1 // SPDX-License-Identifier: GPL-2.0-or-later
2 /*
3  * This file contains the routines for handling the MMU.
4  *
5  *    Copyright (C) 2007 Xilinx, Inc.  All rights reserved.
6  *
7  *  Derived from arch/ppc/mm/4xx_mmu.c:
8  *  -- paulus
9  *
10  *  Derived from arch/ppc/mm/init.c:
11  *    Copyright (C) 1995-1996 Gary Thomas (gdt@linuxppc.org)
12  *
13  *  Modifications by Paul Mackerras (PowerMac) (paulus@cs.anu.edu.au)
14  *  and Cort Dougan (PReP) (cort@cs.nmt.edu)
15  *    Copyright (C) 1996 Paul Mackerras
16  *  Amiga/APUS changes by Jesper Skov (jskov@cygnus.co.uk).
17  *
18  *  Derived from "arch/i386/mm/init.c"
19  *    Copyright (C) 1991, 1992, 1993, 1994  Linus Torvalds
20  */
21 
22 #include <linux/mm.h>
23 #include <linux/init.h>
24 
25 #include <asm/tlbflush.h>
26 #include <asm/mmu_context.h>
27 
28 mm_context_t next_mmu_context;
29 unsigned long context_map[LAST_CONTEXT / BITS_PER_LONG + 1];
30 atomic_t nr_free_contexts;
31 struct mm_struct *context_mm[LAST_CONTEXT+1];
32 
33 /*
34  * Initialize the context management stuff.
35  */
mmu_context_init(void)36 void __init mmu_context_init(void)
37 {
38 	/*
39 	 * The use of context zero is reserved for the kernel.
40 	 * This code assumes FIRST_CONTEXT < 32.
41 	 */
42 	context_map[0] = (1 << FIRST_CONTEXT) - 1;
43 	next_mmu_context = FIRST_CONTEXT;
44 	atomic_set(&nr_free_contexts, LAST_CONTEXT - FIRST_CONTEXT + 1);
45 }
46 
47 /*
48  * Steal a context from a task that has one at the moment.
49  *
50  * This isn't an LRU system, it just frees up each context in
51  * turn (sort-of pseudo-random replacement :).  This would be the
52  * place to implement an LRU scheme if anyone were motivated to do it.
53  */
steal_context(void)54 void steal_context(void)
55 {
56 	struct mm_struct *mm;
57 
58 	/* free up context `next_mmu_context' */
59 	/* if we shouldn't free context 0, don't... */
60 	if (next_mmu_context < FIRST_CONTEXT)
61 		next_mmu_context = FIRST_CONTEXT;
62 	mm = context_mm[next_mmu_context];
63 	flush_tlb_mm(mm);
64 	destroy_context(mm);
65 }
66