112 lines
3.8 KiB
C
112 lines
3.8 KiB
C
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/* SPDX-License-Identifier: GPL-2.0 */
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#ifndef _ASM_ALTERNATIVE_H
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#define _ASM_ALTERNATIVE_H
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#ifndef __ASSEMBLY__
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#include <linux/types.h>
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#include <linux/stddef.h>
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#include <linux/stringify.h>
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#include <asm/asm.h>
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struct alt_instr {
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s32 instr_offset; /* offset to original instruction */
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s32 replace_offset; /* offset to replacement instruction */
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u16 feature; /* feature bit set for replacement */
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u8 instrlen; /* length of original instruction */
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u8 replacementlen; /* length of new instruction */
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} __packed;
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/*
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* Debug flag that can be tested to see whether alternative
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* instructions were patched in already:
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*/
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extern int alternatives_patched;
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extern struct alt_instr __alt_instructions[], __alt_instructions_end[];
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extern void alternative_instructions(void);
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extern void apply_alternatives(struct alt_instr *start, struct alt_instr *end);
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#define b_replacement(num) "664"#num
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#define e_replacement(num) "665"#num
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#define alt_end_marker "663"
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#define alt_slen "662b-661b"
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#define alt_total_slen alt_end_marker"b-661b"
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#define alt_rlen(num) e_replacement(num)"f-"b_replacement(num)"f"
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#define __OLDINSTR(oldinstr, num) \
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"661:\n\t" oldinstr "\n662:\n" \
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".fill -(((" alt_rlen(num) ")-(" alt_slen ")) > 0) * " \
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"((" alt_rlen(num) ")-(" alt_slen ")) / 4, 4, 0x03400000\n"
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#define OLDINSTR(oldinstr, num) \
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__OLDINSTR(oldinstr, num) \
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alt_end_marker ":\n"
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#define alt_max_short(a, b) "((" a ") ^ (((" a ") ^ (" b ")) & -(-((" a ") < (" b ")))))"
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/*
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* Pad the second replacement alternative with additional NOPs if it is
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* additionally longer than the first replacement alternative.
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*/
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#define OLDINSTR_2(oldinstr, num1, num2) \
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"661:\n\t" oldinstr "\n662:\n" \
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".fill -((" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")) > 0) * " \
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"(" alt_max_short(alt_rlen(num1), alt_rlen(num2)) " - (" alt_slen ")) / 4, " \
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"4, 0x03400000\n" \
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alt_end_marker ":\n"
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#define ALTINSTR_ENTRY(feature, num) \
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" .long 661b - .\n" /* label */ \
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" .long " b_replacement(num)"f - .\n" /* new instruction */ \
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" .short " __stringify(feature) "\n" /* feature bit */ \
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" .byte " alt_total_slen "\n" /* source len */ \
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" .byte " alt_rlen(num) "\n" /* replacement len */
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#define ALTINSTR_REPLACEMENT(newinstr, feature, num) /* replacement */ \
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b_replacement(num)":\n\t" newinstr "\n" e_replacement(num) ":\n\t"
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/* alternative assembly primitive: */
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#define ALTERNATIVE(oldinstr, newinstr, feature) \
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OLDINSTR(oldinstr, 1) \
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".pushsection .altinstructions,\"a\"\n" \
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ALTINSTR_ENTRY(feature, 1) \
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".popsection\n" \
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".subsection 1\n" \
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ALTINSTR_REPLACEMENT(newinstr, feature, 1) \
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".previous\n"
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#define ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2)\
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OLDINSTR_2(oldinstr, 1, 2) \
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".pushsection .altinstructions,\"a\"\n" \
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ALTINSTR_ENTRY(feature1, 1) \
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ALTINSTR_ENTRY(feature2, 2) \
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".popsection\n" \
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".subsection 1\n" \
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ALTINSTR_REPLACEMENT(newinstr1, feature1, 1) \
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ALTINSTR_REPLACEMENT(newinstr2, feature2, 2) \
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".previous\n"
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/*
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* Alternative instructions for different CPU types or capabilities.
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*
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* This allows to use optimized instructions even on generic binary
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* kernels.
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*
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* length of oldinstr must be longer or equal the length of newinstr
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* It can be padded with nops as needed.
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*
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* For non barrier like inlines please define new variants
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* without volatile and memory clobber.
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*/
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#define alternative(oldinstr, newinstr, feature) \
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(asm volatile (ALTERNATIVE(oldinstr, newinstr, feature) : : : "memory"))
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#define alternative_2(oldinstr, newinstr1, feature1, newinstr2, feature2) \
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(asm volatile(ALTERNATIVE_2(oldinstr, newinstr1, feature1, newinstr2, feature2) ::: "memory"))
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#endif /* __ASSEMBLY__ */
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#endif /* _ASM_ALTERNATIVE_H */
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