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Groups > linux.kernel > #1250455
| From | Andrey Ryabinin <aryabinin@virtuozzo.com> |
|---|---|
| Newsgroups | linux.kernel |
| Subject | [PATCH v5 1/2] compiler, atomics: Provide READ_ONCE_NOCHECK() |
| Date | 2015-10-19 10:40 +0200 |
| Message-ID | <qle94-7rs-19@gated-at.bofh.it> (permalink) |
| References | <qj721-6Fq-17@gated-at.bofh.it> <qle93-7rs-13@gated-at.bofh.it> |
| Organization | linux.* mail to news gateway |
Some code may perform racy by design memory reads. This could be
harmless, yet such code may produce KASAN warnings.
To hide such accesses from KASAN this patch introduces
READ_ONCE_NOCHECK() macro. KASAN will not check the memory
accessed by READ_ONCE_NOCHECK(). The KernelThreadSanitizer (KTSAN)
is going to ignore it as well.
This patch creates __read_once_size_nocheck() a clone of
__read_once_size(). The only difference between them is
'no_sanitized_address' attribute appended to '*_nocheck' function.
This attribute tells the compiler that instrumentation of memory
accesses should not be applied to that function. We declare it as
static '__maybe_unsed' because GCC is not capable to inline such
function: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368
With KASAN=n READ_ONCE_NOCHECK() is just a clone of READ_ONCE().
Signed-off-by: Andrey Ryabinin <aryabinin@virtuozzo.com>
---
include/linux/compiler-gcc.h | 13 +++++++++
include/linux/compiler.h | 66 +++++++++++++++++++++++++++++++++++---------
2 files changed, 66 insertions(+), 13 deletions(-)
diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index dfaa7b3..8efb40e 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -237,12 +237,25 @@
#define KASAN_ABI_VERSION 3
#endif
+#if GCC_VERSION >= 40902
+/*
+ * Tell the compiler that address safety instrumentation (KASAN)
+ * should not be applied to that function.
+ * Conflicts with inlining: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368
+ */
+#define __no_sanitize_address __attribute__((no_sanitize_address))
+#endif
+
#endif /* gcc version >= 40000 specific checks */
#if !defined(__noclone)
#define __noclone /* not needed */
#endif
+#if !defined(__no_sanitize_address)
+#define __no_sanitize_address
+#endif
+
/*
* A trick to suppress uninitialized variable warning without generating any
* code
diff --git a/include/linux/compiler.h b/include/linux/compiler.h
index c836eb2..3d78103 100644
--- a/include/linux/compiler.h
+++ b/include/linux/compiler.h
@@ -198,19 +198,45 @@ void ftrace_likely_update(struct ftrace_branch_data *f, int val, int expect);
#include <uapi/linux/types.h>
-static __always_inline void __read_once_size(const volatile void *p, void *res, int size)
+#define __READ_ONCE_SIZE \
+({ \
+ switch (size) { \
+ case 1: *(__u8 *)res = *(volatile __u8 *)p; break; \
+ case 2: *(__u16 *)res = *(volatile __u16 *)p; break; \
+ case 4: *(__u32 *)res = *(volatile __u32 *)p; break; \
+ case 8: *(__u64 *)res = *(volatile __u64 *)p; break; \
+ default: \
+ barrier(); \
+ __builtin_memcpy((void *)res, (const void *)p, size); \
+ barrier(); \
+ } \
+})
+
+static __always_inline
+void __read_once_size(const volatile void *p, void *res, int size)
{
- switch (size) {
- case 1: *(__u8 *)res = *(volatile __u8 *)p; break;
- case 2: *(__u16 *)res = *(volatile __u16 *)p; break;
- case 4: *(__u32 *)res = *(volatile __u32 *)p; break;
- case 8: *(__u64 *)res = *(volatile __u64 *)p; break;
- default:
- barrier();
- __builtin_memcpy((void *)res, (const void *)p, size);
- barrier();
- }
+ __READ_ONCE_SIZE;
+}
+
+#ifdef CONFIG_KASAN
+/*
+ * This function is not 'inline' because __no_sanitize_address confilcts
+ * with inlining. Attempt to inline it may cause a build failure.
+ * https://gcc.gnu.org/bugzilla/show_bug.cgi?id=67368
+ * '__maybe_unused' allows us to avoid defined-but-not-used warnings.
+ */
+static __no_sanitize_address __maybe_unused
+void __read_once_size_nocheck(const volatile void *p, void *res, int size)
+{
+ __READ_ONCE_SIZE;
+}
+#else
+static __always_inline
+void __read_once_size_nocheck(const volatile void *p, void *res, int size)
+{
+ __READ_ONCE_SIZE;
}
+#endif
static __always_inline void __write_once_size(volatile void *p, void *res, int size)
{
@@ -248,8 +274,22 @@ static __always_inline void __write_once_size(volatile void *p, void *res, int s
* required ordering.
