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Commit fce877e3 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Ingo Molnar
Browse files

bitops: Ensure the compile time HWEIGHT is only used for such 



Avoid accidental misuse by failing to compile things

Suggested-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarPeter Zijlstra <a.p.zijlstra@chello.nl>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
LKML-Reference: <new-submission>
Signed-off-by: default avatarIngo Molnar <mingo@elte.hu>
parent 8c48e444

arch/x86/kernel/cpu/perf_event.c

+7 −3
Original line number Diff line number Diff line
@@ -93,13 +93,16 @@ struct cpu_hw_events { 
	struct perf_event	*event_list[X86_PMC_IDX_MAX]; /* in enabled order */

};



#define EVENT_CONSTRAINT(c, n, m) {	\

#define __EVENT_CONSTRAINT(c, n, m, w) {\

	{ .idxmsk64[0] = (n) },		\

	.code = (c),			\

	.cmask = (m),			\

	.weight = HWEIGHT64((u64)(n)),	\

	.weight = (w),			\

}



#define EVENT_CONSTRAINT(c, n, m)	\

	__EVENT_CONSTRAINT(c, n, m, HWEIGHT(n))



#define INTEL_EVENT_CONSTRAINT(c, n)	\

	EVENT_CONSTRAINT(c, n, INTEL_ARCH_EVTSEL_MASK)
@@ -2622,7 +2625,8 @@ void __init init_hw_perf_events(void) 
	register_die_notifier(&perf_event_nmi_notifier);



	unconstrained = (struct event_constraint)

		EVENT_CONSTRAINT(0, (1ULL << x86_pmu.num_events) - 1, 0);

		__EVENT_CONSTRAINT(0, (1ULL << x86_pmu.num_events) - 1,

				   0, x86_pmu.num_events);



	pr_info("... version:                %d\n",     x86_pmu.version);

	pr_info("... bit width:              %d\n",     x86_pmu.event_bits);

include/linux/bitops.h

+22 −11
Original line number Diff line number Diff line
@@ -45,8 +45,13 @@ static inline unsigned long hweight_long(unsigned long w) 
	return sizeof(w) == 4 ? hweight32(w) : hweight64(w);

}



/*

 * Clearly slow versions of the hweightN() functions, their benefit is

 * of course compile time evaluation of constant arguments.

 */

#define HWEIGHT8(w)					\

      (	(!!((w) & (1ULL << 0))) +	\

      (	BUILD_BUG_ON_ZERO(!__builtin_constant_p(w)) +	\

	(!!((w) & (1ULL << 0))) +			\

	(!!((w) & (1ULL << 1))) +			\

	(!!((w) & (1ULL << 2))) +			\

	(!!((w) & (1ULL << 3))) +			\
@@ -55,9 +60,15 @@ static inline unsigned long hweight_long(unsigned long w) 
	(!!((w) & (1ULL << 6))) +			\

	(!!((w) & (1ULL << 7)))	)



#define HWEIGHT16(w) (HWEIGHT8(w)  + HWEIGHT8(w >> 8))

#define HWEIGHT32(w) (HWEIGHT16(w) + HWEIGHT16(w >> 16))

#define HWEIGHT64(w) (HWEIGHT32(w) + HWEIGHT32(w >> 32))

#define HWEIGHT16(w) (HWEIGHT8(w)  + HWEIGHT8((w) >> 8))

#define HWEIGHT32(w) (HWEIGHT16(w) + HWEIGHT16((w) >> 16))

#define HWEIGHT64(w) (HWEIGHT32(w) + HWEIGHT32((w) >> 32))



/*

 * Type invariant version that simply casts things to the

 * largest type.

 */

#define HWEIGHT(w)   HWEIGHT64((u64)(w))



/**

 * rol32 - rotate a 32-bit value left