1 files changed, 276 insertions, 0 deletions
diff --git a/arch/arm/mm/context.c b/arch/arm/mm/context.c
new file mode 100644
index 000000000..4204ffa2d
--- /dev/null
+++ b/arch/arm/mm/context.c
@@ -0,0 +1,276 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ *  linux/arch/arm/mm/context.c
+ *
+ *  Copyright (C) 2002-2003 Deep Blue Solutions Ltd, all rights reserved.
+ *  Copyright (C) 2012 ARM Limited
+ *
+ *  Author: Will Deacon <will.deacon@arm.com>
+ */
+#include <linux/init.h>
+#include <linux/sched.h>
+#include <linux/mm.h>
+#include <linux/smp.h>
+#include <linux/percpu.h>
+
+#include <asm/mmu_context.h>
+#include <asm/smp_plat.h>
+#include <asm/thread_notify.h>
+#include <asm/tlbflush.h>
+#include <asm/proc-fns.h>
+
+/*
+ * On ARMv6, we have the following structure in the Context ID:
+ *
+ * 31                         7          0
+ * +-------------------------+-----------+
+ * |      process ID         |   ASID    |
+ * +-------------------------+-----------+
+ * |              context ID             |
+ * +-------------------------------------+
+ *
+ * The ASID is used to tag entries in the CPU caches and TLBs.
+ * The context ID is used by debuggers and trace logic, and
+ * should be unique within all running processes.
+ *
+ * In big endian operation, the two 32 bit words are swapped if accessed
+ * by non-64-bit operations.
+ */
+#define ASID_FIRST_VERSION	(1ULL << ASID_BITS)
+#define NUM_USER_ASIDS		ASID_FIRST_VERSION
+
+static DEFINE_RAW_SPINLOCK(cpu_asid_lock);
+static atomic64_t asid_generation = ATOMIC64_INIT(ASID_FIRST_VERSION);
+static DECLARE_BITMAP(asid_map, NUM_USER_ASIDS);
+
+static DEFINE_PER_CPU(atomic64_t, active_asids);
+static DEFINE_PER_CPU(u64, reserved_asids);
+static cpumask_t tlb_flush_pending;
+
+#ifdef CONFIG_ARM_ERRATA_798181
+void a15_erratum_get_cpumask(int this_cpu, struct mm_struct *mm,
+			     cpumask_t *mask)
+{
+	int cpu;
+	unsigned long flags;
+	u64 context_id, asid;
+
+	raw_spin_lock_irqsave(&cpu_asid_lock, flags);
+	context_id = mm->context.id.counter;
+	for_each_online_cpu(cpu) {
+		if (cpu == this_cpu)
+			continue;
+		/*
+		 * We only need to send an IPI if the other CPUs are
+		 * running the same ASID as the one being invalidated.
+		 */
+		asid = per_cpu(active_asids, cpu).counter;
+		if (asid == 0)
+			asid = per_cpu(reserved_asids, cpu);
+		if (context_id == asid)
+			cpumask_set_cpu(cpu, mask);
+	}
+	raw_spin_unlock_irqrestore(&cpu_asid_lock, flags);
+}
+#endif
+
+#ifdef CONFIG_ARM_LPAE
+/*
+ * With LPAE, the ASID and page tables are updated atomicly, so there is
+ * no need for a reserved set of tables (the active ASID tracking prevents
+ * any issues across a rollover).
+ */
+#define cpu_set_reserved_ttbr0()
+#else
+static void cpu_set_reserved_ttbr0(void)
+{
+	u32 ttb;
+	/*
+	 * Copy TTBR1 into TTBR0.
+	 * This points at swapper_pg_dir, which contains only global
+	 * entries so any speculative walks are perfectly safe.
+	 */
+	asm volatile(
+	"	mrc	p15, 0, %0, c2, c0, 1		@ read TTBR1\n"
+	"	mcr	p15, 0, %0, c2, c0, 0		@ set TTBR0\n"
+	: "=r" (ttb));
+	isb();
+}
+#endif
+
+#ifdef CONFIG_PID_IN_CONTEXTIDR
+static int contextidr_notifier(struct notifier_block *unused, unsigned long cmd,
+			       void *t)
+{
+	u32 contextidr;
+	pid_t pid;
+	struct thread_info *thread = t;
+
+	if (cmd != THREAD_NOTIFY_SWITCH)
+		return NOTIFY_DONE;
+
+	pid = task_pid_nr(thread_task(thread)) << ASID_BITS;
+	asm volatile(
+	"	mrc	p15, 0, %0, c13, c0, 1\n"
+	"	and	%0, %0, %2\n"
+	"	orr	%0, %0, %1\n"
+	"	mcr	p15, 0, %0, c13, c0, 1\n"
+	: "=r" (contextidr), "+r" (pid)
+	: "I" (~ASID_MASK));
+	isb();
+
+	return NOTIFY_OK;
+}
+
+static struct notifier_block contextidr_notifier_block = {
+	.notifier_call = contextidr_notifier,
+};
+
+static int __init contextidr_notifier_init(void)
+{
+	return thread_register_notifier(&contextidr_notifier_block);
+}
+arch_initcall(contextidr_notifier_init);
+#endif
+
+static void flush_context(unsigned int cpu)
+{
+	int i;
+	u64 asid;
+
+	/* Update the list of reserved ASIDs and the ASID bitmap. */
+	bitmap_clear(asid_map, 0, NUM_USER_ASIDS);
+	for_each_possible_cpu(i) {
+		asid = atomic64_xchg(&per_cpu(active_asids, i), 0);
+		/*
+		 * If this CPU has already been through a
+		 * rollover, but hasn't run another task in
+		 * the meantime, we must preserve its reserved
+		 * ASID, as this is the only trace we have of
+		 * the process it is still running.