*/
-#define READ_ONCE(x) \
- ({ union { typeof(x) __val; char __c[1]; } __u; __read_once_size(&(x), __u.__c, sizeof(x)); __u.__val; })
+#define __READ_ONCE(x, check) \
+({ \
+ union { typeof(x) __val; char __c[1]; } __u; \
+ if (check) \
+ __read_once_size(&(x), __u.__c, sizeof(x)); \
+ else \
+ __read_once_size_nocheck(&(x), __u.__c, sizeof(x)); \
+ __u.__val; \
+})
+#define READ_ONCE(x) __READ_ONCE(x, 1)
+
+/*
+ * Use READ_ONCE_NOCHECK() instead of READ_ONCE() if you need
+ * to hide memory access from KASAN.
+ */
+#define READ_ONCE_NOCHECK(x) __READ_ONCE(x, 0)
#define WRITE_ONCE(x, val) \
({ \
--
2.4.9
--
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[PATCH v2 0/2] Silence KASAN warnings in get_wchan() Andrey Ryabinin <aryabinin@virtuozzo.com> - 2015-10-13 14:50 +0200
[PATCH v3 0/2] Silence KASAN warnings in get_wchan() Andrey Ryabinin <aryabinin@virtuozzo.com> - 2015-10-13 17:30 +0200
[PATCH v3 1/2] Provide READ_ONCE_NOCHECK() Andrey Ryabinin <aryabinin@virtuozzo.com> - 2015-10-13 17:40 +0200
[tip:locking/urgent] compiler, atomics: Provide READ_ONCE_NOCHECK () tip-bot for Andrey Ryabinin <tipbot@zytor.com> - 2015-10-14 17:40 +0200
Re: [tip:locking/urgent] compiler, atomics: Provide READ_ONCE_NOCHECK () "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-10-14 17:50 +0200
Re: [tip:locking/urgent] compiler, atomics: Provide READ_ONCE_NOCHECK () Dmitry Vyukov <dvyukov@google.com> - 2015-10-14 18:00 +0200
Re: [tip:locking/urgent] compiler, atomics: Provide READ_ONCE_NOCHECK () Dmitry Vyukov <dvyukov@google.com> - 2015-10-14 18:10 +0200
Re: [tip:locking/urgent] compiler, atomics: Provide READ_ONCE_NOCHECK () Peter Zijlstra <peterz@infradead.org> - 2015-10-14 18:20 +0200
Re: [tip:locking/urgent] compiler, atomics: Provide READ_ONCE_NOCHECK () Dmitry Vyukov <dvyukov@google.com> - 2015-10-14 18:20 +0200
Re: [tip:locking/urgent] compiler, atomics: Provide READ_ONCE_NOCHECK () Andy Lutomirski <luto@amacapital.net> - 2015-10-14 18:30 +0200
Re: [tip:locking/urgent] compiler, atomics: Provide READ_ONCE_NOCHECK () Peter Zijlstra <peterz@infradead.org> - 2015-10-14 18:40 +0200
Re: [tip:locking/urgent] compiler, atomics: Provide READ_ONCE_NOCHECK () Ingo Molnar <mingo@kernel.org> - 2015-10-14 19:50 +0200
Re: [tip:locking/urgent] compiler, atomics: Provide READ_ONCE_NOCHECK () Andy Lutomirski <luto@amacapital.net> - 2015-10-14 20:00 +0200
Re: [tip:locking/urgent] compiler, atomics: Provide READ_ONCE_NOCHECK () Peter Zijlstra <peterz@infradead.org> - 2015-10-14 18:30 +0200
Re: [tip:locking/urgent] compiler, atomics: Provide READ_ONCE_NOCHECK () Dmitry Vyukov <dvyukov@google.com> - 2015-10-14 18:40 +0200
Re: [tip:locking/urgent] compiler, atomics: Provide READ_ONCE_NOCHECK () Peter Zijlstra <peterz@infradead.org> - 2015-10-14 19:00 +0200
Re: [tip:locking/urgent] compiler, atomics: Provide READ_ONCE_NOCHECK () "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-10-14 18:30 +0200
Re: [tip:locking/urgent] compiler, atomics: Provide READ_ONCE_NOCHECK () Dmitry Vyukov <dvyukov@google.com> - 2015-10-14 18:40 +0200
Re: [tip:locking/urgent] compiler, atomics: Provide READ_ONCE_NOCHECK () "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-10-14 19:10 +0200
Re: [tip:locking/urgent] compiler, atomics: Provide READ_ONCE_NOCHECK () Dmitry Vyukov <dvyukov@google.com> - 2015-10-14 19:30 +0200
Re: [tip:locking/urgent] compiler, atomics: Provide READ_ONCE_NOCHECK () "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-10-14 19:40 +0200
