Re: [GIT RFC PULL kcsan] KCSAN commits for 5.5

From: Paul E. McKenney
Date: Wed Nov 20 2019 - 10:06:06 EST

On Wed, Nov 20, 2019 at 10:45:56AM +0100, Ingo Molnar wrote:
>
> hi Paul,
>
> * Paul E. McKenney <paulmck@xxxxxxxxxx> wrote:
>
> > Hello, Ingo,
> >
> > This pull request contains base kernel concurrency sanitizer
> > (KCSAN) enablement for x86, courtesy of Marco Elver. KCSAN is a
> > sampling watchpoint-based data-race detector, and is documented in
> > Documentation/dev-tools/kcsan.rst. KCSAN was announced in September,
> > and much feedback has since been incorporated:
> >
> > http://lkml.kernel.org/r/CANpmjNPJ_bHjfLZCAPV23AXFfiPiyXXqqu72n6TgWzb2Gnu1eA@xxxxxxxxxxxxxx
> >
> > The data races located thus far have resulted in a number of fixes:
> >
> > https://github.com/google/ktsan/wiki/KCSAN#upstream-fixes-of-data-races-found-by-kcsan
> >
> > Additional information may be found here:
> >
> > https://lore.kernel.org/lkml/20191114180303.66955-1-elver@xxxxxxxxxx/
> >
> > This has been subject to kbuild test robot and -next testing. The
> > -next testing located a Kconfig conflict called out here:
> >
> > https://lore.kernel.org/lkml/20191119183042.5839ef00@xxxxxxxxxxxxxxxx/
> >
> > Marco is satisfied with Stephen's resolution, and it looks good to me
> > as well.
> >
> > The following changes since commit 31f4f5b495a62c9a8b15b1c3581acd5efeb9af8c:
> >
> > Linux 5.4-rc7 (2019-11-10 16:17:15 -0800)
> >
> > are available in the git repository at:
> >
> > git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu.git for-mingo
> >
> > for you to fetch changes up to 40d04110f87940b6a03bf0aa19cd29e84f465f20:
> >
> > x86, kcsan: Enable KCSAN for x86 (2019-11-16 07:23:16 -0800)
> >
> > ----------------------------------------------------------------
> > Marco Elver (9):
> > 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
> > 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/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 +
> > 45 files changed, 2623 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
>
> Thanks - this looks clean and well-structured to me.
>
> The biggest interaction with locking code is via the
> include/asm-generic/atomic-instrumented.h changes:
>
> > include/asm-generic/atomic-instrumented.h | 393 ++++++++++---------
>
> But this is basically an instrumentation-cleanup patch that factors out
> the KASAN callbacks, and then ~2 more lines to add in the KCSAN
> callbacks, so in reality it's an overall win.
>
> I couldn't help to notice & fix a few minor details while reading the
> patches, see the patch below. :-)

<red face> I will arrange for better English-language review in the
future. In the meantime, thank you!

> Anyway, I pulled it into tip:WIP.locking/kcsan with the intention of
> merging it over into tip:locking/kcsan in a couple of days if all goes
> well.

And thank you again!

Thanx, Paul

> If anyone on Cc: has any objections then please holler!
>
> Thanks,
>
> Ingo
>
> =======================>
> From: Ingo Molnar <mingo@xxxxxxxxxx>
> Date: Wed, 20 Nov 2019 10:41:43 +0100
> Subject: [PATCH] kcsan: Improve code readability
>
> - 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.
>
> Signed-off-by: Ingo Molnar <mingo@xxxxxxxxxx>
> ---
> arch/x86/Kconfig | 2 +-
> include/linux/compiler-clang.h | 2 +-
> include/linux/compiler.h | 2 +-
> include/linux/kcsan-checks.h | 22 ++++++---------
> include/linux/kcsan.h | 23 ++++++----------
> include/linux/seqlock.h | 8 +++---
> kernel/kcsan/atomic.h | 2 +-
> kernel/kcsan/core.c | 59 ++++++++++++++++++----------------------
> kernel/kcsan/debugfs.c | 62 ++++++++++++++++++++----------------------
> kernel/kcsan/encoding.h | 25 +++++++++--------
> kernel/kcsan/kcsan.h | 11 ++++----
> kernel/kcsan/report.c | 42 ++++++++++++++--------------
> kernel/kcsan/test.c | 6 ++--
> kernel/sched/Makefile | 2 +-
> lib/Kconfig.kcsan | 16 +++++------
> 15 files changed, 131 insertions(+), 153 deletions(-)
>
> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> index 94351b2be3ca..a436266da7b9 100644
> --- a/arch/x86/Kconfig
> +++ b/arch/x86/Kconfig
> @@ -226,7 +226,7 @@ config X86
> select VIRT_TO_BUS
> select X86_FEATURE_NAMES if PROC_FS
> select PROC_PID_ARCH_STATUS if PROC_FS
> - select HAVE_ARCH_KCSAN if X86_64
> + select HAVE_ARCH_KCSAN if X86_64
>
> config INSTRUCTION_DECODER
> def_bool y
> diff --git a/include/linux/compiler-clang.h b/include/linux/compiler-clang.h
> index a213eb55e725..2cb42d8bdedc 100644
> --- a/include/linux/compiler-clang.h
> +++ b/include/linux/compiler-clang.h
> @@ -16,7 +16,7 @@
> #define KASAN_ABI_VERSION 5
>
> #if __has_feature(address_sanitizer) || __has_feature(hwaddress_sanitizer)
> -/* emulate gcc's __SANITIZE_ADDRESS__ flag */
> +/* Emulate GCC's __SANITIZE_ADDRESS__ flag */
> #define __SANITIZE_ADDRESS__
> #define __no_sanitize_address \
> __attribute__((no_sanitize("address", "hwaddress")))
> diff --git a/include/linux/compiler.h b/include/linux/compiler.h
> index 7d3e77781578..ad8c76144a3c 100644
> --- a/include/linux/compiler.h
> +++ b/include/linux/compiler.h
> @@ -313,7 +313,7 @@ unsigned long read_word_at_a_time(const void *addr)
> #include <linux/kcsan.h>
>
> /*
> - * data_race: macro to document that accesses in an expression may conflict with
> + * data_race(): macro to document that accesses in an expression may conflict with
> * other concurrent accesses resulting in data races, but the resulting
> * behaviour is deemed safe regardless.
