From e80704272f5c3f80d315144b5eeaf867082c94ad Mon Sep 17 00:00:00 2001 From: Marco Elver Date: Mon, 9 Aug 2021 13:25:09 +0200 Subject: kcsan: test: Defer kcsan_test_init() after kunit initialization When the test is built into the kernel (not a module), kcsan_test_init() and kunit_init() both use late_initcall(), which means kcsan_test_init() might see a NULL debugfs_rootdir as parent dentry, resulting in kcsan_test_init() and kcsan_debugfs_init() both trying to create a debugfs node named "kcsan" in debugfs root. One of them will show an error and be unsuccessful. Defer kcsan_test_init() until we're sure kunit was initialized. Signed-off-by: Marco Elver Signed-off-by: Paul E. McKenney --- kernel/kcsan/kcsan_test.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) (limited to 'kernel') diff --git a/kernel/kcsan/kcsan_test.c b/kernel/kcsan/kcsan_test.c index dc55fd5a36fc..df041bdb6088 100644 --- a/kernel/kcsan/kcsan_test.c +++ b/kernel/kcsan/kcsan_test.c @@ -1224,7 +1224,7 @@ static void kcsan_test_exit(void) tracepoint_synchronize_unregister(); } -late_initcall(kcsan_test_init); +late_initcall_sync(kcsan_test_init); module_exit(kcsan_test_exit); MODULE_LICENSE("GPL v2"); -- cgit v1.2.3-70-g09d2 From 80804284103ab95e1fe92f167af690ef4c9a6560 Mon Sep 17 00:00:00 2001 From: Marco Elver Date: Mon, 9 Aug 2021 13:25:10 +0200 Subject: kcsan: test: Use kunit_skip() to skip tests Use the new kunit_skip() to skip tests if requirements were not met. Signed-off-by: Marco Elver Signed-off-by: Paul E. McKenney --- kernel/kcsan/kcsan_test.c | 11 +++++++---- 1 file changed, 7 insertions(+), 4 deletions(-) (limited to 'kernel') diff --git a/kernel/kcsan/kcsan_test.c b/kernel/kcsan/kcsan_test.c index df041bdb6088..d93f226327af 100644 --- a/kernel/kcsan/kcsan_test.c +++ b/kernel/kcsan/kcsan_test.c @@ -29,6 +29,11 @@ #include #include +#define KCSAN_TEST_REQUIRES(test, cond) do { \ + if (!(cond)) \ + kunit_skip((test), "Test requires: " #cond); \ +} while (0) + #ifdef CONFIG_CC_HAS_TSAN_COMPOUND_READ_BEFORE_WRITE #define __KCSAN_ACCESS_RW(alt) (KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE) #else @@ -642,8 +647,7 @@ static void test_read_plain_atomic_write(struct kunit *test) }; bool match_expect = false; - if (IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS)) - return; + KCSAN_TEST_REQUIRES(test, !IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS)); begin_test_checks(test_kernel_read, test_kernel_write_atomic); do { @@ -665,8 +669,7 @@ static void test_read_plain_atomic_rmw(struct kunit *test) }; bool match_expect = false; - if (IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS)) - return; + KCSAN_TEST_REQUIRES(test, !IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS)); begin_test_checks(test_kernel_read, test_kernel_atomic_rmw); do { -- cgit v1.2.3-70-g09d2 From ade3a58b2d40555701143930ead3d44d0b52ca9e Mon Sep 17 00:00:00 2001 From: Marco Elver Date: Mon, 9 Aug 2021 13:25:11 +0200 Subject: kcsan: test: Fix flaky test case If CONFIG_KCSAN_REPORT_VALUE_CHANGE_ONLY=n, then we may also see data races between the writers only. If we get unlucky and never capture a read-write data race, but only the write-write data races, then the test_no_value_change* test cases may incorrectly fail. The second problem is that the initial value needs to be reset, as otherwise we might actually observe a value change at the start. Fix it by also looking for the write-write data races, and resetting the value to what will be written. Signed-off-by: Marco Elver Signed-off-by: Paul E. McKenney --- kernel/kcsan/kcsan_test.c | 22 ++++++++++++++++++---- 1 file changed, 18 insertions(+), 4 deletions(-) (limited to 'kernel') diff --git a/kernel/kcsan/kcsan_test.c b/kernel/kcsan/kcsan_test.c index d93f226327af..e282c1166373 100644 --- a/kernel/kcsan/kcsan_test.c +++ b/kernel/kcsan/kcsan_test.c @@ -493,17 +493,24 @@ static void test_concurrent_races(struct kunit *test) __no_kcsan static void test_novalue_change(struct kunit *test) { - const struct expect_report expect = { + const struct expect_report expect_rw = { .access = { { test_kernel_write_nochange, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE }, { test_kernel_read, &test_var, sizeof(test_var), 0 }, }, }; + const struct expect_report expect_ww = { + .access = { + { test_kernel_write_nochange, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE }, + { test_kernel_write_nochange, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE }, + }, + }; bool match_expect = false; + test_kernel_write_nochange(); /* Reset value. */ begin_test_checks(test_kernel_write_nochange, test_kernel_read); do { - match_expect = report_matches(&expect); + match_expect = report_matches(&expect_rw) || report_matches(&expect_ww); } while (!end_test_checks(match_expect)); if (IS_ENABLED(CONFIG_KCSAN_REPORT_VALUE_CHANGE_ONLY)) KUNIT_EXPECT_FALSE(test, match_expect); @@ -518,17 +525,24 @@ static void test_novalue_change(struct kunit *test) __no_kcsan static void test_novalue_change_exception(struct kunit *test) { - const struct expect_report expect = { + const struct expect_report expect_rw = { .access = { { test_kernel_write_nochange_rcu, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE }, { test_kernel_read, &test_var, sizeof(test_var), 0 }, }, }; + const struct expect_report expect_ww = { + .access = { + { test_kernel_write_nochange_rcu, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE }, + { test_kernel_write_nochange_rcu, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE }, + }, + }; bool match_expect = false; + test_kernel_write_nochange_rcu(); /* Reset value. */ begin_test_checks(test_kernel_write_nochange_rcu, test_kernel_read); do { - match_expect = report_matches(&expect); + match_expect = report_matches(&expect_rw) || report_matches(&expect_ww); } while (!end_test_checks(match_expect)); KUNIT_EXPECT_TRUE(test, match_expect); } -- cgit v1.2.3-70-g09d2 From 55a55fec5015b326235873b925a5882ac56ecaa2 Mon Sep 17 00:00:00 2001 From: Marco Elver Date: Mon, 9 Aug 2021 13:25:12 +0200 Subject: kcsan: Add ability to pass instruction pointer of access to reporting Add the ability to pass an explicitly set instruction pointer of access from check_access() all the way through to reporting. In preparation of using it in reporting. Signed-off-by: Marco Elver Signed-off-by: Paul E. McKenney --- kernel/kcsan/core.c | 55 ++++++++++++++++++++++++++++----------------------- kernel/kcsan/kcsan.h | 8 ++++---- kernel/kcsan/report.c | 20 ++++++++++--------- 3 files changed, 45 insertions(+), 38 deletions(-) (limited to 'kernel') diff --git a/kernel/kcsan/core.c b/kernel/kcsan/core.c index 76e67d1e02d4..bffd1d95addb 100644 --- a/kernel/kcsan/core.c +++ b/kernel/kcsan/core.c @@ -350,6 +350,7 @@ void kcsan_restore_irqtrace(struct task_struct *task) static noinline void kcsan_found_watchpoint(const volatile void *ptr, size_t size, int type, + unsigned long ip, atomic_long_t *watchpoint, long encoded_watchpoint) { @@ -396,7 +397,7 @@ static noinline void kcsan_found_watchpoint(const volatile void *ptr, if (consumed) { kcsan_save_irqtrace(current); - kcsan_report_set_info(ptr, size, type, watchpoint - watchpoints); + kcsan_report_set_info(ptr, size, type, ip, watchpoint - watchpoints); kcsan_restore_irqtrace(current); } else { /* @@ -416,7 +417,7 @@ static noinline void kcsan_found_watchpoint(const volatile void *ptr, } static noinline void -kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type) +kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type, unsigned long ip) { const bool is_write = (type & KCSAN_ACCESS_WRITE) != 0; const bool is_assert = (type & KCSAN_ACCESS_ASSERT) != 0; @@ -568,8 +569,8 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type) if (is_assert && value_change == KCSAN_VALUE_CHANGE_TRUE) atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_ASSERT_FAILURES]); - kcsan_report_known_origin(ptr, size, type, value_change, - watchpoint - watchpoints, + kcsan_report_known_origin(ptr, size, type, ip, + value_change, watchpoint - watchpoints, old, new, access_mask); } else if (value_change == KCSAN_VALUE_CHANGE_TRUE) { /* Inferring a race, since the value should not have changed. */ @@ -578,8 +579,10 @@ kcsan_setup_watchpoint(const volatile void *ptr, size_t size, int type) if (is_assert) atomic_long_inc(&kcsan_counters[KCSAN_COUNTER_ASSERT_FAILURES]); - if (IS_ENABLED(CONFIG_KCSAN_REPORT_RACE_UNKNOWN_ORIGIN) || is_assert) - kcsan_report_unknown_origin(ptr, size, type, old, new, access_mask); + if (IS_ENABLED(CONFIG_KCSAN_REPORT_RACE_UNKNOWN_ORIGIN) || is_assert) { + kcsan_report_unknown_origin(ptr, size, type, ip, + old, new, access_mask); + } } /* @@ -596,8 +599,8 @@ out: user_access_restore(ua_flags); } -static __always_inline void check_access(const volatile void *ptr, size_t size, - int type) +static __always_inline void +check_access(const volatile void *ptr, size_t size, int type, unsigned long ip) { const bool is_write = (type & KCSAN_ACCESS_WRITE) != 0; atomic_long_t *watchpoint; @@ -625,13 +628,12 @@ static __always_inline void check_access(const volatile void *ptr, size_t size, */ if (unlikely(watchpoint != NULL)) - kcsan_found_watchpoint(ptr, size, type, watchpoint, - encoded_watchpoint); + kcsan_found_watchpoint(ptr, size, type, ip, watchpoint, encoded_watchpoint); else { struct kcsan_ctx *ctx = get_ctx(); /* Call only once in fast-path. */ if (unlikely(should_watch(ptr, size, type, ctx))) - kcsan_setup_watchpoint(ptr, size, type); + kcsan_setup_watchpoint(ptr, size, type, ip); else if (unlikely(ctx->scoped_accesses.prev)) kcsan_check_scoped_accesses(); } @@ -757,7 +759,7 @@ kcsan_begin_scoped_access(const volatile void *ptr, size_t size, int type, { struct kcsan_ctx *ctx = get_ctx(); - __kcsan_check_access(ptr, size, type); + check_access(ptr, size, type, _RET_IP_); ctx->disable_count++; /* Disable KCSAN, in case list debugging is on. */ @@ -802,7 +804,7 @@ EXPORT_SYMBOL(kcsan_end_scoped_access); void __kcsan_check_access(const volatile void *ptr, size_t size, int type) { - check_access(ptr, size, type); + check_access(ptr, size, type, _RET_IP_); } EXPORT_SYMBOL(__kcsan_check_access); @@ -823,7 +825,7 @@ EXPORT_SYMBOL(__kcsan_check_access); void __tsan_read##size(void *ptr); \ void __tsan_read##size(void *ptr) \ { \ - check_access(ptr, size, 0); \ + check_access(ptr, size, 0, _RET_IP_); \ } \ EXPORT_SYMBOL(__tsan_read##size); \ void __tsan_unaligned_read##size(void *ptr) \ @@ -832,7 +834,7 @@ EXPORT_SYMBOL(__kcsan_check_access); void __tsan_write##size(void *ptr); \ void __tsan_write##size(void *ptr) \ { \ - check_access(ptr, size, KCSAN_ACCESS_WRITE); \ + check_access(ptr, size, KCSAN_ACCESS_WRITE, _RET_IP_); \ } \ EXPORT_SYMBOL(__tsan_write##size); \ void __tsan_unaligned_write##size(void *ptr) \ @@ -842,7 +844,8 @@ EXPORT_SYMBOL(__kcsan_check_access); void __tsan_read_write##size(void *ptr) \ { \ check_access(ptr, size, \ - KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE); \ + KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE, \ + _RET_IP_); \ } \ EXPORT_SYMBOL(__tsan_read_write##size); \ void __tsan_unaligned_read_write##size(void *ptr) \ @@ -858,14 +861,14 @@ DEFINE_TSAN_READ_WRITE(16); void __tsan_read_range(void *ptr, size_t size); void __tsan_read_range(void *ptr, size_t size) { - check_access(ptr, size, 0); + check_access(ptr, size, 0, _RET_IP_); } EXPORT_SYMBOL(__tsan_read_range); void __tsan_write_range(void *ptr, size_t size); void __tsan_write_range(void *ptr, size_t size) { - check_access(ptr, size, KCSAN_ACCESS_WRITE); + check_access(ptr, size, KCSAN_ACCESS_WRITE, _RET_IP_); } EXPORT_SYMBOL(__tsan_write_range); @@ -886,7 +889,8 @@ EXPORT_SYMBOL(__tsan_write_range); IS_ALIGNED((unsigned long)ptr, size); \ if (IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS) && is_atomic) \ return; \ - check_access(ptr, size, is_atomic ? KCSAN_ACCESS_ATOMIC : 0); \ + check_access(ptr, size, is_atomic ? KCSAN_ACCESS_ATOMIC : 0, \ + _RET_IP_); \ } \ EXPORT_SYMBOL(__tsan_volatile_read##size); \ void __tsan_unaligned_volatile_read##size(void *ptr) \ @@ -901,7 +905,8 @@ EXPORT_SYMBOL(__tsan_write_range); return; \ check_access(ptr, size, \ KCSAN_ACCESS_WRITE | \ - (is_atomic ? KCSAN_ACCESS_ATOMIC : 0)); \ + (is_atomic ? KCSAN_ACCESS_ATOMIC : 0), \ + _RET_IP_); \ } \ EXPORT_SYMBOL(__tsan_volatile_write##size); \ void __tsan_unaligned_volatile_write##size(void *ptr) \ @@ -955,7 +960,7 @@ EXPORT_SYMBOL(__tsan_init); u##bits __tsan_atomic##bits##_load(const u##bits *ptr, int memorder) \ { \ if (!IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS)) { \ - check_access(ptr, bits / BITS_PER_BYTE, KCSAN_ACCESS_ATOMIC); \ + check_access(ptr, bits / BITS_PER_BYTE, KCSAN_ACCESS_ATOMIC, _RET_IP_); \ } \ return __atomic_load_n(ptr, memorder); \ } \ @@ -965,7 +970,7 @@ EXPORT_SYMBOL(__tsan_init); { \ if (!IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS)) { \ check_access(ptr, bits / BITS_PER_BYTE, \ - KCSAN_ACCESS_WRITE | KCSAN_ACCESS_ATOMIC); \ + KCSAN_ACCESS_WRITE | KCSAN_ACCESS_ATOMIC, _RET_IP_); \ } \ __atomic_store_n(ptr, v, memorder); \ } \ @@ -978,7 +983,7 @@ EXPORT_SYMBOL(__tsan_init); if (!IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS)) { \ check_access(ptr, bits / BITS_PER_BYTE, \ KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE | \ - KCSAN_ACCESS_ATOMIC); \ + KCSAN_ACCESS_ATOMIC, _RET_IP_); \ } \ return __atomic_##op##suffix(ptr, v, memorder); \ } \ @@ -1010,7 +1015,7 @@ EXPORT_SYMBOL(__tsan_init); if (!IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS)) { \ check_access(ptr, bits / BITS_PER_BYTE, \ KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE | \ - KCSAN_ACCESS_ATOMIC); \ + KCSAN_ACCESS_ATOMIC, _RET_IP_); \ } \ return __atomic_compare_exchange_n(ptr, exp, val, weak, mo, fail_mo); \ } \ @@ -1025,7 +1030,7 @@ EXPORT_SYMBOL(__tsan_init); if (!IS_ENABLED(CONFIG_KCSAN_IGNORE_ATOMICS)) { \ check_access(ptr, bits / BITS_PER_BYTE, \ KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE | \ - KCSAN_ACCESS_ATOMIC); \ + KCSAN_ACCESS_ATOMIC, _RET_IP_); \ } \ __atomic_compare_exchange_n(ptr, &exp, val, 0, mo, fail_mo); \ return exp; \ diff --git a/kernel/kcsan/kcsan.h b/kernel/kcsan/kcsan.h index f36e25c497ed..ae33c2a7f07e 100644 --- a/kernel/kcsan/kcsan.h +++ b/kernel/kcsan/kcsan.h @@ -121,7 +121,7 @@ enum kcsan_value_change { * to be consumed by the reporting thread. No report is printed yet. */ void kcsan_report_set_info(const volatile void *ptr, size_t size, int access_type, - int watchpoint_idx); + unsigned long ip, int watchpoint_idx); /* * The calling thread observed that the watchpoint it set up was hit and @@ -129,14 +129,14 @@ void kcsan_report_set_info(const volatile void *ptr, size_t size, int access_typ * thread. */ void kcsan_report_known_origin(const volatile void *ptr, size_t size, int access_type, - enum kcsan_value_change value_change, int watchpoint_idx, - u64 old, u64 new, u64 mask); + unsigned long ip, enum kcsan_value_change value_change, + int watchpoint_idx, u64 old, u64 new, u64 mask); /* * No other thread was observed to race with the access, but the data value * before and after the stall differs. Reports a race of "unknown origin". */ void kcsan_report_unknown_origin(const volatile void *ptr, size_t size, int access_type, - u64 old, u64 new, u64 mask); + unsigned long ip, u64 old, u64 new, u64 mask); #endif /* _KERNEL_KCSAN_KCSAN_H */ diff --git a/kernel/kcsan/report.c b/kernel/kcsan/report.c index 21137929d428..50c4119f5cc0 100644 --- a/kernel/kcsan/report.c +++ b/kernel/kcsan/report.c @@ -31,6 +31,7 @@ struct access_info { int access_type; int task_pid; int cpu_id; + unsigned long ip; }; /* @@ -576,21 +577,22 @@ discard: } static struct access_info prepare_access_info(const volatile void *ptr, size_t size, - int access_type) + int access_type, unsigned long ip) { return (struct access_info) { .ptr = ptr, .size = size, .access_type = access_type, .task_pid = in_task() ? task_pid_nr(current) : -1, - .cpu_id = raw_smp_processor_id() + .cpu_id = raw_smp_processor_id(), + .ip = ip, }; } void kcsan_report_set_info(const volatile void *ptr, size_t size, int access_type, - int watchpoint_idx) + unsigned long ip, int watchpoint_idx) { - const struct access_info ai = prepare_access_info(ptr, size, access_type); + const struct access_info ai = prepare_access_info(ptr, size, access_type, ip); unsigned long flags; kcsan_disable_current(); @@ -603,10 +605,10 @@ void kcsan_report_set_info(const volatile void *ptr, size_t size, int access_typ } void kcsan_report_known_origin(const volatile void *ptr, size_t size, int access_type, - enum kcsan_value_change value_change, int watchpoint_idx, - u64 old, u64 new, u64 mask) + unsigned long ip, enum kcsan_value_change value_change, + int watchpoint_idx, u64 old, u64 new, u64 mask) { - const struct access_info ai = prepare_access_info(ptr, size, access_type); + const struct access_info ai = prepare_access_info(ptr, size, access_type, ip); struct other_info *other_info = &other_infos[watchpoint_idx]; unsigned long flags = 0; @@ -637,9 +639,9 @@ out: } void kcsan_report_unknown_origin(const volatile void *ptr, size_t