| Message ID | 20241208204708.3742696-3-ubizjak@gmail.com (mailing list archive) |
|---|---|
| State | New |
| Headers | show |
| Series | Enable strict percpu address space checks | expand |
On Sun, Dec 08, 2024 at 09:45:17PM +0100, Uros Bizjak wrote: > Define TYPEOF_UNQUAL() to use __typeof_unqual__() as typeof operator > when available, to return unqualified type of the expression. > > Current version of sparse doesn't know anything about __typeof_unqual__() > operator. Avoid the usage of __typeof_unqual__() when sparse checking > is active to prevent sparse errors with unknowing keyword. Ooooh, new toys. I suppose __unqual_scalar_typeof() wants to be using this when available?
On Mon, Dec 9, 2024 at 12:30 PM Peter Zijlstra <peterz@infradead.org> wrote: > > On Sun, Dec 08, 2024 at 09:45:17PM +0100, Uros Bizjak wrote: > > Define TYPEOF_UNQUAL() to use __typeof_unqual__() as typeof operator > > when available, to return unqualified type of the expression. > > > > Current version of sparse doesn't know anything about __typeof_unqual__() > > operator. Avoid the usage of __typeof_unqual__() when sparse checking > > is active to prevent sparse errors with unknowing keyword. > > Ooooh, new toys. > > I suppose __unqual_scalar_typeof() wants to be using this when > available? Yes, the attached patch compiles and boots OK. Uros. diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h index 5d6544545658..87a9ce3ebd13 100644 --- a/include/linux/compiler_types.h +++ b/include/linux/compiler_types.h @@ -486,15 +486,19 @@ struct ftrace_likely_data { * __unqual_scalar_typeof(x) - Declare an unqualified scalar type, leaving * non-scalar types unchanged. */ + +#if defined(CONFIG_CC_HAS_TYPEOF_UNQUAL) && !defined(__CHECKER__) +# define __unqual_scalar_typeof(x) __typeof_unqual__(x) +#else /* * Prefer C11 _Generic for better compile-times and simpler code. Note: 'char' * is not type-compatible with 'signed char', and we define a separate case. */ -#define __scalar_type_to_expr_cases(type) \ + #define __scalar_type_to_expr_cases(type) \ unsigned type: (unsigned type)0, \ signed type: (signed type)0 -#define __unqual_scalar_typeof(x) typeof( \ + #define __unqual_scalar_typeof(x) typeof( \ _Generic((x), \ char: (char)0, \ __scalar_type_to_expr_cases(char), \ @@ -503,6 +507,7 @@ struct ftrace_likely_data { __scalar_type_to_expr_cases(long), \ __scalar_type_to_expr_cases(long long), \ default: (x))) +#endif /* Is this type a native word size -- useful for atomic operations */ #define __native_word(t) \
On Mon, Dec 9, 2024 at 12:30 PM Peter Zijlstra <peterz@infradead.org> wrote: > > On Sun, Dec 08, 2024 at 09:45:17PM +0100, Uros Bizjak wrote: > > Define TYPEOF_UNQUAL() to use __typeof_unqual__() as typeof operator > > when available, to return unqualified type of the expression. > > > > Current version of sparse doesn't know anything about __typeof_unqual__() > > operator. Avoid the usage of __typeof_unqual__() when sparse checking > > is active to prevent sparse errors with unknowing keyword. > > Ooooh, new toys. > > I suppose __unqual_scalar_typeof() wants to be using this when > available? Not only that, the new toy enables clang to check kernel's address spaces in a generic way using address_space attribute. Please find attached a follow-up patch that enables __percpu checks for all targets, supported by clang. Clang is a little bit pickier than gcc about named address space declarations (it warns for use of duplicated address space attribute), so the patch in addition to the obvious +# define __percpu_qual __attribute__((address_space(3))) also fixes a couple of macros that could result in a duplicated address space attribute. The patch, applied as a follow-up to the series, survives allyesconfig compilation with clang-19 and