forked from Minki/linux
6c94f27ac8
Instead of using absolute addresses for both the exception location and the fixup, use offsets relative to the exception table entry values. Not only does this cut the size of the exception table in half, it is also a prerequisite for KASLR, since absolute exception table entries are subject to dynamic relocation, which is incompatible with the sorting of the exception table that occurs at build time. This patch also introduces the _ASM_EXTABLE preprocessor macro (which exists on x86 as well) and its _asm_extable assembly counterpart, as shorthands to emit exception table entries. Acked-by: Will Deacon <will.deacon@arm.com> Signed-off-by: Ard Biesheuvel <ard.biesheuvel@linaro.org> Signed-off-by: Catalin Marinas <catalin.marinas@arm.com>
94 lines
2.2 KiB
C
94 lines
2.2 KiB
C
/*
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* Copyright (C) 2013 ARM Ltd.
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU General Public License version 2 as
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* published by the Free Software Foundation.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU General Public License for more details.
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*
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* You should have received a copy of the GNU General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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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 <asm/uaccess.h>
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#ifndef __AARCH64EB__
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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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return fls64(mask) >> 3;
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}
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#define zero_bytemask(mask) (mask)
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#else /* __AARCH64EB__ */
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#include <asm-generic/word-at-a-time.h>
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#endif
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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, %3\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, #0x7\n"
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" bic %2, %2, #0x7\n"
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" ldr %0, [%2]\n"
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" lsl %1, %1, #0x3\n"
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#ifndef __AARCH64EB__
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" lsr %0, %0, %1\n"
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#else
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" lsl %0, %0, %1\n"
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#endif
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" b 2b\n"
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" .popsection\n"
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_ASM_EXTABLE(1b, 3b)
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: "=&r" (ret), "=&r" (offset)
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: "r" (addr), "Q" (*(unsigned long *)addr));
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return ret;
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}
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#endif /* __ASM_WORD_AT_A_TIME_H */
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