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2020-08-30kcsan: Use tracing-safe version of prandomMarco Elver1-6/+29
In the core runtime, we must minimize any calls to external library functions to avoid any kind of recursion. This can happen even though instrumentation is disabled for called functions, but tracing is enabled. Most recently, prandom_u32() added a tracepoint, which can cause problems for KCSAN even if the rcuidle variant is used. For example: kcsan -> prandom_u32() -> trace_prandom_u32_rcuidle -> srcu_read_lock_notrace -> __srcu_read_lock -> kcsan ... While we could disable KCSAN in kcsan_setup_watchpoint(), this does not solve other unexpected behaviour we may get due recursing into functions that may not be tolerant to such recursion: __srcu_read_lock -> kcsan -> ... -> __srcu_read_lock Therefore, switch to using prandom_u32_state(), which is uninstrumented, and does not have a tracepoint. Link: https://lkml.kernel.org/r/20200821063043.1949509-1-elver@google.com Link: https://lkml.kernel.org/r/20200820172046.GA177701@elver.google.com Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-08-24kcsan: Optimize debugfs stats countersMarco Elver1-11/+11
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 <elver@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-08-24kcsan: Show message if enabled earlyMarco Elver1-2/+6
Show a message in the kernel log if KCSAN was enabled early. Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-08-24kcsan: Add missing CONFIG_KCSAN_IGNORE_ATOMICS checksMarco Elver1-8/+22
Add missing CONFIG_KCSAN_IGNORE_ATOMICS checks for the builtin atomics instrumentation. Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-08-24kcsan: Skew delay to be longer for certain access typesMarco Elver1-3/+7
For compound instrumentation and assert accesses, skew the watchpoint delay to be longer if randomized. This is useful to improve race detection for such accesses. For compound accesses we should increase the delay as we've aggregated both read and write instrumentation. By giving up 1 call into the runtime, we're less likely to set up a watchpoint and thus less likely to detect a race. We can balance this by increasing the watchpoint delay. For assert accesses, we know these are of increased interest, and we wish to increase our chances of detecting races for such checks. Note that, kcsan_udelay_{task,interrupt} define the upper bound delays. When randomized, delays are uniformly distributed between [0, delay]. Skewing the delay does not break this promise as long as the defined upper bounds are still adhered to. The current skew results in delays uniformly distributed between [delay/2, delay]. Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-08-24kcsan: Support compounded read-write instrumentationMarco Elver1-5/+18
Add support for compounded read-write instrumentation if supported by the compiler. Adds the necessary instrumentation functions, and a new type which is used to generate a more descriptive report. Furthermore, such compounded memory access instrumentation is excluded from the "assume aligned writes up to word size are atomic" rule, because we cannot assume that the compiler emits code that is atomic for compound ops. LLVM/Clang added support for the feature in: https://github.com/llvm/llvm-project/commit/785d41a261d136b64ab6c15c5d35f2adc5ad53e3 The new instrumentation is emitted for sets of memory accesses in the same basic block to the same address with at least one read appearing before a write. These typically result from compound operations such as ++, --, +=, -=, |=, &=, etc. but also equivalent forms such as "var = var + 1". Where the compiler determines that it is equivalent to emit a call to a single __tsan_read_write instead of separate __tsan_read and __tsan_write, we can then benefit from improved performance and better reporting for such access patterns. The new reports now show that the ops are both reads and writes, for example: read-write to 0xffffffff90548a38 of 8 bytes by task 143 on cpu 3: test_kernel_rmw_array+0x45/0xa0 access_thread+0x71/0xb0 kthread+0x21e/0x240 ret_from_fork+0x22/0x30 read-write to 0xffffffff90548a38 of 8 bytes by task 144 on cpu 2: test_kernel_rmw_array+0x45/0xa0 access_thread+0x71/0xb0 kthread+0x21e/0x240 ret_from_fork+0x22/0x30 Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-08-24kcsan: Add support for atomic builtinsMarco Elver1-0/+110
