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-rw-r--r--arch/arm64/mm/context.c422
1 files changed, 422 insertions, 0 deletions
diff --git a/arch/arm64/mm/context.c b/arch/arm64/mm/context.c
new file mode 100644
index 0000000000..188197590f
--- /dev/null
+++ b/arch/arm64/mm/context.c
@@ -0,0 +1,422 @@
+// SPDX-License-Identifier: GPL-2.0-only
+/*
+ * Based on arch/arm/mm/context.c
+ *
+ * Copyright (C) 2002-2003 Deep Blue Solutions Ltd, all rights reserved.
+ * Copyright (C) 2012 ARM Ltd.
+ */
+
+#include <linux/bitfield.h>
+#include <linux/bitops.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/mm.h>
+
+#include <asm/cpufeature.h>
+#include <asm/mmu_context.h>
+#include <asm/smp.h>
+#include <asm/tlbflush.h>
+
+static u32 asid_bits;
+static DEFINE_RAW_SPINLOCK(cpu_asid_lock);
+
+static atomic64_t asid_generation;
+static unsigned long *asid_map;
+
+static DEFINE_PER_CPU(atomic64_t, active_asids);
+static DEFINE_PER_CPU(u64, reserved_asids);
+static cpumask_t tlb_flush_pending;
+
+static unsigned long max_pinned_asids;
+static unsigned long nr_pinned_asids;
+static unsigned long *pinned_asid_map;
+
+#define ASID_MASK (~GENMASK(asid_bits - 1, 0))
+#define ASID_FIRST_VERSION (1UL << asid_bits)
+
+#define NUM_USER_ASIDS ASID_FIRST_VERSION
+#define ctxid2asid(asid) ((asid) & ~ASID_MASK)
+#define asid2ctxid(asid, genid) ((asid) | (genid))
+
+/* Get the ASIDBits supported by the current CPU */
+static u32 get_cpu_asid_bits(void)
+{
+ u32 asid;
+ int fld = cpuid_feature_extract_unsigned_field(read_cpuid(ID_AA64MMFR0_EL1),
+ ID_AA64MMFR0_EL1_ASIDBITS_SHIFT);
+
+ switch (fld) {
+ default:
+ pr_warn("CPU%d: Unknown ASID size (%d); assuming 8-bit\n",
+ smp_processor_id(), fld);
+ fallthrough;
+ case ID_AA64MMFR0_EL1_ASIDBITS_8:
+ asid = 8;
+ break;
+ case ID_AA64MMFR0_EL1_ASIDBITS_16:
+ asid = 16;
+ }
+
+ return asid;
+}
+
+/* Check if the current cpu's ASIDBits is compatible with asid_bits */
+void verify_cpu_asid_bits(void)
+{
+ u32 asid = get_cpu_asid_bits();
+
+ if (asid < asid_bits) {
+ /*
+ * We cannot decrease the ASID size at runtime, so panic if we support
+ * fewer ASID bits than the boot CPU.
+ */
+ pr_crit("CPU%d: smaller ASID size(%u) than boot CPU (%u)\n",
+ smp_processor_id(), asid, asid_bits);
+ cpu_panic_kernel();
+ }
+}
+
+static void set_kpti_asid_bits(unsigned long *map)
+{
+ unsigned int len = BITS_TO_LONGS(NUM_USER_ASIDS) * sizeof(unsigned long);
+ /*
+ * In case of KPTI kernel/user ASIDs are allocated in
+ * pairs, the bottom bit distinguishes the two: if it
+ * is set, then the ASID will map only userspace. Thus
+ * mark even as reserved for kernel.
+ */
+ memset(map, 0xaa, len);
+}
+
+static void set_reserved_asid_bits(void)
+{
+ if (pinned_asid_map)
+ bitmap_copy(asid_map, pinned_asid_map, NUM_USER_ASIDS);
+ else if (arm64_kernel_unmapped_at_el0())
+ set_kpti_asid_bits(asid_map);
+ else
+ bitmap_clear(asid_map, 0, NUM_USER_ASIDS);
+}
+
+#define asid_gen_match(asid) \
+ (!(((asid) ^ atomic64_read(&asid_generation)) >> asid_bits))
+
+static void flush_context(void)
+{
+ int i;
+ u64 asid;
+
+ /* Update the list of reserved ASIDs and the ASID bitmap. */
+ set_reserved_asid_bits();
+
+ for_each_possible_cpu(i) {
+ asid = atomic64_xchg_relaxed(&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(ctxid2asid(asid), asid_map);
+ per_cpu(reserved_asids, i) = asid;
+ }
+
+ /*
+ * Queue a TLB invalidation for each CPU to perform on next
+ * context-switch
+ */
+ cpumask_setall(&tlb_flush_pending);
+}
+
+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)
+{
+ static u32 cur_idx = 1;
+ u64 asid = atomic64_read(&mm->context.id);
+ u64 generation = atomic64_read(&asid_generation);
+
+ if (asid != 0) {
+ u64 newasid = asid2ctxid(ctxid2asid(asid), generation);
+
+ /*
+ * 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;
+
+ /*
+ * If it is pinned, we can keep using it. Note that reserved
+ * takes priority, because even if it is also pinned, we need to
+ * update the generation into the reserved_asids.
