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 
33 extern unsigned int cpu_last_asid;
34 
35 void __init_new_context(struct task_struct *tsk, struct mm_struct *mm);
36 void __new_context(struct mm_struct *mm);
37 
38 #ifdef CONFIG_PID_IN_CONTEXTIDR
39 static 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
48 static 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  */
56 static 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 
67 static 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 
78 static 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
114 static 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  */
137 static inline void
138 enter_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  */
148 static inline void
149 switch_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
162