1 files changed, 349 insertions, 0 deletions
diff --git a/arch/powerpc/mm/book3s64/mmu_context.c b/arch/powerpc/mm/book3s64/mmu_context.c
new file mode 100644
index 000000000..c766e4c26
--- /dev/null
+++ b/arch/powerpc/mm/book3s64/mmu_context.c
@@ -0,0 +1,349 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+/*
+ *  MMU context allocation for 64-bit kernels.
+ *
+ *  Copyright (C) 2004 Anton Blanchard, IBM Corp. <anton@samba.org>
+ */
+
+#include <linux/sched.h>
+#include <linux/kernel.h>
+#include <linux/errno.h>
+#include <linux/string.h>
+#include <linux/types.h>
+#include <linux/mm.h>
+#include <linux/pkeys.h>
+#include <linux/spinlock.h>
+#include <linux/idr.h>
+#include <linux/export.h>
+#include <linux/gfp.h>
+#include <linux/slab.h>
+#include <linux/cpu.h>
+
+#include <asm/mmu_context.h>
+#include <asm/pgalloc.h>
+
+#include "internal.h"
+
+static DEFINE_IDA(mmu_context_ida);
+
+static int alloc_context_id(int min_id, int max_id)
+{
+	return ida_alloc_range(&mmu_context_ida, min_id, max_id, GFP_KERNEL);
+}
+
+#ifdef CONFIG_PPC_64S_HASH_MMU
+void __init hash__reserve_context_id(int id)
+{
+	int result = ida_alloc_range(&mmu_context_ida, id, id, GFP_KERNEL);
+
+	WARN(result != id, "mmu: Failed to reserve context id %d (rc %d)\n", id, result);
+}
+
+int hash__alloc_context_id(void)
+{
+	unsigned long max;
+
+	if (mmu_has_feature(MMU_FTR_68_BIT_VA))
+		max = MAX_USER_CONTEXT;
+	else
+		max = MAX_USER_CONTEXT_65BIT_VA;
+
+	return alloc_context_id(MIN_USER_CONTEXT, max);
+}
+EXPORT_SYMBOL_GPL(hash__alloc_context_id);
+#endif
+
+#ifdef CONFIG_PPC_64S_HASH_MMU
+static int realloc_context_ids(mm_context_t *ctx)
+{
+	int i, id;
+
+	/*
+	 * id 0 (aka. ctx->id) is special, we always allocate a new one, even if
+	 * there wasn't one allocated previously (which happens in the exec
+	 * case where ctx is newly allocated).
+	 *
+	 * We have to be a bit careful here. We must keep the existing ids in
+	 * the array, so that we can test if they're non-zero to decide if we
+	 * need to allocate a new one. However in case of error we must free the
+	 * ids we've allocated but *not* any of the existing ones (or risk a
+	 * UAF). That's why we decrement i at the start of the error handling
+	 * loop, to skip the id that we just tested but couldn't reallocate.
+	 */
+	for (i = 0; i < ARRAY_SIZE(ctx->extended_id); i++) {
+		if (i == 0 || ctx->extended_id[i]) {
+			id = hash__alloc_context_id();
+			if (id < 0)
+				goto error;
+
+			ctx->extended_id[i] = id;
+		}
+	}
+
+	/* The caller expects us to return id */
+	return ctx->id;
+
+error:
+	for (i--; i >= 0; i--) {
+		if (ctx->extended_id[i])
+			ida_free(&mmu_context_ida, ctx->extended_id[i]);
+	}
+
+	return id;
+}
+
+static int hash__init_new_context(struct mm_struct *mm)
+{
+	int index;
+
+	mm->context.hash_context = kmalloc(sizeof(struct hash_mm_context),
+					   GFP_KERNEL);
+	if (!mm->context.hash_context)
+		return -ENOMEM;
+
+	/*
+	 * The old code would re-promote on fork, we don't do that when using
+	 * slices as it could cause problem promoting slices that have been
+	 * forced down to 4K.