Re: [tip:locking/urgent] compiler, atomics: Provide READ_ONCE_NOCHECK () "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-10-14 18:10 +0200
Re: [tip:locking/urgent] compiler, atomics: Provide READ_ONCE_NOCHECK () Andrey Ryabinin <aryabinin@virtuozzo.com> - 2015-10-14 18:20 +0200
Re: [tip:locking/urgent] compiler, atomics: Provide READ_ONCE_NOCHECK () Dmitry Vyukov <dvyukov@google.com> - 2015-10-14 18:40 +0200
Re: [tip:locking/urgent] compiler, atomics: Provide READ_ONCE_NOCHECK () "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-10-14 19:10 +0200
linux-next: build problems (Was: [PATCH v3 1/2] Provide READ_ONCE_NOCHECK()) Stephen Rothwell <sfr@canb.auug.org.au> - 2015-10-15 11:20 +0200
Re: linux-next: build problems (Was: [PATCH v3 1/2] Provide READ_ONCE_NOCHECK()) Andrey Ryabinin <aryabinin@virtuozzo.com> - 2015-10-15 12:10 +0200
[PATCH] compiler, READ_ONCE: Fix build failure with some older GCC Andrey Ryabinin <aryabinin@virtuozzo.com> - 2015-10-15 12:30 +0200
Re: [PATCH] compiler, READ_ONCE: Fix build failure with some older GCC Ingo Molnar <mingo@kernel.org> - 2015-10-15 13:40 +0200
[PATCH v3 2/2] x86/process: Silence KASAN warnings in get_wchan() Andrey Ryabinin <aryabinin@virtuozzo.com> - 2015-10-13 17:40 +0200
[tip:locking/urgent] x86/mm: Silence KASAN warnings in get_wchan( ) tip-bot for Andrey Ryabinin <tipbot@zytor.com> - 2015-10-14 17:40 +0200
[PATCH v4 2/2] x86/mm: Silence KASAN warnings in get_wchan() Andrey Ryabinin <aryabinin@virtuozzo.com> - 2015-10-16 11:50 +0200
[PATCH v4 0/2] Andrey Ryabinin <aryabinin@virtuozzo.com> - 2015-10-16 11:50 +0200
[PATCH v4 1/2] compiler, atomics: Provide READ_ONCE_NOKSAN() Andrey Ryabinin <aryabinin@virtuozzo.com> - 2015-10-16 11:50 +0200
Re: [PATCH v4 1/2] compiler, atomics: Provide READ_ONCE_NOKSAN() Peter Zijlstra <peterz@infradead.org> - 2015-10-16 12:10 +0200
Re: [PATCH v4 1/2] compiler, atomics: Provide READ_ONCE_NOKSAN() Andrey Ryabinin <aryabinin@virtuozzo.com> - 2015-10-16 13:00 +0200
Re: [PATCH v4 1/2] compiler, atomics: Provide READ_ONCE_NOKSAN() Peter Zijlstra <peterz@infradead.org> - 2015-10-16 13:10 +0200
Re: [PATCH v4 1/2] compiler, atomics: Provide READ_ONCE_NOKSAN() Borislav Petkov <bp@alien8.de> - 2015-10-16 12:40 +0200
Re: [PATCH v4 1/2] compiler, atomics: Provide READ_ONCE_NOKSAN() Andrey Ryabinin <aryabinin@virtuozzo.com> - 2015-10-16 14:00 +0200
Re: [PATCH v4 1/2] compiler, atomics: Provide READ_ONCE_NOKSAN() Ingo Molnar <mingo@kernel.org> - 2015-10-18 09:30 +0200
Re: [PATCH v4 1/2] compiler, atomics: Provide READ_ONCE_NOKSAN() "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2015-10-16 18:10 +0200
[PATCH v4 0/2] Silence KASAN warnings in get_wchan() Andrey Ryabinin <aryabinin@virtuozzo.com> - 2015-10-16 11:50 +0200
[PATCH v5 2/2] x86/mm: Silence KASAN warnings in get_wchan() Andrey Ryabinin <aryabinin@virtuozzo.com> - 2015-10-19 10:40 +0200
[tip:x86/urgent] x86/mm, kasan: Silence KASAN warnings in get_wchan() tip-bot for Andrey Ryabinin <tipbot@zytor.com> - 2015-10-20 11:50 +0200
[PATCH v5 0/2] Silence KASAN warnings in get_wchan() Andrey Ryabinin <aryabinin@virtuozzo.com> - 2015-10-19 10:40 +0200
[PATCH v5 1/2] compiler, atomics: Provide READ_ONCE_NOCHECK() Andrey Ryabinin <aryabinin@virtuozzo.com> - 2015-10-19 10:40 +0200
[tip:x86/urgent] compiler, atomics, kasan: Provide READ_ONCE_NOCHECK() tip-bot for Andrey Ryabinin <tipbot@zytor.com> - 2015-10-20 11:50 +0200
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