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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>
#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));
}
/*
* TCR.T0SZ value to use when the ID map is active. Usually equals
* TCR_T0SZ(VA_BITS), unless system RAM is positioned very high in
* physical memory, in which case it will be smaller.
*/
extern u64 idmap_t0sz;
static inline bool __cpu_uses_extended_idmap(void)
{
return (!IS_ENABLED(CONFIG_ARM64_VA_BITS_48) &&
unlikely(idmap_t0sz != TCR_T0SZ(VA_BITS)));
}
/*
* Set TCR.T0SZ to its default value (based on VA_BITS)
*/
static inline void cpu_set_default_tcr_t0sz(void)
{
unsigned long tcr;
if (!__cpu_uses_extended_idmap())
return;
asm volatile (
" mrs %0, tcr_el1 ;"
" bfi %0, %1, %2, %3 ;"
" msr tcr_el1, %0 ;"
" isb"
: "=&r" (tcr)
: "r"(TCR_T0SZ(VA_BITS)), "I"(TCR_T0SZ_OFFSET), "I"(TCR_TxSZ_WIDTH));
}
/*
* It would be nice to return ASIDs back to the allocator, but unfortunately
* that introduces a race with a generation rollover where we could erroneously
* free an ASID allocated in a future generation. We could workaround this by
* freeing the ASID from the context of the dying mm (e.g. in arch_exit_mmap),
* but we'd then need to make sure that we didn't dirty any TLBs afterwards.
* Setting a reserved TTBR0 or EPD0 would work, but it all gets ugly when you
* take CPU migration into account.
*/
#define destroy_context(mm) do { } while(0)
void check_and_switch_context(struct mm_struct *mm, unsigned int cpu);
#define init_new_context(tsk,mm) ({ atomic64_set(&(mm)->context.id, 0); 0; })
/*
* 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();
if (prev == next)
return;
/*
* 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;
}
check_and_switch_context(next, cpu);
}
#define deactivate_mm(tsk,mm) do { } while (0)
#define activate_mm(prev,next) switch_mm(prev, next, NULL)
#endif
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