Re: [PATCH v4 0/2] arm64: Fix kcsan test_barrier fail and panic

Re: [PATCH v4 0/2] arm64: Fix kcsan test_barrier fail and panic

[Kefeng Wang]

Sorry for using wrong script with uncorrected maintainers, please ignore.

On 2022/5/23 19:26, Kefeng Wang wrote:
> Fix selftest and kcsan_test() module fail when KCSAN_STRICT
> and KCSAN_WEAK_MEMORY enabled on ARM64.
>
> v4:
> - Use 2 spaces after a sentence-ending '.', suggested by Marco
> - Collect Ack/Review
>
> v3:
> - update dma_mb()'s description and add the generic definition,
>    also asm-generic change is moved into patch1, suggested by Marco.
> v2:
> - Add documents about dma_mb(), suggested by Mike and Will.
> - drop Fixes tag and update changlog, suggested by Mike.
>
>
> Kefeng Wang (2):
>    asm-generic: Add memory barrier dma_mb()
>    arm64: kcsan: Support detecting more missing memory barriers
>
>   Documentation/memory-barriers.txt | 11 ++++++-----
>   arch/arm64/include/asm/barrier.h  | 12 ++++++------
>   include/asm-generic/barrier.h     |  8 ++++++++
>   3 files changed, 20 insertions(+), 11 deletions(-)
>

Re: [PATCH v4 0/2] arm64: Fix kcsan test_barrier fail and panic

[Kefeng Wang]

Sorry for using wrong script with uncorrected maintainers, please ignore.

On 2022/5/23 19:26, Kefeng Wang wrote:
> Fix selftest and kcsan_test() module fail when KCSAN_STRICT
> and KCSAN_WEAK_MEMORY enabled on ARM64.
>
> v4:
> - Use 2 spaces after a sentence-ending '.', suggested by Marco
> - Collect Ack/Review
>
> v3:
> - update dma_mb()'s description and add the generic definition,
>    also asm-generic change is moved into patch1, suggested by Marco.
> v2:
> - Add documents about dma_mb(), suggested by Mike and Will.
> - drop Fixes tag and update changlog, suggested by Mike.
>
>
> Kefeng Wang (2):
>    asm-generic: Add memory barrier dma_mb()
>    arm64: kcsan: Support detecting more missing memory barriers
>
>   Documentation/memory-barriers.txt | 11 ++++++-----
>   arch/arm64/include/asm/barrier.h  | 12 ++++++------
>   include/asm-generic/barrier.h     |  8 ++++++++
>   3 files changed, 20 insertions(+), 11 deletions(-)
>

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[PATCH v4 0/2] arm64: Fix kcsan test_barrier fail and panic

[Kefeng Wang]

Fix selftest and kcsan_test() module fail when KCSAN_STRICT
and KCSAN_WEAK_MEMORY enabled on ARM64.

v4:
- Use 2 spaces after a sentence-ending '.', suggested by Marco
- Collect Ack/Review

v3:
- update dma_mb()'s description and add the generic definition,
  also asm-generic change is moved into patch1, suggested by Marco.
v2:
- Add documents about dma_mb(), suggested by Mike and Will.
- drop Fixes tag and update changlog, suggested by Mike.


Kefeng Wang (2):
  asm-generic: Add memory barrier dma_mb()
  arm64: kcsan: Support detecting more missing memory barriers

 Documentation/memory-barriers.txt | 11 ++++++-----
 arch/arm64/include/asm/barrier.h  | 12 ++++++------
 include/asm-generic/barrier.h     |  8 ++++++++
 3 files changed, 20 insertions(+), 11 deletions(-)

-- 
2.35.3

[PATCH v4 0/2] arm64: Fix kcsan test_barrier fail and panic

[Kefeng Wang]

Fix selftest and kcsan_test() module fail when KCSAN_STRICT
and KCSAN_WEAK_MEMORY enabled on ARM64.

v4:
- Use 2 spaces after a sentence-ending '.', suggested by Marco
- Collect Ack/Review

v3:
- update dma_mb()'s description and add the generic definition,
  also asm-generic change is moved into patch1, suggested by Marco.
v2:
- Add documents about dma_mb(), suggested by Mike and Will.
- drop Fixes tag and update changlog, suggested by Mike.