+	 *
+	 * For book3s we have MMU_NO_CONTEXT set to be ~0. Hence check
+	 * explicitly against context.id == 0. This ensures that we properly
+	 * initialize context slice details for newly allocated mm's (which will
+	 * have id == 0) and don't alter context slice inherited via fork (which
+	 * will have id != 0).
+	 *
+	 * We should not be calling init_new_context() on init_mm. Hence a
+	 * check against 0 is OK.
+	 */
+	if (mm->context.id == 0) {
+		memset(mm->context.hash_context, 0, sizeof(struct hash_mm_context));
+		slice_init_new_context_exec(mm);
+	} else {
+		/* This is fork. Copy hash_context details from current->mm */
+		memcpy(mm->context.hash_context, current->mm->context.hash_context, sizeof(struct hash_mm_context));
+#ifdef CONFIG_PPC_SUBPAGE_PROT
+		/* inherit subpage prot details if we have one. */
+		if (current->mm->context.hash_context->spt) {
+			mm->context.hash_context->spt = kmalloc(sizeof(struct subpage_prot_table),
+								GFP_KERNEL);
+			if (!mm->context.hash_context->spt) {
+				kfree(mm->context.hash_context);
+				return -ENOMEM;
+			}
+		}
+#endif
+	}
+
+	index = realloc_context_ids(&mm->context);
+	if (index < 0) {
+#ifdef CONFIG_PPC_SUBPAGE_PROT
+		kfree(mm->context.hash_context->spt);
+#endif
+		kfree(mm->context.hash_context);
+		return index;
+	}
+
+	pkey_mm_init(mm);
+	return index;
+}
+
+void hash__setup_new_exec(void)
+{
+	slice_setup_new_exec();
+
+	slb_setup_new_exec();
+}
+#else
+static inline int hash__init_new_context(struct mm_struct *mm)
+{
+	BUILD_BUG();
+	return 0;
+}
+#endif
+
+static int radix__init_new_context(struct mm_struct *mm)
+{
+	unsigned long rts_field;
+	int index, max_id;
+
+	max_id = (1 << mmu_pid_bits) - 1;
+	index = alloc_context_id(mmu_base_pid, max_id);
+	if (index < 0)
+		return index;
+
+	/*
+	 * set the process table entry,
+	 */
+	rts_field = radix__get_tree_size();
+	process_tb[index].prtb0 = cpu_to_be64(rts_field | __pa(mm->pgd) | RADIX_PGD_INDEX_SIZE);
+
+	/*
+	 * Order the above store with subsequent update of the PID
+	 * register (at which point HW can start loading/caching
+	 * the entry) and the corresponding load by the MMU from
+	 * the L2 cache.
+	 */
+	asm volatile("ptesync;isync" : : : "memory");
+
+#ifdef CONFIG_PPC_64S_HASH_MMU
+	mm->context.hash_context = NULL;
+#endif
+
+	return index;
+}
+
+int init_new_context(struct task_struct *tsk, struct mm_struct *mm)
+{
+	int index;
+
+	if (radix_enabled())
+		index = radix__init_new_context(mm);
+	else
+		index = hash__init_new_context(mm);
+
+	if (index < 0)
+		return index;
+
+	mm->context.id = index;
+
+	mm->context.pte_frag = NULL;
+	mm->context.pmd_frag = NULL;
+#ifdef CONFIG_SPAPR_TCE_IOMMU
+	mm_iommu_init(mm);
+#endif
+	atomic_set(&mm->context.active_cpus, 0);
+	atomic_set(&mm->context.copros, 0);
+
+	return 0;
+}
+
+void __destroy_context(int context_id)
+{
+	ida_free(&mmu_context_ida, context_id);
+}
+EXPORT_SYMBOL_GPL(__destroy_context);
+
+static void destroy_contexts(mm_context_t *ctx)
+{
+	if (radix_enabled()) {
+		ida_free(&mmu_context_ida, ctx->id);
+	} else {
+#ifdef CONFIG_PPC_64S_HASH_MMU
+		int index, context_id;
+
+		for (index = 0; index < ARRAY_SIZE(ctx->extended_id); index++) {
+			context_id = ctx->extended_id[index];
+			if (context_id)