size, int access_type, - u64 old, u64 new, u64 mask) + unsigned long ip, u64 old, u64 new, u64 mask) { - const struct access_info ai = prepare_access_info(ptr, size, access_type); + const struct access_info ai = prepare_access_info(ptr, size, access_type, ip); unsigned long flags; kcsan_disable_current(); -- cgit v1.2.3-70-g09d2 From f4c87dbbef2638f6da6e29b5e998e3b1dcdb08ee Mon Sep 17 00:00:00 2001 From: Marco Elver Date: Mon, 9 Aug 2021 13:25:13 +0200 Subject: kcsan: Save instruction pointer for scoped accesses Save the instruction pointer for scoped accesses, so that it becomes possible for the reporting code to construct more accurate stack traces that will show the start of the scope. Signed-off-by: Marco Elver Signed-off-by: Paul E. McKenney --- include/linux/kcsan-checks.h | 3 +++ kernel/kcsan/core.c | 12 +++++++++--- 2 files changed, 12 insertions(+), 3 deletions(-) (limited to 'kernel') diff --git a/include/linux/kcsan-checks.h b/include/linux/kcsan-checks.h index 9fd0ad80fef6..5f5965246877 100644 --- a/include/linux/kcsan-checks.h +++ b/include/linux/kcsan-checks.h @@ -100,9 +100,12 @@ void kcsan_set_access_mask(unsigned long mask); /* Scoped access information. */ struct kcsan_scoped_access { struct list_head list; + /* Access information. */ const volatile void *ptr; size_t size; int type; + /* Location where scoped access was set up. */ + unsigned long ip; }; /* * Automatically call kcsan_end_scoped_access() when kcsan_scoped_access goes diff --git a/kernel/kcsan/core.c b/kernel/kcsan/core.c index bffd1d95addb..8b20af541776 100644 --- a/kernel/kcsan/core.c +++ b/kernel/kcsan/core.c @@ -202,6 +202,9 @@ static __always_inline struct kcsan_ctx *get_ctx(void) return in_task() ? ¤t->kcsan_ctx : raw_cpu_ptr(&kcsan_cpu_ctx); } +static __always_inline void +check_access(const volatile void *ptr, size_t size, int type, unsigned long ip); + /* Check scoped accesses; never inline because this is a slow-path! */ static noinline void kcsan_check_scoped_accesses(void) { @@ -210,8 +213,10 @@ static noinline void kcsan_check_scoped_accesses(void) struct kcsan_scoped_access *scoped_access; ctx->scoped_accesses.prev = NULL; /* Avoid recursion. */ - list_for_each_entry(scoped_access, &ctx->scoped_accesses, list) - __kcsan_check_access(scoped_access->ptr, scoped_access->size, scoped_access->type); + list_for_each_entry(scoped_access, &ctx->scoped_accesses, list) { + check_access(scoped_access->ptr, scoped_access->size, + scoped_access->type, scoped_access->ip); + } ctx->scoped_accesses.prev = prev_save; } @@ -767,6 +772,7 @@ kcsan_begin_scoped_access(const volatile void *ptr, size_t size, int type, sa->ptr = ptr; sa->size = size; sa->type = type; + sa->ip = _RET_IP_; if (!ctx->scoped_accesses.prev) /* Lazy initialize list head. */ INIT_LIST_HEAD(&ctx->scoped_accesses); @@ -798,7 +804,7 @@ void kcsan_end_scoped_access(struct kcsan_scoped_access *sa) ctx->disable_count--; - __kcsan_check_access(sa->ptr, sa->size, sa->type); + check_access(sa->ptr, sa->size, sa->type, sa->ip); } EXPORT_SYMBOL(kcsan_end_scoped_access); -- cgit v1.2.3-70-g09d2 From 6c65eb75686fc2068c926a73c9c3631b5f0e4c9c Mon Sep 17 00:00:00 2001 From: Marco Elver Date: Mon, 9 Aug 2021 13:25:14 +0200 Subject: kcsan: Start stack trace with explicit location if provided If an explicit access address is set, as is done for scoped accesses, always start the stack trace from that location. get_stack_skipnr() is changed into sanitize_stack_entries(), which if given an address, scans the stack trace for a matching function and then replaces that entry with the explicitly provided address. The previous reports for scoped accesses were all over the place, which could be quite confusing. We now always point at the start of the scope. Signed-off-by: Marco Elver Signed-off-by: Paul E. McKenney --- kernel/kcsan/kcsan_test.c | 19 +++++++++------- kernel/kcsan/report.c | 55 ++++++++++++++++++++++++++++++++++++++++++----- 2 files changed, 61 insertions(+), 13 deletions(-) (limited to 'kernel') diff --git a/kernel/kcsan/kcsan_test.c b/kernel/kcsan/kcsan_test.c index e282c1166373..a3b12429e1d3 100644 --- a/kernel/kcsan/kcsan_test.c +++ b/kernel/kcsan/kcsan_test.c @@ -338,7 +338,10 @@ static noinline void test_kernel_assert_bits_nochange(void) ASSERT_EXCLUSIVE_BITS(test_var, ~TEST_CHANGE_BITS); } -/* To