Kefeng Wang (2):
  asm-generic: Add memory barrier dma_mb()
  arm64: kcsan: Support detecting more missing memory barriers

 Documentation/memory-barriers.txt | 11 ++++++-----
 arch/arm64/include/asm/barrier.h  | 12 ++++++------
 include/asm-generic/barrier.h     |  8 ++++++++
 3 files changed, 20 insertions(+), 11 deletions(-)

-- 
2.35.3


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[PATCH v4 1/2] asm-generic: Add memory barrier dma_mb()

[Kefeng Wang]

The memory barrier dma_mb() is introduced by commit a76a37777f2c
("iommu/arm-smmu-v3: Ensure queue is read after updating prod pointer"),
which is used to ensure that prior (both reads and writes) accesses
to memory by a CPU are ordered w.r.t. a subsequent MMIO write.

Reviewed-by: Arnd Bergmann <arnd@arndb.de> # for asm-generic
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
---
 Documentation/memory-barriers.txt | 11 ++++++-----
 include/asm-generic/barrier.h     |  8 ++++++++
 2 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt
index b12df9137e1c..832b5d36e279 100644
--- a/Documentation/memory-barriers.txt
+++ b/Documentation/memory-barriers.txt
@@ -1894,6 +1894,7 @@ There are some more advanced barrier functions:
 
  (*) dma_wmb();
  (*) dma_rmb();
+ (*) dma_mb();
 
      These are for use with consistent memory to guarantee the ordering
      of writes or reads of shared memory accessible to both the CPU and a
@@ -1925,11 +1926,11 @@ There are some more advanced barrier functions:
      The dma_rmb() allows us guarantee the device has released ownership
      before we read the data from the descriptor, and the dma_wmb() allows
      us to guarantee the data is written to the descriptor before the device
-     can see it now has ownership.  Note that, when using writel(), a prior
-     wmb() is not needed to guarantee that the cache coherent memory writes
-     have completed before writing to the MMIO region.  The cheaper
-     writel_relaxed() does not provide this guarantee and must not be used
-     here.
+     can see it now has ownership.  The dma_mb() implies both a dma_rmb() and
+     a dma_wmb().  Note that, when using writel(), a prior wmb() is not needed
+     to guarantee that the cache coherent memory writes have completed before
+     writing to the MMIO region.  The cheaper writel_relaxed() does not provide
+     this guarantee and must not be used here.
 
      See the subsection "Kernel I/O barrier effects" for more information on
      relaxed I/O accessors and the Documentation/core-api/dma-api.rst file for
diff --git a/include/asm-generic/barrier.h b/include/asm-generic/barrier.h
index fd7e8fbaeef1..961f4d88f9ef 100644
--- a/include/asm-generic/barrier.h
+++ b/include/asm-generic/barrier.h
@@ -38,6 +38,10 @@
 #define wmb()	do { kcsan_wmb(); __wmb(); } while (0)
 #endif
 
+#ifdef __dma_mb
+#define dma_mb()	do { kcsan_mb(); __dma_mb(); } while (0)
+#endif
+
 #ifdef __dma_rmb
 #define dma_rmb()	do { kcsan_rmb(); __dma_rmb(); } while (0)
 #endif
@@ -65,6 +69,10 @@
 #define wmb()	mb()
 #endif
 
+#ifndef dma_mb
+#define dma_mb()	mb()
+#endif
+
 #ifndef dma_rmb
 #define dma_rmb()	rmb()
 #endif
-- 
2.35.3

[PATCH v4 1/2] asm-generic: Add memory barrier dma_mb()

[Kefeng Wang]

The memory barrier dma_mb() is introduced by commit a76a37777f2c
("iommu/arm-smmu-v3: Ensure queue is read after updating prod pointer"),
which is used to ensure that prior (both reads and writes) accesses
to memory by a CPU are ordered w.r.t. a subsequent MMIO write.

Reviewed-by: Arnd Bergmann <arnd@arndb.de> # for asm-generic
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
---
 Documentation/memory-barriers.txt | 11 ++++++-----
 include/asm-generic/barrier.h     |  8 ++++++++
 2 files changed, 14 insertions(+), 5 deletions(-)

diff --git a/Documentation/memory-barriers.txt b/Documentation/memory-barriers.txt
index b12df9137e1c..832b5d36e279 100644
--- a/Documentation/memory-barriers.txt
+++ b/Documentation/memory-barriers.txt
@@ -1894,6 +1894,7 @@ There are some more advanced barrier functions:
 
  (*) dma_wmb();
  (*) dma_rmb();
+ (*) dma_mb();
 
      These are for use with consistent memory to guarantee the ordering
      of writes or reads of shared memory accessible to both the CPU and a
@@ -1925,11 +1926,11 @@ There are some more advanced barrier functions:
      The dma_rmb() allows us guarantee the device has released ownership
      before we read the data from the descriptor, and the dma_wmb() allows
      us to guarantee the data is written to the descriptor before the device
-     can see it now has ownership.  Note that, when using writel(), a prior
-     wmb() is not needed to guarantee that the cache coherent memory writes
-     have completed before writing to the MMIO region.  The cheaper
-     writel_relaxed() does not provide this guarantee and must not be used
-     here.
+     can see it now has ownership.  The dma_mb() implies both a dma_rmb() and
+     a dma_wmb().  Note that, when using writel(), a prior wmb() is not needed
+     to guarantee that the cache coherent memory writes have completed before
+     writing to the MMIO region.  The cheaper writel_relaxed() does not provide
+     this guarantee and must not be used here.
 