> *
> diff --git a/include/linux/kcsan-checks.h b/include/linux/kcsan-checks.h
> index e78220661086..ef3ee233a3fa 100644
> --- a/include/linux/kcsan-checks.h
> +++ b/include/linux/kcsan-checks.h
> @@ -8,17 +8,17 @@
> /*
> * Access type modifiers.
> */
> -#define KCSAN_ACCESS_WRITE 0x1
> +#define KCSAN_ACCESS_WRITE 0x1
> #define KCSAN_ACCESS_ATOMIC 0x2
>
> /*
> - * __kcsan_*: Always calls into runtime when KCSAN is enabled. This may be used
> + * __kcsan_*: Always calls into the runtime when KCSAN is enabled. This may be used
> * even in compilation units that selectively disable KCSAN, but must use KCSAN
> - * to validate access to an address. Never use these in header files!
> + * to validate access to an address. Never use these in header files!
> */
> #ifdef CONFIG_KCSAN
> /**
> - * __kcsan_check_access - check generic access for data race
> + * __kcsan_check_access - check generic access for data races
> *
> * @ptr address of access
> * @size size of access
> @@ -32,7 +32,7 @@ static inline void __kcsan_check_access(const volatile void *ptr, size_t size,
> #endif
>
> /*
> - * kcsan_*: Only calls into runtime when the particular compilation unit has
> + * kcsan_*: Only calls into the runtime when the particular compilation unit has
> * KCSAN instrumentation enabled. May be used in header files.
> */
> #ifdef __SANITIZE_THREAD__
> @@ -77,16 +77,12 @@ static inline void kcsan_check_access(const volatile void *ptr, size_t size,
> kcsan_check_access(ptr, size, KCSAN_ACCESS_WRITE)
>
> /*
> - * Check for atomic accesses: if atomic access are not ignored, this simply
> - * aliases to kcsan_check_access, otherwise becomes a no-op.
> + * Check for atomic accesses: if atomic accesses are not ignored, this simply
> + * aliases to kcsan_check_access(), otherwise becomes a no-op.
> */
> #ifdef CONFIG_KCSAN_IGNORE_ATOMICS
> -#define kcsan_check_atomic_read(...) \
> - do { \
> - } while (0)
> -#define kcsan_check_atomic_write(...) \
> - do { \
> - } while (0)
> +#define kcsan_check_atomic_read(...) do { } while (0)
> +#define kcsan_check_atomic_write(...) do { } while (0)
> #else
> #define kcsan_check_atomic_read(ptr, size) \
> kcsan_check_access(ptr, size, KCSAN_ACCESS_ATOMIC)
> diff --git a/include/linux/kcsan.h b/include/linux/kcsan.h
> index 9047048fee84..1019e3a2c689 100644
> --- a/include/linux/kcsan.h
> +++ b/include/linux/kcsan.h
> @@ -94,21 +94,14 @@ void kcsan_atomic_next(int n);
>
> #else /* CONFIG_KCSAN */
>
> -static inline void kcsan_init(void) { }
> -
> -static inline void kcsan_disable_current(void) { }
> -
> -static inline void kcsan_enable_current(void) { }
> -
> -static inline void kcsan_nestable_atomic_begin(void) { }
> -
> -static inline void kcsan_nestable_atomic_end(void) { }
> -
> -static inline void kcsan_flat_atomic_begin(void) { }
> -
> -static inline void kcsan_flat_atomic_end(void) { }
> -
> -static inline void kcsan_atomic_next(int n) { }
> +static inline void kcsan_init(void) { }
> +static inline void kcsan_disable_current(void) { }
> +static inline void kcsan_enable_current(void) { }
> +static inline void kcsan_nestable_atomic_begin(void) { }
> +static inline void kcsan_nestable_atomic_end(void) { }
> +static inline void kcsan_flat_atomic_begin(void) { }
> +static inline void kcsan_flat_atomic_end(void) { }
> +static inline void kcsan_atomic_next(int n) { }
>
> #endif /* CONFIG_KCSAN */
>
> diff --git a/include/linux/seqlock.h b/include/linux/seqlock.h
> index af5169a7f0c0..239701cae376 100644
> --- a/include/linux/seqlock.h
> +++ b/include/linux/seqlock.h
> @@ -48,7 +48,7 @@
> *
> * As a consequence, we take the following best-effort approach for raw usage
> * via seqcount_t under KCSAN: upon beginning a seq-reader critical section,
> - * pessimistically mark then next KCSAN_SEQLOCK_REGION_MAX memory accesses as
> + * pessimistically mark the next KCSAN_SEQLOCK_REGION_MAX memory accesses as
> * atomics; if there is a matching read_seqcount_retry() call, no following
> * memory operations are considered atomic. Usage of seqlocks via seqlock_t
> * interface is not affected.
