Fix x86_this_cpu_variable_test_bit(), which is implemented with
wrong asm template, where argument 2 (count argument) is considered
as percpu variable. However, x86_this_cpu_test_bit() is currently
used exclusively with constant bit number argument, so the called
x86_this_cpu_variable_test_bit() function is never instantiated.
The fix introduces named assembler operands to prevent this kind
of errors.
Also rewrite the whole family of x86_this_cpu_test_bit() functions
as macros, so standard __my_cpu_var() and raw_cpu_read() macros
can be used on percpu variables. This approach considerably
simplifies implementation of functions and also introduces standard
checks on accessed percpu variables.
No functional changes intended.
Signed-off-by: Uros Bizjak <[email protected]>
Cc: Ingo Molnar <[email protected]>
Cc: Andy Lutomirski <[email protected]>
Cc: Brian Gerst <[email protected]>
Cc: Denys Vlasenko <[email protected]>
Cc: H. Peter Anvin <[email protected]>
Cc: Linus Torvalds <[email protected]>
Cc: Peter Zijlstra <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Josh Poimboeuf <[email protected]>
---
arch/um/include/asm/cpufeature.h | 3 +-
arch/x86/include/asm/cpufeature.h | 3 +-
arch/x86/include/asm/percpu.h | 51 +++++++++++++------------------
3 files changed, 24 insertions(+), 33 deletions(-)
diff --git a/arch/um/include/asm/cpufeature.h b/arch/um/include/asm/cpufeature.h
index 66fe06db872f..1eb8b834fbec 100644
--- a/arch/um/include/asm/cpufeature.h
+++ b/arch/um/include/asm/cpufeature.h
@@ -38,8 +38,7 @@ extern const char * const x86_bug_flags[NBUGINTS*32];
#define this_cpu_has(bit) \
(__builtin_constant_p(bit) && REQUIRED_MASK_BIT_SET(bit) ? 1 : \
- x86_this_cpu_test_bit(bit, \
- (unsigned long __percpu *)&cpu_info.x86_capability))
+ x86_this_cpu_test_bit(bit, cpu_info.x86_capability))
/*
* This macro is for detection of features which need kernel
diff --git a/arch/x86/include/asm/cpufeature.h b/arch/x86/include/asm/cpufeature.h
index f95e1c8b7c01..7d527467ab9c 100644
--- a/arch/x86/include/asm/cpufeature.h
+++ b/arch/x86/include/asm/cpufeature.h
@@ -127,8 +127,7 @@ extern const char * const x86_bug_flags[NBUGINTS*32];
#define this_cpu_has(bit) \
(__builtin_constant_p(bit) && REQUIRED_MASK_BIT_SET(bit) ? 1 : \
- x86_this_cpu_test_bit(bit, \
- (unsigned long __percpu *)&cpu_info.x86_capability))
+ x86_this_cpu_test_bit(bit, cpu_info.x86_capability))
/*
* This macro is for detection of features which need kernel
diff --git a/arch/x86/include/asm/percpu.h b/arch/x86/include/asm/percpu.h
index 20696df5d567..d6ff0db32209 100644
--- a/arch/x86/include/asm/percpu.h
+++ b/arch/x86/include/asm/percpu.h
@@ -96,7 +96,7 @@
#endif /* CONFIG_SMP */
#define __my_cpu_type(var) typeof(var) __percpu_seg_override
-#define __my_cpu_ptr(ptr) (__my_cpu_type(*ptr)*)(__force uintptr_t)(ptr)
+#define __my_cpu_ptr(ptr) (__my_cpu_type(*(ptr))*)(__force uintptr_t)(ptr)
#define __my_cpu_var(var) (*__my_cpu_ptr(&(var)))
#define __percpu_arg(x) __percpu_prefix "%" #x
#define __force_percpu_arg(x) __force_percpu_prefix "%" #x
@@ -568,36 +568,29 @@ do { \
#define this_cpu_read_stable_8(pcp) ({ BUILD_BUG(); (typeof(pcp))0; })
#endif
-static __always_inline bool x86_this_cpu_constant_test_bit(unsigned int nr,
- const unsigned long __percpu *addr)
-{
- unsigned long __percpu *a =
- (unsigned long __percpu *)addr + nr / BITS_PER_LONG;
-
-#ifdef CONFIG_X86_64
- return ((1UL << (nr % BITS_PER_LONG)) & raw_cpu_read_8(*a)) != 0;
-#else
- return ((1UL << (nr % BITS_PER_LONG)) & raw_cpu_read_4(*a)) != 0;
-#endif
-}
-
-static inline bool x86_this_cpu_variable_test_bit(int nr,
- const unsigned long __percpu *addr)
-{
- bool oldbit;
-
- asm volatile("btl "__percpu_arg(2)",%1"
- CC_SET(c)
- : CC_OUT(c) (oldbit)
- : "m" (*__my_cpu_ptr((unsigned long __percpu *)(addr))), "Ir" (nr));
+#define x86_this_cpu_constant_test_bit(_nr, _var) \
+({ \
+ unsigned long __percpu *addr__ = \
+ (unsigned long __percpu *)&(_var) + ((_nr) / BITS_PER_LONG); \
+ !!((1UL << ((_nr) % BITS_PER_LONG)) & raw_cpu_read(*addr__)); \
+})
- return oldbit;
-}
+#define x86_this_cpu_variable_test_bit(_nr, _var) \
+({ \
+ bool oldbit; \
+ \
+ asm volatile("btl %[nr], " __percpu_arg([var]) \
+ CC_SET(c) \
+ : CC_OUT(c) (oldbit) \
+ : [var] "m" (__my_cpu_var(_var)), \
+ [nr] "rI" (_nr)); \
+ oldbit; \
+})
-#define x86_this_cpu_test_bit(nr, addr) \
- (__builtin_constant_p((nr)) \
- ? x86_this_cpu_constant_test_bit((nr), (addr)) \
- : x86_this_cpu_variable_test_bit((nr), (addr)))
+#define x86_this_cpu_test_bit(_nr, _var) \
+ (__builtin_constant_p(_nr) \
+ ? x86_this_cpu_constant_test_bit(_nr, _var) \
+ : x86_this_cpu_variable_test_bit(_nr, _var))
#include <asm-generic/percpu.h>
--
2.42.0
* Uros Bizjak <[email protected]> wrote:
> Fix x86_this_cpu_variable_test_bit(), which is implemented with
> wrong asm template, where argument 2 (count argument) is considered
> as percpu variable. However, x86_this_cpu_test_bit() is currently
> used exclusively with constant bit number argument, so the called
> x86_this_cpu_variable_test_bit() function is never instantiated.
> The fix introduces named assembler operands to prevent this kind
> of errors.
>
> Also rewrite the whole family of x86_this_cpu_test_bit() functions
> as macros, so standard __my_cpu_var() and raw_cpu_read() macros
> can be used on percpu variables. This approach considerably
> simplifies implementation of functions and also introduces standard
> checks on accessed percpu variables.
>
> No functional changes intended.
Could you please split this into at least two patches?
Hint: 'also' in a changelog paragraph is an indicator of a new patch
being justified, in like 80% of the cases. :-)
Thanks,
Ingo