      See the subsection "Kernel I/O barrier effects" for more information on
      relaxed I/O accessors and the Documentation/core-api/dma-api.rst file for
diff --git a/include/asm-generic/barrier.h b/include/asm-generic/barrier.h
index fd7e8fbaeef1..961f4d88f9ef 100644
--- a/include/asm-generic/barrier.h
+++ b/include/asm-generic/barrier.h
@@ -38,6 +38,10 @@
 #define wmb()	do { kcsan_wmb(); __wmb(); } while (0)
 #endif
 
+#ifdef __dma_mb
+#define dma_mb()	do { kcsan_mb(); __dma_mb(); } while (0)
+#endif
+
 #ifdef __dma_rmb
 #define dma_rmb()	do { kcsan_rmb(); __dma_rmb(); } while (0)
 #endif
@@ -65,6 +69,10 @@
 #define wmb()	mb()
 #endif
 
+#ifndef dma_mb
+#define dma_mb()	mb()
+#endif
+
 #ifndef dma_rmb
 #define dma_rmb()	rmb()
 #endif
-- 
2.35.3


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[PATCH v4 2/2] arm64: kcsan: Support detecting more missing memory barriers

[Kefeng Wang]

As "kcsan: Support detecting a subset of missing memory barriers"[1]
introduced KCSAN_STRICT/KCSAN_WEAK_MEMORY which make kcsan detects
more missing memory barrier, but arm64 don't have KCSAN instrumentation
for barriers, so the new selftest test_barrier() and test cases for
memory barrier instrumentation in kcsan_test module will fail, even
panic on selftest.

Let's prefix all barriers with __ on arm64, as asm-generic/barriers.h
defined the final instrumented version of these barriers, which will
fix the above issues.

Note, barrier instrumentation that can be disabled via __no_kcsan with
appropriate compiler-support (and not just with objtool help), see
commit bd3d5bd1a0ad ("kcsan: Support WEAK_MEMORY with Clang where no
objtool support exists"), it adds disable_sanitizer_instrumentation to
__no_kcsan attribute which will remove all sanitizer instrumentation fully
(with Clang 14.0). Meanwhile, GCC does the same thing with no_sanitize.

[1] https://lore.kernel.org/linux-mm/20211130114433.2580590-1-elver@google.com/

Acked-by: Marco Elver <elver@google.com>
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
---
 arch/arm64/include/asm/barrier.h | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/include/asm/barrier.h b/arch/arm64/include/asm/barrier.h
index 9f3e2c3d2ca0..2cfc4245d2e2 100644
--- a/arch/arm64/include/asm/barrier.h
+++ b/arch/arm64/include/asm/barrier.h
@@ -50,13 +50,13 @@
 #define pmr_sync()	do {} while (0)
 #endif
 
-#define mb()		dsb(sy)
-#define rmb()		dsb(ld)
-#define wmb()		dsb(st)
+#define __mb()		dsb(sy)
+#define __rmb()		dsb(ld)
+#define __wmb()		dsb(st)
 
-#define dma_mb()	dmb(osh)
-#define dma_rmb()	dmb(oshld)
-#define dma_wmb()	dmb(oshst)
+#define __dma_mb()	dmb(osh)
+#define __dma_rmb()	dmb(oshld)
+#define __dma_wmb()	dmb(oshst)
 
 #define io_stop_wc()	dgh()
 
-- 
2.35.3

[PATCH v4 2/2] arm64: kcsan: Support detecting more missing memory barriers

[Kefeng Wang]

As "kcsan: Support detecting a subset of missing memory barriers"[1]
introduced KCSAN_STRICT/KCSAN_WEAK_MEMORY which make kcsan detects
more missing memory barrier, but arm64 don't have KCSAN instrumentation
for barriers, so the new selftest test_barrier() and test cases for
memory barrier instrumentation in kcsan_test module will fail, even
panic on selftest.