+				ida_free(&mmu_context_ida, context_id);
+		}
+		kfree(ctx->hash_context);
+#else
+		BUILD_BUG(); // radix_enabled() should be constant true
+#endif
+	}
+}
+
+static void pmd_frag_destroy(void *pmd_frag)
+{
+	int count;
+	struct page *page;
+
+	page = virt_to_page(pmd_frag);
+	/* drop all the pending references */
+	count = ((unsigned long)pmd_frag & ~PAGE_MASK) >> PMD_FRAG_SIZE_SHIFT;
+	/* We allow PTE_FRAG_NR fragments from a PTE page */
+	if (atomic_sub_and_test(PMD_FRAG_NR - count, &page->pt_frag_refcount)) {
+		pgtable_pmd_page_dtor(page);
+		__free_page(page);
+	}
+}
+
+static void destroy_pagetable_cache(struct mm_struct *mm)
+{
+	void *frag;
+
+	frag = mm->context.pte_frag;
+	if (frag)
+		pte_frag_destroy(frag);
+
+	frag = mm->context.pmd_frag;
+	if (frag)
+		pmd_frag_destroy(frag);
+	return;
+}
+
+void destroy_context(struct mm_struct *mm)
+{
+#ifdef CONFIG_SPAPR_TCE_IOMMU
+	WARN_ON_ONCE(!list_empty(&mm->context.iommu_group_mem_list));
+#endif
+	/*
+	 * For tasks which were successfully initialized we end up calling
+	 * arch_exit_mmap() which clears the process table entry. And
+	 * arch_exit_mmap() is called before the required fullmm TLB flush
+	 * which does a RIC=2 flush. Hence for an initialized task, we do clear
+	 * any cached process table entries.
+	 *
+	 * The condition below handles the error case during task init. We have
+	 * set the process table entry early and if we fail a task
+	 * initialization, we need to ensure the process table entry is zeroed.
+	 * We need not worry about process table entry caches because the task
+	 * never ran with the PID value.
+	 */
+	if (radix_enabled())
+		process_tb[mm->context.id].prtb0 = 0;
+	else
+		subpage_prot_free(mm);
+	destroy_contexts(&mm->context);
+	mm->context.id = MMU_NO_CONTEXT;
+}
+
+void arch_exit_mmap(struct mm_struct *mm)
+{
+	destroy_pagetable_cache(mm);
+
+	if (radix_enabled()) {
+		/*
+		 * Radix doesn't have a valid bit in the process table
+		 * entries. However we know that at least P9 implementation
+		 * will avoid caching an entry with an invalid RTS field,
+		 * and 0 is invalid. So this will do.
+		 *
+		 * This runs before the "fullmm" tlb flush in exit_mmap,
+		 * which does a RIC=2 tlbie to clear the process table
+		 * entry. See the "fullmm" comments in tlb-radix.c.
+		 *
+		 * No barrier required here after the store because
+		 * this process will do the invalidate, which starts with
+		 * ptesync.
+		 */
+		process_tb[mm->context.id].prtb0 = 0;
+	}
+}
+
+#ifdef CONFIG_PPC_RADIX_MMU
+void radix__switch_mmu_context(struct mm_struct *prev, struct mm_struct *next)
+{
+	mtspr(SPRN_PID, next->context.id);
+	isync();
+}
+#endif
+
+/**
+ * cleanup_cpu_mmu_context - Clean up MMU details for this CPU (newly offlined)
+ *
+ * This clears the CPU from mm_cpumask for all processes, and then flushes the
+ * local TLB to ensure TLB coherency in case the CPU is onlined again.
+ *
+ * KVM guest translations are not necessarily flushed here. If KVM started
+ * using mm_cpumask or the Linux APIs which do, this would have to be resolved.
+ */
+#ifdef CONFIG_HOTPLUG_CPU
+void cleanup_cpu_mmu_context(void)
+{
+	int cpu = smp_processor_id();
+
+	clear_tasks_mm_cpumask(cpu);
+	tlbiel_all();
+}
+#endif