> @@ -265,7 +265,7 @@ static inline void raw_write_seqcount_end(seqcount_t *s)
> * usual consistency guarantee. It is one wmb cheaper, because we can
> * collapse the two back-to-back wmb()s.
> *
> - * Note that, writes surrounding the barrier should be declared atomic (e.g.
> + * Note that writes surrounding the barrier should be declared atomic (e.g.
> * via WRITE_ONCE): a) to ensure the writes become visible to other threads
> * atomically, avoiding compiler optimizations; b) to document which writes are
> * meant to propagate to the reader critical section. This is necessary because
> @@ -465,7 +465,7 @@ static inline unsigned read_seqbegin(const seqlock_t *sl)
> {
> unsigned ret = read_seqcount_begin(&sl->seqcount);
>
> - kcsan_atomic_next(0); /* non-raw usage, assume closing read_seqretry */
> + kcsan_atomic_next(0); /* non-raw usage, assume closing read_seqretry() */
> kcsan_flat_atomic_begin();
> return ret;
> }
> @@ -473,7 +473,7 @@ static inline unsigned read_seqbegin(const seqlock_t *sl)
> static inline unsigned read_seqretry(const seqlock_t *sl, unsigned start)
> {
> /*
> - * Assume not nested: read_seqretry may be called multiple times when
> + * Assume not nested: read_seqretry() may be called multiple times when
> * completing read critical section.
> */
> kcsan_flat_atomic_end();
> diff --git a/kernel/kcsan/atomic.h b/kernel/kcsan/atomic.h
> index c9c3fe628011..576e03ddd6a3 100644
> --- a/kernel/kcsan/atomic.h
> +++ b/kernel/kcsan/atomic.h
> @@ -6,7 +6,7 @@
> #include <linux/jiffies.h>
>
> /*
> - * Helper that returns true if access to ptr should be considered as an atomic
> + * Helper that returns true if access to @ptr should be considered an atomic
> * access, even though it is not explicitly atomic.
> *
> * List all volatile globals that have been observed in races, to suppress
> diff --git a/kernel/kcsan/core.c b/kernel/kcsan/core.c
> index d9410d58c93e..3314fc29e236 100644
> --- a/kernel/kcsan/core.c
> +++ b/kernel/kcsan/core.c
> @@ -19,10 +19,10 @@ bool kcsan_enabled;
>
> /* Per-CPU kcsan_ctx for interrupts */
> static DEFINE_PER_CPU(struct kcsan_ctx, kcsan_cpu_ctx) = {
> - .disable_count = 0,
> - .atomic_next = 0,
> - .atomic_nest_count = 0,
> - .in_flat_atomic = false,
> + .disable_count = 0,
> + .atomic_next = 0,
> + .atomic_nest_count = 0,
> + .in_flat_atomic = false,
> };
>
> /*
> @@ -50,11 +50,11 @@ static DEFINE_PER_CPU(struct kcsan_ctx, kcsan_cpu_ctx) = {
> * slot=9: [10, 11, 9]
> * slot=63: [64, 65, 63]
> */
> -#define NUM_SLOTS (1 + 2 * KCSAN_CHECK_ADJACENT)
> +#define NUM_SLOTS (1 + 2*KCSAN_CHECK_ADJACENT)
> #define SLOT_IDX(slot, i) (slot + ((i + KCSAN_CHECK_ADJACENT) % NUM_SLOTS))
>
> /*
> - * SLOT_IDX_FAST is used in fast-path. Not first checking the address's primary
> + * SLOT_IDX_FAST is used in the fast-path. Not first checking the address's primary
> * slot (middle) is fine if we assume that data races occur rarely. The set of
> * indices {SLOT_IDX(slot, i) | i in [0, NUM_SLOTS)} is equivalent to
> * {SLOT_IDX_FAST(slot, i) | i in [0, NUM_SLOTS)}.
> @@ -68,9 +68,9 @@ static DEFINE_PER_CPU(struct kcsan_ctx, kcsan_cpu_ctx) = {
> * zero-initialized state matches INVALID_WATCHPOINT.
> *
> * Add NUM_SLOTS-1 entries to account for overflow; this helps avoid having to
> - * use more complicated SLOT_IDX_FAST calculation with modulo in fast-path.
> + * use more complicated SLOT_IDX_FAST calculation with modulo in the fast-path.