Let's prefix all barriers with __ on arm64, as asm-generic/barriers.h
defined the final instrumented version of these barriers, which will
fix the above issues.

Note, barrier instrumentation that can be disabled via __no_kcsan with
appropriate compiler-support (and not just with objtool help), see
commit bd3d5bd1a0ad ("kcsan: Support WEAK_MEMORY with Clang where no
objtool support exists"), it adds disable_sanitizer_instrumentation to
__no_kcsan attribute which will remove all sanitizer instrumentation fully
(with Clang 14.0). Meanwhile, GCC does the same thing with no_sanitize.

[1] https://lore.kernel.org/linux-mm/20211130114433.2580590-1-elver@google.com/

Acked-by: Marco Elver <elver@google.com>
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
---
 arch/arm64/include/asm/barrier.h | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/include/asm/barrier.h b/arch/arm64/include/asm/barrier.h
index 9f3e2c3d2ca0..2cfc4245d2e2 100644
--- a/arch/arm64/include/asm/barrier.h
+++ b/arch/arm64/include/asm/barrier.h
@@ -50,13 +50,13 @@
 #define pmr_sync()	do {} while (0)
 #endif
 
-#define mb()		dsb(sy)
-#define rmb()		dsb(ld)
-#define wmb()		dsb(st)
+#define __mb()		dsb(sy)
+#define __rmb()		dsb(ld)
+#define __wmb()		dsb(st)
 
-#define dma_mb()	dmb(osh)
-#define dma_rmb()	dmb(oshld)
-#define dma_wmb()	dmb(oshst)
+#define __dma_mb()	dmb(osh)
+#define __dma_rmb()	dmb(oshld)
+#define __dma_wmb()	dmb(oshst)
 
 #define io_stop_wc()	dgh()
 
-- 
2.35.3


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Re: [PATCH v4 2/2] arm64: kcsan: Support detecting more missing memory barriers

[Catalin Marinas]

On Mon, May 23, 2022 at 07:31:26PM +0800, Kefeng Wang wrote:
> As "kcsan: Support detecting a subset of missing memory barriers"[1]
> introduced KCSAN_STRICT/KCSAN_WEAK_MEMORY which make kcsan detects
> more missing memory barrier, but arm64 don't have KCSAN instrumentation
> for barriers, so the new selftest test_barrier() and test cases for
> memory barrier instrumentation in kcsan_test module will fail, even
> panic on selftest.
> 
> Let's prefix all barriers with __ on arm64, as asm-generic/barriers.h
> defined the final instrumented version of these barriers, which will
> fix the above issues.
> 
> Note, barrier instrumentation that can be disabled via __no_kcsan with
> appropriate compiler-support (and not just with objtool help), see
> commit bd3d5bd1a0ad ("kcsan: Support WEAK_MEMORY with Clang where no
> objtool support exists"), it adds disable_sanitizer_instrumentation to
> __no_kcsan attribute which will remove all sanitizer instrumentation fully
> (with Clang 14.0). Meanwhile, GCC does the same thing with no_sanitize.
> 
> [1] https://lore.kernel.org/linux-mm/20211130114433.2580590-1-elver@google.com/
> 
> Acked-by: Marco Elver <elver@google.com>
> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>

Acked-by: Catalin Marinas <catalin.marinas@arm.com>

I'll leave the series to Will to queue for 5.20.

Thanks.

-- 
Catalin

Re: [PATCH v4 2/2] arm64: kcsan: Support detecting more missing memory barriers

[Catalin Marinas]

On Mon, May 23, 2022 at 07:31:26PM +0800, Kefeng Wang wrote:
> As "kcsan: Support detecting a subset of missing memory barriers"[1]
> introduced KCSAN_STRICT/KCSAN_WEAK_MEMORY which make kcsan detects
> more missing memory barrier, but arm64 don't have KCSAN instrumentation
> for barriers, so the new selftest test_barrier() and test cases for
> memory barrier instrumentation in kcsan_test module will fail, even
> panic on selftest.
> 
> Let's prefix all barriers with __ on arm64, as asm-generic/barriers.h
> defined the final instrumented version of these barriers, which will
> fix the above issues.
> 
> Note, barrier instrumentation that can be disabled via __no_kcsan with
> appropriate compiler-support (and not just with objtool help), see
> commit bd3d5bd1a0ad ("kcsan: Support WEAK_MEMORY with Clang where no
> objtool support exists"), it adds disable_sanitizer_instrumentation to
> __no_kcsan attribute which will remove all sanitizer instrumentation fully
> (with Clang 14.0). Meanwhile, GCC does the same thing with no_sanitize.
> 
> [1] https://lore.kernel.org/linux-mm/20211130114433.2580590-1-elver@google.com/
> 
> Acked-by: Marco Elver <elver@google.com>
> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>

Acked-by: Catalin Marinas <catalin.marinas@arm.com>

I'll leave the series to Will to queue for 5.20.