Some architectures (currently e.g. s390 partially) implement atomics using the compiler's atomic builtins (__atomic_*, __sync_*). To support enabling KCSAN on such architectures in future, or support experimental use of these builtins, implement support for them. We should also avoid breaking KCSAN kernels due to use (accidental or otherwise) of atomic builtins in drivers, as has happened in the past: https://lkml.kernel.org/r/5231d2c0-41d9-6721-e15f-a7eedf3ce69e@infradead.org The instrumentation is subtly different from regular reads/writes: TSAN instrumentation replaces the use of atomic builtins with a call into the runtime, and the runtime's job is to also execute the desired atomic operation. We rely on the __atomic_* compiler builtins, available with all KCSAN-supported compilers, to implement each TSAN atomic instrumentation function. Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-08-01Merge branch 'kcsan' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into locking/coreIngo Molnar1-0/+9
Pull v5.9 KCSAN bits from Paul E. McKenney. Perhaps the most important change is that GCC 11 now has all fixes in place to support KCSAN, so GCC support can be enabled again. Signed-off-by: Ingo Molnar <mingo@kernel.org>
2020-07-31kcsan: Improve IRQ state trace reportingMarco Elver1-0/+23
To improve the general usefulness of the IRQ state trace events with KCSAN enabled, save and restore the trace information when entering and exiting the KCSAN runtime as well as when generating a KCSAN report. Without this, reporting the IRQ trace events (whether via a KCSAN report or outside of KCSAN via a lockdep report) is rather useless due to continuously being touched by KCSAN. This is because if KCSAN is enabled, every instrumented memory access causes changes to IRQ trace events (either by KCSAN disabling/enabling interrupts or taking report_lock when generating a report). Before "lockdep: Prepare for NMI IRQ state tracking", KCSAN avoided touching the IRQ trace events via raw_local_irq_save/restore() and lockdep_off/on(). Fixes: 248591f5d257 ("kcsan: Make KCSAN compatible with new IRQ state tracking") Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: https://lore.kernel.org/r/20200729110916.3920464-2-elver@google.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2020-07-10kcsan: Make KCSAN compatible with new IRQ state trackingMarco Elver1-3/+2
The new IRQ state tracking code does not honor lockdep_off(), and as such we should again permit tracing by using non-raw functions in core.c. Update the lockdep_off() comment in report.c, to reflect the fact there is still a potential risk of deadlock due to using printk() from scheduler code. Suggested-by: Peter Zijlstra (Intel) <peterz@infradead.org> Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Ingo Molnar <mingo@kernel.org> Link: https://lkml.kernel.org/r/20200624113246.GA170324@elver.google.com
2020-06-29kcsan: Silence -Wmissing-prototypes warning with W=1Marco Elver1-0/+9
The functions here should not be forward declared for explicit use elsewhere in the kernel, as they should only be emitted by the compiler due to sanitizer instrumentation. Add forward declarations a line above their definition to shut up warnings in W=1 builds. Link: https://lkml.kernel.org/r/202006060103.jSCpnV1g%lkp@intel.com Reported-by: kernel test robot <lkp@intel.com> Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-06-11kcsan: Support distinguishing volatile accessesMarco Elver1-0/+43
