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5b673a48c5
Add some text to the macro magic for future reference and against failing human memory. Requested-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Borislav Petkov <bp@suse.de> Cc: Andy Lutomirski <luto@amacapital.net> Cc: Borislav Petkov <bp@alien8.de> Cc: Brian Gerst <brgerst@gmail.com> Cc: Denys Vlasenko <dvlasenk@redhat.com> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Thomas Gleixner <tglx@linutronix.de> Signed-off-by: Ingo Molnar <mingo@kernel.org>
101 lines
2.3 KiB
C
101 lines
2.3 KiB
C
#ifndef _ASM_X86_ALTERNATIVE_ASM_H
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#define _ASM_X86_ALTERNATIVE_ASM_H
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#ifdef __ASSEMBLY__
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#include <asm/asm.h>
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#ifdef CONFIG_SMP
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.macro LOCK_PREFIX
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672: lock
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.pushsection .smp_locks,"a"
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.balign 4
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.long 672b - .
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.popsection
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.endm
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#else
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.macro LOCK_PREFIX
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.endm
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#endif
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/*
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* Issue one struct alt_instr descriptor entry (need to put it into
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* the section .altinstructions, see below). This entry contains
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* enough information for the alternatives patching code to patch an
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* instruction. See apply_alternatives().
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*/
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.macro altinstruction_entry orig alt feature orig_len alt_len pad_len
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.long \orig - .
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.long \alt - .
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.word \feature
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.byte \orig_len
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.byte \alt_len
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.byte \pad_len
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.endm
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/*
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* Define an alternative between two instructions. If @feature is
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* present, early code in apply_alternatives() replaces @oldinstr with
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* @newinstr. ".skip" directive takes care of proper instruction padding
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* in case @newinstr is longer than @oldinstr.
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*/
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.macro ALTERNATIVE oldinstr, newinstr, feature
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140:
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\oldinstr
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141:
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.skip -(((144f-143f)-(141b-140b)) > 0) * ((144f-143f)-(141b-140b)),0x90
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142:
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.pushsection .altinstructions,"a"
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altinstruction_entry 140b,143f,\feature,142b-140b,144f-143f,142b-141b
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.popsection
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.pushsection .altinstr_replacement,"ax"
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143:
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\newinstr
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144:
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.popsection
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.endm
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#define old_len 141b-140b
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#define new_len1 144f-143f
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#define new_len2 145f-144f
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/*
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* max without conditionals. Idea adapted from:
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* http://graphics.stanford.edu/~seander/bithacks.html#IntegerMinOrMax
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*/
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#define alt_max_short(a, b) ((a) ^ (((a) ^ (b)) & -(-((a) < (b)))))
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/*
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* Same as ALTERNATIVE macro above but for two alternatives. If CPU
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* has @feature1, it replaces @oldinstr with @newinstr1. If CPU has
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* @feature2, it replaces @oldinstr with @feature2.
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*/
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.macro ALTERNATIVE_2 oldinstr, newinstr1, feature1, newinstr2, feature2
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140:
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\oldinstr
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141:
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.skip -((alt_max_short(new_len1, new_len2) - (old_len)) > 0) * \
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(alt_max_short(new_len1, new_len2) - (old_len)),0x90
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142:
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.pushsection .altinstructions,"a"
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altinstruction_entry 140b,143f,\feature1,142b-140b,144f-143f,142b-141b
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altinstruction_entry 140b,144f,\feature2,142b-140b,145f-144f,142b-141b
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.popsection
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.pushsection .altinstr_replacement,"ax"
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143:
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\newinstr1
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144:
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\newinstr2
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145:
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.popsection
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.endm
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#endif /* __ASSEMBLY__ */
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#endif /* _ASM_X86_ALTERNATIVE_ASM_H */
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