+ */
+ if (refcount_read(&mm->context.pinned))
+ return newasid;
+
+ /*
+ * We had a valid ASID in a previous life, so try to re-use
+ * it if possible.
+ */
+ if (!__test_and_set_bit(ctxid2asid(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 #2 (index 1), as we use ASID #0 when setting
+ * a reserved TTBR0 for the init_mm and we allocate ASIDs in even/odd
+ * pairs.
+ */
+ asid = find_next_zero_bit(asid_map, NUM_USER_ASIDS, cur_idx);
+ if (asid != NUM_USER_ASIDS)
+ goto set_asid;
+
+ /* We're out of ASIDs, so increment the global generation count */
+ generation = atomic64_add_return_relaxed(ASID_FIRST_VERSION,
+ &asid_generation);
+ flush_context();
+
+ /* We have more ASIDs than CPUs, so this will always succeed */
+ asid = find_next_zero_bit(asid_map, NUM_USER_ASIDS, 1);
+
+set_asid:
+ __set_bit(asid, asid_map);
+ cur_idx = asid;
+ return asid2ctxid(asid, generation);
+}
+
+void check_and_switch_context(struct mm_struct *mm)
+{
+ unsigned long flags;
+ unsigned int cpu;
+ u64 asid, old_active_asid;
+
+ if (system_supports_cnp())
+ cpu_set_reserved_ttbr0();
+
+ asid = atomic64_read(&mm->context.id);
+
+ /*
+ * The memory ordering here is subtle.
+ * If our active_asids is non-zero and the ASID matches the current
+ * generation, then we update the active_asids entry with a relaxed
+ * cmpxchg. Racing with a concurrent rollover means that either:
+ *
+ * - We get a zero back from the cmpxchg and end up waiting on the
+ * lock. Taking the lock synchronises with the rollover and so
+ * we are forced to see the updated generation.
+ *
+ * - We get a valid ASID back from the cmpxchg, which means the
+ * relaxed xchg in flush_context will treat us as reserved
+ * because atomic RmWs are totally ordered for a given location.
+ */
+ old_active_asid = atomic64_read(this_cpu_ptr(&active_asids));
+ if (old_active_asid && asid_gen_match(asid) &&
+ atomic64_cmpxchg_relaxed(this_cpu_ptr(&active_asids),
+ old_active_asid, 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_gen_match(asid)) {
+ asid = new_context(mm);
+ atomic64_set(&mm->context.id, asid);
+ }
+
+ cpu = smp_processor_id();
+ if (cpumask_test_and_clear_cpu(cpu, &tlb_flush_pending))
+ local_flush_tlb_all();
+
+ atomic64_set(this_cpu_ptr(&active_asids), asid);
+ raw_spin_unlock_irqrestore(&cpu_asid_lock, flags);
+
+switch_mm_fastpath:
+
+ arm64_apply_bp_hardening();
+
+ /*
+ * Defer TTBR0_EL1 setting for user threads to uaccess_enable() when
+ * emulating PAN.
+ */
+ if (!system_uses_ttbr0_pan())
+ cpu_switch_mm(mm->pgd, mm);
+}
+
+unsigned long arm64_mm_context_get(struct mm_struct *mm)
+{
+ unsigned long flags;
+ u64 asid;
+
+ if (!pinned_asid_map)
+ return 0;
+
+ raw_spin_lock_irqsave(&cpu_asid_lock, flags);
+
+ asid = atomic64_read(&mm->context.id);
+
+ if (refcount_inc_not_zero(&mm->context.pinned))
+ goto out_unlock;
+
+ if (nr_pinned_asids >= max_pinned_asids) {
+ asid = 0;
+ goto out_unlock;
+ }
+
+ if (!asid_gen_match(asid)) {
+ /*
+ * We went through one or more rollover since that ASID was
+ * used. Ensure that it is still valid, or generate a new one.
