Commit cb0f8003 authored by Kumar Kartikeya Dwivedi's avatar Kumar Kartikeya Dwivedi Committed by Alexei Starovoitov
Browse files

bitops: Add non-atomic bitops for pointers 



cpumap needs to set, clear, and test the lowest bit in skb pointer in
various places. To make these checks less noisy, add pointer friendly
bitop macros that also do some typechecking to sanitize the argument.

These wrap the non-atomic bitops __set_bit, __clear_bit, and test_bit
but for pointer arguments. Pointer's address has to be passed in and it
is treated as an unsigned long *, since width and representation of
pointer and unsigned long match on targets Linux supports. They are
prefixed with double underscore to indicate lack of atomicity.

Signed-off-by: default avatarKumar Kartikeya Dwivedi <memxor@gmail.com>
Signed-off-by: default avatarAlexei Starovoitov <ast@kernel.org>
Reviewed-by: default avatarToke Høiland-Jørgensen <toke@redhat.com>
Link: https://lore.kernel.org/bpf/20210702111825.491065-3-memxor@gmail.com
parent fe21cb91

include/linux/bitops.h

+50 −0
Original line number Diff line number Diff line
@@ -4,6 +4,7 @@ 


#include <asm/types.h>

#include <linux/bits.h>

#include <linux/typecheck.h>



#include <uapi/linux/kernel.h>
@@ -253,6 +254,55 @@ static __always_inline void __assign_bit(long nr, volatile unsigned long *addr, 
		__clear_bit(nr, addr);

}



/**

 * __ptr_set_bit - Set bit in a pointer's value

 * @nr: the bit to set

 * @addr: the address of the pointer variable

 *

 * Example:

 *	void *p = foo();

 *	__ptr_set_bit(bit, &p);

 */

#define __ptr_set_bit(nr, addr)                         \

	({                                              \

		typecheck_pointer(*(addr));             \

		__set_bit(nr, (unsigned long *)(addr)); \

	})



/**

 * __ptr_clear_bit - Clear bit in a pointer's value

 * @nr: the bit to clear

 * @addr: the address of the pointer variable

 *

 * Example:

 *	void *p = foo();

 *	__ptr_clear_bit(bit, &p);

 */

#define __ptr_clear_bit(nr, addr)                         \

	({                                                \

		typecheck_pointer(*(addr));               \

		__clear_bit(nr, (unsigned long *)(addr)); \

	})



/**

 * __ptr_test_bit - Test bit in a pointer's value

 * @nr: the bit to test

 * @addr: the address of the pointer variable

 *

 * Example:

 *	void *p = foo();

 *	if (__ptr_test_bit(bit, &p)) {

 *	        ...

 *	} else {

 *		...

 *	}

 */

#define __ptr_test_bit(nr, addr)                       \

	({                                             \

		typecheck_pointer(*(addr));            \

		test_bit(nr, (unsigned long *)(addr)); \

	})



#ifdef __KERNEL__



#ifndef set_mask_bits

include/linux/typecheck.h

+9 −0
Original line number Diff line number Diff line
@@ -22,4 +22,13 @@ 
	(void)__tmp; \

})



/*

 * Check at compile time that something is a pointer type.

 */

#define typecheck_pointer(x) \

({	typeof(x) __dummy; \

	(void)sizeof(*__dummy); \

	1; \

})



#endif		/* TYPECHECK_H_INCLUDED */