1 files changed, 246 insertions, 0 deletions
diff --git a/arch/arm64/include/asm/mmu_context.h b/arch/arm64/include/asm/mmu_context.h
new file mode 100644
index 000000000..39ec0b8a6
--- /dev/null
+++ b/arch/arm64/include/asm/mmu_context.h
@@ -0,0 +1,246 @@
+/*
+ * 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
+
+#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>
+
+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)
+{
+	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(VA_BITS))
+#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_addr_t pgd_phys = virt_to_phys(pgdp);
+
+	replace_phys = (void *)__pa_symbol(idmap_cpu_replace_ttbr1);
+
+	cpu_install_idmap();
+	replace_phys(pgd_phys);
+	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 */