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b776078025
Rewrite load_unaligned_zeropad() to not require .fixup text. This is easiest done using asm-goto-output, where we can stick a C label in the exception table entry. The fallback version isn't nearly so nice but should work. Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org> Reviewed-by: Josh Poimboeuf <jpoimboe@redhat.com> Link: https://lore.kernel.org/r/20211110101326.141775772@infradead.org
135 lines
3.1 KiB
C
135 lines
3.1 KiB
C
/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _ASM_WORD_AT_A_TIME_H
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#define _ASM_WORD_AT_A_TIME_H
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#include <linux/kernel.h>
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/*
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* This is largely generic for little-endian machines, but the
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* optimal byte mask counting is probably going to be something
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* that is architecture-specific. If you have a reliably fast
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* bit count instruction, that might be better than the multiply
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* and shift, for example.
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*/
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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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#ifdef CONFIG_64BIT
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/*
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* Jan Achrenius on G+: microoptimized version of
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* the simpler "(mask & ONEBYTES) * ONEBYTES >> 56"
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* that works for the bytemasks without having to
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* mask them first.
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*/
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static inline long count_masked_bytes(unsigned long mask)
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{
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return mask*0x0001020304050608ul >> 56;
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}
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#else /* 32-bit case */
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/* Carl Chatfield / Jan Achrenius G+ version for 32-bit */
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static inline long count_masked_bytes(long mask)
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{
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/* (000000 0000ff 00ffff ffffff) -> ( 1 1 2 3 ) */
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long a = (0x0ff0001+mask) >> 23;
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/* Fix the 1 for 00 case */
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return a & mask;
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}
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#endif
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/* Return nonzero if it has a zero */
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static inline unsigned long has_zero(unsigned long a, unsigned long *bits, 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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static inline unsigned long prep_zero_mask(unsigned long a, unsigned long bits, const struct word_at_a_time *c)
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{
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return bits;
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}
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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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/* The mask we created is directly usable as a bytemask */
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#define zero_bytemask(mask) (mask)
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static inline unsigned long find_zero(unsigned long mask)
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{
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return count_masked_bytes(mask);
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}
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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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#ifdef CONFIG_CC_HAS_ASM_GOTO_OUTPUT
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static inline unsigned long load_unaligned_zeropad(const void *addr)
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{
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unsigned long offset, data;
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unsigned long ret;
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asm_volatile_goto(
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"1: mov %[mem], %[ret]\n"
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_ASM_EXTABLE(1b, %l[do_exception])
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: [ret] "=r" (ret)
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: [mem] "m" (*(unsigned long *)addr)
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: : do_exception);
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return ret;
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do_exception:
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offset = (unsigned long)addr & (sizeof(long) - 1);
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addr = (void *)((unsigned long)addr & ~(sizeof(long) - 1));
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data = *(unsigned long *)addr;
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ret = data >> offset * 8;
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return ret;
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}
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#else /* !CONFIG_CC_HAS_ASM_GOTO_OUTPUT */
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static inline unsigned long load_unaligned_zeropad(const void *addr)
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{
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unsigned long offset, data;
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unsigned long ret, err = 0;
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asm( "1: mov %[mem], %[ret]\n"
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"2:\n"
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_ASM_EXTABLE_FAULT(1b, 2b)
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: [ret] "=&r" (ret), "+a" (err)
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: [mem] "m" (*(unsigned long *)addr));
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if (unlikely(err)) {
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offset = (unsigned long)addr & (sizeof(long) - 1);
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addr = (void *)((unsigned long)addr & ~(sizeof(long) - 1));
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data = *(unsigned long *)addr;
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ret = data >> offset * 8;
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}
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return ret;
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}
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#endif /* CONFIG_CC_HAS_ASM_GOTO_OUTPUT */
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#endif /* _ASM_WORD_AT_A_TIME_H */
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