produces a bootable kernel. The patch was tested only for x86_64 target, for other targets a couple of trivial fixes would be necessary (a cast or a substitution of typeof() with TYPEOF_UNQUAL()). AFAICS, the same approach using clang's address_space attribute can be implemented to also check other address spaces: __user, __iommu and __rcu. Uros. diff --git a/include/asm-generic/percpu.h b/include/asm-generic/percpu.h index 02aeca21479a..4109d828a564 100644 --- a/include/asm-generic/percpu.h +++ b/include/asm-generic/percpu.h @@ -16,7 +16,12 @@ * space qualifier). */ #ifndef __percpu_qual -# define __percpu_qual +# if __has_attribute(address_space) && \ + defined(CONFIG_CC_HAS_TYPEOF_UNQUAL) && !defined(__CHECKER__) +# define __percpu_qual __attribute__((address_space(3))) +# else +# define __percpu_qual +# endif #endif #ifdef CONFIG_SMP diff --git a/include/linux/device.h b/include/linux/device.h index 667cb6db9019..1d6a55d5250a 100644 --- a/include/linux/device.h +++ b/include/linux/device.h @@ -431,9 +431,9 @@ static inline int __devm_add_action_or_reset(struct device *dev, void (*action)( * RETURNS: * Pointer to allocated memory on success, NULL on failure. */ -#define devm_alloc_percpu(dev, type) \ - ((typeof(type) __percpu *)__devm_alloc_percpu((dev), sizeof(type), \ - __alignof__(type))) +#define devm_alloc_percpu(dev, type) \ + ((TYPEOF_UNQUAL(type) __percpu *)__devm_alloc_percpu((dev), \ + sizeof(type), __alignof__(type))) void __percpu *__devm_alloc_percpu(struct device *dev, size_t size, size_t align); diff --git a/include/linux/percpu.h b/include/linux/percpu.h index 52b5ea663b9f..c3bf040aba66 100644 --- a/include/linux/percpu.h +++ b/include/linux/percpu.h @@ -148,13 +148,13 @@ extern void __percpu *pcpu_alloc_noprof(size_t size, size_t align, bool reserved alloc_hooks(pcpu_alloc_noprof(_size, _align, true, GFP_KERNEL)) #define alloc_percpu_gfp(type, gfp) \ - (typeof(type) __percpu *)__alloc_percpu_gfp(sizeof(type), \ + (TYPEOF_UNQUAL(type) __percpu *)__alloc_percpu_gfp(sizeof(type), \ __alignof__(type), gfp) #define alloc_percpu(type) \ - (typeof(type) __percpu *)__alloc_percpu(sizeof(type), \ + (TYPEOF_UNQUAL(type) __percpu *)__alloc_percpu(sizeof(type), \ __alignof__(type)) #define alloc_percpu_noprof(type) \ - ((typeof(type) __percpu *)pcpu_alloc_noprof(sizeof(type), \ + ((TYPEOF_UNQUAL(type) __percpu *)pcpu_alloc_noprof(sizeof(type), \ __alignof__(type), false, GFP_KERNEL)) extern void free_percpu(void __percpu *__pdata);
diff --git a/include/linux/compiler.h b/include/linux/compiler.h index 469a64dd6495..ec0429d7a153 100644 --- a/include/linux/compiler.h +++ b/include/linux/compiler.h @@ -321,6 +321,19 @@ static inline void *offset_to_ptr(const int *off) */ #define prevent_tail_call_optimization() mb() +/* + * Define TYPEOF_UNQUAL() to use __typeof_unqual__() as typeof + * operator when available, to return unqualified type of the exp. + * + * XXX: Remove test for __CHECKER__ once + * sparse learns about __typeof_unqual__. + */ +#if defined(CONFIG_CC_HAS_TYPEOF_UNQUAL) && !defined(__CHECKER__) +# define TYPEOF_UNQUAL(exp) __typeof_unqual__(exp) +#else +# define TYPEOF_UNQUAL(exp) __typeof__(exp) +#endif + #include <asm/rwonce.h> #endif /* __LINUX_COMPILER_H */ diff --git a/init/Kconfig b/init/Kconfig index a20e6efd3f0f..c1f9eb3d5f2e 100644 --- a/init/Kconfig +++ b/init/Kconfig @@ -894,6 +894,9 @@ config ARCH_WANT_BATCHED_UNMAP_TLB_FLUSH config CC_HAS_INT128 def_bool !$(cc-option,$(m64-flag) -D__SIZEOF_INT128__=0) && 64BIT +config CC_HAS_TYPEOF_UNQUAL + def_bool $(success,echo 'int foo (int a) { __typeof_unqual__(a) b = a; return b; }' | $(CC) -x c - -S -o /dev/null) + config CC_IMPLICIT_FALLTHROUGH string default "-Wimplicit-fallthrough=5" if CC_IS_GCC && $(cc-option,-Wimplicit-fallthrough=5)