> */
> -static atomic_long_t watchpoints[CONFIG_KCSAN_NUM_WATCHPOINTS + NUM_SLOTS - 1];
> +static atomic_long_t watchpoints[CONFIG_KCSAN_NUM_WATCHPOINTS + NUM_SLOTS-1];
>
> /*
> * Instructions to skip watching counter, used in should_watch(). We use a
> @@ -78,7 +78,8 @@ static atomic_long_t watchpoints[CONFIG_KCSAN_NUM_WATCHPOINTS + NUM_SLOTS - 1];
> */
> static DEFINE_PER_CPU(long, kcsan_skip);
>
> -static inline atomic_long_t *find_watchpoint(unsigned long addr, size_t size,
> +static inline atomic_long_t *find_watchpoint(unsigned long addr,
> + size_t size,
> bool expect_write,
> long *encoded_watchpoint)
> {
> @@ -110,8 +111,8 @@ static inline atomic_long_t *find_watchpoint(unsigned long addr, size_t size,
> return NULL;
> }
>
> -static inline atomic_long_t *insert_watchpoint(unsigned long addr, size_t size,
> - bool is_write)
> +static inline atomic_long_t *
> +insert_watchpoint(unsigned long addr, size_t size, bool is_write)
> {
> const int slot = watchpoint_slot(addr);
> const long encoded_watchpoint = encode_watchpoint(addr, size, is_write);
> @@ -120,21 +121,16 @@ static inline atomic_long_t *insert_watchpoint(unsigned long addr, size_t size,
>
> /* Check slot index logic, ensuring we stay within array bounds. */
> BUILD_BUG_ON(SLOT_IDX(0, 0) != KCSAN_CHECK_ADJACENT);
> - BUILD_BUG_ON(SLOT_IDX(0, KCSAN_CHECK_ADJACENT + 1) != 0);
> - BUILD_BUG_ON(SLOT_IDX(CONFIG_KCSAN_NUM_WATCHPOINTS - 1,
> - KCSAN_CHECK_ADJACENT) !=
> - ARRAY_SIZE(watchpoints) - 1);
> - BUILD_BUG_ON(SLOT_IDX(CONFIG_KCSAN_NUM_WATCHPOINTS - 1,
> - KCSAN_CHECK_ADJACENT + 1) !=
> - ARRAY_SIZE(watchpoints) - NUM_SLOTS);
> + BUILD_BUG_ON(SLOT_IDX(0, KCSAN_CHECK_ADJACENT+1) != 0);
> + BUILD_BUG_ON(SLOT_IDX(CONFIG_KCSAN_NUM_WATCHPOINTS-1, KCSAN_CHECK_ADJACENT) != ARRAY_SIZE(watchpoints)-1);
> + BUILD_BUG_ON(SLOT_IDX(CONFIG_KCSAN_NUM_WATCHPOINTS-1, KCSAN_CHECK_ADJACENT+1) != ARRAY_SIZE(watchpoints) - NUM_SLOTS);
>
> for (i = 0; i < NUM_SLOTS; ++i) {
> long expect_val = INVALID_WATCHPOINT;
>
> /* Try to acquire this slot. */
> watchpoint = &watchpoints[SLOT_IDX(slot, i)];
> - if (atomic_long_try_cmpxchg_relaxed(watchpoint, &expect_val,
> - encoded_watchpoint))
> + if (atomic_long_try_cmpxchg_relaxed(watchpoint, &expect_val, encoded_watchpoint))
> return watchpoint;
> }
>
> @@ -150,11 +146,10 @@ static inline atomic_long_t *insert_watchpoint(unsigned long addr, size_t size,
> * 2. the thread that set up the watchpoint already removed it;
> * 3. the watchpoint was removed and then re-used.
> */
> -static inline bool try_consume_watchpoint(atomic_long_t *watchpoint,
> - long encoded_watchpoint)
> +static inline bool
> +try_consume_watchpoint(atomic_long_t *watchpoint, long encoded_watchpoint)
> {
> - return atomic_long_try_cmpxchg_relaxed(watchpoint, &encoded_watchpoint,
> - CONSUMED_WATCHPOINT);
> + return atomic_long_try_cmpxchg_relaxed(watchpoint, &encoded_watchpoint, CONSUMED_WATCHPOINT);
> }
>
> /*
> @@ -162,14 +157,13 @@ static inline bool try_consume_watchpoint(atomic_long_t *watchpoint,
> */
> static inline bool remove_watchpoint(atomic_long_t *watchpoint)
> {
> - return atomic_long_xchg_relaxed(watchpoint, INVALID_WATCHPOINT) !=
> - CONSUMED_WATCHPOINT;
> + return atomic_long_xchg_relaxed(watchpoint, INVALID_WATCHPOINT) != CONSUMED_WATCHPOINT;
> }
>
> static inline struct kcsan_ctx *get_ctx(void)
> {
> /*
> - * In interrupt, use raw_cpu_ptr to avoid unnecessary checks, that would
> + * In interrupts, use raw_cpu_ptr to avoid unnecessary checks, that would
> * also result in calls that generate warnings in uaccess regions.
