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/*
* Based on arch/arm/include/asm/mmu_context.h
*
* Copyright (C) 1996 Russell King.
* Copyright (C) 2012 ARM Ltd.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef __ASM_MMU_CONTEXT_H
#define __ASM_MMU_CONTEXT_H
#include <linux/compiler.h>
#include <linux/sched.h>
#include <asm/cacheflush.h>
#include <asm/proc-fns.h>
#include <asm-generic/mm_hooks.h>
#include <asm/cputype.h>
#include <asm/pgtable.h>
#define MAX_ASID_BITS 16
extern unsigned int cpu_last_asid;
void __init_new_context(struct task_struct *tsk, struct mm_struct *mm);
void __new_context(struct mm_struct *mm);
#ifdef CONFIG_PID_IN_CONTEXTIDR
static inline void contextidr_thread_switch(struct task_struct *next)
{
asm(
" msr contextidr_el1, %0\n"
" isb"
:
: "r" (task_pid_nr(next)));
}
#else
static inline void contextidr_thread_switch(struct task_struct *next)
{
}
#endif
/*
* Set TTBR0 to empty_zero_page. No translations will be possible via TTBR0.
*/
static inline void cpu_set_reserved_ttbr0(void)
{
unsigned long ttbr = page_to_phys(empty_zero_page);
asm(
" msr ttbr0_el1, %0 // set TTBR0\n"
" isb"
:
: "r" (ttbr));
}
static inline void switch_new_context(struct mm_struct *mm)
{
unsigned long flags;
__new_context(mm);
local_irq_save(flags);
cpu_switch_mm(mm->pgd, mm);
local_irq_restore(flags);
}
static inline void check_and_switch_context(struct mm_struct *mm,
struct task_struct *tsk)
{
/*
* Required during context switch to avoid speculative page table
* walking with the wrong TTBR.
*/
cpu_set_reserved_ttbr0();
if (!((mm->context.id ^ cpu_last_asid) >> MAX_ASID_BITS))
/*
* The ASID is from the current generation, just switch to the
* new pgd. This condition is only true for calls from
* context_switch() and interrupts are already disabled.
*/
cpu_switch_mm(mm->pgd, mm);
else if (irqs_disabled())
/*
* Defer the new ASID allocation until after the context
* switch critical region since __new_context() cannot be
* called with interrupts disabled.
*/
set_ti_thread_flag(task_thread_info(tsk), TIF_SWITCH_MM);
else
/*
* That is a direct call to switch_mm() or activate_mm() with
* interrupts enabled and a new context.
*/
switch_new_context(mm);
}
#define init_new_context(tsk,mm) (__init_new_context(tsk,mm),0)
#define destroy_context(mm) do { } while(0)
#define finish_arch_post_lock_switch \
finish_arch_post_lock_switch
static inline void finish_arch_post_lock_switch(void)
{
if (test_and_clear_thread_flag(TIF_SWITCH_MM)) {
struct mm_struct *mm = current->mm;
unsigned long flags;
__new_context(mm);
local_irq_save(flags);
cpu_switch_mm(mm->pgd, mm);
local_irq_restore(flags);
}
}
/*
* This is called when "tsk" is about to enter lazy TLB mode.
*
* mm: describes the currently active mm context
* tsk: task which is entering lazy tlb
* cpu: cpu number which is entering lazy tlb
*
* tsk->mm will be NULL
*/
static inline void
enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
{
}
/*
* This is the actual mm switch as far as the scheduler
* is concerned. No registers are touched. We avoid
* calling the CPU specific function when the mm hasn't
* actually changed.
*/
static inline void
switch_mm(struct mm_struct *prev, struct mm_struct *next,
struct task_struct *tsk)
{
unsigned int cpu = smp_processor_id();
/*
* init_mm.pgd does not contain any user mappings and it is always
* active for kernel addresses in TTBR1. Just set the reserved TTBR0.
*/
if (next == &init_mm) {
cpu_set_reserved_ttbr0();
return;
}
if (!cpumask_test_and_set_cpu(cpu, mm_cpumask(next)) || prev != next)
check_and_switch_context(next, tsk);
}
#define deactivate_mm(tsk,mm) do { } while (0)
#define activate_mm(prev,next) switch_mm(prev, next, NULL)
#endif