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Date: Wed, 20 Nov 2019 22:01:22 +0100
From: Marco Elver <elver@...gle.com>
To: "Paul E. McKenney" <paulmck@...nel.org>
Cc: Ingo Molnar <mingo@...nel.org>,
LKML <linux-kernel@...r.kernel.org>,
Stephen Rothwell <sfr@...b.auug.org.au>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
Thomas Gleixner <tglx@...utronix.de>,
Will Deacon <will.deacon@....com>,
Mark Rutland <mark.rutland@....com>,
Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: [GIT RFC PULL kcsan] KCSAN commits for 5.5
On Wed, 20 Nov 2019 at 16:06, Paul E. McKenney <paulmck@...nel.org> wrote:
>
> On Wed, Nov 20, 2019 at 10:45:56AM +0100, Ingo Molnar wrote:
> >
> > hi Paul,
> >
> > * Paul E. McKenney <paulmck@...nel.org> 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@mail.gmail.com
> > >
> > > 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@google.com/
> > >
> > > 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@canb.auug.org.au/
> > >
> > > 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!
Thank you for the readability improvements, checked and all looks good to me!
Many thanks!
-- Marco
> Thanx, Paul
>
> > If anyone on Cc: has any objections then please holler!
> >
> > Thanks,
> >
> > Ingo
> >
> > =======================>
> > From: Ingo Molnar <mingo@...nel.org>
> > 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@...nel.org>
> > ---
> > 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() ? ¤t->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
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