> */
> return in_task() ? &current->kcsan_ctx : raw_cpu_ptr(&kcsan_cpu_ctx);
> @@ -260,7 +254,8 @@ static inline unsigned int get_delay(void)
> */
>
> static noinline void kcsan_found_watchpoint(const volatile void *ptr,
> - size_t size, bool is_write,
> + size_t size,
> + bool is_write,
> atomic_long_t *watchpoint,
> long encoded_watchpoint)
> {
> @@ -296,8 +291,8 @@ static noinline void kcsan_found_watchpoint(const volatile void *ptr,
> user_access_restore(flags);
> }
>
> -static noinline void kcsan_setup_watchpoint(const volatile void *ptr,
> - size_t size, bool is_write)
> +static noinline void
> +kcsan_setup_watchpoint(const volatile void *ptr, size_t size, bool is_write)
> {
> atomic_long_t *watchpoint;
> union {
> @@ -346,8 +341,8 @@ static noinline void kcsan_setup_watchpoint(const volatile void *ptr,
> watchpoint = insert_watchpoint((unsigned long)ptr, size, is_write);
> if (watchpoint == NULL) {
> /*
> - * Out of capacity: the size of `watchpoints`, and the frequency
> - * with which `should_watch()` returns true should be tweaked so
> + * Out of capacity: the size of 'watchpoints', and the frequency
> + * with which should_watch() returns true should be tweaked so
> * that this case happens very rarely.
> */
> kcsan_counter_inc(KCSAN_COUNTER_NO_CAPACITY);
> diff --git a/kernel/kcsan/debugfs.c b/kernel/kcsan/debugfs.c
> index 041d520a0183..bec42dab32ee 100644
> --- a/kernel/kcsan/debugfs.c
> +++ b/kernel/kcsan/debugfs.c
> @@ -24,39 +24,31 @@ static atomic_long_t counters[KCSAN_COUNTER_COUNT];
> * whitelist or blacklist.
> */
> static struct {
> - unsigned long *addrs; /* array of addresses */
> - size_t size; /* current size */
> - int used; /* number of elements used */
> - bool sorted; /* if elements are sorted */
> - bool whitelist; /* if list is a blacklist or whitelist */
> + unsigned long *addrs; /* array of addresses */
> + size_t size; /* current size */
> + int used; /* number of elements used */
> + bool sorted; /* if elements are sorted */
> + bool whitelist; /* if list is a blacklist or whitelist */
> } report_filterlist = {
> - .addrs = NULL,
> - .size = 8, /* small initial size */
> - .used = 0,
> - .sorted = false,
> - .whitelist = false, /* default is blacklist */
> + .addrs = NULL,
> + .size = 8, /* small initial size */
> + .used = 0,
> + .sorted = false,
> + .whitelist = false, /* default is blacklist */
> };
> static DEFINE_SPINLOCK(report_filterlist_lock);
>
> static const char *counter_to_name(enum kcsan_counter_id id)
> {
> switch (id) {
> - case KCSAN_COUNTER_USED_WATCHPOINTS:
> - return "used_watchpoints";
> - case KCSAN_COUNTER_SETUP_WATCHPOINTS:
> - return "setup_watchpoints";
> - case KCSAN_COUNTER_DATA_RACES:
> - return "data_races";
> - case KCSAN_COUNTER_NO_CAPACITY:
> - return "no_capacity";
> - case KCSAN_COUNTER_REPORT_RACES:
> - return "report_races";
> - case KCSAN_COUNTER_RACES_UNKNOWN_ORIGIN:
> - return "races_unknown_origin";
> - case KCSAN_COUNTER_UNENCODABLE_ACCESSES:
> - return "unencodable_accesses";
> - case KCSAN_COUNTER_ENCODING_FALSE_POSITIVES:
> - return "encoding_false_positives";
> + case KCSAN_COUNTER_USED_WATCHPOINTS: return "used_watchpoints";
> + case KCSAN_COUNTER_SETUP_WATCHPOINTS: return "setup_watchpoints";
> + case KCSAN_COUNTER_DATA_RACES: return "data_races";
> + case KCSAN_COUNTER_NO_CAPACITY: return "no_capacity";
> + case KCSAN_COUNTER_REPORT_RACES: return "report_races";
> + case KCSAN_COUNTER_RACES_UNKNOWN_ORIGIN: return "races_unknown_origin";
> + case KCSAN_COUNTER_UNENCODABLE_ACCESSES: return "unencodable_accesses";
> + case KCSAN_COUNTER_ENCODING_FALSE_POSITIVES: return "encoding_false_positives";
> case KCSAN_COUNTER_COUNT:
> BUG();
> }
> @@ -116,7 +108,7 @@ bool kcsan_skip_report_debugfs(unsigned long func_addr)
>
> if (!kallsyms_lookup_size_offset(func_addr, &symbolsize, &offset))
> return false;
> - func_addr -= offset; /* get function start */