In the kernel, the "volatile" keyword is used in various concurrent contexts, whether in low-level synchronization primitives or for legacy reasons. If supported by the compiler, it will be assumed that aligned volatile accesses up to sizeof(long long) (matching compiletime_assert_rwonce_type()) are atomic. Recent versions of Clang [1] (GCC tentative [2]) can instrument volatile accesses differently. Add the option (required) to enable the instrumentation, and provide the necessary runtime functions. None of the updated compilers are widely available yet (Clang 11 will be the first release to support the feature). [1] https://github.com/llvm/llvm-project/commit/5a2c31116f412c3b6888be361137efd705e05814 [2] https://gcc.gnu.org/pipermail/gcc-patches/2020-April/544452.html This change allows removing of any explicit checks in primitives such as READ_ONCE() and WRITE_ONCE(). [ bp: Massage commit message a bit. ] Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Borislav Petkov <bp@suse.de> Signed-off-by: Thomas Gleixner <tglx@linutronix.de> Acked-by: Will Deacon <will@kernel.org> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Link: https://lkml.kernel.org/r/20200521142047.169334-4-elver@google.com
2020-05-06kcsan: Add __kcsan_{enable,disable}_current() variantsMarco Elver1-0/+7
The __kcsan_{enable,disable}_current() variants only call into KCSAN if KCSAN is enabled for the current compilation unit. Note: This is typically not what we want, as we usually want to ensure that even calls into other functions still have KCSAN disabled. These variants may safely be used in header files that are shared between regular kernel code and code that does not link the KCSAN runtime. Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-04-13kcsan: Add support for scoped accessesMarco Elver1-8/+75
This adds support for scoped accesses, where the memory range is checked for the duration of the scope. The feature is implemented by inserting the relevant access information into a list of scoped accesses for the current execution context, which are then checked (until removed) on every call (through instrumentation) into the KCSAN runtime. An alternative, more complex, implementation could set up a watchpoint for the scoped access, and keep the watchpoint set up. This, however, would require first exposing a handle to the watchpoint, as well as dealing with cases such as accesses by the same thread while the watchpoint is still set up (and several more cases). It is also doubtful if this would provide any benefit, since the majority of delay where the watchpoint is set up is likely due to the injected delays by KCSAN. Therefore, the implementation in this patch is simpler and avoids hurting KCSAN's main use-case (normal data race detection); it also implicitly increases scoped-access race-detection-ability due to increased probability of setting up watchpoints by repeatedly calling __kcsan_check_access() throughout the scope of the access. The implementation required adding an additional conditional branch to the fast-path. However, the microbenchmark showed a *speedup* of ~5% on the fast-path. This appears to be due to subtly improved codegen by GCC from moving get_ctx() and associated load of preempt_count earlier. Suggested-by: Boqun Feng <boqun.feng@gmail.com> Suggested-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-04-13kcsan: Avoid blocking producers in prepare_report()Marco Elver1-10/+21
To avoid deadlock in case watchers can be interrupted, we need to ensure that producers of the struct other_info can never be blocked by an unrelated consumer. (Likely to occur with KCSAN_INTERRUPT_WATCHER.) There are several cases that can lead to this scenario, for example: 1. A watchpoint A was set up by task T1, but interrupted by interrupt I1. Some other thread (task or interrupt) finds watchpoint A consumes it, and sets other_info. Then I1 also finds some unrelated watchpoint B, consumes it, but is blocked because other_info is in use. T1 cannot consume other_info because I1 never returns -> deadlock. 