b9a50f7490
DCACHE_WORD_ACCESS uses the word-at-a-time API for optimised string comparisons in the vfs layer. This patch implements support for load_unaligned_zeropad for ARM CPUs with native support for unaligned memory accesses (v6+) when running little-endian. Reviewed-by: Nicolas Pitre <nico@linaro.org> Signed-off-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Russell King <rmk+kernel@arm.linux.org.uk>
96 lines
2 KiB
C
96 lines
2 KiB
C
#ifndef __ASM_ARM_WORD_AT_A_TIME_H
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#define __ASM_ARM_WORD_AT_A_TIME_H
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#ifndef __ARMEB__
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/*
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* Little-endian word-at-a-time zero byte handling.
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* Heavily based on the x86 algorithm.
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*/
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#include <linux/kernel.h>
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struct word_at_a_time {
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const unsigned long one_bits, high_bits;
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};
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#define WORD_AT_A_TIME_CONSTANTS { REPEAT_BYTE(0x01), REPEAT_BYTE(0x80) }
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static inline unsigned long has_zero(unsigned long a, unsigned long *bits,
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const struct word_at_a_time *c)
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{
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unsigned long mask = ((a - c->one_bits) & ~a) & c->high_bits;
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*bits = mask;
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return mask;
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}
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#define prep_zero_mask(a, bits, c) (bits)
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static inline unsigned long create_zero_mask(unsigned long bits)
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{
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bits = (bits - 1) & ~bits;
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return bits >> 7;
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}
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static inline unsigned long find_zero(unsigned long mask)
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{
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unsigned long ret;
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#if __LINUX_ARM_ARCH__ >= 5
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/* We have clz available. */
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ret = fls(mask) >> 3;
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#else
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/* (000000 0000ff 00ffff ffffff) -> ( 1 1 2 3 ) */
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ret = (0x0ff0001 + mask) >> 23;
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/* Fix the 1 for 00 case */
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ret &= mask;
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#endif
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return ret;
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}
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#ifdef CONFIG_DCACHE_WORD_ACCESS
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#define zero_bytemask(mask) (mask)
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/*
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* Load an unaligned word from kernel space.
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*
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* In the (very unlikely) case of the word being a page-crosser
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* and the next page not being mapped, take the exception and
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* return zeroes in the non-existing part.
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*/
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static inline unsigned long load_unaligned_zeropad(const void *addr)
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{
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unsigned long ret, offset;
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/* Load word from unaligned pointer addr */
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asm(
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"1: ldr %0, [%2]\n"
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"2:\n"
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" .pushsection .fixup,\"ax\"\n"
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" .align 2\n"
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"3: and %1, %2, #0x3\n"
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" bic %2, %2, #0x3\n"
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" ldr %0, [%2]\n"
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" lsl %1, %1, #0x3\n"
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" lsr %0, %0, %1\n"
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" b 2b\n"
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" .popsection\n"
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" .pushsection __ex_table,\"a\"\n"
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" .align 3\n"
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" .long 1b, 3b\n"
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" .popsection"
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: "=&r" (ret), "=&r" (offset)
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: "r" (addr), "Qo" (*(unsigned long *)addr));
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return ret;
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}
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#endif /* DCACHE_WORD_ACCESS */
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#else /* __ARMEB__ */
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#include <asm-generic/word-at-a-time.h>
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#endif
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#endif /* __ASM_ARM_WORD_AT_A_TIME_H */
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