> + func_addr -= offset; /* Get function start */
>
> spin_lock_irqsave(&report_filterlist_lock, flags);
> if (report_filterlist.used == 0)
> @@ -195,6 +187,7 @@ static ssize_t insert_report_filterlist(const char *func)
>
> out:
> spin_unlock_irqrestore(&report_filterlist_lock, flags);
> +
> return ret;
> }
>
> @@ -226,8 +219,8 @@ static int debugfs_open(struct inode *inode, struct file *file)
> return single_open(file, show_info, NULL);
> }
>
> -static ssize_t debugfs_write(struct file *file, const char __user *buf,
> - size_t count, loff_t *off)
> +static ssize_t
> +debugfs_write(struct file *file, const char __user *buf, size_t count, loff_t *off)
> {
> char kbuf[KSYM_NAME_LEN];
> char *arg;
> @@ -264,10 +257,13 @@ static ssize_t debugfs_write(struct file *file, const char __user *buf,
> return count;
> }
>
> -static const struct file_operations debugfs_ops = { .read = seq_read,
> - .open = debugfs_open,
> - .write = debugfs_write,
> - .release = single_release };
> +static const struct file_operations debugfs_ops =
> +{
> + .read = seq_read,
> + .open = debugfs_open,
> + .write = debugfs_write,
> + .release = single_release
> +};
>
> void __init kcsan_debugfs_init(void)
> {
> diff --git a/kernel/kcsan/encoding.h b/kernel/kcsan/encoding.h
> index e17bdac0e54b..b63890e86449 100644
> --- a/kernel/kcsan/encoding.h
> +++ b/kernel/kcsan/encoding.h
> @@ -10,7 +10,8 @@
> #include "kcsan.h"
>
> #define SLOT_RANGE PAGE_SIZE
> -#define INVALID_WATCHPOINT 0
> +
> +#define INVALID_WATCHPOINT 0
> #define CONSUMED_WATCHPOINT 1
>
> /*
> @@ -34,24 +35,24 @@
> * Both these are assumed to be very unlikely. However, in case it still happens
> * happens, the report logic will filter out the false positive (see report.c).
> */
> -#define WATCHPOINT_ADDR_BITS (BITS_PER_LONG - 1 - WATCHPOINT_SIZE_BITS)
> +#define WATCHPOINT_ADDR_BITS (BITS_PER_LONG-1 - WATCHPOINT_SIZE_BITS)
>
> /*
> * Masks to set/retrieve the encoded data.
> */
> -#define WATCHPOINT_WRITE_MASK BIT(BITS_PER_LONG - 1)
> +#define WATCHPOINT_WRITE_MASK BIT(BITS_PER_LONG-1)
> #define WATCHPOINT_SIZE_MASK \
> - GENMASK(BITS_PER_LONG - 2, BITS_PER_LONG - 2 - WATCHPOINT_SIZE_BITS)
> + GENMASK(BITS_PER_LONG-2, BITS_PER_LONG-2 - WATCHPOINT_SIZE_BITS)
> #define WATCHPOINT_ADDR_MASK \
> - GENMASK(BITS_PER_LONG - 3 - WATCHPOINT_SIZE_BITS, 0)
> + GENMASK(BITS_PER_LONG-3 - WATCHPOINT_SIZE_BITS, 0)
>
> static inline bool check_encodable(unsigned long addr, size_t size)
> {
> return size <= MAX_ENCODABLE_SIZE;
> }
>
> -static inline long encode_watchpoint(unsigned long addr, size_t size,
> - bool is_write)
> +static inline long
> +encode_watchpoint(unsigned long addr, size_t size, bool is_write)
> {
> return (long)((is_write ? WATCHPOINT_WRITE_MASK : 0) |
> (size << WATCHPOINT_ADDR_BITS) |
> @@ -59,17 +60,17 @@ static inline long encode_watchpoint(unsigned long addr, size_t size,
> }
>
> static inline bool decode_watchpoint(long watchpoint,
> - unsigned long *addr_masked, size_t *size,
> + unsigned long *addr_masked,
> + size_t *size,
> bool *is_write)
> {
> if (watchpoint == INVALID_WATCHPOINT ||
> watchpoint == CONSUMED_WATCHPOINT)
> return false;
>
> - *addr_masked = (unsigned long)watchpoint & WATCHPOINT_ADDR_MASK;
> - *size = ((unsigned long)watchpoint & WATCHPOINT_SIZE_MASK) >>
> - WATCHPOINT_ADDR_BITS;
> - *is_write = !!((unsigned long)watchpoint & WATCHPOINT_WRITE_MASK);
> + *addr_masked = (unsigned long)watchpoint & WATCHPOINT_ADDR_MASK;
> + *size = ((unsigned long)watchpoint & WATCHPOINT_SIZE_MASK) >> WATCHPOINT_ADDR_BITS;
> + *is_write = !!((unsigned long)watchpoint & WATCHPOINT_WRITE_MASK);
>
> return true;
> }
> diff --git a/kernel/kcsan/kcsan.h b/kernel/kcsan/kcsan.h
> index 1bb2f1c0d61e..d3b9a96ac8a4 100644
> --- a/kernel/kcsan/kcsan.h
> +++ b/kernel/kcsan/kcsan.h
> @@ -72,14 +72,14 @@ enum kcsan_counter_id {
> /*
> * Increment/decrement counter with given id; avoid calling these in fast-path.