Thanks.

-- 
Catalin

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Re: [PATCH v4 2/2] arm64: kcsan: Support detecting more missing memory barriers

[Kefeng Wang]

Hi Will and Catalin, kindly ping...

On 2022/5/23 22:16, Mark Rutland wrote:
> On Mon, May 23, 2022 at 07:31:26PM +0800, Kefeng Wang wrote:
>> As "kcsan: Support detecting a subset of missing memory barriers"[1]
>> introduced KCSAN_STRICT/KCSAN_WEAK_MEMORY which make kcsan detects
>> more missing memory barrier, but arm64 don't have KCSAN instrumentation
>> for barriers, so the new selftest test_barrier() and test cases for
>> memory barrier instrumentation in kcsan_test module will fail, even
>> panic on selftest.
>>
>> Let's prefix all barriers with __ on arm64, as asm-generic/barriers.h
>> defined the final instrumented version of these barriers, which will
>> fix the above issues.
>>
>> Note, barrier instrumentation that can be disabled via __no_kcsan with
>> appropriate compiler-support (and not just with objtool help), see
>> commit bd3d5bd1a0ad ("kcsan: Support WEAK_MEMORY with Clang where no
>> objtool support exists"), it adds disable_sanitizer_instrumentation to
>> __no_kcsan attribute which will remove all sanitizer instrumentation fully
>> (with Clang 14.0). Meanwhile, GCC does the same thing with no_sanitize.
>>
>> [1] https://lore.kernel.org/linux-mm/20211130114433.2580590-1-elver@google.com/
>>
>> Acked-by: Marco Elver <elver@google.com>
>> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
> Having built this with GCC 12.1.0 and LLVM 14.0.0, I think this patch itself
> doesn't introduce any new problems, and logically makes sense. With that in
> mind:
>
>    Acked-by: Mark Rutland <mark.rutland@arm.com>
>
> As an aside, having scanned the resulting vmlinux with objdump, there are
> plenty of latent issues where we get KCSAN instrumentation where we don't want
> it (e.g. early/late in arm64's entry-common.o). The bulk of those are due to
> missing `nonistr` or `__always_inline`, which we'll need to fix up.
>
> Thanks,
> Mark.
>
>> ---
>>   arch/arm64/include/asm/barrier.h | 12 ++++++------
>>   1 file changed, 6 insertions(+), 6 deletions(-)
>>
>> diff --git a/arch/arm64/include/asm/barrier.h b/arch/arm64/include/asm/barrier.h
>> index 9f3e2c3d2ca0..2cfc4245d2e2 100644
>> --- a/arch/arm64/include/asm/barrier.h
>> +++ b/arch/arm64/include/asm/barrier.h
>> @@ -50,13 +50,13 @@
>>   #define pmr_sync()	do {} while (0)
>>   #endif
>>   
>> -#define mb()		dsb(sy)
>> -#define rmb()		dsb(ld)
>> -#define wmb()		dsb(st)
>> +#define __mb()		dsb(sy)
>> +#define __rmb()		dsb(ld)
>> +#define __wmb()		dsb(st)
>>   
>> -#define dma_mb()	dmb(osh)
>> -#define dma_rmb()	dmb(oshld)
>> -#define dma_wmb()	dmb(oshst)
>> +#define __dma_mb()	dmb(osh)
>> +#define __dma_rmb()	dmb(oshld)
>> +#define __dma_wmb()	dmb(oshst)
>>   
>>   #define io_stop_wc()	dgh()
>>   
>> -- 
>> 2.35.3
>>
> .

Re: [PATCH v4 2/2] arm64: kcsan: Support detecting more missing memory barriers

[Kefeng Wang]

Hi Will and Catalin, kindly ping...

