#ifndef _ASM_X86_BITOPS_H #define _ASM_X86_BITOPS_H /* * Copyright 1992, Linus Torvalds. * * Note: inlines with more than a single statement should be marked * __always_inline to avoid problems with older gcc's inlining heuristics. */ #ifndef _LINUX_BITOPS_H #error only can be included directly #endif #include #include #include #include #if BITS_PER_LONG == 32 # define _BITOPS_LONG_SHIFT 5 #elif BITS_PER_LONG == 64 # define _BITOPS_LONG_SHIFT 6 #else # error "Unexpected BITS_PER_LONG" #endif #define BIT_64(n) (U64_C(1) << (n)) /* * These have to be done with inline assembly: that way the bit-setting * is guaranteed to be atomic. All bit operations return 0 if the bit * was cleared before the operation and != 0 if it was not. * * bit 0 is the LSB of addr; bit 32 is the LSB of (addr+1). */ #if __GNUC__ < 4 || (__GNUC__ == 4 && __GNUC_MINOR__ < 1) /* Technically wrong, but this avoids compilation errors on some gcc versions. */ #define BITOP_ADDR(x) "=m" (*(volatile long *) (x)) #else #define BITOP_ADDR(x) "+m" (*(volatile long *) (x)) #endif #define ADDR BITOP_ADDR(addr) /* * We do the locked ops that don't return the old value as * a mask operation on a byte. */ #define IS_IMMEDIATE(nr) (__builtin_constant_p(nr)) #define CONST_MASK_ADDR(nr, addr) BITOP_ADDR((void *)(addr) + ((nr)>>3)) #define CONST_MASK(nr) (1 << ((nr) & 7)) /** * set_bit - Atomically set a bit in memory * @nr: the bit to set * @addr: the address to start counting from * * This function is atomic and may not be reordered. See __set_bit() * if you do not require the atomic guarantees. * * Note: there are no guarantees that this function will not be reordered * on non x86 architectures, so if you are writing portable code, * make sure not to rely on its reordering guarantees. * * Note that @nr may be almost arbitrarily large; this function is not * restricted to acting on a single-word quantity. */ static __always_inline void set_bit(long nr, volatile unsigned long *addr) { if (IS_IMMEDIATE(nr)) { asm volatile(LOCK_PREFIX "orb %1,%0" : CONST_MASK_ADDR(nr, addr) : "iq" ((u8)CONST_MASK(nr)) : "memory"); } else { asm volatile(LOCK_PREFIX "bts %1,%0" : BITOP_ADDR(addr) : "Ir" (nr) : "memory"); } } /** * __set_bit - Set a bit in memory * @nr: the bit to set * @addr: the address to start counting from * * Unlike set_bit(), this function is non-atomic and may be reordered. * If it's called on the same region of memory simultaneously, the effect * may be that only one operation succeeds. */ static __always_inline void __set_bit(long nr, volatile unsigned long *addr) { asm volatile("bts %1,%0" : ADDR : "Ir" (nr) : "memory"); } /** * clear_bit - Clears a bit in memory * @nr: Bit to clear * @addr: Address to start counting from * * clear_bit() is atomic and may not be reordered. However, it does * not contain a memory barrier, so if it is used for locking purposes, * you should call smp_mb__before_atomic() and/or smp_mb__after_atomic() * in order to ensure changes are visible on other processors. */ static __always_inline void clear_bit(long nr, volatile unsigned long *addr) { if (IS_IMMEDIATE(nr)) { asm volatile(LOCK_PREFIX "andb %1,%0" : CONST_MASK_ADDR(nr, addr) : "iq" ((u8)~CONST_MASK(nr))); } else { asm volatile(LOCK_PREFIX "btr %1,%0" : BITOP_ADDR(addr) : "Ir" (nr)); } } /* * clear_bit_unlock - Clears a bit in memory * @nr: Bit to clear * @addr: Address to start counting from * * clear_bit() is atomic and implies release semantics before the memory * operation. It can be used for an unlock. */ static __always_inline void clear_bit_unlock(long nr, volatile unsigned long *addr) { barrier(); clear_bit(nr, addr); } static __always_inline void __clear_bit(long nr, volatile unsigned long *addr) { asm volatile("btr %1,%0" : ADDR : "Ir" (nr)); } /* * __clear_bit_unlock - Clears a bit in memory * @nr: Bit to clear * @addr: Address to start counting from * * __clear_bit() is non-atomic and implies release semantics before the memory * operation. It can be used for an unlock if no other CPUs can concurrently * modify other bits in the word. * * No memory barrier is required here, because x86 cannot reorder stores past * older loads. Same principle as spin_unlock. */ static __always_inline void __clear_bit_unlock(long nr, volatile unsigned long *addr) { barrier(); __clear_bit(nr, addr); } /** * __change_bit - Toggle a bit in memory * @nr: the bit to change * @addr: the address to start counting from * * Unlike change_bit(), this function is non-atomic and may be reordered. * If it's called on the same region of memory simultaneously, the effect * may be that only one operation succeeds. */ static __always_inline void __change_bit(long nr, volatile unsigned long *addr) { asm volatile("btc %1,%0" : ADDR : "Ir" (nr)); } /** * change_bit - Toggle a bit in memory * @nr: Bit to change * @addr: Address to start counting from * * change_bit() is atomic and may not be reordered. * Note that @nr may be almost arbitrarily large; this function is not * restricted to acting on a single-word quantity. */ static __always_inline void change_bit(long nr, volatile unsigned long *addr) { if (IS_IMMEDIATE(nr)) { asm volatile(LOCK_PREFIX "xorb %1,%0" : CONST_MASK_ADDR(nr, addr) : "iq" ((u8)CONST_MASK(nr))); } else { asm volatile(LOCK_PREFIX "btc %1,%0" : BITOP_ADDR(addr) : "Ir" (nr)); } } /** * test_and_set_bit - Set a bit and return its old value * @nr: Bit to set * @addr: Address to count from * * This operation is atomic and cannot be reordered. * It also implies a memory barrier. */ static __always_inline int test_and_set_bit(long nr, volatile unsigned long *addr) { GEN_BINARY_RMWcc(LOCK_PREFIX "bts", *addr, "Ir", nr, "%0", "c"); } /** * test_and_set_bit_lock - Set a bit and return its old value for lock * @nr: Bit to set * @addr: Address to count from * * This is the same as test_and_set_bit on x86. */ static __always_inline int test_and_set_bit_lock(long nr, volatile unsigned long *addr) { return test_and_set_bit(nr, addr); } /** * __test_and_set_bit - Set a bit and return its old value * @nr: Bit to set * @addr: Address to count from * * This operation is non-atomic and can be reordered. * If two examples of this operation race, one can appear to succeed * but actually fail. You must protect multiple accesses with a lock. */ static __always_inline int __test_and_set_bit(long nr, volatile unsigned long *addr) { unsigned char oldbit; asm("bts %2,%1\n\t" "setc %0" : "=qm" (oldbit), ADDR : "Ir" (nr)); return oldbit; } /** * test_and_clear_bit - Clear a bit and return its old value * @nr: Bit to clear * @addr: Address to count from * * This operation is atomic and cannot be reordered. * It also implies a memory barrier. */ static __always_inline int test_and_clear_bit(long nr, volatile unsigned long *addr) { GEN_BINARY_RMWcc(LOCK_PREFIX "btr", *addr, "Ir", nr, "%0", "c"); } /** * __test_and_clear_bit - Clear a bit and return its old value * @nr: Bit to clear * @addr: Address to count from * * This operation is non-atomic and can be reordered. * If two examples of this operation race, one can appear to succeed * but actually fail. You must protect multiple accesses with a lock. * * Note: the operation is performed atomically with respect to * the local CPU, but not other CPUs. Portable code should not * rely on this behaviour. * KVM relies on this behaviour on x86 for modifying memory that is also * accessed from a hypervisor on the same CPU if running in a VM: don't change * this without also updating arch/x86/kernel/kvm.c */ static __always_inline int __test_and_clear_bit(long nr, volatile unsigned long *addr) { unsigned char oldbit; asm volatile("btr %2,%1\n\t" "setc %0" : "=qm" (oldbit), ADDR : "Ir" (nr)); return oldbit; } /* WARNING: non atomic and it can be reordered! */ static __always_inline int __test_and_change_bit(long nr, volatile unsigned long *addr) { unsigned char oldbit; asm volatile("btc %2,%1\n\t" "setc %0" : "=qm" (oldbit), ADDR : "Ir" (nr) : "memory"); return oldbit; } /** * test_and_change_bit - Change a bit and return its old value * @nr: Bit to change * @addr: Address to count from * * This operation is atomic and cannot be reordered. * It also implies a memory barrier. */ static __always_inline int test_and_change_bit(long nr, volatile unsigned long *addr) { GEN_BINARY_RMWcc(LOCK_PREFIX "btc", *addr, "Ir", nr, "%0", "c"); } static __always_inline int constant_test_bit(long nr, const volatile unsigned long *addr) { return ((1UL << (nr & (BITS_PER_LONG-1))) & (addr[nr >> _BITOPS_LONG_SHIFT])) != 0; } static __always_inline int variable_test_bit(long nr, volatile