> */
> -void kcsan_counter_inc(enum kcsan_counter_id id);
> -void kcsan_counter_dec(enum kcsan_counter_id id);
> +extern void kcsan_counter_inc(enum kcsan_counter_id id);
> +extern void kcsan_counter_dec(enum kcsan_counter_id id);
>
> /*
> * Returns true if data races in the function symbol that maps to func_addr
> * (offsets are ignored) should *not* be reported.
> */
> -bool kcsan_skip_report_debugfs(unsigned long func_addr);
> +extern bool kcsan_skip_report_debugfs(unsigned long func_addr);
>
> enum kcsan_report_type {
> /*
> @@ -99,10 +99,11 @@ enum kcsan_report_type {
> */
> KCSAN_REPORT_RACE_UNKNOWN_ORIGIN,
> };
> +
> /*
> * Print a race report from thread that encountered the race.
> */
> -void kcsan_report(const volatile void *ptr, size_t size, bool is_write,
> - bool value_change, int cpu_id, enum kcsan_report_type type);
> +extern void kcsan_report(const volatile void *ptr, size_t size, bool is_write,
> + bool value_change, int cpu_id, enum kcsan_report_type type);
>
> #endif /* _KERNEL_KCSAN_KCSAN_H */
> diff --git a/kernel/kcsan/report.c b/kernel/kcsan/report.c
> index ead5610bafa7..0eea05a3135b 100644
> --- a/kernel/kcsan/report.c
> +++ b/kernel/kcsan/report.c
> @@ -22,13 +22,13 @@
> * the reports, with reporting being in the slow-path.
> */
> static struct {
> - const volatile void *ptr;
> - size_t size;
> - bool is_write;
> - int task_pid;
> - int cpu_id;
> - unsigned long stack_entries[NUM_STACK_ENTRIES];
> - int num_stack_entries;
> + const volatile void *ptr;
> + size_t size;
> + bool is_write;
> + int task_pid;
> + int cpu_id;
> + unsigned long stack_entries[NUM_STACK_ENTRIES];
> + int num_stack_entries;
> } other_info = { .ptr = NULL };
>
> /*
> @@ -40,8 +40,8 @@ static DEFINE_SPINLOCK(report_lock);
> /*
> * Special rules to skip reporting.
> */
> -static bool skip_report(bool is_write, bool value_change,
> - unsigned long top_frame)
> +static bool
> +skip_report(bool is_write, bool value_change, unsigned long top_frame)
> {
> if (IS_ENABLED(CONFIG_KCSAN_REPORT_VALUE_CHANGE_ONLY) && is_write &&
> !value_change) {
> @@ -105,6 +105,7 @@ static int sym_strcmp(void *addr1, void *addr2)
>
> snprintf(buf1, sizeof(buf1), "%pS", addr1);
> snprintf(buf2, sizeof(buf2), "%pS", addr2);
> +
> return strncmp(buf1, buf2, sizeof(buf1));
> }
>
> @@ -116,8 +117,7 @@ static bool print_report(const volatile void *ptr, size_t size, bool is_write,
> enum kcsan_report_type type)
> {
> unsigned long stack_entries[NUM_STACK_ENTRIES] = { 0 };
> - int num_stack_entries =
> - stack_trace_save(stack_entries, NUM_STACK_ENTRIES, 1);
> + 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;
>
> @@ -131,7 +131,7 @@ static bool print_report(const volatile void *ptr, size_t size, bool is_write,
> other_skipnr = get_stack_skipnr(other_info.stack_entries,
> other_info.num_stack_entries);
>
> - /* value_change is only known for the other thread */
> + /* @value_change is only known for the other thread */
> if (skip_report(other_info.is_write, value_change,
> other_info.stack_entries[other_skipnr]))
> return false;
> @@ -241,13 +241,12 @@ static bool prepare_report(unsigned long *flags, const volatile void *ptr,
> if (other_info.ptr != NULL)
> break; /* still in use, retry */
>
> - other_info.ptr = ptr;
> - other_info.size = size;
> - other_info.is_write = is_write;
> - other_info.task_pid = in_task() ? task_pid_nr(current) : -1;
> - other_info.cpu_id = cpu_id;
> - other_info.num_stack_entries = stack_trace_save(
> - other_info.stack_entries, NUM_STACK_ENTRIES, 1);
> + other_info.ptr = ptr;
> + other_info.size = size;
> + other_info.is_write = is_write;
> + other_info.task_pid = in_task() ? task_pid_nr(current) : -1;
> + other_info.cpu_id = cpu_id;
> + other_info.num_stack_entries = stack_trace_save(other_info.stack_entries, NUM_STACK_ENTRIES, 1);
>
> spin_unlock_irqrestore(&report_lock, *flags);
>
> @@ -299,6 +298,7 @@ static bool prepare_report(unsigned long *flags, const volatile void *ptr,
> }
>
> spin_unlock_irqrestore(&report_lock, *flags);
> +
> goto retry;
> }
>
> @@ -309,9 +309,7 @@ void kcsan_report(const volatile void *ptr, size_t size, bool is_write,
>
> kcsan_disable_current();
> if (prepare_report(&flags, ptr, size, is_write, cpu_id, type)) {
> - if (print_report(ptr, size, is_write, value_change, cpu_id,
> - type) &&
> - panic_on_warn)
> + if (print_report(ptr, size, is_write, value_change, cpu_id, type) && panic_on_warn)