On 2022/5/23 22:16, Mark Rutland wrote:
> On Mon, May 23, 2022 at 07:31:26PM +0800, Kefeng Wang wrote:
>> As "kcsan: Support detecting a subset of missing memory barriers"[1]
>> introduced KCSAN_STRICT/KCSAN_WEAK_MEMORY which make kcsan detects
>> more missing memory barrier, but arm64 don't have KCSAN instrumentation
>> for barriers, so the new selftest test_barrier() and test cases for
>> memory barrier instrumentation in kcsan_test module will fail, even
>> panic on selftest.
>>
>> Let's prefix all barriers with __ on arm64, as asm-generic/barriers.h
>> defined the final instrumented version of these barriers, which will
>> fix the above issues.
>>
>> Note, barrier instrumentation that can be disabled via __no_kcsan with
>> appropriate compiler-support (and not just with objtool help), see
>> commit bd3d5bd1a0ad ("kcsan: Support WEAK_MEMORY with Clang where no
>> objtool support exists"), it adds disable_sanitizer_instrumentation to
>> __no_kcsan attribute which will remove all sanitizer instrumentation fully
>> (with Clang 14.0). Meanwhile, GCC does the same thing with no_sanitize.
>>
>> [1] https://lore.kernel.org/linux-mm/20211130114433.2580590-1-elver@google.com/
>>
>> Acked-by: Marco Elver <elver@google.com>
>> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
> Having built this with GCC 12.1.0 and LLVM 14.0.0, I think this patch itself
> doesn't introduce any new problems, and logically makes sense. With that in
> mind:
>
>    Acked-by: Mark Rutland <mark.rutland@arm.com>
>
> As an aside, having scanned the resulting vmlinux with objdump, there are
> plenty of latent issues where we get KCSAN instrumentation where we don't want
> it (e.g. early/late in arm64's entry-common.o). The bulk of those are due to
> missing `nonistr` or `__always_inline`, which we'll need to fix up.
>
> Thanks,
> Mark.
>
>> ---
>>   arch/arm64/include/asm/barrier.h | 12 ++++++------
>>   1 file changed, 6 insertions(+), 6 deletions(-)
>>
>> diff --git a/arch/arm64/include/asm/barrier.h b/arch/arm64/include/asm/barrier.h
>> index 9f3e2c3d2ca0..2cfc4245d2e2 100644
>> --- a/arch/arm64/include/asm/barrier.h
>> +++ b/arch/arm64/include/asm/barrier.h
>> @@ -50,13 +50,13 @@
>>   #define pmr_sync()	do {} while (0)
>>   #endif
>>   
>> -#define mb()		dsb(sy)
>> -#define rmb()		dsb(ld)
>> -#define wmb()		dsb(st)
>> +#define __mb()		dsb(sy)
>> +#define __rmb()		dsb(ld)
>> +#define __wmb()		dsb(st)
>>   
>> -#define dma_mb()	dmb(osh)
>> -#define dma_rmb()	dmb(oshld)
>> -#define dma_wmb()	dmb(oshst)
>> +#define __dma_mb()	dmb(osh)
>> +#define __dma_rmb()	dmb(oshld)
>> +#define __dma_wmb()	dmb(oshst)
>>   
>>   #define io_stop_wc()	dgh()
>>   
>> -- 
>> 2.35.3
>>
> .

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Re: [PATCH v4 2/2] arm64: kcsan: Support detecting more missing memory barriers

[Mark Rutland]

On Mon, May 23, 2022 at 07:31:26PM +0800, Kefeng Wang wrote:
> As "kcsan: Support detecting a subset of missing memory barriers"[1]
> introduced KCSAN_STRICT/KCSAN_WEAK_MEMORY which make kcsan detects
> more missing memory barrier, but arm64 don't have KCSAN instrumentation
> for barriers, so the new selftest test_barrier() and test cases for
> memory barrier instrumentation in kcsan_test module will fail, even
> panic on selftest.
> 
> Let's prefix all barriers with __ on arm64, as asm-generic/barriers.h
> defined the final instrumented version of these barriers, which will
> fix the above issues.
> 
> Note, barrier instrumentation that can be disabled via __no_kcsan with
> appropriate compiler-support (and not just with objtool help), see
> commit bd3d5bd1a0ad ("kcsan: Support WEAK_MEMORY with Clang where no
> objtool support exists"), it adds disable_sanitizer_instrumentation to
> __no_kcsan attribute which will remove all sanitizer instrumentation fully
> (with Clang 14.0). Meanwhile, GCC does the same thing with no_sanitize.
> 
> [1] https://lore.kernel.org/linux-mm/20211130114433.2580590-1-elver@google.com/
> 
> Acked-by: Marco Elver <elver@google.com>
> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>

Having built this with GCC 12.1.0 and LLVM 14.0.0, I think this patch itself
doesn't introduce any new problems, and logically makes sense. With that in
mind:

  Acked-by: Mark Rutland <mark.rutland@arm.com>

As an aside, having scanned the resulting vmlinux with objdump, there are
plenty of latent issues where we get KCSAN instrumentation where we don't want
it (e.g. early/late in arm64's entry-common.o). The bulk of those are due to
missing `nonistr` or `__always_inline`, which we'll need to fix up.