const unsigned long *addr) { unsigned char oldbit; asm volatile("bt %2,%1\n\t" "setc %0" : "=qm" (oldbit) : "m" (*(unsigned long *)addr), "Ir" (nr)); return oldbit; } #if 0 /* Fool kernel-doc since it doesn't do macros yet */ /** * test_bit - Determine whether a bit is set * @nr: bit number to test * @addr: Address to start counting from */ static int test_bit(int nr, const volatile unsigned long *addr); #endif #define test_bit(nr, addr) \ (__builtin_constant_p((nr)) \ ? constant_test_bit((nr), (addr)) \ : variable_test_bit((nr), (addr))) /** * __ffs - find first set bit in word * @word: The word to search * * Undefined if no bit exists, so code should check against 0 first. */ static __always_inline unsigned long __ffs(unsigned long word) { asm("rep; bsf %1,%0" : "=r" (word) : "rm" (word)); return word; } /** * ffz - find first zero bit in word * @word: The word to search * * Undefined if no zero exists, so code should check against ~0UL first. */ static __always_inline unsigned long ffz(unsigned long word) { asm("rep; bsf %1,%0" : "=r" (word) : "r" (~word)); return word; } /* * __fls: find last set bit in word * @word: The word to search * * Undefined if no set bit exists, so code should check against 0 first. */ static __always_inline unsigned long __fls(unsigned long word) { asm("bsr %1,%0" : "=r" (word) : "rm" (word)); return word; } #undef ADDR #ifdef __KERNEL__ /** * ffs - find first set bit in word * @x: the word to search * * This is defined the same way as the libc and compiler builtin ffs * routines, therefore differs in spirit from the other bitops. * * ffs(value) returns 0 if value is 0 or the position of the first * set bit if value is nonzero. The first (least significant) bit * is at position 1. */ static __always_inline int ffs(int x) { int r; #ifdef CONFIG_X86_64 /* * AMD64 says BSFL won't clobber the dest reg if x==0; Intel64 says the * dest reg is undefined if x==0, but their CPU architect says its * value is written to set it to the same as before, except that the * top 32 bits will be cleared. * * We cannot do this on 32 bits because at the very least some * 486 CPUs did not behave this way. */ asm("bsfl %1,%0" : "=r" (r) : "rm" (x), "0" (-1)); #elif defined(CONFIG_X86_CMOV) asm("bsfl %1,%0\n\t" "cmovzl %2,%0" : "=&r" (r) : "rm" (x), "r" (-1)); #else asm("bsfl %1,%0\n\t" "jnz 1f\n\t" "movl $-1,%0\n" "1:" : "=r" (r) : "rm" (x)); #endif return r + 1; } /** * fls - find last set bit in word * @x: the word to search * * This is defined in a similar way as the libc and compiler builtin * ffs, but returns the position of the most significant set bit. * * fls(value) returns 0 if value is 0 or the position of the last * set bit if value is nonzero. The last (most significant) bit is * at position 32. */ static __always_inline int fls(int x) { int r; #ifdef CONFIG_X86_64 /* * AMD64 says BSRL won't clobber the dest reg if x==0; Intel64 says the * dest reg is undefined if x==0, but their CPU architect says its * value is written to set it to the same as before, except that the * top 32 bits will be cleared. * * We cannot do this on 32 bits because at the very least some * 486 CPUs did not behave this way. */ asm("bsrl %1,%0" : "=r" (r) : "rm" (x), "0" (-1)); #elif defined(CONFIG_X86_CMOV) asm("bsrl %1,%0\n\t" "cmovzl %2,%0" : "=&r" (r) : "rm" (x), "rm" (-1)); #else asm("bsrl %1,%0\n\t" "jnz 1f\n\t" "movl $-1,%0\n" "1:" : "=r" (r) : "rm" (x)); #endif return r + 1; } /** * fls64 - find last set bit in a 64-bit word * @x: the word to search * * This is defined in a similar way as the libc and compiler builtin * ffsll, but returns the position of the most significant set bit. * * fls64(value) returns 0 if value is 0 or the position of the last * set bit if value is nonzero. The last (most significant) bit is * at position 64. */ #ifdef CONFIG_X86_64 static __always_inline int fls64(__u64 x) { int bitpos = -1; /* * AMD64 says BSRQ won't clobber the dest reg if x==0; Intel64 says the * dest reg is undefined if x==0, but their CPU architect says its * value is written to set it to the same as before. */ asm("bsrq %1,%q0" : "+r" (bitpos) : "rm" (x)); return bitpos + 1; } #else #include #endif #include #include #include #include #include #include #endif /* __KERNEL__ */ #endif /* _ASM_X86_BITOPS_H */