> panic("panic_on_warn set ...\n");
>
> release_report(&flags, type);
> diff --git a/kernel/kcsan/test.c b/kernel/kcsan/test.c
> index 0bae63c5ca65..cc6000239dc0 100644
> --- a/kernel/kcsan/test.c
> +++ b/kernel/kcsan/test.c
> @@ -34,7 +34,7 @@ static bool test_encode_decode(void)
> if (WARN_ON(!check_encodable(addr, size)))
> return false;
>
> - /* encode and decode */
> + /* Encode and decode */
> {
> const long encoded_watchpoint =
> encode_watchpoint(addr, size, is_write);
> @@ -42,7 +42,7 @@ static bool test_encode_decode(void)
> size_t verif_size;
> bool verif_is_write;
>
> - /* check special watchpoints */
> + /* Check special watchpoints */
> if (WARN_ON(decode_watchpoint(
> INVALID_WATCHPOINT, &verif_masked_addr,
> &verif_size, &verif_is_write)))
> @@ -52,7 +52,7 @@ static bool test_encode_decode(void)
> &verif_size, &verif_is_write)))
> return false;
>
> - /* check decoding watchpoint returns same data */
> + /* Check decoding watchpoint returns same data */
> if (WARN_ON(!decode_watchpoint(
> encoded_watchpoint, &verif_masked_addr,
> &verif_size, &verif_is_write)))
> diff --git a/kernel/sched/Makefile b/kernel/sched/Makefile
> index e9307a9c54e7..5fc9c9b70862 100644
> --- a/kernel/sched/Makefile
> +++ b/kernel/sched/Makefile
> @@ -7,7 +7,7 @@ endif
> # that is not a function of syscall inputs. E.g. involuntary context switches.
> KCOV_INSTRUMENT := n
>
> -# There are numerous races here, however, most of them due to plain accesses.
> +# There are numerous data races here, however, most of them are due to plain accesses.
> # This would make it even harder for syzbot to find reproducers, because these
> # bugs trigger without specific input. Disable by default, but should re-enable
> # eventually.
> diff --git a/lib/Kconfig.kcsan b/lib/Kconfig.kcsan
> index 5dd464e52ab4..3f78b1434375 100644
> --- a/lib/Kconfig.kcsan
> +++ b/lib/Kconfig.kcsan
> @@ -6,7 +6,6 @@ config HAVE_ARCH_KCSAN
> menuconfig KCSAN
> bool "KCSAN: watchpoint-based dynamic data race detector"
> depends on HAVE_ARCH_KCSAN && !KASAN && STACKTRACE
> - default n
> help
> Kernel Concurrency Sanitizer is a dynamic data race detector, which
> uses a watchpoint-based sampling approach to detect races. See
> @@ -16,13 +15,12 @@ if KCSAN
>
> config KCSAN_DEBUG
> bool "Debugging of KCSAN internals"
> - default n
>
> config KCSAN_SELFTEST
> bool "Perform short selftests on boot"
> default y
> help
> - Run KCSAN selftests on boot. On test failure, causes kernel to panic.
> + Run KCSAN selftests on boot. On test failure, causes the kernel to panic.
>
> config KCSAN_EARLY_ENABLE
> bool "Early enable during boot"
> @@ -62,7 +60,8 @@ config KCSAN_DELAY_RANDOMIZE
> default y
> help
> If delays should be randomized, where the maximum is KCSAN_UDELAY_*.
> - If false, the chosen delays are always KCSAN_UDELAY_* defined above.
> + If false, the chosen delays are always the KCSAN_UDELAY_* values
> + as defined above.
>
> config KCSAN_SKIP_WATCH
> int "Skip instructions before setting up watchpoint"
> @@ -86,9 +85,9 @@ config KCSAN_SKIP_WATCH_RANDOMIZE
> # 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
> # {READ,WRITE}_ONCE, atomic_*, bitops, etc.), and (b) complicate the design
> -# without real benefit. The main purpose of the below options are for use in
> -# fuzzer configs to control reported data races, and are not expected to be
> -# switched frequently by a user.
> +# without real benefit. The main purpose of the below options is for use in
> +# fuzzer configs to control reported data races, and they are not expected
> +# to be switched frequently by a user.
>
> config KCSAN_REPORT_RACE_UNKNOWN_ORIGIN
> bool "Report races of unknown origin"
> @@ -103,13 +102,12 @@ config KCSAN_REPORT_VALUE_CHANGE_ONLY
> bool "Only report races where watcher observed a data value change"
> default y
> help
> - If enabled and a conflicting write is observed via watchpoint, but
> + If enabled and a conflicting write is observed via a watchpoint, but
> the data value of the memory location was observed to remain
> unchanged, do not report the data race.
>
> config KCSAN_IGNORE_ATOMICS
> bool "Do not instrument marked atomic accesses"
> - default n
> help
> If enabled, never instruments marked atomic accesses. This results in
> not reporting data races where one access is atomic and the other is