arch/arm64/include/asm/mmu_context.h - linux - Git at Google

 /* SPDX-License-Identifier: GPL-2.0-only */
 /*
  * Based on arch/arm/include/asm/mmu_context.h
  *
  * Copyright (C) 1996 Russell King.
  * Copyright (C) 2012 ARM Ltd.
  */
 #ifndef __ASM_MMU_CONTEXT_H
 #define __ASM_MMU_CONTEXT_H

 #ifndef __ASSEMBLY__

 #include <linux/compiler.h>
 #include <linux/sched.h>
 #include <linux/sched/hotplug.h>
 #include <linux/mm_types.h>

 #include <asm/cacheflush.h>
 #include <asm/cpufeature.h>
 #include <asm/proc-fns.h>
 #include <asm-generic/mm_hooks.h>
 #include <asm/cputype.h>
 #include <asm/pgtable.h>
 #include <asm/sysreg.h>
 #include <asm/tlbflush.h>

 extern bool rodata_full;

 static inline void contextidr_thread_switch(struct task_struct *next)
 {
 	if (!IS_ENABLED(CONFIG_PID_IN_CONTEXTIDR))
 		return;

 	write_sysreg(task_pid_nr(next), contextidr_el1);
 	isb();
 }

 /*
  * Set TTBR0 to empty_zero_page. No translations will be possible via TTBR0.
  */
 static inline void cpu_set_reserved_ttbr0(void)
 {
 	unsigned long ttbr = phys_to_ttbr(__pa_symbol(empty_zero_page));

 	write_sysreg(ttbr, ttbr0_el1);
 	isb();
 }

 static inline void cpu_switch_mm(pgd_t *pgd, struct mm_struct *mm)
 {
 	BUG_ON(pgd == swapper_pg_dir);
 	cpu_set_reserved_ttbr0();
 	cpu_do_switch_mm(virt_to_phys(pgd),mm);
 }

 /*
  * 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;
 extern u64 idmap_ptrs_per_pgd;

 static inline bool __cpu_uses_extended_idmap(void)
 {
 	if (IS_ENABLED(CONFIG_ARM64_VA_BITS_52))
 		return false;

 	return unlikely(idmap_t0sz != TCR_T0SZ(VA_BITS));
 }

 /*
  * True if the extended ID map requires an extra level of translation table
  * to be configured.
  */
 static inline bool __cpu_uses_extended_idmap_level(void)
 {
 	return ARM64_HW_PGTABLE_LEVELS(64 - idmap_t0sz) > CONFIG_PGTABLE_LEVELS;
 }

 /*
  * Set TCR.T0SZ to its default value (based on VA_BITS)
  */
 static inline void __cpu_set_tcr_t0sz(unsigned long t0sz)
 {
 	unsigned long tcr;

 	if (!__cpu_uses_extended_idmap())
 		return;

 	tcr = read_sysreg(tcr_el1);
 	tcr &= ~TCR_T0SZ_MASK;
 	tcr |= t0sz << TCR_T0SZ_OFFSET;
 	write_sysreg(tcr, tcr_el1);
 	isb();
 }

 #define cpu_set_default_tcr_t0sz()	__cpu_set_tcr_t0sz(TCR_T0SZ(vabits_actual))
 #define cpu_set_idmap_tcr_t0sz()	__cpu_set_tcr_t0sz(idmap_t0sz)

 /*
  * Remove the idmap from TTBR0_EL1 and install the pgd of the active mm.
  *
  * The idmap lives in the same VA range as userspace, but uses global entries
  * and may use a different TCR_EL1.T0SZ. To avoid issues resulting from
  * speculative TLB fetches, we must temporarily install the reserved page
  * tables while we invalidate the TLBs and set up the correct TCR_EL1.T0SZ.
  *
  * If current is a not a user task, the mm covers the TTBR1_EL1 page tables,
  * which should not be installed in TTBR0_EL1. In this case we can leave the
  * reserved page tables in place.
  */
 static inline void cpu_uninstall_idmap(void)
 {
 	struct mm_struct *mm = current->active_mm;

