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Subject[PATCH 3.19 71/75] arm64: percpu: Make this_cpu accessors pre-empt safe
Date
3.19-stable review patch.  If anyone has any objections, please let me know.

------------------

From: Steve Capper <steve.capper@linaro.org>

commit f3eab7184ddcd4867cf42e3274ba24a66e1e093d upstream.

this_cpu operations were implemented for arm64 in:
5284e1b arm64: xchg: Implement cmpxchg_double
f97fc81 arm64: percpu: Implement this_cpu operations

Unfortunately, it is possible for pre-emption to take place between
address generation and data access. This can lead to cases where data
is being manipulated by this_cpu for a different CPU than it was
called on. Which effectively breaks the spec.

This patch disables pre-emption for the this_cpu operations
guaranteeing that address generation and data manipulation take place
without a pre-emption in-between.

Fixes: 5284e1b4bc8a ("arm64: xchg: Implement cmpxchg_double")
Fixes: f97fc810798c ("arm64: percpu: Implement this_cpu operations")
Reported-by: Mark Rutland <mark.rutland@arm.com>
Acked-by: Will Deacon <will.deacon@arm.com>
Signed-off-by: Steve Capper <steve.capper@linaro.org>
[catalin.marinas@arm.com: remove space after type cast]
Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

---
arch/arm64/include/asm/cmpxchg.h | 30 ++++++++++++++++++++------
arch/arm64/include/asm/percpu.h | 44 +++++++++++++++++++++++++++++----------
2 files changed, 56 insertions(+), 18 deletions(-)

--- a/arch/arm64/include/asm/cmpxchg.h
+++ b/arch/arm64/include/asm/cmpxchg.h
@@ -246,14 +246,30 @@ static inline unsigned long __cmpxchg_mb
__ret; \
})

-#define this_cpu_cmpxchg_1(ptr, o, n) cmpxchg_local(raw_cpu_ptr(&(ptr)), o, n)
-#define this_cpu_cmpxchg_2(ptr, o, n) cmpxchg_local(raw_cpu_ptr(&(ptr)), o, n)
-#define this_cpu_cmpxchg_4(ptr, o, n) cmpxchg_local(raw_cpu_ptr(&(ptr)), o, n)
-#define this_cpu_cmpxchg_8(ptr, o, n) cmpxchg_local(raw_cpu_ptr(&(ptr)), o, n)
+#define _protect_cmpxchg_local(pcp, o, n) \
+({ \
+ typeof(*raw_cpu_ptr(&(pcp))) __ret; \
+ preempt_disable(); \
+ __ret = cmpxchg_local(raw_cpu_ptr(&(pcp)), o, n); \
+ preempt_enable(); \
+ __ret; \
+})
+
+#define this_cpu_cmpxchg_1(ptr, o, n) _protect_cmpxchg_local(ptr, o, n)
+#define this_cpu_cmpxchg_2(ptr, o, n) _protect_cmpxchg_local(ptr, o, n)
+#define this_cpu_cmpxchg_4(ptr, o, n) _protect_cmpxchg_local(ptr, o, n)
+#define this_cpu_cmpxchg_8(ptr, o, n) _protect_cmpxchg_local(ptr, o, n)

-#define this_cpu_cmpxchg_double_8(ptr1, ptr2, o1, o2, n1, n2) \
- cmpxchg_double_local(raw_cpu_ptr(&(ptr1)), raw_cpu_ptr(&(ptr2)), \
- o1, o2, n1, n2)
+#define this_cpu_cmpxchg_double_8(ptr1, ptr2, o1, o2, n1, n2) \
+({ \
+ int __ret; \
+ preempt_disable(); \
+ __ret = cmpxchg_double_local( raw_cpu_ptr(&(ptr1)), \
+ raw_cpu_ptr(&(ptr2)), \
+ o1, o2, n1, n2); \
+ preempt_enable(); \
+ __ret; \
+})

#define cmpxchg64(ptr,o,n) cmpxchg((ptr),(o),(n))
#define cmpxchg64_local(ptr,o,n) cmpxchg_local((ptr),(o),(n))
--- a/arch/arm64/include/asm/percpu.h
+++ b/arch/arm64/include/asm/percpu.h
@@ -204,25 +204,47 @@ static inline unsigned long __percpu_xch
return ret;
}

+#define _percpu_read(pcp) \
+({ \
+ typeof(pcp) __retval; \
+ preempt_disable(); \
+ __retval = (typeof(pcp))__percpu_read(raw_cpu_ptr(&(pcp)), \
+ sizeof(pcp)); \
+ preempt_enable(); \
+ __retval; \
+})
+
+#define _percpu_write(pcp, val) \
+do { \
+ preempt_disable(); \
+ __percpu_write(raw_cpu_ptr(&(pcp)), (unsigned long)(val), \
+ sizeof(pcp)); \
+ preempt_enable(); \
+} while(0) \
+
+#define _pcp_protect(operation, pcp, val) \
+({ \
+ typeof(pcp) __retval; \
+ preempt_disable(); \
+ __retval = (typeof(pcp))operation(raw_cpu_ptr(&(pcp)), \
+ (val), sizeof(pcp)); \
+ preempt_enable(); \
+ __retval; \
+})
+
#define _percpu_add(pcp, val) \
- __percpu_add(raw_cpu_ptr(&(pcp)), val, sizeof(pcp))
+ _pcp_protect(__percpu_add, pcp, val)

-#define _percpu_add_return(pcp, val) (typeof(pcp)) (_percpu_add(pcp, val))
+#define _percpu_add_return(pcp, val) _percpu_add(pcp, val)

#define _percpu_and(pcp, val) \
- __percpu_and(raw_cpu_ptr(&(pcp)), val, sizeof(pcp))
+ _pcp_protect(__percpu_and, pcp, val)

#define _percpu_or(pcp, val) \
- __percpu_or(raw_cpu_ptr(&(pcp)), val, sizeof(pcp))
-
-#define _percpu_read(pcp) (typeof(pcp)) \
- (__percpu_read(raw_cpu_ptr(&(pcp)), sizeof(pcp)))
-
-#define _percpu_write(pcp, val) \
- __percpu_write(raw_cpu_ptr(&(pcp)), (unsigned long)(val), sizeof(pcp))
+ _pcp_protect(__percpu_or, pcp, val)

#define _percpu_xchg(pcp, val) (typeof(pcp)) \
- (__percpu_xchg(raw_cpu_ptr(&(pcp)), (unsigned long)(val), sizeof(pcp)))
+ _pcp_protect(__percpu_xchg, pcp, (unsigned long)(val))

#define this_cpu_add_1(pcp, val) _percpu_add(pcp, val)
#define this_cpu_add_2(pcp, val) _percpu_add(pcp, val)



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