1. 根目录:
2. arch
3. m68k
4. include
5. asm
6. mmu_context.h

#ifndef __M68K_MMU_CONTEXT_H
#define __M68K_MMU_CONTEXT_H

#include <asm-generic/mm_hooks.h>

static inline void enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
{
}

#ifdef CONFIG_MMU

#if defined(CONFIG_COLDFIRE)

#include <asm/atomic.h>
#include <asm/bitops.h>
#include <asm/mcfmmu.h>
#include <asm/mmu.h>

#define NO_CONTEXT		256
#define LAST_CONTEXT		255
#define FIRST_CONTEXT		1

extern unsigned long context_map[];
extern mm_context_t next_mmu_context;

extern atomic_t nr_free_contexts;
extern struct mm_struct *context_mm[LAST_CONTEXT+1];
extern void steal_context(void);

static inline void get_mmu_context(struct mm_struct *mm)
{
	mm_context_t ctx;

	if (mm->context != NO_CONTEXT)
		return;
	while (atomic_dec_and_test_lt(&nr_free_contexts)) {
		atomic_inc(&nr_free_contexts);
		steal_context();
	}
	ctx = next_mmu_context;
	while (test_and_set_bit(ctx, context_map)) {
		ctx = find_next_zero_bit(context_map, LAST_CONTEXT+1, ctx);
		if (ctx > LAST_CONTEXT)
			ctx = 0;
	}
	next_mmu_context = (ctx + 1) & LAST_CONTEXT;
	mm->context = ctx;
	context_mm[ctx] = mm;
}

/*
 * Set up the context for a new address space.
 */
#define init_new_context(tsk, mm)	(((mm)->context = NO_CONTEXT), 0)

/*
 * We're finished using the context for an address space.
 */
static inline void destroy_context(struct mm_struct *mm)
{
	if (mm->context != NO_CONTEXT) {
		clear_bit(mm->context, context_map);
		mm->context = NO_CONTEXT;
		atomic_inc(&nr_free_contexts);
	}
}

static inline void set_context(mm_context_t context, pgd_t *pgd)
{
	__asm__ __volatile__ ("movec %0,%%asid" : : "d" (context));
}

static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
	struct task_struct *tsk)
{
	get_mmu_context(tsk->mm);
	set_context(tsk->mm->context, next->pgd);
}

/*
 * After we have set current->mm to a new value, this activates
 * the context for the new mm so we see the new mappings.
 */
static inline void activate_mm(struct mm_struct *active_mm,
	struct mm_struct *mm)
{
	get_mmu_context(mm);
	set_context(mm->context, mm->pgd);
}

#define deactivate_mm(tsk, mm) do { } while (0)

extern void mmu_context_init(void);
#define prepare_arch_switch(next) load_ksp_mmu(next)

static inline void load_ksp_mmu(struct task_struct *task)
{
	unsigned long flags;
	struct mm_struct *mm;
	int asid;
	pgd_t *pgd;
	pmd_t *pmd;
	pte_t *pte;
	unsigned long mmuar;

	local_irq_save(flags);
	mmuar = task->thread.ksp;

	/* Search for a valid TLB entry, if one is found, don't remap */
	mmu_write(MMUAR, mmuar);
	mmu_write(MMUOR, MMUOR_STLB | MMUOR_ADR);
	if (mmu_read(MMUSR) & MMUSR_HIT)
		goto end;

	if (mmuar >= PAGE_OFFSET) {
		mm = &init_mm;
	} else {
		pr_info("load_ksp_mmu: non-kernel mm found: 0x%p\n", task->mm);
		mm = task->mm;
	}

	if (!mm)
		goto bug;

	pgd = pgd_offset(mm, mmuar);
	if (pgd_none(*pgd))
		goto bug;

	pmd = pmd_offset(pgd, mmuar);
	if (pmd_none(*pmd))
		goto bug;

	pte = (mmuar >= PAGE_OFFSET) ? pte_offset_kernel(pmd, mmuar)
				     : pte_offset_map(pmd, mmuar);
	if (pte_none(*pte) || !pte_present(*pte))
		goto bug;

	set_pte(pte, pte_mkyoung(*pte));
	asid = mm->context & 0xff;
	if (!pte_dirty(*pte) && mmuar <= PAGE_OFFSET)
		set_pte(pte, pte_wrprotect(*pte));

	mmu_write(MMUTR, (mmuar & PAGE_MASK) | (asid << MMUTR_IDN) |
		(((int)(pte->pte) & (int)CF_PAGE_MMUTR_MASK)
		>> CF_PAGE_MMUTR_SHIFT) | MMUTR_V);

	mmu_write(MMUDR, (pte_val(*pte) & PAGE_MASK) |
		((pte->pte) & CF_PAGE_MMUDR_MASK) | MMUDR_SZ_8KB | MMUDR_X);

	mmu_write(MMUOR, MMUOR_ACC | MMUOR_UAA);

	goto end;

bug:
	pr_info("ksp load failed: mm=0x%p ksp=0x08%lx\n", mm, mmuar);
end:
	local_irq_restore(flags);
}