 	cpu_set_reserved_ttbr0();
 	local_flush_tlb_all();
 	cpu_set_default_tcr_t0sz();

 	if (mm != &init_mm && !system_uses_ttbr0_pan())
 		cpu_switch_mm(mm->pgd, mm);
 }

 static inline void cpu_install_idmap(void)
 {
 	cpu_set_reserved_ttbr0();
 	local_flush_tlb_all();
 	cpu_set_idmap_tcr_t0sz();

 	cpu_switch_mm(lm_alias(idmap_pg_dir), &init_mm);
 }

 /*
  * Atomically replaces the active TTBR1_EL1 PGD with a new VA-compatible PGD,
  * avoiding the possibility of conflicting TLB entries being allocated.
  */
 static inline void cpu_replace_ttbr1(pgd_t *pgdp)
 {
 	typedef void (ttbr_replace_func)(phys_addr_t);
 	extern ttbr_replace_func idmap_cpu_replace_ttbr1;
 	ttbr_replace_func *replace_phys;

 	/* phys_to_ttbr() zeros lower 2 bits of ttbr with 52-bit PA */
 	phys_addr_t ttbr1 = phys_to_ttbr(virt_to_phys(pgdp));

 	if (system_supports_cnp() && !WARN_ON(pgdp != lm_alias(swapper_pg_dir))) {
 		/*
 		 * cpu_replace_ttbr1() is used when there's a boot CPU
 		 * up (i.e. cpufeature framework is not up yet) and
 		 * latter only when we enable CNP via cpufeature's
 		 * enable() callback.
 		 * Also we rely on the cpu_hwcap bit being set before
 		 * calling the enable() function.
 		 */
 		ttbr1 |= TTBR_CNP_BIT;
 	}

 	replace_phys = (void *)__pa_symbol(idmap_cpu_replace_ttbr1);

 	cpu_install_idmap();
 	replace_phys(ttbr1);
 	cpu_uninstall_idmap();
 }

 /*
  * 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; })

 #ifdef CONFIG_ARM64_SW_TTBR0_PAN
 static inline void update_saved_ttbr0(struct task_struct *tsk,
 				      struct mm_struct *mm)
 {
 	u64 ttbr;

 	if (!system_uses_ttbr0_pan())
 		return;

 	if (mm == &init_mm)
 		ttbr = __pa_symbol(empty_zero_page);
 	else
 		ttbr = virt_to_phys(mm->pgd) | ASID(mm) << 48;

 	WRITE_ONCE(task_thread_info(tsk)->ttbr0, ttbr);
 }
 #else
 static inline void update_saved_ttbr0(struct task_struct *tsk,
 				      struct mm_struct *mm)
 {
 }
 #endif

 static inline void
 enter_lazy_tlb(struct mm_struct *mm, struct task_struct *tsk)
 {
 	/*
 	 * We don't actually care about the ttbr0 mapping, so point it at the
 	 * zero page.
 	 */
 	update_saved_ttbr0(tsk, &init_mm);
 }

 static inline void __switch_mm(struct mm_struct *next)
 {
 	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;
 	}

 	check_and_switch_context(next, cpu);
 }

 static inline void
 switch_mm(struct mm_struct *prev, struct mm_struct *next,
 	  struct task_struct *tsk)
 {
 	if (prev != next)
 		__switch_mm(next);

 	/*
 	 * Update the saved TTBR0_EL1 of the scheduled-in task as the previous
 	 * value may have not been initialised yet (activate_mm caller) or the
 	 * ASID has changed since the last run (following the context switch
 	 * of another thread of the same process).
 	 */
 	update_saved_ttbr0(tsk, next);
 }

 #define deactivate_mm(tsk,mm)	do { } while (0)
 #define activate_mm(prev,next)	switch_mm(prev, next, current)

 void verify_cpu_asid_bits(void);
 void post_ttbr_update_workaround(void);