2. A watchpoint A was set up by task T1, but interrupted by interrupt I1, which also sets up a watchpoint B. Some other thread finds watchpoint A, and consumes it and sets up other_info with its information. Similarly some other thread finds watchpoint B and consumes it, but is then blocked because other_info is in use. When I1 continues it sees its watchpoint was consumed, and that it must wait for other_info, which currently contains information to be consumed by T1. However, T1 cannot unblock other_info because I1 never returns -> deadlock. To avoid this, we need to ensure that producers of struct other_info always have a usable other_info entry. This is obviously not the case with only a single instance of struct other_info, as concurrent producers must wait for the entry to be released by some consumer (which may be locked up as illustrated above). While it would be nice if producers could simply call kmalloc() and append their instance of struct other_info to a list, we are very limited in this code path: since KCSAN can instrument the allocators themselves, calling kmalloc() could lead to deadlock or corrupted allocator state. Since producers of the struct other_info will always succeed at try_consume_watchpoint(), preceding the call into kcsan_report(), we know that the particular watchpoint slot cannot simply be reused or consumed by another potential other_info producer. If we move removal of a watchpoint after reporting (by the consumer of struct other_info), we can see a consumed watchpoint as a held lock on elements of other_info, if we create a one-to-one mapping of a watchpoint to an other_info element. Therefore, the simplest solution is to create an array of struct other_info that is as large as the watchpoints array in core.c, and pass the watchpoint index to kcsan_report() for producers and consumers, and change watchpoints to be removed after reporting is done. With a default config on a 64-bit system, the array other_infos consumes ~37KiB. For most systems today this is not a problem. On smaller memory constrained systems, the config value CONFIG_KCSAN_NUM_WATCHPOINTS can be reduced appropriately. Overall, this change is a simplification of the prepare_report() code, and makes some of the checks (such as checking if at least one access is a write) redundant. Tested: $ tools/testing/selftests/rcutorture/bin/kvm.sh \ --cpus 12 --duration 10 --kconfig "CONFIG_DEBUG_INFO=y \ CONFIG_KCSAN=y CONFIG_KCSAN_ASSUME_PLAIN_WRITES_ATOMIC=n \ CONFIG_KCSAN_REPORT_VALUE_CHANGE_ONLY=n \ CONFIG_KCSAN_REPORT_ONCE_IN_MS=100000 CONFIG_KCSAN_VERBOSE=y \ CONFIG_KCSAN_INTERRUPT_WATCHER=y CONFIG_PROVE_LOCKING=y" \ --configs TREE03 => No longer hangs and runs to completion as expected. Reported-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-04-13kcsan: Introduce report access_info and other_infoMarco Elver1-4/+2
Improve readability by introducing access_info and other_info structs, and in preparation of the following commit in this series replaces the single instance of other_info with an array of size 1. No functional change intended. Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-03-25kcsan: Fix a typo in a commentQiujun Huang1-1/+1
s/slots slots/slots/ Signed-off-by: Qiujun Huang <hqjagain@gmail.com> Reviewed-by: Nick Desaulniers <ndesaulniers@google.com> [elver: commit message] Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-03-25kcsan: Add current->state to implicitly atomic accessesMarco Elver1-7/+15
Add volatile current->state to list of implicitly atomic accesses. This is in preparation to eventually enable KCSAN on kernel/sched (which currently still has KCSAN_SANITIZE := n). Since accesses that match the special check in atomic.h are rare, it makes more sense to move this check to the slow-path, avoiding the additional compare in the fast-path. With the microbenchmark, a speedup of ~6% is measured. Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-03-25kcsan: Add option for verbose reportingMarco Elver1-2/+2
Adds CONFIG_KCSAN_VERBOSE to optionally enable more verbose reports. Currently information about the reporting task's held locks and IRQ trace events are shown, if they are enabled. Signed-off-by: Marco Elver <elver@google.com> Suggested-by: Qian Cai <cai@lca.pw> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-03-25kcsan: Add option to allow watcher interruptionsMarco Elver1-24/+10