Thanks,
Mark.

> ---
>  arch/arm64/include/asm/barrier.h | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/barrier.h b/arch/arm64/include/asm/barrier.h
> index 9f3e2c3d2ca0..2cfc4245d2e2 100644
> --- a/arch/arm64/include/asm/barrier.h
> +++ b/arch/arm64/include/asm/barrier.h
> @@ -50,13 +50,13 @@
>  #define pmr_sync()	do {} while (0)
>  #endif
>  
> -#define mb()		dsb(sy)
> -#define rmb()		dsb(ld)
> -#define wmb()		dsb(st)
> +#define __mb()		dsb(sy)
> +#define __rmb()		dsb(ld)
> +#define __wmb()		dsb(st)
>  
> -#define dma_mb()	dmb(osh)
> -#define dma_rmb()	dmb(oshld)
> -#define dma_wmb()	dmb(oshst)
> +#define __dma_mb()	dmb(osh)
> +#define __dma_rmb()	dmb(oshld)
> +#define __dma_wmb()	dmb(oshst)
>  
>  #define io_stop_wc()	dgh()
>  
> -- 
> 2.35.3
> 

Re: [PATCH v4 2/2] arm64: kcsan: Support detecting more missing memory barriers

[Mark Rutland]

On Mon, May 23, 2022 at 07:31:26PM +0800, Kefeng Wang wrote:
> As "kcsan: Support detecting a subset of missing memory barriers"[1]
> introduced KCSAN_STRICT/KCSAN_WEAK_MEMORY which make kcsan detects
> more missing memory barrier, but arm64 don't have KCSAN instrumentation
> for barriers, so the new selftest test_barrier() and test cases for
> memory barrier instrumentation in kcsan_test module will fail, even
> panic on selftest.
> 
> Let's prefix all barriers with __ on arm64, as asm-generic/barriers.h
> defined the final instrumented version of these barriers, which will
> fix the above issues.
> 
> Note, barrier instrumentation that can be disabled via __no_kcsan with
> appropriate compiler-support (and not just with objtool help), see
> commit bd3d5bd1a0ad ("kcsan: Support WEAK_MEMORY with Clang where no
> objtool support exists"), it adds disable_sanitizer_instrumentation to
> __no_kcsan attribute which will remove all sanitizer instrumentation fully
> (with Clang 14.0). Meanwhile, GCC does the same thing with no_sanitize.
> 
> [1] https://lore.kernel.org/linux-mm/20211130114433.2580590-1-elver@google.com/
> 
> Acked-by: Marco Elver <elver@google.com>
> Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>

Having built this with GCC 12.1.0 and LLVM 14.0.0, I think this patch itself
doesn't introduce any new problems, and logically makes sense. With that in
mind:

  Acked-by: Mark Rutland <mark.rutland@arm.com>

As an aside, having scanned the resulting vmlinux with objdump, there are
plenty of latent issues where we get KCSAN instrumentation where we don't want
it (e.g. early/late in arm64's entry-common.o). The bulk of those are due to
missing `nonistr` or `__always_inline`, which we'll need to fix up.

Thanks,
Mark.

> ---
>  arch/arm64/include/asm/barrier.h | 12 ++++++------
>  1 file changed, 6 insertions(+), 6 deletions(-)
> 
> diff --git a/arch/arm64/include/asm/barrier.h b/arch/arm64/include/asm/barrier.h
> index 9f3e2c3d2ca0..2cfc4245d2e2 100644
> --- a/arch/arm64/include/asm/barrier.h
> +++ b/arch/arm64/include/asm/barrier.h
> @@ -50,13 +50,13 @@
>  #define pmr_sync()	do {} while (0)
>  #endif
>  
> -#define mb()		dsb(sy)
> -#define rmb()		dsb(ld)
> -#define wmb()		dsb(st)
> +#define __mb()		dsb(sy)
> +#define __rmb()		dsb(ld)
> +#define __wmb()		dsb(st)
>  
> -#define dma_mb()	dmb(osh)
> -#define dma_rmb()	dmb(oshld)
> -#define dma_wmb()	dmb(oshst)
> +#define __dma_mb()	dmb(osh)
> +#define __dma_rmb()	dmb(oshld)
> +#define __dma_wmb()	dmb(oshst)
>  
>  #define io_stop_wc()	dgh()
>  
> -- 
> 2.35.3
> 

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[PATCH v4 2/2] arm64: kcsan: Support detecting more missing memory barriers

[Kefeng Wang]

As "kcsan: Support detecting a subset of missing memory barriers"[1]
introduced KCSAN_STRICT/KCSAN_WEAK_MEMORY which make kcsan detects
more missing memory barrier, but arm64 don't have KCSAN instrumentation
for barriers, so the new selftest test_barrier() and test cases for
memory barrier instrumentation in kcsan_test module will fail, even
panic on selftest.