 #endif /* !__ASSEMBLY__ */

 #endif /* !__ASM_MMU_CONTEXT_H */
	/* SPDX-License-Identifier: GPL-2.0-only */
	/*
	* Based on arch/arm/include/asm/mmu_context.h
	*
	* Copyright (C) 1996 Russell King.
	* Copyright (C) 2012 ARM Ltd.
	*/
	#ifndef __ASM_MMU_CONTEXT_H
	#define __ASM_MMU_CONTEXT_H

	#ifndef __ASSEMBLY__

	#include <linux/compiler.h>
	#include <linux/sched.h>
	#include <linux/sched/hotplug.h>
	#include <linux/mm_types.h>

	#include <asm/cacheflush.h>
	#include <asm/cpufeature.h>
	#include <asm/proc-fns.h>
	#include <asm-generic/mm_hooks.h>
	#include <asm/cputype.h>
	#include <asm/pgtable.h>
	#include <asm/sysreg.h>
	#include <asm/tlbflush.h>

	extern bool rodata_full;

	static inline void contextidr_thread_switch(struct task_struct *next)
	{
	if (!IS_ENABLED(CONFIG_PID_IN_CONTEXTIDR))
	return;

	write_sysreg(task_pid_nr(next), contextidr_el1);
	isb();
	}

	/*
	* Set TTBR0 to empty_zero_page. No translations will be possible via TTBR0.
	*/
	static inline void cpu_set_reserved_ttbr0(void)
	{
	unsigned long ttbr = phys_to_ttbr(__pa_symbol(empty_zero_page));

	write_sysreg(ttbr, ttbr0_el1);
	isb();
	}

	static inline void cpu_switch_mm(pgd_t pgd, struct mm_struct mm)
	{
	BUG_ON(pgd == swapper_pg_dir);
	cpu_set_reserved_ttbr0();
	cpu_do_switch_mm(virt_to_phys(pgd),mm);
	}

	/*
	* 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;
	extern u64 idmap_ptrs_per_pgd;

	static inline bool __cpu_uses_extended_idmap(void)
	{
	if (IS_ENABLED(CONFIG_ARM64_VA_BITS_52))
	return false;

	return unlikely(idmap_t0sz != TCR_T0SZ(VA_BITS));
	}

	/*
	* True if the extended ID map requires an extra level of translation table
	* to be configured.
	*/
	static inline bool __cpu_uses_extended_idmap_level(void)
	{
	return ARM64_HW_PGTABLE_LEVELS(64 - idmap_t0sz) > CONFIG_PGTABLE_LEVELS;
	}

	/*
	* Set TCR.T0SZ to its default value (based on VA_BITS)
	*/
	static inline void __cpu_set_tcr_t0sz(unsigned long t0sz)
	{
	unsigned long tcr;

	if (!__cpu_uses_extended_idmap())
	return;

	tcr = read_sysreg(tcr_el1);
	tcr &= ~TCR_T0SZ_MASK;
	tcr \|= t0sz << TCR_T0SZ_OFFSET;
	write_sysreg(tcr, tcr_el1);
	isb();
	}

	#define cpu_set_default_tcr_t0sz() __cpu_set_tcr_t0sz(TCR_T0SZ(vabits_actual))
	#define cpu_set_idmap_tcr_t0sz() __cpu_set_tcr_t0sz(idmap_t0sz)

