On Thu, 2019-11-14 at 19:02 +0100, 'Marco Elver' via kasan-dev wrote: > This is the patch-series for the Kernel Concurrency Sanitizer (KCSAN). > KCSAN is a sampling watchpoint-based *data race detector*. More details > are included in **Documentation/dev-tools/kcsan.rst**. This patch-series > only enables KCSAN for x86, but we expect adding support for other > architectures is relatively straightforward (we are aware of > experimental ARM64 and POWER support). Just booting x86 systems because kcsan_setup_watchpoint() disabled hard irqs? [ 8.926145][ T0] ------------[ cut here ]------------ [ 8.927850][ T0] DEBUG_LOCKS_WARN_ON(!current->hardirqs_enabled) [ 80] WARNING: CPU: 0 PID: 0 at kernel/locking/lockdep.c:4406 check_flags.part.26+0x102/0x240 [ 8.933072][ T0] Modules linked in: [ 8.933072][ T0] CPU: 0 PID: 0 Comm: swapper/0 Not tainted 5.4.0-rc8-next- 20191119+ #2 [ 8.933072][ T0] Hardware name: HP ProLiant XL420 Gen9/ProLiant XL420 Gen9, BIOS U19 12/27/2015 [ 8.933072][ T0] RIP: 0010:check_flags.part.26+0x102/0x240 [ 8.933072][ T0] Code: 7b a2 e8 51 6d 15 00 44 8b 05 fa df 45 01 45 85 c0 0f 85 27 76 00 00 48 c7 c6 02 d6 3b a2 48 c7 c7 79 36 3b a2 e8 2f 9f f5 ff <0f> e9 0d 76 00 00 65 48 8b 3c 25 40 3f 01 00 e8 89 f0 ff ff e8 [ 8.933072][ T0] RSP: 0000:ffffffffa2603860 EFLAGS: 00010086 [ 8.933072][ T0] RAX: 0000000000000000 RBX: ffffffffa2617b40 RCX: 0000000000000000 [ 8.933072][ T0] RDX: 0000000000000000 RSI: 0000000000000001 RDI: 0000000000000000 [ 8.933072][ T0] RBP: ffffffffa2603868 R08: 0000000000000000 R09: 0000ffffa27bcad4 [ 8.933072][ T0] R10: 0000ffffffffffff R11: 0000ffffa27bcad7 R12: 0000000000000168 [ 8.933072][ T0] R13: 0000000000092cc0 R14: 0000000000000246 R15: ffffffffa1664c89 [ 8.933072][ T0] FS: 0000000000000000(0000) GS:ffff8987f3000000(0000) knlGS:0000000000000000 [ 8.933072][ T0] CS: 0010 DS: 0000 ES: 0000 CR0: 0000000080050033 [ 8.933072][ T0] CR2: ffff898bfc9ff000 CR3: 000000033dc0e001 CR4: 00000000001606f0 [ 8.933072][ T0] Call Trace: [ 8.933072][ T0] lock_is_held_type+0x66/0x13072][ T0] ? rcu_is_watching+0x79/0xa0 [ 8.933072][ T0] ? create_object+0x69/0x690 [ 8.933072][ T0] rcu_read_lock_sched_held+0x7f/0xa0 [ 8.933072][ T0] kmem_cache_alloc+0x3b2/0x420 [ 8.933072][ T0] ? create_object+0x69/0x690 [ 8.933072][ T0] create_object+0x69/0x690 [ 8.933072][ T0] ? find_next_bit+0x7b/0xa0 [ 8.933072][ T0] kmemleak_alloc_percpu+0xde/0x170 [ 8.933072][ T0] pcpu_alloc+0x683/0xc90 [ 8.933072][ T0] __alloc_percpu+0x2d/0x40 [ 8.933072][ T0] alloc_vfsmnt+0xd1/0x380 [ 8.933072][ T0] vfs_create_mount+0x7f/0x2e0 [ 8.933072][ T0] ? proc_get_tree+0x4d/0x60 [ 8.933072][ T0] fc_mount+0x6d/0x80 [ 8.933072][ T0] pid_ns_prepare_proc+0x133/0x190 [ 8.933072][ T0] alloc_pid+0x5c3/0x600 [ 8.933072][ T0] copy_process+0x1ca3/0x3480 [ 8.933072][ T0] ? __lock_acquire+0x739/0x25d0 [ 8.933072][ T0] _do_fork+0xaa/0x9c0 [ 8.933072][ T0] ? rcu_blocking_is_gp+0x83/0xb0 [ 8.933072][ T0] ? synchronize_rcu_expedited+0x80/0x6c0 [ 8.933072][ T0] ? rcu_blocking_is_gp+0x83/0xb0 [ 8.933072][ T0] ? rest_init+0x381/0x381 [ 8.933072][ T0] kernel_thread+0xb0/0xe0 [ 8.933072][ T0] ? rest_init+0x381/0x381 [ 8.933072][ T0] rest_init+0x31/0x381 [ 8.933072][ st_init+0x17/0x29 [ 8.933072][ T0] start_kernel+0x6ac/0x6d0 [ 8.933072][ T0] x86_64_start_reservations+0x24/0x26 [ 8.933072][ T0] x86_64_start_kernel+0xef/0xf6 [ 8.933072][ T0] secondary_startup_64+0xb6/0xc0 [ 8.933072][ T0] irq event stamp: 75594 [ 8.933072][ T0] hardirqs last enabled at (75593): [<ffffffffa1203d52>] trace_hardirqs_on_thunk+0x1a/0x1c [ 8.933072][ T0] hardirqs last disabled at (75594): [<ffffffffa14b4f96>] kcsan_setup_watchpoint+0x96/0x200 [ 8.933072][ T0] softirqs last enabled at (75592): [<ffffffffa200034c>] __do_softirq+0x34c/0x57c [ 8.933072][ T0] softirqs last disabled at (75585): [<ffffffffa12c6fb2>] irq_exit+0xa2/0xc0 [ 8.933072][ T0] ---[ end trace f4a667495da45c20 ]--- [ 8.933072][ T0] possible reason: unannotated irqs-on. [ 8.933072][ T0] irq event stamp: 75594 [ 8.933072][ T0] hardirqs last enabled at (75593): [<ffffffffa1203d52>] trace_hardirqs_on_thunk+0x1a/0x1c [ 8.933072][ T0] hardirqs last disabled at (75594): [<ffffffffa14b4f96>] kcsan_setup_watchpoint+0x96/0x200 [ 8.933072][ T0] softirqs last enabled at (75592): [<ffffffffa200034c>] __do_softirq+0x34c/0x57c [ 8.933072][ T0] softirqs last disabled at (75585): [<ffffffffa12c6fb2>] irq_exit+0xa2/0xc0 > > To gather early feedback, we announced KCSAN back in September, and have > integrated the feedback where possible: > http://lkml.kernel.org/r/CANpmjNPJ_bHjfLZCAPV23AXFfiPiyXXqqu72n6TgWzb2Gnu1eA@xxxxxxxxxxxxxx > > The current list of known upstream fixes for data races found by KCSAN > can be found here: > https://github.com/google/ktsan/wiki/KCSAN#upstream-fixes-of-data-races-found-by-kcsan > > We want to point out and acknowledge the work surrounding the LKMM, > including several articles that motivate why data races are dangerous > [1, 2], justifying a data race detector such as KCSAN. > > [1] https://lwn.net/Articles/793253/ > [2] https://lwn.net/Articles/799218/ > > Race conditions vs. data races > ------------------------------ > > Race conditions are logic bugs, where unexpected interleaving of racing > concurrent operations result in an erroneous state. > > Data races on the other hand are defined at the *memory model/language > level*. Many data races are also harmful race conditions, which a tool > like KCSAN reports! However, not all data races are race conditions and > vice-versa. KCSAN's intent is to report data races according to the > LKMM. A data race detector can only work at the memory model/language > level. > > Deeper analysis, to find high-level race conditions only, requires > conveying the intended kernel logic to a tool. This requires (1) the > developer writing a specification or model of their code, and then (2) > the tool verifying that the implementation matches. This has been done > for small bits of code using model checkers and other formal methods, > but does not scale to the level of what can be covered with a dynamic > analysis based data race detector such as KCSAN. > > For reasons outlined in [1, 2], data races can be much more subtle, but > can cause no less harm than high-level race conditions. > > Changelog > --------- > v4: > * Major changes: > - Optimizations resulting in performance improvement of 33% (on > microbenchmark). > - Deal with nested interrupts for atomic_next. > - Simplify report.c (removing double-locking as well), in preparation > for KCSAN_REPORT_VALUE_CHANGE_ONLY. > - Add patch to introduce "data_race(expr)" macro. > - Introduce KCSAN_REPORT_VALUE_CHANGE_ONLY option for further filtering of data > races: if a conflicting write was observed via a watchpoint, only report the > data race if a value change was observed as well. The option will be enabled > by default on syzbot. (rcu-functions will be excluded from this filter at > request of Paul McKenney.) Context: > http://lkml.kernel.org/r/CANpmjNOepvb6+zJmDePxj21n2rctM4Sp4rJ66x_J-L1UmNK54A@xxxxxxxxxxxxxx > > v3: http://lkml.kernel.org/r/20191104142745.14722-1-elver@xxxxxxxxxx > * Major changes: > - Add microbenchmark. > - Add instruction watchpoint skip randomization. > - Refactor API and core runtime fast-path