/* SPDX-License-Identifier: GPL-2.0 */
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/*
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* Kernel Electric-Fence (KFENCE). For more info please see
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* Documentation/dev-tools/kfence.rst.
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*
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* Copyright (C) 2020, Google LLC.
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*/
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#ifndef MM_KFENCE_KFENCE_H
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#define MM_KFENCE_KFENCE_H
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#include <linux/mm.h>
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#include <linux/slab.h>
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#include <linux/spinlock.h>
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#include <linux/types.h>
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#include "../slab.h" /* for struct kmem_cache */
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/*
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* Get the canary byte pattern for @addr. Use a pattern that varies based on the
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* lower 3 bits of the address, to detect memory corruptions with higher
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* probability, where similar constants are used.
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*/
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#define KFENCE_CANARY_PATTERN(addr) ((u8)0xaa ^ (u8)((unsigned long)(addr) & 0x7))
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/* Maximum stack depth for reports. */
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#define KFENCE_STACK_DEPTH 64
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/* KFENCE object states. */
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enum kfence_object_state {
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KFENCE_OBJECT_UNUSED, /* Object is unused. */
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KFENCE_OBJECT_ALLOCATED, /* Object is currently allocated. */
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KFENCE_OBJECT_FREED, /* Object was allocated, and then freed. */
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};
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/* Alloc/free tracking information. */
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struct kfence_track {
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pid_t pid;
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int num_stack_entries;
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unsigned long stack_entries[KFENCE_STACK_DEPTH];
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};
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/* KFENCE metadata per guarded allocation. */
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struct kfence_metadata {
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struct list_head list; /* Freelist node; access under kfence_freelist_lock. */
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struct rcu_head rcu_head; /* For delayed freeing. */
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/*
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* Lock protecting below data; to ensure consistency of the below data,
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* since the following may execute concurrently: __kfence_alloc(),
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* __kfence_free(), kfence_handle_page_fault(). However, note that we
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* cannot grab the same metadata off the freelist twice, and multiple
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* __kfence_alloc() cannot run concurrently on the same metadata.
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*/
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raw_spinlock_t lock;
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/* The current state of the object; see above. */
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enum kfence_object_state state;
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/*
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* Allocated object address; cannot be calculated from size, because of
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* alignment requirements.
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*
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* Invariant: ALIGN_DOWN(addr, PAGE_SIZE) is constant.
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*/
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unsigned long addr;
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/*
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* The size of the original allocation.
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*/
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size_t size;
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/*
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* The kmem_cache cache of the last allocation; NULL if never allocated
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* or the cache has already been destroyed.
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*/
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struct kmem_cache *cache;
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/*
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* In case of an invalid access, the page that was unprotected; we
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* optimistically only store one address.
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*/
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unsigned long unprotected_page;
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/* Allocation and free stack information. */
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struct kfence_track alloc_track;
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struct kfence_track free_track;
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};
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extern struct kfence_metadata kfence_metadata[CONFIG_KFENCE_NUM_OBJECTS];
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/* KFENCE error types for report generation. */
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enum kfence_error_type {
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KFENCE_ERROR_OOB, /* Detected a out-of-bounds access. */
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KFENCE_ERROR_UAF, /* Detected a use-after-free access. */
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KFENCE_ERROR_CORRUPTION, /* Detected a memory corruption on free. */
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KFENCE_ERROR_INVALID, /* Invalid access of unknown type. */
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KFENCE_ERROR_INVALID_FREE, /* Invalid free. */
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};
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void kfence_report_error(unsigned long address, bool is_write, struct pt_regs *regs,
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const struct kfence_metadata *meta, enum kfence_error_type type);
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void kfence_print_object(struct seq_file *seq, const struct kfence_metadata *meta);
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#endif /* MM_KFENCE_KFENCE_H */
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