	/*
	* Remove the idmap from TTBR0_EL1 and install the pgd of the active mm.
	*
	* The idmap lives in the same VA range as userspace, but uses global entries
	* and may use a different TCR_EL1.T0SZ. To avoid issues resulting from
	* speculative TLB fetches, we must temporarily install the reserved page
	* tables while we invalidate the TLBs and set up the correct TCR_EL1.T0SZ.
	*
	* If current is a not a user task, the mm covers the TTBR1_EL1 page tables,
	* which should not be installed in TTBR0_EL1. In this case we can leave the
	* reserved page tables in place.
	*/
	static inline void cpu_uninstall_idmap(void)
	{
	struct mm_struct *mm = current->active_mm;

	cpu_set_reserved_ttbr0();
	local_flush_tlb_all();
	cpu_set_default_tcr_t0sz();

	if (mm != &init_mm && !system_uses_ttbr0_pan())
	cpu_switch_mm(mm->pgd, mm);
	}

	static inline void cpu_install_idmap(void)
	{
	cpu_set_reserved_ttbr0();
	local_flush_tlb_all();
	cpu_set_idmap_tcr_t0sz();

	cpu_switch_mm(lm_alias(idmap_pg_dir), &init_mm);
	}

	/*
	* Atomically replaces the active TTBR1_EL1 PGD with a new VA-compatible PGD,
	* avoiding the possibility of conflicting TLB entries being allocated.
	*/
	static inline void cpu_replace_ttbr1(pgd_t *pgdp)
	{
	typedef void (ttbr_replace_func)(phys_addr_t);
	extern ttbr_replace_func idmap_cpu_replace_ttbr1;
	ttbr_replace_func *replace_phys;

	/* phys_to_ttbr() zeros lower 2 bits of ttbr with 52-bit PA */
	phys_addr_t ttbr1 = phys_to_ttbr(virt_to_phys(pgdp));

	if (system_supports_cnp() && !WARN_ON(pgdp != lm_alias(swapper_pg_dir))) {
	/*
	* cpu_replace_ttbr1() is used when there's a boot CPU
	* up (i.e. cpufeature framework is not up yet) and
	* latter only when we enable CNP via cpufeature's
	* enable() callback.
	* Also we rely on the cpu_hwcap bit being set before
	* calling the enable() function.
	*/
	ttbr1 \|= TTBR_CNP_BIT;
	}

	replace_phys = (void *)__pa_symbol(idmap_cpu_replace_ttbr1);

	cpu_install_idmap();
	replace_phys(ttbr1);
	cpu_uninstall_idmap();
	}

	/*
	* 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; })

	#ifdef CONFIG_ARM64_SW_TTBR0_PAN
	static inline void update_saved_ttbr0(struct task_struct *tsk,
	struct mm_struct *mm)
	{
	u64 ttbr;

	if (!system_uses_ttbr0_pan())
	return;

	if (mm == &init_mm)
	ttbr = __pa_symbol(empty_zero_page);
	else
	ttbr = virt_to_phys(mm->pgd) \| ASID(mm) << 48;

	WRITE_ONCE(task_thread_info(tsk)->ttbr0, ttbr);
	}
	#else
	static inline void update_saved_ttbr0(struct task_struct *tsk,
	struct mm_struct *mm)
	{
	}
	#endif

	static inline void
	enter_lazy_tlb(struct mm_struct mm, struct task_struct tsk)
	{
	/*
	* We don't actually care about the ttbr0 mapping, so point it at the
	* zero page.
	*/
	update_saved_ttbr0(tsk, &init_mm);
	}

	static inline void __switch_mm(struct mm_struct *next)
	{
	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;
	}

	check_and_switch_context(next, cpu);
	}

	static inline void
	switch_mm(struct mm_struct prev, struct mm_struct next,
	struct task_struct *tsk)
	{
	if (prev != next)
	__switch_mm(next);

	/*
	* Update the saved TTBR0_EL1 of the scheduled-in task as the previous
	* value may have not been initialised yet (activate_mm caller) or the
	* ASID has changed since the last run (following the context switch
	* of another thread of the same process).
	*/
	update_saved_ttbr0(tsk, next);
	}

	#define deactivate_mm(tsk,mm) do { } while (0)
	#define activate_mm(prev,next) switch_mm(prev, next, current)

	void verify_cpu_asid_bits(void);
	void post_ttbr_update_workaround(void);

	#endif /* !__ASSEMBLY__ */

	#endif /* !__ASM_MMU_CONTEXT_H */