Add option to allow interrupts while a watchpoint is set up. This can be enabled either via CONFIG_KCSAN_INTERRUPT_WATCHER or via the boot parameter 'kcsan.interrupt_watcher=1'. Note that, currently not all safe per-CPU access primitives and patterns are accounted for, which could result in false positives. For example, asm-generic/percpu.h uses plain operations, which by default are instrumented. On interrupts and subsequent accesses to the same variable, KCSAN would currently report a data race with this option. Therefore, this option should currently remain disabled by default, but may be enabled for specific test scenarios. To avoid new warnings, changes all uses of smp_processor_id() to use the raw version (as already done in kcsan_found_watchpoint()). The exact SMP processor id is for informational purposes in the report, and correctness is not affected. Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>
2020-03-21kcsan: Add kcsan_set_access_mask() supportMarco Elver1-4/+39
When setting up an access mask with kcsan_set_access_mask(), KCSAN will only report races if concurrent changes to bits set in access_mask are observed. Conveying access_mask via a separate call avoids introducing overhead in the common-case fast-path. Acked-by: John Hubbard <jhubbard@nvidia.com> Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org>
2020-03-21kcsan: Introduce kcsan_value_change typeMarco Elver1-16/+22
Introduces kcsan_value_change type, which explicitly points out if we either observed a value-change (TRUE), or we could not observe one but cannot rule out a value-change happened (MAYBE). The MAYBE state can either be reported or not, depending on configuration preferences. A follow-up patch introduces the FALSE state, which should never be reported. No functional change intended. Acked-by: John Hubbard <jhubbard@nvidia.com> Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org>
2020-03-21kcsan: Expose core configuration parameters as module paramsMarco Elver1-5/+19
This adds early_boot, udelay_{task,interrupt}, and skip_watch as module params. The latter parameters are useful to modify at runtime to tune KCSAN's performance on new systems. This will also permit auto-tuning these parameters to maximize overall system performance and KCSAN's race detection ability. None of the parameters are used in the fast-path and referring to them via static variables instead of CONFIG constants will not affect performance. Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Cc: Qian Cai <cai@lca.pw>
2020-03-21kcsan: Introduce KCSAN_ACCESS_ASSERT access typeMarco Elver1-6/+38
The KCSAN_ACCESS_ASSERT access type may be used to introduce dummy reads and writes to assert certain properties of concurrent code, where bugs could not be detected as normal data races. For example, a variable that is only meant to be written by a single CPU, but may be read (without locking) by other CPUs must still be marked properly to avoid data races. However, concurrent writes, regardless if WRITE_ONCE() or not, would be a bug. Using kcsan_check_access(&x, sizeof(x), KCSAN_ACCESS_ASSERT) would allow catching such bugs. To support KCSAN_ACCESS_ASSERT the following notable changes were made: * If an access is of type KCSAN_ASSERT_ACCESS, disable various filters that only apply to data races, so that all races that KCSAN observes are reported. * Bug reports that involve an ASSERT access type will be reported as "KCSAN: assert: race in ..." instead of "data-race"; this will help more easily distinguish them. * Update a few comments to just mention 'races' where we do not always mean pure data races. Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org>
2020-03-21kcsan: Fix 0-sized checksMarco Elver1-0/+7
Instrumentation of arbitrary memory-copy functions, such as user-copies, may be called with size of 0, which could lead to false positives. To avoid this, add a comparison in check_access() for size==0, which will be optimized out for constant sized instrumentation (__tsan_{read,write}N), and therefore not affect the common-case fast-path. Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org>
2020-03-21kcsan: Add option to assume plain aligned writes up to word size are atomicMarco Elver1-5/+17
This adds option KCSAN_ASSUME_PLAIN_WRITES_ATOMIC. If enabled, plain aligned writes up to word size are assumed to be atomic, and also not subject to other unsafe compiler optimizations resulting in data races. This option has been enabled by default to reflect current kernel-wide preferences. Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org>