Let's prefix all barriers with __ on arm64, as asm-generic/barriers.h
defined the final instrumented version of these barriers, which will
fix the above issues.

Note, barrier instrumentation that can be disabled via __no_kcsan with
appropriate compiler-support (and not just with objtool help), see
commit bd3d5bd1a0ad ("kcsan: Support WEAK_MEMORY with Clang where no
objtool support exists"), it adds disable_sanitizer_instrumentation to
__no_kcsan attribute which will remove all sanitizer instrumentation fully
(with Clang 14.0). Meanwhile, GCC does the same thing with no_sanitize.

[1] https://lore.kernel.org/linux-mm/20211130114433.2580590-1-elver@google.com/

Acked-by: Marco Elver <elver@google.com>
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
---
 arch/arm64/include/asm/barrier.h | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/include/asm/barrier.h b/arch/arm64/include/asm/barrier.h
index 9f3e2c3d2ca0..2cfc4245d2e2 100644
--- a/arch/arm64/include/asm/barrier.h
+++ b/arch/arm64/include/asm/barrier.h
@@ -50,13 +50,13 @@
 #define pmr_sync()	do {} while (0)
 #endif
 
-#define mb()		dsb(sy)
-#define rmb()		dsb(ld)
-#define wmb()		dsb(st)
+#define __mb()		dsb(sy)
+#define __rmb()		dsb(ld)
+#define __wmb()		dsb(st)
 
-#define dma_mb()	dmb(osh)
-#define dma_rmb()	dmb(oshld)
-#define dma_wmb()	dmb(oshst)
+#define __dma_mb()	dmb(osh)
+#define __dma_rmb()	dmb(oshld)
+#define __dma_wmb()	dmb(oshst)
 
 #define io_stop_wc()	dgh()
 
-- 
2.35.3

[PATCH v4 2/2] arm64: kcsan: Support detecting more missing memory barriers

[Kefeng Wang]

As "kcsan: Support detecting a subset of missing memory barriers"[1]
introduced KCSAN_STRICT/KCSAN_WEAK_MEMORY which make kcsan detects
more missing memory barrier, but arm64 don't have KCSAN instrumentation
for barriers, so the new selftest test_barrier() and test cases for
memory barrier instrumentation in kcsan_test module will fail, even
panic on selftest.

Let's prefix all barriers with __ on arm64, as asm-generic/barriers.h
defined the final instrumented version of these barriers, which will
fix the above issues.

Note, barrier instrumentation that can be disabled via __no_kcsan with
appropriate compiler-support (and not just with objtool help), see
commit bd3d5bd1a0ad ("kcsan: Support WEAK_MEMORY with Clang where no
objtool support exists"), it adds disable_sanitizer_instrumentation to
__no_kcsan attribute which will remove all sanitizer instrumentation fully
(with Clang 14.0). Meanwhile, GCC does the same thing with no_sanitize.

[1] https://lore.kernel.org/linux-mm/20211130114433.2580590-1-elver@google.com/

Acked-by: Marco Elver <elver@google.com>
Signed-off-by: Kefeng Wang <wangkefeng.wang@huawei.com>
---
 arch/arm64/include/asm/barrier.h | 12 ++++++------
 1 file changed, 6 insertions(+), 6 deletions(-)

diff --git a/arch/arm64/include/asm/barrier.h b/arch/arm64/include/asm/barrier.h
index 9f3e2c3d2ca0..2cfc4245d2e2 100644
--- a/arch/arm64/include/asm/barrier.h
+++ b/arch/arm64/include/asm/barrier.h
@@ -50,13 +50,13 @@
 #define pmr_sync()	do {} while (0)
 #endif
 
-#define mb()		dsb(sy)
-#define rmb()		dsb(ld)
-#define wmb()		dsb(st)
+#define __mb()		dsb(sy)
+#define __rmb()		dsb(ld)
+#define __wmb()		dsb(st)
 
-#define dma_mb()	dmb(osh)
-#define dma_rmb()	dmb(oshld)
-#define dma_wmb()	dmb(oshst)
+#define __dma_mb()	dmb(osh)
+#define __dma_rmb()	dmb(oshld)
+#define __dma_wmb()	dmb(oshst)
 
 #define io_stop_wc()	dgh()
 
-- 
2.35.3


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