check that scoped assertions do trigger anywhere in scope. */ +/* + * Scoped assertions do trigger anywhere in scope. However, the report should + * still only point at the start of the scope. + */ static noinline void test_enter_scope(void) { int x = 0; @@ -845,22 +848,22 @@ static void test_assert_exclusive_writer_scoped(struct kunit *test) { test_kernel_write_nochange, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE }, }, }; - const struct expect_report expect_anywhere = { + const struct expect_report expect_inscope = { .access = { { test_enter_scope, &test_var, sizeof(test_var), KCSAN_ACCESS_ASSERT | KCSAN_ACCESS_SCOPED }, { test_kernel_write_nochange, &test_var, sizeof(test_var), KCSAN_ACCESS_WRITE }, }, }; bool match_expect_start = false; - bool match_expect_anywhere = false; + bool match_expect_inscope = false; begin_test_checks(test_kernel_assert_writer_scoped, test_kernel_write_nochange); do { match_expect_start |= report_matches(&expect_start); - match_expect_anywhere |= report_matches(&expect_anywhere); - } while (!end_test_checks(match_expect_start && match_expect_anywhere)); + match_expect_inscope |= report_matches(&expect_inscope); + } while (!end_test_checks(match_expect_inscope)); KUNIT_EXPECT_TRUE(test, match_expect_start); - KUNIT_EXPECT_TRUE(test, match_expect_anywhere); + KUNIT_EXPECT_FALSE(test, match_expect_inscope); } __no_kcsan @@ -889,9 +892,9 @@ static void test_assert_exclusive_access_scoped(struct kunit *test) do { match_expect_start |= report_matches(&expect_start1) || report_matches(&expect_start2); match_expect_inscope |= report_matches(&expect_inscope); - } while (!end_test_checks(match_expect_start && match_expect_inscope)); + } while (!end_test_checks(match_expect_inscope)); KUNIT_EXPECT_TRUE(test, match_expect_start); - KUNIT_EXPECT_TRUE(test, match_expect_inscope); + KUNIT_EXPECT_FALSE(test, match_expect_inscope); } /* diff --git a/kernel/kcsan/report.c b/kernel/kcsan/report.c index 50c4119f5cc0..4849cde9db9b 100644 --- a/kernel/kcsan/report.c +++ b/kernel/kcsan/report.c @@ -8,6 +8,7 @@ #include #include #include +#include #include #include #include @@ -301,6 +302,48 @@ static int get_stack_skipnr(const unsigned long stack_entries[], int num_entries return skip; } +/* + * Skips to the first entry that matches the function of @ip, and then replaces + * that entry with @ip, returning the entries to skip. + */ +static int +replace_stack_entry(unsigned long stack_entries[], int num_entries, unsigned long ip) +{ + unsigned long symbolsize, offset; + unsigned long target_func; + int skip; + + if (kallsyms_lookup_size_offset(ip, &symbolsize, &offset)) + target_func = ip - offset; + else + goto fallback; + + for (skip = 0; skip < num_entries; ++skip) { + unsigned long func = stack_entries[skip]; + + if (!kallsyms_lookup_size_offset(func, &symbolsize, &offset)) + goto fallback; + func -= offset; + + if (func == target_func) { + stack_entries[skip] = ip; + return skip; + } + } + +fallback: + /* Should not happen; the resulting stack trace is likely misleading. */ + WARN_ONCE(1, "Cannot find frame for %pS in stack trace", (void *)ip); + return get_stack_skipnr(stack_entries, num_entries); +} + +static int +sanitize_stack_entries(unsigned long stack_entries[], int num_entries, unsigned long ip) +{ + return ip ? replace_stack_entry(stack_entries, num_entries, ip) : + get_stack_skipnr(stack_entries, num_entries); +} + /* Compares symbolized strings of addr1 and addr2. */ static int sym_strcmp(void *addr1, void *addr2) { @@ -328,12 +371,12 @@ static void print_verbose_info(struct task_struct *task) static void print_report(enum kcsan_value_change value_change, const struct access_info *ai, - const struct other_info *other_info, + struct other_info *other_info, u64 old, u64 new, u64 mask) { 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 skipnr = sanitize_stack_entries(stack_entries, num_stack_entries, ai->ip); unsigned long this_frame = stack_entries[skipnr]; unsigned long other_frame = 0; int other_skipnr = 0; /* silence uninit warnings */ @@ -345,8 +388,9 @@ static void print_report(enum kcsan_value_change value_change, return; if (other_info) { - other_skipnr = get_stack_skipnr(other_info->stack_entries, - other_info->num_stack_entries); + other_skipnr = sanitize_stack_entries(other_info->stack_entries, + other_info->num_stack_entries, + other_info->ai.ip); other_frame = other_info->stack_entries[other_skipnr]; /* @value_change is only known for the other thread */ @@ -585,7 +629,8 @@ static struct access_info prepare_access_info(const volatile void *ptr, size_t s .access_type = access_type, .task_pid = in_task() ? task_pid_nr(current) : -1, .cpu_id = raw_smp_processor_id(), - .ip = ip, + /* Only replace stack entry with @ip if scoped access. */ + .ip = (access_type & KCSAN_ACCESS_SCOPED) ? ip : 0, }; } -- cgit v1.2.3-70-g09d2 From d627c537c2585875bba071bbfa7cda20328f982b Mon Sep 17 00:00:00 2001 From: Marco Elver Date: Mon, 9 Aug 2021 13:25:15 +0200 Subject: kcsan: Support reporting scoped read-write access type Support generating the string representation of scoped read-write accesses for completeness. They will become required in planned changes. Signed-off-by: Marco Elver Signed-off-by: Paul E. McKenney --- kernel/kcsan/kcsan_test.c | 8 +++++--- kernel/kcsan/report.c | 4 ++++ 2 files changed, 9 insertions(+), 3 deletions(-) (limited to 'kernel') diff --git a/kernel/kcsan/kcsan_test.c b/kernel/kcsan/kcsan_test.c index a3b12429e1d3..660729238588 100644 --- a/kernel/kcsan/kcsan_test.c +++ b/kernel/kcsan/kcsan_test.c @@ -210,10 +210,12 @@ static bool report_matches(const struct expect_report *r) "read-write" : "write") : "read"); + const bool is_atomic = (ty & KCSAN_ACCESS_ATOMIC); + const bool is_scoped = (ty & KCSAN_ACCESS_SCOPED); const char *const access_type_aux = - (ty & KCSAN_ACCESS_ATOMIC) ? - " (marked)" : - ((ty & KCSAN_ACCESS_SCOPED) ? " (scoped)" : ""); + (is_atomic && is_scoped) ? " (marked, scoped)" + : (is_atomic ? " (marked)" + : (is_scoped ? " (scoped)" : "")); if (i == 1) { /* Access 2 */ diff --git a/kernel/kcsan/report.c b/kernel/kcsan/report.c index 4849cde9db9b..fc15077991c4 100644 --- a/kernel/kcsan/report.c +++ b/kernel/kcsan/report.c @@ -247,6 +247,10 @@ static const char *get_access_type(int type) return "write (scoped)"; case KCSAN_ACCESS_SCOPED | KCSAN_ACCESS_WRITE | KCSAN_ACCESS_ATOMIC: return "write (marked, scoped)"; + case KCSAN_ACCESS_SCOPED | KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE: + return "read-write (scoped)"; + case KCSAN_ACCESS_SCOPED | KCSAN_ACCESS_COMPOUND | KCSAN_ACCESS_WRITE | KCSAN_ACCESS_ATOMIC: + return "read-write (marked, scoped)"; default: BUG(); } -- cgit v1.2.3-70-g09d2 From 78c3d954e2b3c323d6ba0a7294a490fef43efc57 Mon Sep 17 00:00:00 2001 From: Marco Elver Date: Mon, 9 Aug 2021 13:25:16 +0200 Subject: kcsan: Move ctx to start of argument list It is clearer if ctx is at the start of the function argument list; it'll be more consistent when adding functions with varying arguments but all requiring ctx. No functional change intended. Signed-off-by: Marco Elver Signed-off-by: Paul E. McKenney --- kernel/kcsan/core.c | 8 ++++---- 1 file changed, 4 insertions(+), 4 deletions(-) (limited to 'kernel') diff --git a/kernel/kcsan/core.c b/kernel/kcsan/core.c index 8b20af541776..4b84c8e7884b 100644 --- a/kernel/kcsan/core.c +++ b/kernel/kcsan/core.c @@ -222,7 +222,7 @@ static noinline void kcsan_check_scoped_accesses(void) /* Rules for generic atomic accesses. Called from fast-path. */ static __always_inline bool -is_atomic(const volatile void *ptr, size_t size, int type, struct kcsan_ctx *ctx) +is_atomic(struct kcsan_ctx *ctx, const volatile void *ptr, size_t size, int type) { if (type & KCSAN_ACCESS_ATOMIC) return true; @@ -259,7 +259,7 @@ is_atomic(const volatile void *ptr, size_t size, int type, struct kcsan_ctx *ctx } static __always_inline bool -should_watch(const volatile void *ptr, size_t size, int type, struct kcsan_ctx *ctx) +should_watch(struct kcsan_ctx *ctx, const volatile void *ptr, size_t size, int type) { /* * Never set up watchpoints when memory operations are atomic. @@ -268,7 +268,7 @@ should_watch(const volatile void *ptr, size_t size, int type, struct kcsan_ctx * * should not count towards skipped instructions, and (2) to actually * decrement kcsan_atomic_next for consecutive instruction stream. */ - if (is_atomic(ptr, size, type, ctx)) + if (is_atomic(ctx, ptr, size, type)) return false; if (this_cpu_dec_return(kcsan_skip) >= 0) @@ -637,7 +637,7 @@ check_access(const volatile void *ptr, size_t size, int type, unsigned long ip) else { struct kcsan_ctx *ctx = get_ctx(); /* Call only once in fast-path. */ - if (unlikely(should_watch(ptr, size, type, ctx))) + if (unlikely(should_watch(ctx, ptr, size, type))) kcsan_setup_watchpoint(ptr, size, type, ip); else if (unlikely(ctx->scoped_accesses.prev)) kcsan_check_scoped_accesses(); -- cgit v1.2.3-70-g09d2 From ac20e39e8d254da3f82b5ed2afc7bb1e804d32c9 Mon Sep 17 00:00:00 2001 From: Marco Elver Date: Fri, 13 Aug 2021 10:10:55 +0200 Subject: kcsan: selftest: Cleanup and add missing __init Make test_encode_decode() more readable and add missing __init. Signed-off-by: Marco Elver Signed-off-by: Paul E. McKenney --- kernel/kcsan/selftest.c | 72 +++++++++++++++++++++---------------------------- 1 file changed, 30 insertions(+), 42 deletions(-) (limited to 'kernel') diff --git a/kernel/kcsan/selftest.c b/kernel/kcsan/selftest.c index 7f29cb0f5e63..b4295a3892b7 100644 --- a/kernel/kcsan/selftest.c +++ b/kernel/kcsan/selftest.c @@ -18,7 +18,7 @@ #define ITERS_PER_TEST 2000 /* Test requirements. */ -static bool test_requires(void) +static bool __init test_requires(void) { /* random should be initialized for the below tests */ return prandom_u32() + prandom_u32() != 0; @@ -28,14 +28,18 @@ static bool test_requires(void) * Test watchpoint encode and decode: check that encoding some access's info, * and then subsequent decode preserves the access's info. */ -static bool test_encode_decode(void) +static bool __init test_encode_decode(void) { int i; for (i = 0; i < ITERS_PER_TEST; ++i) { size_t size = prandom_u32_max(MAX_ENCODABLE_SIZE) + 1; bool is_write = !!prandom_u32_max(2); + unsigned long verif_masked_addr; + long encoded_watchpoint; + bool verif_is_write; unsigned long addr; + size_t verif_size; prandom_bytes(&addr, sizeof(addr)); if (addr < PAGE_SIZE) @@ -44,53 +48,37 @@ static bool test_encode_decode(void) if (WARN_ON(!check_encodable(addr, size))) return false; - /* Encode and decode */ - { - const long encoded_watchpoint = - encode_watchpoint(addr, size, is_write); - unsigned long verif_masked_addr; - size_t verif_size; - bool verif_is_write; - - /* Check special watchpoints */ - if (WARN_ON(decode_watchpoint( - INVALID_WATCHPOINT, &verif_masked_addr, - &verif_size, &verif_is_write))) - return false; - if (WARN_ON(decode_watchpoint( - CONSUMED_WATCHPOINT, &verif_masked_addr, - &verif_size, &verif_is_write))) - return false; - - /* Check decoding watchpoint returns same data */ - if (WARN_ON(!decode_watchpoint( - encoded_watchpoint, &verif_masked_addr, - &verif_size, &verif_is_write))) - return false; - if (WARN_ON(verif_masked_addr != - (addr & WATCHPOINT_ADDR_MASK))) - goto fail; - if (WARN_ON(verif_size != size)) - goto fail; - if (WARN_ON(is_write != verif_is_write)) - goto fail; - - continue; -fail: - pr_err("%s fail: %s %zu bytes @ %lx -> encoded: %lx -> %s %zu bytes @ %lx\n", - __func__, is_write ? "write" : "read", size, - addr, encoded_watchpoint, - verif_is_write ? "write" : "read", verif_size, - verif_masked_addr); + encoded_watchpoint = encode_watchpoint(addr, size, is_write); + + /* Check special watchpoints */ + if (WARN_ON(decode_watchpoint(INVALID_WATCHPOINT, &verif_masked_addr, &verif_size, &verif_is_write))) return false; - } + if (WARN_ON(decode_watchpoint(CONSUMED_WATCHPOINT, &verif_masked_addr, &verif_size, &verif_is_write))) + return false; + + /* Check decoding watchpoint returns same data */ + if (WARN_ON(!decode_watchpoint(encoded_watchpoint, &verif_masked_addr, &verif_size, &verif_is_write))) + return false; + if (WARN_ON(verif_masked_addr != (addr & WATCHPOINT_ADDR_MASK))) + goto fail; + if (WARN_ON(verif_size != size)) + goto fail; + if (WARN_ON(is_write != verif_is_write)) + goto fail; + + continue; +fail: + pr_err("%s fail: %s %zu bytes @ %lx -> encoded: %lx -> %s %zu bytes @ %lx\n", + __func__, is_write ? "write" : "read", size, addr, encoded_watchpoint, + verif_is_write ? "write" : "read", verif_size, verif_masked_addr); + return false; } return true; } /* Test access matching function. */ -static bool test_matching_access(void) +static bool __init test_matching_access(void) { if (WARN_ON(!matching_access(10, 1, 10, 1))) return false; -- cgit v1.2.3-70-g09d2