and slow-path. Compared to > the previous version, with a default config and benchmarked using the > added microbenchmark, this version is 3.8x faster. > - Make __tsan_unaligned __alias of generic accesses. > - Rename kcsan_{begin,end}_atomic -> > kcsan_{nestable,flat}_atomic_{begin,end} > - For filter list in debugfs.c use kmalloc+krealloc instead of > kvmalloc. > - Split Documentation into separate patch. > > v2: http://lkml.kernel.org/r/20191017141305.146193-1-elver@xxxxxxxxxx > * Major changes: > - Replace kcsan_check_access(.., {true, false}) with > kcsan_check_{read,write}. > - Change atomic-instrumented.h to use __atomic_check_{read,write}. > - Use common struct kcsan_ctx in task_struct and for per-CPU interrupt > contexts. > > v1: http://lkml.kernel.org/r/20191016083959.186860-1-elver@xxxxxxxxxx > > Marco Elver (10): > kcsan: Add Kernel Concurrency Sanitizer infrastructure > include/linux/compiler.h: Introduce data_race(expr) macro > kcsan: Add Documentation entry in dev-tools > objtool, kcsan: Add KCSAN runtime functions to whitelist > build, kcsan: Add KCSAN build exceptions > seqlock, kcsan: Add annotations for KCSAN > seqlock: Require WRITE_ONCE surrounding raw_seqcount_barrier > asm-generic, kcsan: Add KCSAN instrumentation for bitops > locking/atomics, kcsan: Add KCSAN instrumentation > x86, kcsan: Enable KCSAN for x86 > > Documentation/dev-tools/index.rst | 1 + > Documentation/dev-tools/kcsan.rst | 256 +++++++++ > MAINTAINERS | 11 + > Makefile | 3 +- > arch/x86/Kconfig | 1 + > arch/x86/boot/Makefile | 2 + > arch/x86/boot/compressed/Makefile | 2 + > arch/x86/entry/vdso/Makefile | 3 + > arch/x86/include/asm/bitops.h | 6 +- > arch/x86/kernel/Makefile | 4 + > arch/x86/kernel/cpu/Makefile | 3 + > arch/x86/lib/Makefile | 4 + > arch/x86/mm/Makefile | 4 + > arch/x86/purgatory/Makefile | 2 + > arch/x86/realmode/Makefile | 3 + > arch/x86/realmode/rm/Makefile | 3 + > drivers/firmware/efi/libstub/Makefile | 2 + > include/asm-generic/atomic-instrumented.h | 393 +++++++------- > include/asm-generic/bitops-instrumented.h | 18 + > include/linux/compiler-clang.h | 9 + > include/linux/compiler-gcc.h | 7 + > include/linux/compiler.h | 57 +- > include/linux/kcsan-checks.h | 97 ++++ > include/linux/kcsan.h | 115 ++++ > include/linux/sched.h | 4 + > include/linux/seqlock.h | 51 +- > init/init_task.c | 8 + > init/main.c | 2 + > kernel/Makefile | 6 + > kernel/kcsan/Makefile | 11 + > kernel/kcsan/atomic.h | 27 + > kernel/kcsan/core.c | 626 ++++++++++++++++++++++ > kernel/kcsan/debugfs.c | 275 ++++++++++ > kernel/kcsan/encoding.h | 94 ++++ > kernel/kcsan/kcsan.h | 108 ++++ > kernel/kcsan/report.c | 320 +++++++++++ > kernel/kcsan/test.c | 121 +++++ > kernel/sched/Makefile | 6 + > lib/Kconfig.debug | 2 + > lib/Kconfig.kcsan | 118 ++++ > lib/Makefile | 3 + > mm/Makefile | 8 + > scripts/Makefile.kcsan | 6 + > scripts/Makefile.lib | 10 + > scripts/atomic/gen-atomic-instrumented.sh | 17 +- > tools/objtool/check.c | 18 + > 46 files changed, 2641 insertions(+), 206 deletions(-) > create mode 100644 Documentation/dev-tools/kcsan.rst > create mode 100644 include/linux/kcsan-checks.h > create mode 100644 include/linux/kcsan.h > create mode 100644 kernel/kcsan/Makefile > create mode 100644 kernel/kcsan/atomic.h > create mode 100644 kernel/kcsan/core.c > create mode 100644 kernel/kcsan/debugfs.c > create mode 100644 kernel/kcsan/encoding.h > create mode 100644 kernel/kcsan/kcsan.h > create mode 100644 kernel/kcsan/report.c > create mode 100644 kernel/kcsan/test.c > create mode 100644 lib/Kconfig.kcsan > create mode 100644 scripts/Makefile.kcsan > > -- > 2.24.0.rc1.363.gb1bccd3e3d-goog >
