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37 lines
958 B
C
37 lines
958 B
C
/* Copyright (C) 2021,2022 fef <owo@fef.moe>. All rights reserved. */
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#pragma once
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#include <arch/page.h>
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#include <arch/sched.h>
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#include <gay/cdefs.h>
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#include <gay/config.h>
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#include <gay/types.h>
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static inline int smp_cpuid(void)
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{
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#if CFG_SMP
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/*
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* The x86 has a dedicated CPUID instruction that can be used to query
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* pretty much anything except literally the cpu id. Therefore, we make
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* use of the fact that kernel stacks are always aligned to their size.
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* The cpu number is the topmost item on the stack; for cpu 0 this gets
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* pushed in the assembly routine in startup{32,64}.S and for all others
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* ... there is no implementation yet.
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*/
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u_register_t sp;
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#ifdef __x86_64__
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__asm__ volatile("movq %%rsp, %0" : "=r"(sp));
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#else
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__asm__ volatile("movl %%esp, %0" : "=r"(sp));
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#endif
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sp &= ~(KERN_STACK_SIZE - 1);
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return ((int *)sp)[KERN_STACK_SIZE / sizeof(int) - 1];
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#else /* !CFG_SMP */
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return 0;
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#endif /* !CFG_SMP */
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}
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