+		 */
+		if (asid == 0)
+			asid = per_cpu(reserved_asids, i);
+		__set_bit(asid & ~ASID_MASK, asid_map);
+		per_cpu(reserved_asids, i) = asid;
+	}
+
+	/* Queue a TLB invalidate and flush the I-cache if necessary. */
+	cpumask_setall(&tlb_flush_pending);
+
+	if (icache_is_vivt_asid_tagged())
+		__flush_icache_all();
+}
+
+static bool check_update_reserved_asid(u64 asid, u64 newasid)
+{
+	int cpu;
+	bool hit = false;
+
+	/*
+	 * Iterate over the set of reserved ASIDs looking for a match.
+	 * If we find one, then we can update our mm to use newasid
+	 * (i.e. the same ASID in the current generation) but we can't
+	 * exit the loop early, since we need to ensure that all copies
+	 * of the old ASID are updated to reflect the mm. Failure to do
+	 * so could result in us missing the reserved ASID in a future
+	 * generation.
+	 */
+	for_each_possible_cpu(cpu) {
+		if (per_cpu(reserved_asids, cpu) == asid) {
+			hit = true;
+			per_cpu(reserved_asids, cpu) = newasid;
+		}
+	}
+
+	return hit;
+}
+
+static u64 new_context(struct mm_struct *mm, unsigned int cpu)
+{
+	static u32 cur_idx = 1;
+	u64 asid = atomic64_read(&mm->context.id);
+	u64 generation = atomic64_read(&asid_generation);
+
+	if (asid != 0) {
+		u64 newasid = generation | (asid & ~ASID_MASK);
+
+		/*
+		 * If our current ASID was active during a rollover, we
+		 * can continue to use it and this was just a false alarm.
+		 */
+		if (check_update_reserved_asid(asid, newasid))
+			return newasid;
+
+		/*
+		 * We had a valid ASID in a previous life, so try to re-use
+		 * it if possible.,
+		 */
+		asid &= ~ASID_MASK;
+		if (!__test_and_set_bit(asid, asid_map))
+			return newasid;
+	}
+
+	/*
+	 * Allocate a free ASID. If we can't find one, take a note of the
+	 * currently active ASIDs and mark the TLBs as requiring flushes.
+	 * We always count from ASID #1, as we reserve ASID #0 to switch
+	 * via TTBR0 and to avoid speculative page table walks from hitting
+	 * in any partial walk caches, which could be populated from
+	 * overlapping level-1 descriptors used to map both the module
+	 * area and the userspace stack.
+	 */
+	asid = find_next_zero_bit(asid_map, NUM_USER_ASIDS, cur_idx);
+	if (asid == NUM_USER_ASIDS) {
+		generation = atomic64_add_return(ASID_FIRST_VERSION,
+						 &asid_generation);
+		flush_context(cpu);
+		asid = find_next_zero_bit(asid_map, NUM_USER_ASIDS, 1);
+	}
+
+	__set_bit(asid, asid_map);
+	cur_idx = asid;
+	cpumask_clear(mm_cpumask(mm));
+	return asid | generation;
+}
+
+void check_and_switch_context(struct mm_struct *mm, struct task_struct *tsk)
+{
+	unsigned long flags;
+	unsigned int cpu = smp_processor_id();
+	u64 asid;
+
+	check_vmalloc_seq(mm);
+
+	/*
+	 * We cannot update the pgd and the ASID atomicly with classic
+	 * MMU, so switch exclusively to global mappings to avoid
+	 * speculative page table walking with the wrong TTBR.
+	 */
+	cpu_set_reserved_ttbr0();
+
+	asid = atomic64_read(&mm->context.id);
+	if (!((asid ^ atomic64_read(&asid_generation)) >> ASID_BITS)
+	    && atomic64_xchg(&per_cpu(active_asids, cpu), asid))
+		goto switch_mm_fastpath;
+
+	raw_spin_lock_irqsave(&cpu_asid_lock, flags);
+	/* Check that our ASID belongs to the current generation. */
+	asid = atomic64_read(&mm->context.id);
+	if ((asid ^ atomic64_read(&asid_generation)) >> ASID_BITS) {
+		asid = new_context(mm, cpu);
+		atomic64_set(&mm->context.id, asid);
+	}
+
+	if (cpumask_test_and_clear_cpu(cpu, &tlb_flush_pending)) {
+		local_flush_bp_all();
+		local_flush_tlb_all();
+	}
+
+	atomic64_set(&per_cpu(active_asids, cpu), asid);
+	cpumask_set_cpu(cpu, mm_cpumask(mm));
+	raw_spin_unlock_irqrestore(&cpu_asid_lock, flags);
+
+switch_mm_fastpath:
+	cpu_switch_mm(mm->pgd, mm);
+}