+ */
+ asid = new_context(mm);
+ atomic64_set(&mm->context.id, asid);
+ }
+
+ nr_pinned_asids++;
+ __set_bit(ctxid2asid(asid), pinned_asid_map);
+ refcount_set(&mm->context.pinned, 1);
+
+out_unlock:
+ raw_spin_unlock_irqrestore(&cpu_asid_lock, flags);
+
+ asid = ctxid2asid(asid);
+
+ /* Set the equivalent of USER_ASID_BIT */
+ if (asid && arm64_kernel_unmapped_at_el0())
+ asid |= 1;
+
+ return asid;
+}
+EXPORT_SYMBOL_GPL(arm64_mm_context_get);
+
+void arm64_mm_context_put(struct mm_struct *mm)
+{
+ unsigned long flags;
+ u64 asid = atomic64_read(&mm->context.id);
+
+ if (!pinned_asid_map)
+ return;
+
+ raw_spin_lock_irqsave(&cpu_asid_lock, flags);
+
+ if (refcount_dec_and_test(&mm->context.pinned)) {
+ __clear_bit(ctxid2asid(asid), pinned_asid_map);
+ nr_pinned_asids--;
+ }
+
+ raw_spin_unlock_irqrestore(&cpu_asid_lock, flags);
+}
+EXPORT_SYMBOL_GPL(arm64_mm_context_put);
+
+/* Errata workaround post TTBRx_EL1 update. */
+asmlinkage void post_ttbr_update_workaround(void)
+{
+ if (!IS_ENABLED(CONFIG_CAVIUM_ERRATUM_27456))
+ return;
+
+ asm(ALTERNATIVE("nop; nop; nop",
+ "ic iallu; dsb nsh; isb",
+ ARM64_WORKAROUND_CAVIUM_27456));
+}
+
+void cpu_do_switch_mm(phys_addr_t pgd_phys, struct mm_struct *mm)
+{
+ unsigned long ttbr1 = read_sysreg(ttbr1_el1);
+ unsigned long asid = ASID(mm);
+ unsigned long ttbr0 = phys_to_ttbr(pgd_phys);
+
+ /* Skip CNP for the reserved ASID */
+ if (system_supports_cnp() && asid)
+ ttbr0 |= TTBR_CNP_BIT;
+
+ /* SW PAN needs a copy of the ASID in TTBR0 for entry */
+ if (IS_ENABLED(CONFIG_ARM64_SW_TTBR0_PAN))
+ ttbr0 |= FIELD_PREP(TTBR_ASID_MASK, asid);
+
+ /* Set ASID in TTBR1 since TCR.A1 is set */
+ ttbr1 &= ~TTBR_ASID_MASK;
+ ttbr1 |= FIELD_PREP(TTBR_ASID_MASK, asid);
+
+ cpu_set_reserved_ttbr0_nosync();
+ write_sysreg(ttbr1, ttbr1_el1);
+ write_sysreg(ttbr0, ttbr0_el1);
+ isb();
+ post_ttbr_update_workaround();
+}
+
+static int asids_update_limit(void)
+{
+ unsigned long num_available_asids = NUM_USER_ASIDS;
+
+ if (arm64_kernel_unmapped_at_el0()) {
+ num_available_asids /= 2;
+ if (pinned_asid_map)
+ set_kpti_asid_bits(pinned_asid_map);
+ }
+ /*
+ * Expect allocation after rollover to fail if we don't have at least
+ * one more ASID than CPUs. ASID #0 is reserved for init_mm.
+ */
+ WARN_ON(num_available_asids - 1 <= num_possible_cpus());
+ pr_info("ASID allocator initialised with %lu entries\n",
+ num_available_asids);
+
+ /*
+ * There must always be an ASID available after rollover. Ensure that,
+ * even if all CPUs have a reserved ASID and the maximum number of ASIDs
+ * are pinned, there still is at least one empty slot in the ASID map.
+ */
+ max_pinned_asids = num_available_asids - num_possible_cpus() - 2;
+ return 0;
+}
+arch_initcall(asids_update_limit);
+
+static int asids_init(void)
+{
+ asid_bits = get_cpu_asid_bits();
+ atomic64_set(&asid_generation, ASID_FIRST_VERSION);
+ asid_map = bitmap_zalloc(NUM_USER_ASIDS, GFP_KERNEL);
+ if (!asid_map)
+ panic("Failed to allocate bitmap for %lu ASIDs\n",
+ NUM_USER_ASIDS);
+
+ pinned_asid_map = bitmap_zalloc(NUM_USER_ASIDS, GFP_KERNEL);
+ nr_pinned_asids = 0;
+
+ /*
+ * We cannot call set_reserved_asid_bits() here because CPU
+ * caps are not finalized yet, so it is safer to assume KPTI
+ * and reserve kernel ASID's from beginning.
+ */
+ if (IS_ENABLED(CONFIG_UNMAP_KERNEL_AT_EL0))
+ set_kpti_asid_bits(asid_map);
+ return 0;
+}
+early_initcall(asids_init);