frame2) +{ + struct report_time *use_entry = &report_times[0]; + unsigned long invalid_before; + int i; + + BUILD_BUG_ON(CONFIG_KCSAN_REPORT_ONCE_IN_MS != 0 && REPORT_TIMES_SIZE == 0); + + if (CONFIG_KCSAN_REPORT_ONCE_IN_MS == 0) + return false; + + invalid_before = jiffies - msecs_to_jiffies(CONFIG_KCSAN_REPORT_ONCE_IN_MS); + + /* Check if a matching data race report exists. */ + for (i = 0; i < REPORT_TIMES_SIZE; ++i) { + struct report_time *rt = &report_times[i]; + + /* + * Must always select an entry for use to store info as we + * cannot resize report_times; at the end of the scan, use_entry + * will be the oldest entry, which ideally also happened before + * KCSAN_REPORT_ONCE_IN_MS ago. + */ + if (time_before(rt->time, use_entry->time)) + use_entry = rt; + + /* + * Initially, no need to check any further as this entry as well + * as following entries have never been used. + */ + if (rt->time == 0) + break; + + /* Check if entry expired. */ + if (time_before(rt->time, invalid_before)) + continue; /* before KCSAN_REPORT_ONCE_IN_MS ago */ + + /* Reported recently, check if data race matches. */ + if ((rt->frame1 == frame1 && rt->frame2 == frame2) || + (rt->frame1 == frame2 && rt->frame2 == frame1)) + return true; + } + + use_entry->time = jiffies; + use_entry->frame1 = frame1; + use_entry->frame2 = frame2; + return false; +} + +/* * Special rules to skip reporting. */ static bool @@ -132,7 +220,9 @@ static bool print_report(const volatile void *ptr, size_t size, int access_type, unsigned long stack_entries[NUM_STACK_ENTRIES] = { 0 }; int num_stack_entries = stack_trace_save(stack_entries, NUM_STACK_ENTRIES, 1); int skipnr = get_stack_skipnr(stack_entries, num_stack_entries); - int other_skipnr; + unsigned long this_frame = stack_entries[skipnr]; + unsigned long other_frame = 0; + int other_skipnr = 0; /* silence uninit warnings */ /* * Must check report filter rules before starting to print. @@ -143,34 +233,34 @@ static bool print_report(const volatile void *ptr, size_t size, int access_type, if (type == KCSAN_REPORT_RACE_SIGNAL) { other_skipnr = get_stack_skipnr(other_info.stack_entries, other_info.num_stack_entries); + other_frame = other_info.stack_entries[other_skipnr]; /* @value_change is only known for the other thread */ - if (skip_report(other_info.access_type, value_change, - other_info.stack_entries[other_skipnr])) + if (skip_report(other_info.access_type, value_change, other_frame)) return false; } + if (rate_limit_report(this_frame, other_frame)) + return false; + /* Print report header. */ pr_err("==================================================================\n"); switch (type) { case KCSAN_REPORT_RACE_SIGNAL: { - void *this_fn = (void *)stack_entries[skipnr]; - void *other_fn = (void *)other_info.stack_entries[other_skipnr]; int cmp; /* * Order functions lexographically for consistent bug titles. * Do not print offset of functions to keep title short. */ - cmp = sym_strcmp(other_fn, this_fn); + cmp = sym_strcmp((void *)other_frame, (void *)this_frame); pr_err("BUG: KCSAN: data-race in %ps / %ps\n", - cmp < 0 ? other_fn : this_fn, - cmp < 0 ? this_fn : other_fn); + (void *)(cmp < 0 ? other_frame : this_frame), + (void *)(cmp < 0 ? this_frame : other_frame)); } break; case KCSAN_REPORT_RACE_UNKNOWN_ORIGIN: - pr_err("BUG: KCSAN: data-race in %pS\n", - (void *)stack_entries[skipnr]); + pr_err("BUG: KCSAN: data-race in %pS\n", (void *)this_frame); break; default: diff --git a/lib/Kconfig.kcsan b/lib/Kconfig.kcsan index 3f78b1434375..3552990abcfe 100644 --- a/lib/Kconfig.kcsan +++ b/lib/Kconfig.kcsan @@ -81,6 +81,16 @@ config KCSAN_SKIP_WATCH_RANDOMIZE KCSAN_WATCH_SKIP. If false, the chosen value is always KCSAN_WATCH_SKIP. +config KCSAN_REPORT_ONCE_IN_MS + int "Duration in milliseconds, in which any given data race is only reported once" + default 3000 + help + Any given data race is only reported once in the defined time window. + Different data races may still generate reports within a duration + that is smaller than the duration defined here. This allows rate + limiting reporting to avoid flooding the console with reports. + Setting this to 0 disables rate limiting. + # Note that, while some of the below options could be turned into boot # parameters, to optimize for the common use-case, we avoid this because: (a) # it would impact performance (and we want to avoid static branch for all |