From 2e986b81f698e73c95e6456183f27b861f47bb87 Mon Sep 17 00:00:00 2001 From: Marco Elver Date: Mon, 10 Aug 2020 10:06:25 +0200 Subject: [PATCH] kcsan: Optimize debugfs stats counters Remove kcsan_counter_inc/dec() functions, as they perform no other logic, and are no longer needed. This avoids several calls in kcsan_setup_watchpoint() and kcsan_found_watchpoint(), as well as lets the compiler warn us about potential out-of-bounds accesses as the array's size is known at all usage sites at compile-time. Signed-off-by: Marco Elver Signed-off-by: Paul E. McKenney --- kernel/kcsan/core.c | 22 +++++++++++----------- kernel/kcsan/debugfs.c | 21 +++++---------------- kernel/kcsan/kcsan.h | 12 ++++++------ kernel/kcsan/report.c | 2 +- 4 files changed, 23 insertions(+), 34 deletions(-) diff --git a/kernel/kcsan/core.c b/kernel/kcsan/core.c index b176400a2735..8a1ff605ff2d 100644 --- a/kernel/kcsan/core.c +++ b/kernel/kcsan/core.c @@ -367,13 +367,13 @@ static noinline void kcsan_found_watchpoint(const volatile void *ptr, * already removed the watchpoint, or another thread consumed * the watchpoint before this thread. */ - kcsan_counter_inc(KCSAN_COUNTER_REPORT_RACES); + atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_REPORT_RACES]); } if ((type & KCSAN_ACCESS_ASSERT) != 0) - kcsan_counter_inc(KCSAN_COUNTER_ASSERT_FAILURES); + atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_ASSERT_FAILURES]); else - kcsan_counter_inc(KCSAN_COUNTER_DATA_RACES); + atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_DATA_RACES]); user_access_restore(flags); } @@ -414,7 +414,7 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type) goto out; if (!check_encodable((unsigned long)ptr, size)) { - kcsan_counter_inc(KCSAN_COUNTER_UNENCODABLE_ACCESSES); + atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_UNENCODABLE_ACCESSES]); goto out; } @@ -434,12 +434,12 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type) * with which should_watch() returns true should be tweaked so * that this case happens very rarely. */ - kcsan_counter_inc(KCSAN_COUNTER_NO_CAPACITY); + atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_NO_CAPACITY]); goto out_unlock; } - kcsan_counter_inc(KCSAN_COUNTER_SETUP_WATCHPOINTS); - kcsan_counter_inc(KCSAN_COUNTER_USED_WATCHPOINTS); + atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_SETUP_WATCHPOINTS]); + atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_USED_WATCHPOINTS]); /* * Read the current value, to later check and infer a race if the data @@ -541,16 +541,16 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type) * increment this counter. */ if (is_assert && value_change == KCSAN_VALUE_CHANGE_TRUE) - kcsan_counter_inc(KCSAN_COUNTER_ASSERT_FAILURES); + atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_ASSERT_FAILURES]); kcsan_report(ptr, size, type, value_change, KCSAN_REPORT_RACE_SIGNAL, watchpoint - watchpoints); } else if (value_change == KCSAN_VALUE_CHANGE_TRUE) { /* Inferring a race, since the value should not have changed. */ - kcsan_counter_inc(KCSAN_COUNTER_RACES_UNKNOWN_ORIGIN); + atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_RACES_UNKNOWN_ORIGIN]); if (is_assert) - kcsan_counter_inc(KCSAN_COUNTER_ASSERT_FAILURES); + atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_ASSERT_FAILURES]); if (IS_ENABLED(CONFIG_KCSAN_REPORT_RACE_UNKNOWN_ORIGIN) || is_assert) kcsan_report(ptr, size, type, KCSAN_VALUE_CHANGE_TRUE, @@ -563,7 +563,7 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type) * reused after this point. */ remove_watchpoint(watchpoint); - kcsan_counter_dec(KCSAN_COUNTER_USED_WATCHPOINTS); + atomic_long_dec(&kcsan_counters[KCSAN_COUNTER_USED_WATCHPOINTS]); out_unlock: if (!kcsan_interrupt_watcher) local_irq_restore(irq_flags); diff --git a/kernel/kcsan/debugfs.c b/kernel/kcsan/debugfs.c index 6c4914fa2fad..3c8093a371b1 100644 --- a/kernel/kcsan/debugfs.c +++ b/kernel/kcsan/debugfs.c @@ -17,10 +17,7 @@ #include "kcsan.h" -/* - * Statistics counters. - */ -static atomic_long_t counters[KCSAN_COUNTER_COUNT]; +atomic_long_t kcsan_counters[KCSAN_COUNTER_COUNT]; static const char *const counter_names[] = { [KCSAN_COUNTER_USED_WATCHPOINTS] = "used_watchpoints", [KCSAN_COUNTER_SETUP_WATCHPOINTS] = "setup_watchpoints", @@ -53,16 +50,6 @@ static struct { }; static DEFINE_SPINLOCK(report_filterlist_lock); -void kcsan_counter_inc(enum kcsan_counter_id id) -{ - atomic_long_inc(&counters[id]); -} - -void kcsan_counter_dec(enum kcsan_counter_id id) -{ - atomic_long_dec(&counters[id]); -} - /* * The microbenchmark allows benchmarking KCSAN core runtime only. To run * multiple threads, pipe 'microbench=' from multiple tasks into the @@ -206,8 +193,10 @@ static int show_info(struct seq_file *file, void *v) /* show stats */ seq_printf(file, "enabled: %i\n", READ_ONCE(kcsan_enabled)); - for (i = 0; i < KCSAN_COUNTER_COUNT; ++i) - seq_printf(file, "%s: %ld\n", counter_names[i], atomic_long_read(&counters[i])); + for (i = 0; i < KCSAN_COUNTER_COUNT; ++i) { + seq_printf(file, "%s: %ld\n", counter_names[i], + atomic_long_read(&kcsan_counters[i])); + } /* show filter functions, and filter type */ spin_lock_irqsave(&report_filterlist_lock, flags); diff --git a/kernel/kcsan/kcsan.h b/kernel/kcsan/kcsan.h index 29480010dc30..8d4bf3431b3c 100644 --- a/kernel/kcsan/kcsan.h +++ b/kernel/kcsan/kcsan.h @@ -8,6 +8,7 @@ #ifndef _KERNEL_KCSAN_KCSAN_H #define _KERNEL_KCSAN_KCSAN_H +#include #include #include @@ -34,6 +35,10 @@ void kcsan_restore_irqtrace(struct task_struct *task); */ void kcsan_debugfs_init(void); +/* + * Statistics counters displayed via debugfs; should only be modified in + * slow-paths. + */ enum kcsan_counter_id { /* * Number of watchpoints currently in use. @@ -86,12 +91,7 @@ enum kcsan_counter_id { KCSAN_COUNTER_COUNT, /* number of counters */ }; - -/* - * Increment/decrement counter with given id; avoid calling these in fast-path. - */ -extern void kcsan_counter_inc(enum kcsan_counter_id id); -extern void kcsan_counter_dec(enum kcsan_counter_id id); +extern atomic_long_t kcsan_counters[KCSAN_COUNTER_COUNT]; /* * Returns true if data races in the function symbol that maps to func_addr diff --git a/kernel/kcsan/report.c b/kernel/kcsan/report.c index bf1d59449805..d3bf87e6007c 100644 --- a/kernel/kcsan/report.c +++ b/kernel/kcsan/report.c @@ -559,7 +559,7 @@ static bool prepare_report_consumer(unsigned long *flags, * If the actual accesses to not match, this was a false * positive due to watchpoint encoding. */ - kcsan_counter_inc(KCSAN_COUNTER_ENCODING_FALSE_POSITIVES); + atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_ENCODING_FALSE_POSITIVES]); goto discard; } -- 2.20.1