#elif defined(CONFIG_SUN3)
#include <asm/sun3mmu.h>
#include <linux/sched.h>

extern unsigned long get_free_context(struct mm_struct *mm);
extern void clear_context(unsigned long context);

/* set the context for a new task to unmapped */
static inline int init_new_context(struct task_struct *tsk,
				   struct mm_struct *mm)
{
	mm->context = SUN3_INVALID_CONTEXT;
	return 0;
}

/* find the context given to this process, and if it hasn't already
   got one, go get one for it. */
static inline void get_mmu_context(struct mm_struct *mm)
{
	if (mm->context == SUN3_INVALID_CONTEXT)
		mm->context = get_free_context(mm);
}

/* flush context if allocated... */
static inline void destroy_context(struct mm_struct *mm)
{
	if (mm->context != SUN3_INVALID_CONTEXT)
		clear_context(mm->context);
}

static inline void activate_context(struct mm_struct *mm)
{
	get_mmu_context(mm);
	sun3_put_context(mm->context);
}

static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next,
			     struct task_struct *tsk)
{
	activate_context(tsk->mm);
}

#define deactivate_mm(tsk, mm)	do { } while (0)

static inline void activate_mm(struct mm_struct *prev_mm,
			       struct mm_struct *next_mm)
{
	activate_context(next_mm);
}

#else

#include <asm/setup.h>
#include <asm/page.h>
#include <asm/pgalloc.h>

static inline int init_new_context(struct task_struct *tsk,
				   struct mm_struct *mm)
{
	mm->context = virt_to_phys(mm->pgd);
	return 0;
}

#define destroy_context(mm)		do { } while(0)

static inline void switch_mm_0230(struct mm_struct *mm)
{
	unsigned long crp[2] = {
		0x80000000 | _PAGE_TABLE, mm->context
	};
	unsigned long tmp;

	asm volatile (".chip 68030");

	/* flush MC68030/MC68020 caches (they are virtually addressed) */
	asm volatile (
		"movec %%cacr,%0;"
		"orw %1,%0; "
		"movec %0,%%cacr"
		: "=d" (tmp) : "di" (FLUSH_I_AND_D));

	/* Switch the root pointer. For a 030-only kernel,
	 * avoid flushing the whole ATC, we only need to
	 * flush the user entries. The 68851 does this by
	 * itself. Avoid a runtime check here.
	 */
	asm volatile (
#ifdef CPU_M68030_ONLY
		"pmovefd %0,%%crp; "
		"pflush #0,#4"
#else
		"pmove %0,%%crp"
#endif
		: : "m" (crp[0]));

	asm volatile (".chip 68k");
}

static inline void switch_mm_0460(struct mm_struct *mm)
{
	asm volatile (".chip 68040");

	/* flush address translation cache (user entries) */
	asm volatile ("pflushan");

	/* switch the root pointer */
	asm volatile ("movec %0,%%urp" : : "r" (mm->context));

	if (CPU_IS_060) {
		unsigned long tmp;

		/* clear user entries in the branch cache */
		asm volatile (
			"movec %%cacr,%0; "
		        "orl %1,%0; "
		        "movec %0,%%cacr"
			: "=d" (tmp): "di" (0x00200000));
	}

	asm volatile (".chip 68k");
}

static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next, struct task_struct *tsk)
{
	if (prev != next) {
		if (CPU_IS_020_OR_030)
			switch_mm_0230(next);
		else
			switch_mm_0460(next);
	}
}

#define deactivate_mm(tsk,mm)	do { } while (0)

static inline void activate_mm(struct mm_struct *prev_mm,
			       struct mm_struct *next_mm)
{
	next_mm->context = virt_to_phys(next_mm->pgd);

	if (CPU_IS_020_OR_030)
		switch_mm_0230(next_mm);
	else
		switch_mm_0460(next_mm);
}

#endif

#else /* !CONFIG_MMU */

static inline int init_new_context(struct task_struct *tsk, struct mm_struct *mm)
{
	return 0;
}


static inline void switch_mm(struct mm_struct *prev, struct mm_struct *next, struct task_struct *tsk)
{
}

#define destroy_context(mm)	do { } while (0)
#define deactivate_mm(tsk,mm)	do { } while (0)

static inline void activate_mm(struct mm_struct *prev_mm, struct mm_struct *next_mm)
{
}

#endif /* CONFIG_MMU */
#endif /* __M68K_MMU_CONTEXT_H */