2020-03-21kcsan: Make KCSAN compatible with lockdepMarco Elver1-2/+4
We must avoid any recursion into lockdep if KCSAN is enabled on utilities used by lockdep. One manifestation of this is corruption of lockdep's IRQ trace state (if TRACE_IRQFLAGS), resulting in spurious warnings (see below). This commit fixes this by: 1. Using raw_local_irq{save,restore} in kcsan_setup_watchpoint(). 2. Disabling lockdep in kcsan_report(). Tested with: CONFIG_LOCKDEP=y CONFIG_DEBUG_LOCKDEP=y CONFIG_TRACE_IRQFLAGS=y This fix eliminates spurious warnings such as the following one: WARNING: CPU: 0 PID: 2 at kernel/locking/lockdep.c:4406 check_flags.part.0+0x101/0x220 Modules linked in: CPU: 0 PID: 2 Comm: kthreadd Not tainted 5.5.0-rc1+ #11 Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.12.0-1 04/01/2014 RIP: 0010:check_flags.part.0+0x101/0x220 <snip> Call Trace: lock_is_held_type+0x69/0x150 freezer_fork+0x20b/0x370 cgroup_post_fork+0x2c9/0x5c0 copy_process+0x2675/0x3b40 _do_fork+0xbe/0xa30 ? _raw_spin_unlock_irqrestore+0x40/0x50 ? match_held_lock+0x56/0x250 ? kthread_park+0xf0/0xf0 kernel_thread+0xa6/0xd0 ? kthread_park+0xf0/0xf0 kthreadd+0x321/0x3d0 ? kthread_create_on_cpu+0x130/0x130 ret_from_fork+0x3a/0x50 irq event stamp: 64 hardirqs last enabled at (63): [<ffffffff9a7995d0>] _raw_spin_unlock_irqrestore+0x40/0x50 hardirqs last disabled at (64): [<ffffffff992a96d2>] kcsan_setup_watchpoint+0x92/0x460 softirqs last enabled at (32): [<ffffffff990489b8>] fpu__copy+0xe8/0x470 softirqs last disabled at (30): [<ffffffff99048939>] fpu__copy+0x69/0x470 Reported-by: Qian Cai <cai@lca.pw> Signed-off-by: Marco Elver <elver@google.com> Acked-by: Alexander Potapenko <glider@google.com> Tested-by: Qian Cai <cai@lca.pw> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org>
2020-03-21kcsan: Show full access type in reportMarco Elver1-7/+8
This commit adds access-type information to KCSAN's reports as follows: "read", "read (marked)", "write", and "write (marked)". Suggested-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org>
2020-03-21kcsan: Prefer __always_inline for fast-pathMarco Elver1-9/+9
Prefer __always_inline for fast-path functions that are called outside of user_access_save, to avoid generating UACCESS warnings when optimizing for size (CC_OPTIMIZE_FOR_SIZE). It will also avoid future surprises with compiler versions that change the inlining heuristic even when optimizing for performance. Reported-by: Randy Dunlap <rdunlap@infradead.org> Acked-by: Randy Dunlap <rdunlap@infradead.org> # build-tested Signed-off-by: Marco Elver <elver@google.com> Signed-off-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Ingo Molnar <mingo@kernel.org> Link: http://lkml.kernel.org/r/58708908-84a0-0a81-a836-ad97e33dbb62@infradead.org
2019-11-20kcsan: Improve various small stylistic detailsIngo Molnar1-32/+27
Tidy up a few bits: - Fix typos and grammar, improve wording. - Remove spurious newlines that are col80 warning artifacts where the resulting line-break is worse than the disease it's curing. - Use core kernel coding style to improve readability and reduce spurious code pattern variations. - Use better vertical alignment for structure definitions and initialization sequences. - Misc other small details. No change in functionality intended. Cc: linux-kernel@vger.kernel.org Cc: Marco Elver <elver@google.com> Cc: Paul E. McKenney <paulmck@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Paul E. McKenney <paulmck@kernel.org> Cc: Will Deacon <will.deacon@arm.com> Signed-off-by: Ingo Molnar <mingo@kernel.org>
2019-11-16kcsan: Add Kernel Concurrency Sanitizer infrastructureMarco Elver1-0/+626
Kernel Concurrency Sanitizer (KCSAN) is a dynamic data-race detector for kernel space. KCSAN is a sampling watchpoint-based data-race detector. See the included Documentation/dev-tools/kcsan.rst for more details. This patch adds basic infrastructure, but does not yet enable KCSAN for any architecture. Signed-off-by: Marco Elver <elver@google.com> Acked-by: Paul E. McKenney <paulmck@kernel.org> Signed-off-by: Paul E. McKenney <paulmck@kernel.org>