diff options
Diffstat (limited to 'arch/arm/include/asm/word-at-a-time.h')
-rw-r--r-- | arch/arm/include/asm/word-at-a-time.h | 99 |
1 files changed, 99 insertions, 0 deletions
diff --git a/arch/arm/include/asm/word-at-a-time.h b/arch/arm/include/asm/word-at-a-time.h new file mode 100644 index 0000000000..352ab21352 --- /dev/null +++ b/arch/arm/include/asm/word-at-a-time.h @@ -0,0 +1,99 @@ +/* SPDX-License-Identifier: GPL-2.0 */ +#ifndef __ASM_ARM_WORD_AT_A_TIME_H +#define __ASM_ARM_WORD_AT_A_TIME_H + +#ifndef __ARMEB__ + +/* + * Little-endian word-at-a-time zero byte handling. + * Heavily based on the x86 algorithm. + */ +#include <linux/kernel.h> + +struct word_at_a_time { + const unsigned long one_bits, high_bits; +}; + +#define WORD_AT_A_TIME_CONSTANTS { REPEAT_BYTE(0x01), REPEAT_BYTE(0x80) } + +static inline unsigned long has_zero(unsigned long a, unsigned long *bits, + const struct word_at_a_time *c) +{ + unsigned long mask = ((a - c->one_bits) & ~a) & c->high_bits; + *bits = mask; + return mask; +} + +#define prep_zero_mask(a, bits, c) (bits) + +static inline unsigned long create_zero_mask(unsigned long bits) +{ + bits = (bits - 1) & ~bits; + return bits >> 7; +} + +static inline unsigned long find_zero(unsigned long mask) +{ + unsigned long ret; + +#if __LINUX_ARM_ARCH__ >= 5 + /* We have clz available. */ + ret = fls(mask) >> 3; +#else + /* (000000 0000ff 00ffff ffffff) -> ( 1 1 2 3 ) */ + ret = (0x0ff0001 + mask) >> 23; + /* Fix the 1 for 00 case */ + ret &= mask; +#endif + + return ret; +} + +#define zero_bytemask(mask) (mask) + +#else /* __ARMEB__ */ +#include <asm-generic/word-at-a-time.h> +#endif + +#ifdef CONFIG_DCACHE_WORD_ACCESS + +/* + * Load an unaligned word from kernel space. + * + * In the (very unlikely) case of the word being a page-crosser + * and the next page not being mapped, take the exception and + * return zeroes in the non-existing part. + */ +static inline unsigned long load_unaligned_zeropad(const void *addr) +{ + unsigned long ret, offset; + + /* Load word from unaligned pointer addr */ + asm( + "1: ldr %0, [%2]\n" + "2:\n" + " .pushsection .text.fixup,\"ax\"\n" + " .align 2\n" + "3: and %1, %2, #0x3\n" + " bic %2, %2, #0x3\n" + " ldr %0, [%2]\n" + " lsl %1, %1, #0x3\n" +#ifndef __ARMEB__ + " lsr %0, %0, %1\n" +#else + " lsl %0, %0, %1\n" +#endif + " b 2b\n" + " .popsection\n" + " .pushsection __ex_table,\"a\"\n" + " .align 3\n" + " .long 1b, 3b\n" + " .popsection" + : "=&r" (ret), "=&r" (offset) + : "r" (addr), "Qo" (*(unsigned long *)addr)); + + return ret; +} + +#endif /* DCACHE_WORD_ACCESS */ +#endif /* __ASM_ARM_WORD_AT_A_TIME_H */ |