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Linux kernel mirror (for testing)
git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git
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linux
1/*
2 * Based on arch/arm/include/asm/mmu_context.h
3 *
4 * Copyright (C) 1996 Russell King.
5 * Copyright (C) 2012 ARM Ltd.
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License version 2 as
9 * published by the Free Software Foundation.
10 *
11 * This program is distributed in the hope that it will be useful,
12 * but WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
14 * GNU General Public License for more details.
15 *
16 * You should have received a copy of the GNU General Public License
17 * along with this program. If not, see <http://www.gnu.org/licenses/>.
18 */
19#ifndef __ASM_MMU_CONTEXT_H
20#define __ASM_MMU_CONTEXT_H
21
22#include <linux/compiler.h>
23#include <linux/sched.h>
24
25#include <asm/cacheflush.h>
26#include <asm/proc-fns.h>
27#include <asm-generic/mm_hooks.h>
28#include <asm/cputype.h>
29#include <asm/pgtable.h>
30
31#define MAX_ASID_BITS 16
32
33extern unsigned int cpu_last_asid;
34
35void __init_new_context(struct task_struct *tsk, struct mm_struct *mm);
36void __new_context(struct mm_struct *mm);
37
38#ifdef CONFIG_PID_IN_CONTEXTIDR
39static inline void contextidr_thread_switch(struct task_struct *next)
40{
41 asm(
42 " msr contextidr_el1, %0\n"
43 " isb"
44 :
45 : "r" (task_pid_nr(next)));
46}
47#else
48static inline void contextidr_thread_switch(struct task_struct *next)
49{
50}
51#endif
52
53/*
54 * Set TTBR0 to empty_zero_page. No translations will be possible via TTBR0.
55 */
56static inline void cpu_set_reserved_ttbr0(void)
57{
58 unsigned long ttbr = page_to_phys(empty_zero_page);
59
60 asm(
61 " msr ttbr0_el1, %0 // set TTBR0\n"
62 " isb"
63 :
64 : "r" (ttbr));
65}
66
67static inline void switch_new_context(struct mm_struct *mm)
68{
69 unsigned long flags;
70
71 __new_context(mm);
72
73 local_irq_save(flags);
74 cpu_switch_mm(mm->pgd, mm);
75 local_irq_restore(flags);
76}
77
78static inline void check_and_switch_context(struct mm_struct *mm,
79 struct task_struct *tsk)
80{
81 /*
82 * Required during context switch to avoid speculative page table
83 * walking with the wrong TTBR.
84 */
85 cpu_set_reserved_ttbr0();
86
87 if (!((mm->context.id ^ cpu_last_asid) >> MAX_ASID_BITS))
88 /*
89 * The ASID is from the current generation, just switch to the
90 * new pgd. This condition is only true for calls from
91 * context_switch() and interrupts are already disabled.
92 */
93 cpu_switch_mm(mm->pgd, mm);
94 else if (irqs_disabled())
95 /*
96 * Defer the new ASID allocation until after the context
97 * switch critical region since __new_context() cannot be
98 * called with interrupts disabled.
99 */
100 set_ti_thread_flag(task_thread_info(tsk), TIF_SWITCH_MM);
101 else
102 /*
103 * That is a direct call to switch_mm() or activate_mm() with
104 * interrupts enabled and a new context.
105 */
106 switch_new_context(mm);
107}
108
109#define init_new_context(tsk,mm) (__init_new_context(tsk,mm),0)
110#define destroy_context(mm) do { } while(0)
111
112#define finish_arch_post_lock_switch \
113 finish_arch_post_lock_switch
114static inline void finish_arch_post_lock_switch(void)
115{
116 if (test_and_clear_thread_flag(TIF_SWITCH_MM)) {
117 struct mm_struct *mm = current->mm;
118 unsigned long flags;
119
120 __new_context(mm);
121
122 local_irq_save(flags);
123 cpu_switch_mm(mm->pgd, mm);
124 local_irq_restore(flags);
125 }
126}
127
128/*
129 * This is called when "tsk" is about to enter lazy TLB mode.
130 *
131 * mm: describes the currently active mm context
132 * tsk: task which is entering lazy tlb
133 * cpu: cpu number which is entering lazy tlb
134 *
135 * tsk->mm will be NULL
136 */
137static inline void
138enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
139{
140}
141
142/*
143 * This is the actual mm switch as far as the scheduler
144 * is concerned. No registers are touched. We avoid
145 * calling the CPU specific function when the mm hasn't
146 * actually changed.
147 */
148static inline void
149switch_mm(struct mm_struct *prev, struct mm_struct *next,
150 struct task_struct *tsk)
151{
152 unsigned int cpu = smp_processor_id();
153
154 if (!cpumask_test_and_set_cpu(cpu, mm_cpumask(next)) || prev != next)
155 check_and_switch_context(next, tsk);
156}
157
158#define deactivate_mm(tsk,mm) do { } while (0)
159#define activate_mm(prev,next) switch_mm(prev, next, NULL)
160
161#endif